72 replies to this topic

[gruntguru]

Prius has always had an Atkinson cycle ICE but now Toymota has developed a family of engines for non-hybrid vehicles. The 1.0 litre 3cyl improves the economy of the new Aygo from 60 mpg to 78 mpg (US) (3 litres/100 km). Brake thermal efficiency is a claimed 38% from the 1.3L 4 cyl and a CR of 13.5:1.

 

Are we approaching the limits for SI engines? Remember this engine doesn't even have VCR or full electronic valve actuation, both of which will certainly make a difference.

 

http://www.gizmag.co...dc1609-90270322

[malbear]

Prius has always had an Atkinson cycle ICE but now Toymota has developed a family of engines for non-hybrid vehicles. The 1.0 litre 3cyl improves the economy of the new Aygo from 60 mpg to 78 mpg (US) (3 litres/100 km). Brake thermal efficiency is a claimed 38% from the 1.3L 4 cyl and a CR of 13.5:1.

 

Are we approaching the limits for SI engines? Remember this engine doesn't even have VCR or full electronic valve actuation, both of which will certainly make a difference.

 

http://www.gizmag.co...dc1609-90270322

 

 

 

I thought that the atkins cycle also included a turbocharger to compensate for the extreme late closing of the intake valve?

the main idea is for the engine to have a larger expansion stroke than any of the other strokes .

I wonder if there is also an offset bore to the crank?

[mariner]

Ford have already introduced a " super efficiency" 3 cylinder small engine, BMW and GM are close behind with similar type non Atkinson  engines. Fiat has the "Dual -Air" concept which has amazing economy on test cycles (if not real life)..

 

I think we need to see an Aygo equipped with this Atkinson  engine in a group test against the Ford KA, Opel Adam etc of similar size before drawing any conclusions about real world fuel efficiency.for the Toyota engine

 

Certainly the tide inEeurope is turning anti-diesel for the smaller engines as the Euro 6 emissions standard makes them so expensive to build and with SI engines getting to 13:1 Cr and direct injection the efficiemcy gap to Diesel is shrinking. Based on the EU test the gap on small cars is now about 10%.

Edited by mariner, 15 April 2014 - 08:33.

[Kelpiecross]

I have always tried to promote Atkinson Cycle engines ever since I saw a Morris Mini with an 18:1 Atkinson engine years ago. It had a 1.3l engine (instead of 1 litre) to compensate for the slightly lesser power of an Atkinson. It managed nearly 50mpg in normal (light) traffic. As well as the economy the engine idled more smoothly, the exhaust was cooler and quieter - generally it was a better-behaved engine. An engine with Atkinson and reduced pumping losses through variable valve timing (I prefer the LIVC strategy) I think would probably be the ultimate general-purpose engine.

I would have thought that with an 18:1 Atkinson engine the TE would be into the forties. The Atkinson style of operation goes straight to the heart of Otto cycle (is an Atkinson still an Otto - I presume it is) efficiency by "sucking" (that's how I imagine it anyhow) more mechanical work out of the combustion gases. An Atkinson with reduced pumping loss by LIVC (or similar) I think would be the ultimate general purpose (as opposed to racing etc.)engine.

Edited by Kelpiecross, 15 April 2014 - 10:28.

[gruntguru]

 Based on the EU test the gap on small cars is now about 10%.

Is that an mpg comparison or thermal efficiency. If it is mpg the 10% difference would be roughly due to the higher heating value of diesel fuel. The price of diesel fuel is about 10% higher too - at least here in Oz.

[gruntguru]

The Atkinson style of operation goes straight to the heart of Otto cycle (is an Atkinson still an Otto - I presume it is) efficiency by "sucking" (that's how I imagine it anyhow) more mechanical work out of the combustion gases.

Otto is actually an idealised cycle that makes all sorts of approximations that don't happen in real engines eg all the combustion takes place at TDC while the piston is stationary. Atkinsion is only a slight modification to Otto.

 

Think of the increased expansion ratio in an Atkinson engine as capturing some of the energy that is lost due to the exhaust valve opening while there is still pressure in the cylinder.

Edited by gruntguru, 16 April 2014 - 22:57.

[Kelpiecross]

I did actually know the "official" reason - I just like to picture the piston "sucking" extra energy out of the combustion gases.

There is another "homespun" way of picturing why the Atkinson is more efficient. If you imagine an engine with a geometrical capacity of one litre but with a CR of 18:1 (say about double the normal CR) but only being allowed to ingest about 500cc (about half normal) of fuel/air mixture - then immediately after combustion the gas pressure (which is the same as that of a normal 500cc engine) is now acting on an area of piston which is double that of a normal 500cc engine - so the torque/hp immediately after combustion is twice that of a normal 500cc engine. But because of the greater ER the pressure drops off more quickly than with a normal engine you end up not with double the torque but with distinctly more than with a normal engine.

[malbear]

I did actually know the "official" reason - I just like to picture the piston "sucking" extra energy out of the combustion gases.

There is another "homespun" way of picturing why the Atkinson is more efficient. If you imagine an engine with a geometrical capacity of one litre but with a CR of 18:1 (say about double the normal CR) but only being allowed to ingest about 500cc (about half normal) of fuel/air mixture - then immediately after combustion the gas pressure (which is the same as that of a normal 500cc engine) is now acting on an area of piston which is double that of a normal 500cc engine - so the torque/hp immediately after combustion is twice that of a normal 500cc engine. But because of the greater ER the pressure drops off more quickly than with a normal engine you end up not with double the torque but with distinctly more than with a normal engine.

 

It might be just as easy to give it the same treatment that the japs used to give their two strokes with a corrected compression ratio Ie measure the compression only after all the ports (or Valves are closed) european bikes had 12/1 compression while japs had 8/1 corrected ratio

 cheers mal

[gruntguru]

Hmmm - how far open does a port or valve need to be before the flow through it is significant . . . . and while you're at it - how long is a piece of string?

[bigleagueslider]

A BTE of 38% from a small displacement SI production auto engine is quite respectable. But it is theoretically possible to achieve much higher BTEs from recip IC engines. Operating at/near constant volume combustion conditions would help greatly. Increasing combustion cycle pressure ratios is also very effective.

[manolis]

Hello.


Quote from the “Average Auto’s Fuel Economy Rising Fast (TheDetroitBureau)” article:
“Ironically, during the study found one anomaly in the trend towards better fuel economy. Mileage actually dropped 3 mpg for hybrids – though they are still more fuel-efficient overall than internal-combustion-only vehicles, according to the U-M study.”

And quote from the Internet:
“Toyota Motor Corporation and Mazda Motor Corporation reached an agreement in 2010 on the supply of the hybrid technology components, upon which the Toyota Prius is based. Mazda plans to combine this hybrid system with its next-generation SKYACTIV technologies to develop and introduce a hybrid vehicle in Japan, starting in 2013. The fuel efficiency of today’s engines decreases significantly from medium to low loads at low engine speeds. Hybrids can deliver good fuel economy by powering the vehicle at lower loads. However, says Mazda, the wider the internal combustion engine’s inefficient lower load range is, the larger a hybrid’s electric motor and battery need to be to compensate for it. Mazda intends to leverage the efficiencies of the SKYACTIV internal combustion engines to enhance overall hybrid effectiveness with a lighter electric motor and battery. Regenerative braking can thus serve as the predominant source of power to charge the battery. Mazda intends to leverage the efficiencies of the SKYACTIV internal combustion engines to enhance overall hybrid effectiveness with a lighter electric motor and battery. Regenerative braking can thus serve as the predominant source of power to charge the battery.”

With the average mileage increasing in the conventional cars and decreasing in the hybrids, the gap between them shortens dangerously for the hybrids.

Mazda actually says that using high compression ratio (14:1) and Miller cycle (late intake valve closing) their SkyActive-gasoline engines keep their good fuel economy at lower loads.

In numbers:
The 90gr/Km CO2 of the Toyota Prius in the combined European cycle versus:
the 92gr/Km CO2 of the “conventional” Fiat 500 TwinAir,
the 95gr/Km CO2 of the “conventional” Nissan Micra DIG-S and
the 99gr/Km CO2 of the Volvo S30 Diesel,
and the 3.3 lt/100Km of the Mazda 2 SkyActive-G, 1.3, 84bhp,
cannot justify – any longer – the complexity and the additional cost of the Hybrids.

The three of the above engines use a limited Miller cycle with throttle valve and high compression ratio (13:1 and 14:1) to improve the mileage at partial loads.
The engine of the TwinAir (throttle-less) uses a normal compression ratio (10:1) and the MultiAir strategies of Fiat to achieve the same.

The PatAir at http://www.pattakon....ttakonHydro.htm combines the two worlds: all the strategies / modes of Fiat MultiAir, throttle-less operation, unlimited Miller cycles and high compression ratio.
With a gasoline engine keeping the good fuel economy at medium and light loads, who needs the hybrids?


The above quotation is from February 2012 (a published comment in "TheDetroitBureau").


With 78mpg for the Aygo, is there any reason for keeping the Prius in production?


Imagine the Aygo with an unlimited Miller (or Atkinson) cycle, for instance with the http://www.pattakon....akonHyDesmo.htm VVA in the cylinder head:



and with a turbo charger,

and with a variable compression ratio, for instance with the http://www.pattakon....pattakonVCR.htm VCR




The mileage would increase, the power would increase a lot (judging from the 125 of the Ford 1.0 lit engine, the 150bhp can easily be obtained when you have full control over the valves and full control over the compression ratio).

Thanks
Manolis Pattakos

[indigoid]

Mazda actually says that using high compression ratio (14:1) and Miller cycle (late intake valve closing) their SkyActive-gasoline engines keep their good fuel economy at lower loads.

In numbers:
The 90gr/Km CO2 of the Toyota Prius in the combined European cycle versus:
the 92gr/Km CO2 of the “conventional” Fiat 500 TwinAir,
the 95gr/Km CO2 of the “conventional” Nissan Micra DIG-S and
the 99gr/Km CO2 of the Volvo S30 Diesel,
and the 3.3 lt/100Km of the Mazda 2 SkyActive-G, 1.3, 84bhp,
cannot justify – any longer – the complexity and the additional cost of the Hybrids.

 

It would read better if the same measurement was used for all engines. What's the claimed CO2 figure for the Mazda?

[Greg Locock]

The thing is though that a good ic engine will always benefit from some aspects of a hybrid system, and and hybrid will benefit from a better engine, in the right drive cycle.

[Powersteer]

maybe this new atkinson super-economy engine comes with toyota's new variable intake cam control, valvetronic which seems to be constant to change. in low throttle input, the cams can use atkinson's cycle to decrease power rather than via fuel, ignition or throttling the intake in a way bmw has its variable lift valve as throttle. low operation can be very efficient and if coupled with variable exhaust to ******, that would just super impose atkinson cycle compared to how it is being used today. i read that mazda are about to put to production their homogeneous  petrol powered engine with new level claim of fuel economy and low pollutant. few manufacturers have this on their reseach and development cards but it looks like mazda is the first to break cover. 

 

[manolis]

It would read better if the same measurement was used for all engines. What's the claimed CO2 figure for the Mazda?

Hello indigoid.

I agree. And I did search, but Mazda in 2012 avoided giving the CO2 figure.

In the hindsight, however, it seems the figure was not good and Mazda gave the confusing 3.3lit/100Km (at what conditions?).

Searching in the Internet, the small Mazda 2 of 2014 with the SkyActive-G, 1.3, 84bhp engine emits 115grCO2/km, which is too much (and corresponds to some 5.2lit/100Km in the combined European cycle, i.e. some 50% above the initial 3.3lit/100Km of Mazda).

Searching in the Internet, the same story is repeated with Toyota Aygo / Yaris "non-hybrid Atkinson".
Instead of giving the quantity of CO2 emitted per 100Km, Toyota gives – just like Mazda - a confusing 3lit/100Km (if they use the same "cycle" with Mazda, then the (correction) 115grCO2/Km of Mazda 2 is translated into (correction) 104grCO2/Km for the Aygo / Yaris, which is a bad figure.

Let's hope Toyota is much better than Mazda.

Thanks
Manolis Pattakos

Edited by manolis, 23 April 2014 - 04:08.

[manolis]

The thing is though that a good ic engine will always benefit from some aspects of a hybrid system, and and hybrid will benefit from a better engine, in the right drive cycle.

Hello Greg Locock.

With an engine having a, more-or-less, constant bsfc in a wide range of revs and loads, the hybrid technology offers nothing (except more weight, more cost, more complication).

The Atkinson / Miller cycle goes to this direction: with an expansion ratio of, say, 13:1 and throttle-less operation, the efficiency is good even at light loads.
The spark ignition engines can be better than the Diesels.
Mazda uses a compression ratio of 14:1 in their Diesel engines, and the same 14:1 compression ratio in their spark ignition engines (more correctly: an expansion ratio of 14:1 in both cases).

Until now the Hybrids were more green. They were quite more expensive, but they were greener.

The hybrids exploit the inefficiency of the conventional spark ignition engine at specific conditions (like the light load operation). The hybrids keep the engine running at an efficient point of revs / load, store the surplus energy for later use and turn-off the engine.

With the Atkinson / Miller cycle the conventional engines become the same (or more) green with hybrids.
I can't see what the hybrids can offer.

Instead of using the hybrid tech, you can put the extra cost of it on a turbocharger and on a good VCR (like http://www.pattakon....pattakonVCR.htm ).

Thanks
Manolis Pattakos

Edited by manolis, 22 April 2014 - 14:07.

[Powersteer]

thing about battery power is, one would store all that weight for that energy with the trip its about make. the clever bit would be where it got the energy from. hybrid is no more a technology other than energy storage and a good example is, ever since electric came to powertrain in a big way, battery technology has evolved so rapidly compare to electric motor. so the argument of constant bsfc would make redundant hybrids can be questioned, i mean, with hybrid, the energy stored can be equivalent to a car idling all night to charge a battery to be used later in multiple loads yet constant bsfc is far from being achieved if it was to compete with the fuel economy of a car engine at idle let alone if it came from free energy.

 

[malbear]

the use of the term compression ratio in regard to atkins cycle is a bit of a misnomer  as in fact the compression ratio after the intake valve closes could be relativly low . It may be better to refer to the expansion ratio as this is where the efficiency comes from. or even the percentage of the expansion ratio over the compression ratio for example  the change in volume for a 100cc engine for the compression ratio after the intake valve is closed may only be 60cc yet the expansion ratio to the opening of the exhaust valve could be 80cc or 133%

[gruntguru]

I agree. And I did search, but Mazda in 2012 avoided giving the CO2 figure.
In the hindsight, however, it seems the figure was not good and Mazda gave the confusing 3.3lit/100Km (at what conditions?).

Searching in the Internet, the small Mazda 2 of 2014 with the SkyActive-G, 1.3, 84bhp engine emits 115grCO2/km, which is too much (and corresponds to some 5.2lit/100Km in the combined European cycle, i.e. some 50% above the initial 3.3lit/100Km of Mazda).

Searching in the Internet, the same story is repeated with Toyota Aygo / Yaris "non-hybrid Atkinson".
Instead of giving the quantity of CO2 emitted per 100Km, Toyota gives – just like Mazda - a confusing 3lit/100Km (if they use the same "cycle" with Mazda, then the 115gr/100Km CO2 of Mazda 2 is translated into 104gr/100Km CO2 for the Aygo / Yaris, which is a bad figure.
 

Surely lit/100km is directly proportional to CO2/100km. Provided the fuel is the same type each litre will always combust to an identical quatity of CO2.

[Greg Locock]

Regen braking is enabled by a hybrid system, and is probably the biggest single mpg improver.I suppose i was being a  bit loose in terminology and should have said 'the mpg of a conventinal car with a better engine will improve further if some aspects of the bundle of technologies known as hybrid were included" The other part I think is correct, any hybrid will improve with a better engine.

[gruntguru]

Bearing in mind that "better" means different things to hybrid and conventional transmissions.

 

Improving peak engine efficiency at the expense of efficiency elsewhere in the range might be an improvement in a hybrid car but not in others. The reverse is also true of course.

[manolis]

the use of the term compression ratio in regard to atkins cycle is a bit of a misnomer as in fact the compression ratio after the intake valve closes could be relativly low . It may be better to refer to the expansion ratio as this is where the efficiency comes from. or even the percentage of the expansion ratio over the compression ratio for example the change in volume for a 100cc engine for the compression ratio after the intake valve is closed may only be 60cc yet the expansion ratio to the opening of the exhaust valve could be 80cc or 133%

Hello malbear.

With a 13:1 expansion ratio (more correctly: "with a 13:1 geometrical / theoretical expansion ratio", because the exhaust valves open before the BDC) a good Atkinson / Miller cycle engine can operate at an infinity of "effective compression ratios", say from 13:1 to even 1:1 (if the mixture could ignite without compression). It seems the characterizing number is the "expansion ratio".


Miller's patents were fundamental in this area:



It seems he first understood the importance of the "over-expansion" and put it in practice / tests.
His complete patent in pdf format is at http://www.pattakon....ller_patent.pdf


The bad news for the Miller (Atkinson) cycle is that the peak power is substantially lower as compared to the peak power of the same engine operating in the conventional way (non-overexpansion).

It seems that the engine of Toyota Prius (compression ratio 13:1) operates at a maximum effective compression ratio of 10:1 (in the meaning that the intake valves remain open much longer, as compare to the conventional engine, after the BDC in order to allow a good part of the entered air / mixture to return back to the intake manifold; while the cylinder volume is 13 times bigger than the dead volume (compression ratio=(cylinder capacity + dead volume) / dead volume = total cylinder volume / dead volume), the volume of the trapped air / mixture into the cylinder is only 10 times bigger than the dead volume).
At a first approach this means that it handles per crank rotation the same quantity of air as an 1800cc*(10/13)=1400cc conventional engine.
The peak power of 98bhp from 1800cc (2009 Prius model) agrees with it.

For a hybrid this is OK. When additional power is required, the batteries and the electic motors can help.

But for a non-hybrid car this is a problem.
The 1000cc 1KR-FE engine of Toyota / Daihatsu has a peak power of 68bhp in its conventional edition.
Using the Atkinson / miller cycle in a similar extend as in Prius, the engine will operate as being a (10/13)*1000cc, i.e. as a 770cc engine and the peak power will drop to 52bhp.

Is the pain worth the gain? (better fuel efficiency with worse performance).

Here comes the variable compression ratio (VCR) to fix things.

If, when you need more power, you could decrease the compression ratio at 10:1, the engine could deliver again the 68bhp of peak power.

And if you could decrease even more the compression ratio (to, say, 7:1) and put in action a turbocharger, the engine could provide some 150 bhp; note: the 1lt turbocharged Ford engine has already a peak power of 125bhp.

And when the fuel economy / green operation is what matters (urban cycle, for instance), the deactivation of the turbocharger and the increase of the compression (or more correctly of the expansion) ratio, by the VCR, to 13:1 will put the small engine back to the efficient Atkinson / Miller cycle.

Time will show.

Thanks
Manolis Pattakos

Edited by manolis, 23 April 2014 - 06:28.

[Speedman]

Hello

 

The Miller-and the Atkinson engine are actually a 5 stroke engine.

 

The normal Atkinson engine without Turbo has a big future. The engine is more simpler and more cheaper and makes less problem then a turbocharger.

 

I like simple und cheap solutions. Simple solutions are mostly a better solutions.

 

A very interessting engine is the 5-stroke engine with 2 stage expansion cycles.

 

fuenftaktmotor

http://www.youtube.c...fUlEdsLEv5wpapw

 

IlmorUK

http://www.youtube.c.../IlmorUK/videos

 

 

The bad news for the Miller (Atkinson) cycle is that the peak power is substantially lower as compared to the peak power of the same engine operating in the conventional way (non-overexpansion).

 

 

 

Thats not quite right. Thats right for the old generation of Atkinson engine and the new litte cheap atkionson engine for littel cars of Toyota.

The new generation of Atkinson engines doesn't work everytime in the Aktinson Cycle. A new Atkonson engine can also work in the normal process.

The peak power is similar a normal engines.

 

The Atkinson-cycle is only good for partial load.

 

 

best regareds Speedman

Edited by Speedman, 23 April 2014 - 11:01.

[manolis]

Hello
The Miller-and the Atkinson engine are actually a 5 stroke engine.
The normal Atkinson engine without Turbo has a big future. The engine is more simpler and more cheaper and makes less problem then a turbocharger.
I like simple und cheap solutions. Simple solutions are mostly a better solutions.
A very interessting engine is the 5-stroke engine with 2 stage expansion cycles.
fuenftaktmotor
http://www.youtube.c...fUlEdsLEv5wpapw
IlmorUK
http://www.youtube.c.../IlmorUK/videos
Thats not quite right. Thats right for the old generation of Atkinson engine and the new litte cheap atkionson engine for littel cars of Toyota.
The new generation of Atkinson engines doesn't work everytime in the Aktinson Cycle. A new Atkonson engine can also work in the normal process.
The peak power is similar a normal engines.
The Atkinson-cycle is only good for partial load.
best regareds Speedman

Hello Speedman.

The Ilmor engine:



is regarded as 5-stroke engine. It can also be called a "compound engine"

I suppose the 5-strokes are: intake, compression, combustion-transfer to another cylinder, expansion, exhaust.

Scuderi engine is also a compound / 5-stroke engine. Several millions have been lost so far without success.


But the Atkinson / Miller cycle engines are not 5-stroke engines. They are four-strokes: the process starts and completes into the same cylinder. They avoid the "transfer".



The compound engines have a long story.

Quote from http://www.douglas-s.../compoundIC.htm

"Left: Diesel's Series XIV compound engine.

The Diesel compound was a three-cylinder engine intended to give 120 to 150 HP. There were two 4-stroke HP cylinders of 220 mm bore and 400 mm stroke, one either side of a 2-stroke LP cylinder of 510 mm bore and the same 400 mm stroke, in the same arrangement as the Deutz engine above. The gas transfer from HP to LP cylinders was controlled by four water-cooled exhaust valves.

There were many initial problems in testing, concerned with starting and the two-plunger fuel pump, but the most unpleasant surprise was that the efficiency of the engine was not superior- it was much worse than a standard Diesel engine.

Tests revealed that the loss to the cooling water from the four intermediate exhaust valves was a shocking 11.8%, almost half of the heat that one of the cylinders could potentially convert to work. There were also unknown (but suspected to be large) heat losses from the connecting passages for gas transfer, and pumping losses in moving the hot gases from the HP to LP cylinder. "



The Miller cycle engine (or Atkinson / Miller or Atkinson) is different.
It keeps the intake valves wide open for a substantial part of the compression stroke, as explained at http://www.pattakon....ttakonHydro.htm and http://www.pattakon....akonHyDesmo.htm , like:




A good part of the entered air or mixture returns (at low energy loss) back to the intake manifold.
Then the intake valves close and the trapped air / mixture is compressed. After the combustion (always in the same cylinder) follows the expansion stroke (or more correctly the over-expansion stroke) and then it follows the exhaust stroke.



Provided the entry of the surplus air / mixture and its return back to the intake manifold involves no significant friction of any kind (this is why a Miller cycle engine is not good at high revs, this is why the intake valves need to stay wide open till the end of the intake process), the over-expansion gives better fuel efficiency.

To realize the Miller cycle by angularly shifting the intake camshaft (by a phaser) is not the best way. It gives a limited Miller cycle, good for a hydrid like Prius, not good for a non-hybrid car engine.


The electronically controlled MultiAir / UniAir / TwinAir of FIAT / INA is almost ready to operate in an unlimited Atkinson / Miller cycle. This is one of the things the PatAir and the HyDesmo VVA’s do.

In a non-hybrid car engine besides the unlimited (compression ratios from, say, 13:1 to 2:1) Miller cycle you also need the option to operate the engine at the conventional way. This is another thing the PatAir and the HyDesmo do.

If they are combined with a simple - robust - lightweight VCR (like the PatHead VCR at http://www.pattakon....pattakonVCR.htm ) you have all in one (Miller cycle, conventional cycle, high revving, high power density, low fuel consumption).

If you want, you can add a turbocharger, too.



The simpler is not the better.
The simplest engine is the ported two stroke with crankcase scavenging. But it is also a bad engine.



The challenge is to use the electronics to control the mechanisms used.

Lately I drove a new BMW valvetronic and a new Alfa Romeo Mito MultiAir.
The one has a mechanical VVA (the valvetronic) based on extreme construction accuracy (BMW claims for a 0.008mm precision in the main components), the other is based on a moderate mechanical accuracy mechanism and on electronic control based on the feedback.
The vibrations in the gearshift lever show a substantial difference.
The electronic control makes a better job in “balancing” the cylinders.

Besides, the electronic control offers an incredible - for mechanical systems - flexibility:

for instance, a PatAir four inline engine is easy to operate with one cylinder deactivated, with another cylinder running at full load, with another cylinder running at medium load according the "Ingoing Air Control" cycle and with another cylinder running at medium load according the "Outgoing Air Control" cycle. It is also easy to swap, a few dozens of times per second, the above modes among the cylinders.

Just imagine the case you wanted to do the same with the valvetronic of BMW.



It seems the things to come will be much better and at the same time much more complicated, but in a different way: the complication will be in the control, and the control will be electronic.

Thanks
Manolis Pattakos

Edited by manolis, 24 April 2014 - 06:28.

[Speedman]

Hello

 

But the Atkinson / Miller cycle engines are not 5-stroke engines. They are four-strokes: the process starts and completes into the same cylinder. They avoid the "transfer".

 

 

 

The cylces of conventional 4-Stroke engine are not the same as the cycles of Atkinson engine. The Atkinson Engine has actually a cyles more. You can read in many book and this said many engine engineers,  but i want not squabble.

 

 

The simpler is not the better.
The simplest engine is the ported two stroke with crankcase scavenging. But it is also a bad engine.
 

 

 

I didn't say a simplest engine, but i mean simple good engine solutions. Many many expensive luxury car engine are too complicated an has a lot of problems.

 

 

 

Compounding is a very interessting topic. I know a lof of turbocompounding engine concepts but this concepts are mostly expensiv.

 

One of the few turbocompounding engines of Scania.

http://www.scania.de.../turbocompound/

 

 

Just imagine the case you wanted to do the same with the valvetronic of BMW.
 

 

I know a supplier engine engineer of BMW. He said me: BMW wanted a full variable electro magnetic valve system (5 series), but the system was too expensiv, The valvetronic was cheaper. I don't like valvetronic. The system is too high, has too much parts and is not for high rpm and is too expensiv.

 

I prefer the valve system Valvematic of Toyota. Is actually not full variable, but is for high rpm is almost indestructible, low building and is not so expensiv,

 

 

Lately I drove a new BMW valvetronic and a new Alfa Romeo Mito MultiAir.
 

 

The Multiair is a very interessting valve system concept, but the concept is not good been realized.

Multiair has not a  really good petrol consumption

 

 

 

 

Best regards

Speedman

Edited by Speedman, 24 April 2014 - 10:02.

[Kelpiecross]

Speedy - the best variable valve opening system is the Helical Camshaft system. Google it.

[manolis]

Hello Speedman.

I think that for the Ilmor, the Scuderi and the similar engines the "split cycle engine" is a more characteristic term than the "5-stroke engine".


The "Atkinson / Miller" is also a confusing term:

In the Atkinson engine the intake piston stroke is different than the exhaust piston stroke. In the Gomecsys VCR engine the expansion stroke is longer than the intake stroke, i.e. it operates according the Atkinson principle.

In the Miller engine (the Prius of Toyota operates according the Miller principle) the piston stroke is the same for the intake and the exhaust. By keeping the intake valves open for as long as necessary after the BDC, a part of the air / mixture returns to the intake manifold.

Toyota's non-hybrid over-expansion engines operate according the Miller principle, even if Toyota call them Atkinson engines.




Hello Kelpiecross.

Show me in a plot all the valve lift profiles the Williams Helical Camshaft can operate, and I will add in this same plot an infinity of additional, and useful at the same time, modes the PatAir and the HyDesmo can operate.

Unless I am wrong, the variability is the key characteristic of a Variable Valve Actuation system.

Think:
Can the helical camshaft system operate with a medium or a small valve lift?
Can the helical camshaft operate in the conventional cycle without a throttle valve?
Can the helical camshaft operate with a medium or small valve opening duration?

At light loads, you need feedback and electronic control, otherwise the engine cannot operate smoothly neither it can minimize the emissions and the fuel consumption. This is the other characteristic of the PatAir and HyDesmo.
For more details on this significant problem of the mechanical VVA's: http://www.pattakon....onIdleValve.htm


For extreme power density, the mechanical Desmodromic VVA ( DVVA ) at http://www.pattakon....ttakonDesmo.htm is also way more variable:



than the Helical Camshaft.
Rid of restoring valve springs, the DVVA operates from low to extreme revs.

Thanks
Manolis Pattakos

[Speedman]

I know the Helical Camshaft system.

 

And I like the Helical Camshaft. Good for engine with barrel tappet. Good for engine conversion on variable valve system. Really simple and good and the cylinderhead build is low. Not perfect but good.

 

 

There is over 6000 Invention for variable valve system.

 

Many ways  lead to Rome.

Edited by Speedman, 24 April 2014 - 18:28.

[manolis]

Hello Speedman.

You are right.
There is no "best Variable Valve Actuation system".
Each one has its own advantages.
Some combine a lot of them.
Some "show the way" for the things to come.


You write (post 25):

"I know a supplier engine engineer of BMW. He said me: BMW wanted a full variable electro magnetic valve system (5 series), but the system was too expensiv, The valvetronic was cheaper. I don't like valvetronic. The system is too high, has too much parts and is not for high rpm and is too expensiv.
I prefer the valve system Valvematic of Toyota. Is actually not full variable, but is for high rpm is almost indestructible, low building and is not so expensiv,"

Is the Toyota's Valvematic not full variable in the meaning that it cannot go to zero (or almost zero, to get rid of the throttle valve) valve lift?
I think it can.

The valvetronic of BMW, the VVLE of Nissan Infinity and the Valvematic of Toyota are all "lost motion" VVA's, and none of them is really "fully variable".


The following two images are from the http://www.pattakon....nLostMotion.htm .



The above VVA can do everything the valvetronic does (it is a lost motion VVA, too), being way simpler, lightweight and compact.

The following VVA is not a "lost motion" VVA (it does not "cut" a part of the valve duration; it just lowers - from a maximum to zero - the valve lift, effecting substantially to the "actual overlap" too):




Quote from http://www.pattakon....KeyAdv.htm#dvva

"Comparing the DVVA

BMW's valvetronic is a lost-motion VVA. It is variable, but not fully variable. For each valve lift, valvetronic has only one available valve duration (this valve duration is not an optimized one for the specific lift, it is just what the mechanism can give) while DVVA has infinite, and for each valve duration valvetronic has one only available valve lift (again not an optimized valve lift for the specific valve duration, just what the mechanism can give) while DVVA has infinite. The valvetronic is based on a relatively "heavy" oscillating member that "opens" under the camming action of the camshaft and "closes" under the restoring action of a vertical-long-big-spring. The valves in valvetronic need their own conventional valve springs to close. The big springs and the heavy parts restrict valvetronic to not high revving applications (rev limiter at 6800 rpm) and this is why valvetronic is missing from BMW's sport cars.

Nissan's VVEL is also a lost-motion VVA, like valvetronic. It is as variable as valvetronic, but not fully variable. It needs valve springs to restore the valves. The VVEL mechanism is demi-desmodromic: there are valve springs to restore the valves but there are no other springs, like the "vertical-long-big-springs" of the valvetronic mechanism. This is why Nissan's top sport coupe 370Z (VQ37VHR-V6-VVEL) can operate at 7400rpm to provide 94.7bhp/lit specific power. The "maximum rpm" of the same sport engine is set to 7500 rpm (only 100rpm higher than the peak power revs!) saying a lot about the limitations of the current VVAs.

Toyota's "valvematic" has similar limitations to BMW's valvetronic.

In comparison pattakon DVVA provides infinite times more valve lift profiles to better optimize the breathing of the engine, and allows as high revs as the underneath mechanism can stand (block, crankshaft, con-rods, pistons). The ideal VVA is the one that optimizes the breathing of the engine at all revs and every load.
The DVVA, depending on the angular position of its control shafts, can "play" either as Lost Motion VVA (valvetronic for instance), or as Constant Duration VVA (pattakon VVA rod version, for instance), or as a single mode Ducati Desmo valve train, or as anything in-between them.
The one moment DVVA can operate accurately at 300 rpm, 0.15mm valve lift and 50 degrees valve duration, while the next moment DVVA can rev at 15,000 rpm, 14mm valve lift and 360 deg valve duration."


At http://www.pattakon....attakonFVVA.htm it is presented a Fully Variable VVA (the parent of the DVVA ) :



BMW's valvetronic and Toyota's valvematic, and Nissan's VVEL "move" only along a line (a curve) like the O-B-M. If you pick a lift, there is only one possible duration to combine with it (non necessarily a good one; it is just what the linkage gives). If you pick a duration, there is only one valve lift to combine with it (non necessarily a good one; it is just what the mechanism gives).

The FVVA and the DVVA of pattakon are both "fully variable" VVA's.
They can "move" anywhere in the hatched area.
For each valve lift there is an infinity of available valve durations to pick from, and for each valve duration, there is an infinity of available valve lifts to pick from.







Thanks
Manolis Pattakos

Edited by manolis, 25 April 2014 - 04:54.

[Kelpiecross]

I know the Helical Camshaft system.
 
And I like the Helical Camshaft. Good for engine with barrel tappet. Good for engine conversion on variable valve system. Really simple and good and the cylinderhead build is low. Not perfect but good.
 
 
There is over 6000 Invention for variable valve system.
 
Many ways  lead to Rome.

Speedy - you are right - there is an unbelievable number of patents for VVT ideas in patent offices worldwide. But if you study these ideas you will find that most of them are "variations on a theme". There are only about six or seven basic general principles (not including camless/phasing/cam switching etc.) in the 6000 inventions that you mention - most of them are not really original ideas at all.
The Wiki article on VVT lists most of the basic ideas:

http://en.wikipedia....le_valve_timing

Even in this list the last three could probably be thought of as distantly related. I think there is a couple of principles that are not included - but not many. It is a personal opinion but I have always regarded the Helical type to be the most useful variety. The most novel (but maybe the least practical) is possibly the Rover eccentric drive system.
There probably should not be 6000 (or whatever - the number could be more than this) but patent offices in general and the USPTO in particular seem to accept even tiny variations in an idea as "novel" and thus are patentable. There are many VVT "inventions" in the USPTO that appear virtually identical to me.
The general opinion in the trade is that the USPTO pretty much accepts any "invention" then lets the various companies fight it out in court.

[Speedman]

Hello Kelpiecross

 

Speedy - you are right - there is an unbelievable number of patents for VVT ideas in patent offices worldwide. But if you study these ideas you will find that most of them are "variations on a theme". There are only about six or seven basic general principles (not including camless/phasing/cam switching etc.) in the 6000 inventions that you mention - most of them are not really original ideas at all.

 

 

That's right, but the big difference this many patents of variable valve systems,  is the construction cost,  build size and complexity .

 

 

@manolis

 

Do you need a challenge?

Can you construction a simple very light 2-Stroke nitro engine with 10cc and more then 6 HP for RC speed plane?

Conventional special racing 2-Stroke RC-Speed engine are at the limit by circa 5 -5.5 HP

Probably needs more than 28'000 rpm or a many better cylinder filling.

 

best regards

 

Speedman

Edited by Speedman, 25 April 2014 - 08:05.

[manolis]

In order to complete my last post (many people avoid opening "exe" files), here is the Lost Motion version at low lift:



and here is the Constant Duration version at low lift, too:


There are four more GIF animations like the above at http://www.pattakon....nLostMotion.htm (each system is shown at a medium and at a high lift).



Hello Speedman.

You write:
"manolis,
Do you need a challenge?
Can you construction a simple very light 2-Stroke nitro engine with 10cc and more then 6 HP for RC speed plane?
Conventional special racing 2-Stroke RC-Speed engine are at the limit by circa 5 -5.5 HP
Probably needs more than 28'000 rpm or a many better cylinder filling."

If an arrangement can easily do what you describe (without nitro) it is the OPRE_tilting.
Judging from the first OPRE_tilting prototype it will be very light.
The piston stroke halves and the revs go well above 35,000rpm.
The tilting valves (secured on the connecting rods) will control the breathing.
The engine will also be perfectly balanced.

The only challenge I see is to built it at the required construction accuracy, with the correct materials.

I can provide the blueprints.
Can you manufacture it? At what cost? Your rotary-valve prototype engines say you can.

To make it more interesting, we can bet for the peak power and for the weight (or the specific power).

E-mail me for the details.

Thanks
Manolis Pattakos

Edited by manolis, 25 April 2014 - 09:50.

[Speedman]

@Manolis

 

A powerful model engine is a project in a long time. I'm looking for first interesting engine concepte. In moment i can't build a engine, then i haven't machine tools.

 

A big problem is a very short stroke by 2-stroke engine. By 4-stroke engine is a short stroke no problem, but by 2-stroke. The shorter the stroke the more is the airflow will been bad in the cylinder-ports. So there isn't ultra short 2-stroke engine. A good 2-stroke engine has a stroke/bore ratio: 1.2 - 0.8. But a ratio 0.5-0.6 is very very bad by 2-stroke engines.

 

 

Do you know the rocking piston engine (2-stroke and 4-stroke) of Swiss Engineer Mr. Salzmann?

http://www.freepaten...EP0390882B1.pdf

He fictional a 2-stroke engine with asymmetric port-timing. Asymmetric port- timing by 2-Stroke engine is interessting.

 

The exhaust-port closing bevor the transfer-port closing.

He had build this engine with square piston and with circular piston.

 

A good idea, but complicated to build.

 

best regards

Speedman

Edited by Speedman, 25 April 2014 - 10:59.

[Greg Locock]

I'm slightly astonished to see Maniolis seems to take the Scuderi engine seriously. Did I read that right?

[manolis]

Hello Grec Locock.

It is a pity that so many millions of investors’ dollars have been spent for Scuderi’s project.

At the end of the last day of the Engine Expo Stuttgart Germany (2009), a guy came to our (pattakon) booth (which, by the way, was a dozen of meters away from Scuderi’s booth, with the space between the two booths full of chairs for the Open Technology Forum and for the “Engine of the Year” “fiesta”) and started talking for Scuderi’s engine (that year for the first time Scuderi had a demonstration prototype).
I told him that Scuderi’s concept introduces more problems than it solves.
I told him “Scuderi’s concept is a nonsense.”
Then I discovered that he was the owner and head of the company that prepared Scuderi’s prototype (his company was specialized in preparing engines of the big engine makers for exhibitions: by slicing some parts, by painting the cuts, by motorizing the engine to show the parts moving, by illuminating the “concept”).

A year earlier (2008) another guy (early in the morning this time, with the doors still closed for the visitors of the Engine Expo Stuttgart Germany) came to pattakon booth and started talking for Scuderi’s astonishing engine. He asked me to go with him to Scuderi’s booth to explain to me better his thoughts. Finally he was thrilled by the fact that the compression was made in a cylinder and the expansion in another cylinder. When I asked him “and why this is important or useful?” he didn’t know. The guy was the head / manager of another International Exhibition for racing teams.


I think the most critical question for a new, or “new”, idea is whether it solves a problem without introducing a more difficult / serious problem.

The transfer valves of Scuderi’s split cycle engine operate the wrong way (not as the conventional poppet valves wherein the more the pressure, the better the sealing), at difficult conditions (temperature) and at rates much higher than the conventional intake and exhaust valves.
Rudolf Diesel tried (and abandoned as inefficient) a similar concept



Hello Speedman.

You write:
“A big problem is a very short stroke by 2-stroke engine. By 4-stroke engine is a short stroke no problem, but by 2-stroke. The shorter the stroke the more is the airflow will been bad in the cylinder-ports. So there isn't ultra short 2-stroke engine. A good 2-stroke engine has a stroke/bore ratio: 1.2 - 0.8. But a ratio 0.5-0.6 is very very bad by 2-stroke engines.”

I think you have to take another look at the OPRE_tilting.
It is not like the conventional two stroke engines wherein the over-square design worsens the – necessarily - loop scavenging).
In the OPRE_tilting, the shorter the piston stroke (relative to the bore), the better the scavenging. It is a cross-uniflow scavenging. See the animations. It is as efficient as the through-scavenging in the “long stroke” marine low-revs two stroke engines.



Hello Kelpiecross.

The procedure for patenting in the US-PTO (USA) and in the EPO (European) and in the WIPO and in the Chinese Patent Office and in the UK-IPO (Great Britain) and in the Japan Patent Office and in the Korean Patent Office and in the Russian Patent Office is similar.

At the end there is a guy (the examiner) who has to decide if the idea is novel, if it has an inventive step and if it has an industrial applicability.

As in every other job, there are good examiners and bad / incompetent examiners.

There are examiners who listen and accept the opinion of the applicant (if the applicant is right and proves his objections), but there are also examiners who do not know / understand the field of the inventions they examine.

There are also a lot of formalities the applicant has to follow and fees the applicant has to pay (especially in countries wherein a patent attorney is mandatory), There are also dead lines for the applicant to respond otherwise there are penalties and withdrawal of the invention.

By experience, the most important “rule” / law the Patent Offices should follow is the “law of the common sense”.

By the way, only for a small percentage of the applications filed, a patent is finally granted.

As I know the most cost-efficient Patent Office for the English Speaking applicants / inventors is the US-PTO (USA).
The total cost from the initial filing to the final granting of the patent is US1,200$. Three years AFTER the granting of a patent a maintenance fee of US800$ has to be paid (and again after another three years).

The UK-IPO is also a cost-efficient Patent Office. From the initial filing to the granting the total cost is 230 pounds. Then there is an annual maintenance fee of some 100 pounds (it depends on the year from filing).

The EPO is expensive (with the application you have to pay some 2,000Euros). They are not better. They are just more expensive. They are also far away from the “common sense” law. To get an idea: if EPO delays the examination of your application, you – the applicant – has to pay maintenance fees of some 450 Euros per year, without having a patent and without knowing if a patent will be finally granted!

In China, Japan, Korea etc you need a patent attorney and translations etc.

Kelpiecross, the only way to understand the “patenting” system is to file an application for an invention and to get a patent. Otherwise you talk theoretically.

Thanks
Manolis Pattakos

[Kelpiecross]

Manny - I have a pretty fair idea how the patent system works. I know of quite a few people in the inventing/manufacturing/research industries who are very annoyed by the way the USPTO (especially) operates.

[Kelpiecross]

Hello Kelpiecross
 
That's right, but the big difference this many patents of variable valve systems,  is the construction cost,  build size and complexity .

Speedy - I think that is the point I am trying to make - many variations (good and bad) and many variations virtually identical but only a very few basic ideas.

On the subject of small 2-stroke engines - some 2.5cc 2-strokes produce 2.5HP (1000hp/litre) at over 40,000RPM - so I suppose it is primarily a question of getting your 10cc engine to rev to 35,000RPM or so.

On the other hand supercharging may be an idea. I am a regular reader (too regular maybe) of model plane magazines and I have never seen a suggestion of a supercharged model plane engine. 2-strokes can be supercharged quite well - maybe not as well as 4-strokes - but OK. Shouldn't be too difficult to build a model-sized supercharger.

[Speedman]

 Hi

 

On the subject of small 2-stroke engines - some 2.5cc 2-strokes produce 2.5HP (1000hp/litre) at over 40,000RPM - so I suppose it is primarily a question of getting your 10cc engine to rev to 35,000RPM or so.

On the other hand supercharging may be an idea. I am a regular reader (too regular maybe) of model plane magazines and I have never seen a suggestion of a supercharged model plane engine. 2-strokes can be supercharged quite well - maybe not as well as 4-strokes - but OK. Shouldn't be too difficult to build a model-sized supercharger.

 

 

I have a collecting of model engines. And I know rc car engine. 3.5cc till 2.8 HP and max 46'000 RPM but this is not continuous power only for a short time maby max. 5 sec.

 

A high speed rc engine for high-speed airplane, works everytime full power. A 10cc engine with 35'000 RPM is a challenge.

The company Os Max had a 4-Stroke rc engine 20cc with a roots supercharger the power was 2.5 HP, this is too little. A 4-stroke engine has no chance.

A good speed engine with 10cc has today circa 5 HP @ 28'000 RPM.

 

The weight is very importent by rc engines. A  powerful and good rc engine shoud bee a simple and light engine.

 

Do you know speedmodelcar?

http://www.speedmodelcar.com/

 

 

A interessting 2-stroke concept is FST (foekema symmetric two stroke) engine with two exhaust-ports. Interessting but difficult to control.

http://www.2stroke.g...php?t=176&p=900

 

@Manolis

Your engine required 2 crankshafts. This is probably too heavy for a airplane. I need onley one crankshaft for a airscrew.

What is the highest speed you've achieved with your prototype-engine?

 

 

 

best regards

 

Speedman

Edited by Speedman, 25 April 2014 - 18:54.

[Greg Locock]

Oh, thank goodness for that. Many Europeans will remember the Twingle engine, if not, head to your scrapyard and buy an old Puch moped. You are now in proud possession of a productionised Scuderi. Similar problem to the Bourke, pumping your pressurised charge via a transfer port is an opportunity to create friction and also cool the charge down, the latter being energy you expensively put into it. There are other problems, that's the biggy. There are some advantages as well, no doubt.

[manolis]

Hello Greg Locock.

Scuderi’s concept is quite different than the Twingle.
The second is like having a long opposed-piston two-stroke through scavenging (uniflow scavenging); then you bend the cylinder to make a U in order to use a common crankshaft for the two pistons. In comparison to the loop scavenged two-strokes the scavenging improves a lot. But the surface area of the combustion chamber gets more than double.

That is, the Twingle solves a problem of the conventional two-strokes creating another – worse – problem: substantially increased thermal loss to the combustion chamber walls.

But in the Twingle there is no compression in a cylinder, transfer of the “hot” compressed air / mixture to another cylinder and expansion in the second cylinder. (Scuderi’s “split-cycle” engine and Ilmor’s “5-stroke” are both characterized by this sequence of “cycles”: induction and compression in a “cold” cylinder, transfer, expansion and exhaust in “hot” cylinder).


Similarly, Bourke’s engine is different than Scuderi’s.
The real difference of the Bourke from a typical two-stroke is that instead of the crankshaft – connecting rod mechanism, Bourke uses a Scotch Yoke mechanism like:



The Bourke was a good engine for the first few minutes of operation. Then the track roller bearing and the track-ways of the Scotch Yoke start wearing requiring a major repair.
An “evolution” of the Bourke engine is the Revetec engine (the severe reliability problems of the Bourke engine are also the Achilles’ heel of Revetec engine, too; officially Revetec spark ignition prototype achieved a peak BSFC of 207gr/kWh , i.e a 39.5% efficiency).

As the Twingle, also the Bourke engine is not a split-cycle engine.
It has nothing to do with Scuderi’s concept.
The fact that it uses the backside of the piston (and not the crankcase) for the scavenging is a substantial improvement as compared to the conventional two-strokes and does not consume more energy (the pressure at the backside of the piston nevers gets high).

But again Boorke’s engine “solves” a problem by creating a worse one (reliability).



Hello Speedman.

The two crankshafts do not necessarily give a heavier engine. Here is the first OPRE_tilting prototype:



333 cc, bore 84mm, stroke 30+30=60mm
(same bore to stroke ratio with BMW's boxer R1200GS of 2013)
weight: 8.5Kp (19lb) without the exhaust pipe and the carburetor
height: 250mm

Nothing is optimized.
The weight can further drop.
Videos at http://www.pattakon....akonTilting.htm

I don’t know the revs it works (it is a low-budget proof-of-concept prototype).

If you want a single power shaft, just use the one of the two crankshafts.
If you want a reduction of revs for the propeller, use an intermediate gear.

But I think this engine better fits with a pair of counter-rotating propellers, one at the front side and one at the backside, like:



(Diesel OPRE engine youtube video at: http://www.youtube.c...h?v=64TY-x2Cj6Y

This arrangement leaves the casing of the airplane not only rid of inertia and combustion vibrations, but also rid of reaction torque (weight saving, more stable / safer flight).




Think more unconventional.


Thanks
Manolis Pattakos

[Kelpiecross]

Oh, thank goodness for that. Many Europeans will remember the Twingle engine, if not, head to your scrapyard and buy an old Puch moped. You are now in proud possession of a productionised Scuderi. Similar problem to the Bourke, pumping your pressurised charge via a transfer port is an opportunity to create friction and also cool the charge down, the latter being energy you expensively put into it. There are other problems, that's the biggy. There are some advantages as well, no doubt.

I suspect the Ilmor "5-stroke" would suffer from much the same (but maybe not to the same extent) problems as the Scuderi. If you want greater TE from greater expansion of the combustion gases the typical Atkinson Cycle engine would seem to be the more obvious solution. If the Atkinson engine is arranged in the normal fashion with a high geometrical CR/ER and the compression pressure limited by grinding the cam with a lot of LIVC - it is essentially just a conventional engine and would cost the same to make.
The problem is I suppose that you really can't patent and promote (and get in investors' money etc.) what is just a normal engine so we end up with Scuderies/Ilmors etc. etc. which can be promoted.

[Speedman]

Hello

 

If you want a reduction of revs for the propeller, use an intermediate gear.

 

 

A reduction of revs for the propeller would be good, but nobody use a intermediate gear in a RC high speed airplane. A intermediate gear is very too heavy and too big.

 

More weight in a plane and you need more buoyancy (up force) and you had more air resistance
and you need more engine power. That's the problem. This engines are light and very slim and narrow because of the air resistance.

 

best regards

 

Speedman

Edited by Speedman, 26 April 2014 - 08:01.

[manolis]

I suspect the Ilmor "5-stroke" would suffer from much the same (but maybe not to the same extent) problems as the Scuderi. If you want greater TE from greater expansion of the combustion gases the typical Atkinson Cycle engine would seem to be the more obvious solution.

Hello Kelpiecross.

The Scuderi concept differs from Ilmor's 5-stroke concept.
In the first case the one cylinder is for induction - compression, then it happens the transfer to a second cylinder and follows the expansion and the exhaust in the second cylinder.
In the second case (Ilmor) the side cylinders have a normal 4-stroke operation, with the central (low-pressure) cylinder used only for the over-expansion of the exhaust gas exiting from the side cylinders. The exhaust valves of the central cylinder operate at double frequency than the rest valves.

The 226gr/kWh Ilmor claims is translated in 36% thermal efficiency, below the 38% of the simple Prius Miller cycle thermal engine. Does this fuel efficiency, alone, justifies the added complexity?

If the Atkinson engine is arranged in the normal fashion with a high geometrical CR/ER and the compression pressure limited by grinding the cam with a lot of LIVC - it is essentially just a conventional engine and would cost the same to make.
The problem is I suppose that you really can't patent and promote (and get in investors' money etc.) what is just a normal engine so we end up with Scuderies/Ilmors etc. etc. which can be promoted.

The true problem is to make an engine having the Atkinson / Miller fuel efficiency when necessary, and top power density (bhp/cc of displacement or bhp/lb of engine weight) when necessary.

Obviously you need a good VCR (variable compression ratio) system (like the pattakon PatHead VCR; by the way compare its complexity, compactness, weight, functionality etc with those of Toyota's VCR shown at the end of the http://www.pattakon....pattakonVCR.htm web page).

Obviously you also need a VVA with the necessary "variability".

The VCR lowers the compression ratio when necessary, the VVA manages the efficient breathing.

A turbocharger is optional.

For as long as you need green / fuel efficient operation, the engine operates in the Miller / Atkinson cycle with a high expansion ratio.

And when you need power (I mean a lot of power), the expansion ratio drops and the VVA keeps the engine operating in the conventional cycle. If your VVA is reliable at high revs, you do not need a turbocharger (see the video at http://www.pattakon....takonRoller.htm )

By these two "tools" (a good VCR and a good VVA) you can have it all in the same engine.



Hello Speedman.

In most paraglide engines (Simonini etc) there is - as standard - a reduction of the engine revs before the prop. The weight is critical for a paraglider, too, however the gain worth the pain (i.e. the extra weight).

As compared to a similar displacement paraglide engine, the OPRE_tilting is lighter and more compact / slim (it is also vibration free and - depending on the prop arrangement - torque reaction free, both vital characteristics for such use).
I can't see how, in an RC OPRE_tilting, things will change.


Thanks
Manolis Pattakos

Edited by manolis, 26 April 2014 - 08:21.

[Speedman]

Hello

 

Hello Speedman.

In most paraglide engines (Simonini etc) there is - as standard - a reduction of the engine revs before the prop. The weight is critical for a paraglider, too, however the gain worth the pain (i.e. the extra weight).
 

 

 

Thats right, but model RC high speed airplane/engine is more difficult and sensitive than a paraglider. Absolutely nobody one uses a intermediate gear engine (6.5cc - 15cc class). I know this Class since many  many years. 

 

You can't compare a paraglider with a RC F3D model.This is like a comparison of an apple with a pear.

 

 

Such plane speed model is 400 km/h and more quickly. The aerodynamics and the weight is absolutely at the limit. The plane model is made of carbon, the rod is sometime of Titanium or even Beryllium. The piston is made of spezial alluminium with extrem much silicon (30% and more). Piston is machined with diamond tools.

 

 

A few picture of power engines

http://www.verbrenne...otoren-technik/

 

Plane doubble engine

 

 

Speedmodelcar has similar race engines.

 

Edited by Speedman, 26 April 2014 - 11:11.

[manolis]

Hello Speedman.

You wrote:

“the rod is sometime of Titanium or even Beryllium. The piston is made of spezial alluminium with extrem much silicon (30% and more). Piston is machined with diamond tools.”

“A high speed rc engine for high-speed airplane, works everytime full power. A 10cc engine with 35'000 RPM is a challenge.
The company Os Max had a 4-Stroke rc engine 20cc with a roots supercharger the power was 2.5 HP, this is too little. A 4-stroke engine has no chance.
A good speed engine with 10cc has today circa 5 HP @ 28'000 RPM.”

“Do you need a challenge?
Can you construction a simple very light 2-Stroke nitro engine with 10cc and more then 6 HP for RC speed plane?
Conventional special racing 2-Stroke RC-Speed engine are at the limit by circa 5 -5.5 HP
Probably needs more than 28'000 rpm or a many better cylinder filling.”


I see exotic materials and tools; on the other hand, the power density is not that high to justify them.


In order to make 6 HP at 28.000rpm you need a torque of:

6 / (28 * 1.4) = 0.153 mKp = 1.5mNt

With 10cc capacity, this means a torque density of 0.153 / 0.01 = 15.3 mKp / lt


A two stoke of normal size (say those used in the snowmobiles) can make nearly 20 mKp / lt (keeping a good torque at a wide range of revs, obeying various limitations on fuel consumption and emissions and reliability).

Do you know where the real problem of the RC model two strokes is?

Is it the breathing?

Is it the thermal loss?

Thanks
Manolis Pattakos

[gruntguru]

Do you know where the real problem of the RC model two strokes is?

Is it the breathing?

Is it the thermal loss?

Thanks
Manolis Pattakos

Hi Manolis

I think it would be thermal loss (due to the high surface area/volume combustion chamber) and high FMEP inherent in small displacement engines.

Edited by gruntguru, 27 April 2014 - 08:54.

[MatsNorway]

What you mean thermal loss?  Piston gets really hot? What about termal sprayed piston? ports at least can be sprayed.

Edited by MatsNorway, 27 April 2014 - 10:18.

[Speedman]

I see exotic materials and tools; on the other hand, the power density is not that high to justify them.


In order to make 6 HP at 28.000rpm you need a torque of:

6 / (28 * 1.4) = 0.153 mKp = 1.5mNt

With 10cc capacity, this means a torque density of 0.153 / 0.01 = 15.3 mKp / lt


A two stoke of normal size (say those used in the snowmobiles) can make nearly 20 mKp / lt (keeping a good torque at a wide range of revs, obeying various limitations on fuel consumption and emissions and reliability).

Do you know where the real problem of the RC model two strokes is?

Is it the breathing?

Is it the thermal loss?
 

 

Hi Manolis

 

Sorry but your cacalulation is therorie not practice. RC engine are not big engines. That's not the same.

Titanium and Beryllium is in every  race engine absoolutly justify them.

"Engine know how"  for big engines Is not  (100%) transferable to small engines.

 

Less oscillating mass equal more power and less bearings force und less wear and tear.

 

Titanium and Beryllium is lighter and good for small oscillating mass and the strength decreases at high temperatures less.

Otherwise you have high friction and temperature byrod plan bearings.

With your imagination you have no chance in this sport. I know the model engine since circa >30 years.

 

 

Buy an really race model engine an try. You'Il see you theoritic is not practice. A example: 2-Stroke bike engine works with 2% Oil. a model race engine  circa 14-20% Model race engines are a other world then car oder bike engines.

Every good model engine engineer know, a model engine is not a car or bike engine. This are two different worlds.

A other example: The most race model engine (class 2.5cc-15cc) hasn't a piston ring.

 

Do you know where the real problem of the RC model two strokes is?

Is it the breathing?

Is it the thermal loss?
 

 

 

The smaller the motor then the bigger the thermal loss. Very big ship diesel engine has a relatively little thermal loss.  Model engine have a very very big thermal loss.

 

The higher the RPM then bigger problem with breathing.

 

High temperatures in the engine prevent the mechanical strength. The rod bearding will be soft and the rod is faliure.

 

A big problem is aggressive wear. Without modern material have you no chance an high cost.

 

best regards

 

Speedman
 

Edited by Speedman, 27 April 2014 - 12:26.

[Kelpiecross]

Hi Manolis
I think it would be thermal loss (due to the high surface area/volume combustion chamber) and high FMEP inherent in small displacement engines.

What about the traditional 2-stroke problems like the intake and exhaust ports being open at the same time wasting fuel/air mixture and the early opening of the exhaust port wasting cylinder pressure?

[manolis]

Hello Speedman.

You write:
"Hi Manolis
Sorry but your cacalulation is therorie not practice. RC engine are not big engines. That's not the same.
Titanium and Beryllium is in every race engine absoolutly justify them.
"Engine know how" for big engines Is not (100%) transferable to small engines."


Worth mentioning is that the dust of beryllium is more than highly toxic (lug cancer).


The physical laws are applicable in all cases without exemptions.

I search in the internet for small engines dyno tests. At

http://www.osengines...est-rcnitro.pdf

it is the analysis and the dyno test of a small RC engine. Quite smaller than the 10cc.


2-stroke single cylinder
Bore: 16mm
Stroke: 15mm
Capacity: 3.02cc
Peak Power: 2.28bhp at 30.500rpm

Torque desnity (at peak power revs): (2.28/(1.4*30.5*0.00302))= 17,68 mKp / lit

The 3.02cc / cylinder is a substantially smaller capacity than the 10cc cylinder, however its torque density "complies" with the torque density of the normal size two stroke engines.

Supposing that this torque density can be achieved by a 10cc single cylinder 2-stroke engine (I can't see why not), the peak power of a 10cc of similar design at 28,000 rpm will be: 1.4*28*17.68= 6.93 bhp.

The only assumption I do is that the dyno test is not fake (and that since both, the substantially smaller and the substantially bigger 2-strokes can achieve the required torque density, a 10cc 2-stroke is also capable for a similar torque density).



Hello Kelpiecros.

Think that

"The traditional 2-stroke problems like the intake and exhaust ports being open at the same time wasting fuel/air mixture and the early opening of the exhaust port wasting cylinder pressure",

exist (at, more or less, the same degree) in the big capacity 2-stroke engines and in the small capacity RC engines.

Thanks
Manolis Pattakos

Edited by manolis, 29 April 2014 - 15:07.