45 replies to this topic

[desmo]

We've discussed solenoid operated valvetrains here before, but there's another way to get almost infinitely variable valve timing. If this topic gets rolling, I'll get into the specifics and potential advantages and downsides.

[Ray Bell]

So this is hydraulic operation controlled by electronics? Sounds promising...

[desmo]

FoMoCo have done a lot of development work on this concept. Right now the principal downside for racing is weight. It may never be possible to make it weigh less than a conventional cammed valvetrain. The obvious upside is the same freedom in valve timing as allowed by a solenoid system. Either can be controlled electronically. I think that some of the components in the illustrations could be shared by more than one cylinder, perhaps an entire bank. This would get the weight and complication within reason. Ford has made single cylinder prototypes which are very promising.

[Halfwitt]

Its a very good idea, but there must be a manufacturer behind this. The costs would be phenomenal to get these things small enough. To open (and close) valves at 18000 rpm would require massive amounts of power, even if only for an instant. To keep proper control of these would be a great feat. I appreciate that cams and springs (even the pneumatic type) aren't ideal, even when dealing with fixed valve timing, but to get four of these things working around an F1 cylinder without making the cylinder head any bigger would be very difficult. I am sure it will come one day, and then everyone will have to follow. I think the amoiunt of money involved would make a mockery of the FIA resticting engines to V10's. This was done in an attempt to keep costs down, but EVA would send costs spiralling at a much higher rate.....

[tak]

At 18,000 RPM, the the valves open and close 150 times a second, or at 150 Hz. It's actually worse than that, because the valve opening and closing occurs over 250 or so degrees of crankshaft rotation, so actuation is full close to full open to full close in less than 1 revolution, or greater than 300Hz. The Active suspensions of a few years back had frequency responses in the range of 10-50 Hz, and that was severely pushing hydraulic technology. The time response for electronics is no problem--the mechanical side is VERY challanging...

[Billy Gunn]

Desmo,

I'd considered such a system during our earlier discussions on EVA, the reason for doing so was to evaluate whether such a system could recover energy - and this energy recovery is the clue as to why the spring system (be it metal wound or air) has lasted so long. How can we get energy recovery from this?

Idagenagoal

Billy G

[Halfwitt]

Springs are good because they store energy with relatively little heat generation as elastic potential energy, and this is easy to recover. The only losses are hysteresis within the springs.
With EVA, I would say that you would have to use massive currents to move the valve mass, and this energy would be converted to heat at a rate eqaul to the current squared multiplied by the electrical resisitance of the system. Probably only leaves heat exchange as the energy recovery method. I hope someone here will prove me wrong.

[Billy Gunn]

This is going back over old ground again ~ but, my prediction was that the only foreseeable way forward for EVA was to use Piezo technology. That way a portion of the energy may be recoverable in each phase of the actuation.

nnuG ylliB lear eht ton ma I

[desmo]

I have never seen any data on how efficient cam & spring set-ups are at returning rotational torque spent compressing the springs. I wonder what % is lost as heat through the spring's hysteresis and friction at the cam/follower interface. Being desmo, I also wonder how desmodromic systems fare in this regard.

Might the snubber chamber in the illustration store and return some energy or would the relative incopressability of the hydraulic fluid preclude this? Perhaps a hybrid system where the valves are opened hydraulically and closed pneumatically.

Assuming that the electrohydraulic system precludes energy recovery, does that neccessarily disqualify it for racing use? I still wonder if the potential upsides outweigh the loss of mechanical efficiency apparently inherent in an unsprung valvetrain.

[Halfwitt]

No, I would think it is definitely not lack of energy recovery that precludes its use in racing, just the (current) impossibility of making it work, and work reliably. The benefits would probably far outweigh any losses. Saying that, if energy recovery were possible, it would be an added bonus.

[desmo]

Here's another approach, this time electromagnetic with springs.

[desmo]

Here's another similar approach, this time from Siemens in Germany. Click the link below for a (much) larger version of the above image.


http://www.siemens.c...d/evt_at015.jpg

[desmo]

Or we can lose the poppets altogether...

[desmo]

Billy,

As to the energy efficiency of EVA, here's a public disclosure report filed with the SEC by Aura Systems in El Segundo CA, who have a pretty impressive record for developing new tech applications. Note the bold type:

". Electromagnetic Valve Actuators (EVA)

Over the past several years, the Company has been applying its patented
electromagnetic technology to a variety of applications. One application
developed is its electromagnetic valve actuator (EVA), which is an
electromagnetic actuator capable of opening and closing internal combustion
engine valves, replacing the mechanical camshaft on an engine. EVA uses the
power of electromagnets to open and close engine valves, and is capable of
accomplishing this in less than 3/1000 of a second. The engine computer that is
used on virtually all modern automobile engines will send to the EVA electronics
module a valve position command in the same way it will send a fuel injector
command. The EVA electronic module will implement the command, and wait for the
next command from the computer.

Two major benefits arise from the EVA's ability to open and close the
valve electromagnetically: 1) the camshaft and associated mechanical hardware
can be eliminated, and 2) the opening and closing of the intake and exhaust
valves can be commanded by the engine computer. As an example, EVA has been
retrofitted on a 140 HP, 2.3L 4 cylinder Ford engine that is currently running
in the laboratory.

Computer control of the valve timing has potentially material benefits
to engine performance, fuel economy and emissions. With EVA, the computer can
precisely control the amount of air that is allowed into the engine in the same
way that modern fuel injectors control the amount of fuel. By optimizing this
"fuel-air mixture" dynamically as a function of engine RPM and load, optimum
engine performance can be achieved over the entire operating range of the
engine. With a standard camshaft, the engine can be optimized at only one range
of RPM and load conditions. That is why very high performance engines idle
"rough", as they are optimized for high RPM, thereby sacrificing smoothness at
low RPM.

By optimizing the fuel-air mixture dynamically, both performance
(horsepower) and fuel economy will increase, while emissions are expected to
decrease. The implementation of EVA also greatly simplifies the engine
mechanically. The entire camshaft assembly, with includes timing chain,
camshaft, rocker arms, etc. is replaced by very simple valve actuators. Other
emission systems currently on the vehicle, such as the EGR (exhaust gas
recirculation) and IMRC (intake manifold runner control) valves can be
eliminated. Even the throttle assembly can be eliminated by using EVA to
control the amount of air going into the engine. Overall engine cost may be
substantially reduced.

Due to the Company's patented design, EVA requires relative little
power to operate. Lab measurements have shown that the total power required to
operate EVA is typically well under 100 watts/valve. Because of friction and
mechanical losses, a typical camshaft requires 3 to 5 horsepower to operate
(1hp=750 watts).

The Company is currently under contract to retrofit EVA's on different
types of diesel, automobile and motorcycle engines."

Note that the claimed power use for these EVAs is 100w/valve x 10 valves/camshaft in an F1 engine = 1Kw per 10 valves vs. 3 to 5 x .75Kw per cam in a cammed valvetrain. It appears that EVA is potentially more efficient than a camshaft-operated valve train.

wudjathink?
K

[Aerow]

Interesting that there is no mentio of weight saving? Could it be that the magnets (probably rare-earth) are heavier than a mechanical system? The weight would have to be quite a bit higher to offset the benefit of programable valve timing.

To give you an idea on how advanced this concept might be, consider that almost all hydraulic actuators on aircraft do NOT use a magnetic system to actuate the valves on their pcu's (power control units ie actuators). However, I am aware that almost every aerospace actuator supplier is now studying these types of pcu's, called dddv's (direct drive valves).

[Powersteer]

Desmodromics has no energy recovery at all.Maybe the only recovery from desmo actuation is the frequency shock wave it produces during reciprocation. Valve springs has energy recovery but as the RPM rise, recovery is less and valve opening becomes very difficult, load from spring plus mass. The recovery proses of valves springs impose friction as well.


By the way desmo, i don't know how legitimate those claims by Aura systems are. In F1 sometimes camshaft break because of load (not faulty) from opening the valve to quickly. The higher the RPM the harder valve springs are needed so in F1 scale i can see why they break. In this area maybe those claims are logical and why they claim for such low energy needed. very interesting, ciao.

[Powersteer]

Imagine how much power you need to break an F1 camshaft,thats why i'm sceptical about the claims, ciao

[Yelnats]

Desmo, If the diagram at the top of this topic uses hydraulics for it's actuation media I see little future for it in F1. Hydraulic tappets run into problems well below 10 krpm and only so I can't see a totally hydraulicly actuated valve train functioning any place but in the lab.

Cavitation, inertia and fritional losses become overwhelming barriers at high rates of actuation in Hydraulic systems. I presume this is why hydraulic systems are more notable for power that speed.

[koenda]

Desmo>

I've found something too on the net. But it's from a different company, FEV.
Their EVM runs at 6500 rpms.
Details:
http://www.fev.com/0...ed/e_ed_vt.html
but since the picture you showed is the same as on that page, i asume that you have seen it already.

[Marco94]

Powersteer,

The fact that a desmodromic valve actuation does not recover energy is of no consequence. The only energy you are recovering is the energy used to compress the spring. It is exactly the machanism that makes a spring work.

With desmodromic valve actuation you don't need to recover this energy, it is not even there in the first place. Mechanical losses may very well be lower for desmodromic valve actuation. Since the spring does not have to be compressed, you only have forces resulting from the accelaration from the valve. The forces are therefor smaller and losses are smaller as well. Of course that is assuming all other thing remain equal.

Marco.

[Billy Gunn]

Desmo,

Sorry it's taken so long to get back but I've been tapping a source of info on valve gear. His estimations are that power consumption on a F1 engine at 17,000rpm with 4 valves per cylinder and 10 cylinders is that power absorption will be i.t.r.o 120Bhp (90Kw) - he bases this on knowing valve sizes, weights, air spring pressure, and a load of other bits of info which is not normally in the public domain.

The interesting point here is that recovered energy is i.t.r.o 100Bhp (75Kw) - this he said is proven by reducing air spring pressure on an engine (or more correctly tested on a head rig) to get to the point of valve float, at this point recovered energy is lost along with about the 100Bhp off the dyno (or similar increase in power required to drive a rig) - it's one way of telling if you have a valve float problem, when a sudden massive loss of power is detected. As I said in another forum recently - don't confuse 'float' and 'bounce' they are 2 entirely different scenarios.

So we have a net power loss of around 20Bhp - which is cunningly close to the 5Bhp quoted above for a ditch pump engine! and, this could be why the EAV people in CA are deluded that the power required is only 100W per valve! that's a value so close to a light bulb I could tell a joke here - but will refrain, as women and children may be listening.

[desmo]

BG,

I gotta agree, that 100W figure doesn't wanna make it past my B.S. detector. The figures you cite sound eminantly plausible.

If you could steer me in the direction of any other good gearhead fora, I would be most appreciative (if it's bad etiquette to "promote" one forum on another just PM or email me). I like the non-hierarchal way that ideas can be bounced around in a good forum. Books and magazines are good for getting ideas, but developing those ideas into an understanding without some back and forth can sometimes be tough.

Thanks for digging that up.

K [p][Edited by desmo on 09-28-2000]

[Marco94]

Billy Gunn,

Can you exactly explain the difference between "float" and "bounce," I am obviously not to familiar with these English terms.

Marco.

[desmo]

Marco,

Here in very non-technical terms is my understanding of these two types of uncontrolled valve motion. Anyone please feel free to clarify or correct this.

Valve float is when the valve spring cannot close the valve quickly enough and contact is lost between the (in the case of F1) follower and the valve stem for a few degrees of camshaft rotation. Obviously this is a bad thing as the valve's motion is no longer working as designed. As well, the follower is hammering back on the valve stem with each cycle. Ow!

Valve bounce is the valve actually rebounding off the seat after closing. This manifests itself as a series of uncontrolled openings of decreasing amplitude after nominal valve closing. Some valve bounce is normal and inevitable and the valve will go through several periods of bounce as revs rise before it reaches an unacceptable level at some rpm.

Valves in an F1 car, particularly the exhausts, exist in a very unhospitable and extreme environment.

[Billy Gunn]

I've gotta say that sums it up Desmo!
Just think of 'float' as being the point after the cam has accelerated the valve open, and when it reaches the point of maximum lift (the nose of the cam) the valve just carries on opening! or at least does not follow the cam form on the closure side of the profile. This means valve assembly inertia is greater than that resisting it (spring pressure - be it air or metal wound). 'Bounce' (which I believe may be almost non existent in an air spring set up)is when the spring medium surges due to harmonics within the spring (although there also exists exciting forces within the valve itself such as the elasticity of the stem and valve head). If you have 'float' you need more spring load at max lift; whereas if you have 'bounce' then you need more seat load. A road engine will be quoted as something like 100Lb seat load, and 220Lb max lift load.

Kurt: I hope you been reading your post lately![p][Edited by Billy Gunn on 09-28-2000]

[koenda]

I have done some research, and the system is described in sae paper no 970248. I haven't read it yet so maybe monday..

Desmo>
I don't know which developments they have done since the publication of SAE-paper 981908. But here they claim a power usage of 1.07 kW @ 2500 rpm, while the cam-driven uses 0.75 kW.

[Formulaben]

I hate to sound the pessimist, but all this monkey motion could be solved by going rotary or turbine...

[koenda]

too bad it isn't legal, Formulaben ;)

but turbine doesn't run very well at part-load and a rotary engine has a HUGE fuel-consumption..

[DangerMouse]

Nope but gas turbines are great for powering electric motors, also the motors could be the wheel hub and act as the brake as well.

F1 is (was) supposed to explore new technologies - shame it's so hamstrung.

I still think F1 rules should comprise of the current saftey and ride height regs plus a given bucket of fuel to run a race on - how you burn that fuel is entirely up to you, and the amount of fuel is reduced on a yearly bases - this will A) keep speeds down to a reasonable level and B) make the emphasis on ecomony and efficiency which helps everyone.

Lotus developed a gas turbine GP car (which I believe they ran on the Indy 500 as well?) The FIA soon banned it. I beleive it was an American Gas Turbine motor (plus Furguson four wheel drive?) which also got banned at the same time, Enzo probably started moaning.

[Formulaben]

Koenda, or others:
If the rotary has a high fuel consumption, what is the hp/lb of fuel, or better yet, what is the SPECIFIC FUEL CONSUMPTION for the average otto cycle, rotary, turbine, miller cycle, etc? This would be a more accurate representation of the effeciency of the engines.

[marion5drsn]

Subject; Camshaft and the energy and torque to run an ordinary valve system. Firstly a cam is a rotary wedge system, a very simple device in principal. Therefore there is a lot of energy recovered in the backside of the lobe when the cam follower starts down the spring actuated side of lobe. Since in most engines there are more than one spring being opened and closed at the same time, exhaust and intake, the forces involved must cancel one another out to some degree. It doesn’t make any different whether it is a metallic or air spring the forces are the same. If one has revolved a cam at a low speed it is surprising how little effort it takes to revolve a cam at these slow speeds.
The problem, I believe is when the cam is driven at very high rotational speed and surges, seat bounce, spring fatigue, valve float, causing the valve to not follow the cam lobe precisely!
The valve actually jumps off the lobe and fails to follow the lobe surface and then comes down on the lobe in an undesired fashion. I just imagine that this was discovered when engineers used strobe lights in checking the actual valve travel as far back as the 1930s. It isn’t rocket science we know. Nourse, Trans SAE, wrote the Polydyne system of designing cam lobe in 1961. 69585 Also by Thoren in 1952.
Now to the problem of the Aura systems about the 3 t0 5 HP they claim it takes to run a camshaft/valve system.
# 1, They failed to state whether or not they tested the engine in a manner to show that it takes this amount of HP to run the valve system in that same engine that they claim they used only 3.34 HP.
# 2, They failed to state just how many times they tested it and under whose observation.
# 3, How did they come up with the 3 to 5 HP on the regular engine? The way it is stated thy might have tested a 9300 cubic inch V-20 cyl. diesel 2 stroke with four exhaust valves.
# 4, Why did they try to mislead some people by stating the engine used only 100 watts per valve? Shouldn’t they state it in relation to the engine they are supposedly testing it on with all valves installed? Then give it the total just like it was installed on the 4.3L 4 cyl. Ford engine? It sounds as tho they are testing on only one cyl.
I think they are trying to pull the wool over someone’s eyes.
I’m just am old Swedish inspector from Missouri and they have to show me. M. L. Anderson
[p][Edited by marion5drsn on 02-14-2001]

[palmas]

Originally posted by Formulaben
Koenda, or others:
If the rotary has a high fuel consumption, what is the hp/lb of fuel, or better yet, what is the SPECIFIC FUEL CONSUMPTION for the average otto cycle, rotary, turbine, miller cycle, etc? This would be a more accurate representation of the effeciency of the engines.

typical values would be:
Diesel engines 38 to 42% eficiency
Otto engines 35 t0 40% efficiency
turbines 28 to 38% eff.

These values are for market units.

The biggest advantage turbines have are not fuel saving, for shure, but if you compare weight, turbines weight can be only 20% of an engine.
Drivability is also another story!

Anything else you need?

[bleakuzs]

What I have a hard time believing is that above 10k rpm, both opening and closing of the valve via electronics is simply not possible swith todays tecnology. Considering that at 18k you must have 18k Hz of bandwith, since you must open and close the valve via the same soleniod. What we know from speakers and amplifiers, as the bandwith is increased, it takes more energy to produce an equal amount of output energy since there are more cycles to be reproduced.

What I am getting at is that, the EVA that Aura systems seems to be exploring would have to work on a principle similar to a speaker, using only 100 watts of power. In real terms, passing an alternating current through an electromagnetic media, which then acts upon a simple magnet to produce movement, is the only way I see to get the nessecary timing accurate engough. And by simply varying the voltage of the current, you could control the lift and close characteristics of the valve.

To accurately detrmine the possibility of EVA, we must know the valve weight, distance travelled, the threshold of inertia for the srings and cylinder pressure. Also remember that instead of running the cams directly off the crank, you would have to produce the electricity through an alternator. On top of that, the battery package would have to be increaed to acomodate the increased electrical production/consumption.

There are so many more factors. . . . . . .

[Marco94]

I'm not sure how you calculate the 18k bandwidth, but I don't think that is correct. 18000 rpm = 300 rps! so a bandwidth of some 2 kHz seems a little more real to me. Of course it also depends on the profiles of valve opening and closing

Marco.

[marion5drsn]

Billy Gunn; I’ve been reading and studying the statements for several days now of the gentleman who has given the HP required to drive a F1 eng. camshafts.
His figures are 120 Hp or 30 HP per Camshaft. Now we must remember that the cams turn at one-half the speed of the engine or about 8,500 rpm. At this speed the torque required to produce 30 HP is (30 X 5250) / 8,500 rpm = 18.53lbs./ft. This is assuming that this is the rpm that he used to achieve valve float. Now 18.5 lbs.ft. of torque doesn’t sound like much to absorb in camshaft but we must remember that this little core diameter is likely only around one-half an inch in diameter (due to weight reduction) the effect of the torque may be more than we think in regards to the stress. It could be as high as three-quarters of an inch if gundrilled (Hollow). The cams and toothed wheels must be twisting like Chubby Checker (sp). The reversal of torque and vibrations make my eyeballs ache. I can truly sympathize with the engineers that have to see this thru a strobe light. These especially true if the reversals are all the way down thru the shafts and backup to the other cams. This may be something that some people are missing in their appraisal of the EVA. Myself included!
The only thing that has so far been stated in the positive for an EVA is that it is linear and doesn’t have torsional vibration. But it sure looks heavy and bulky. How much copper/steel wire in that thing? Yours, M. L. Anderson
[p][Edited by marion5drsn on 02-16-2001]

[Melbourne Park]

M. L. Anderson said that:

>" The only thing that has so far been stated in the positive for an EVA is that it is linear and doesn’t have torsional vibration. But it sure looks heavy and bulky. ... "

I am not at all an engineer, the only science I have is from a business degree. However there seem to me to be lots of benefits.

For instance, the weight of the camshaft is great because as has been said, it it essentially transferring energy from one valve spring to the next, which as marion5drsn said, is a tough thing to do.

The need for such strong springs is to avoid the bounce / float issues described, and the strong springs increase loads which thereby requires a stronger and therefor heavier camshaft.

But back to the point I was replying to: it seems to me that another advantage of the VAR is that besides the timing issues, people here have discussed how the speed with which air can get into the cylinder is currently the major performance bottlekneck concerning high revs.

A VAR has some real advantages there: at all engine speeds, the valve could be operated at its maximum speed, which would assist getting air in at all speeds, which would have to improve lower speed power.

Secondly at high engine speeds, if the valve could be opened at say twice the speed of a 20,000 RPM engine, would there not be a greater oportunity to get air into the cylinder, and hence shift the RPM bottlekneck a bit higher?




However

[bleakuzs]

I must be in my alter ego today, Homer Simpson. DOH!

BTW, a valve can only open as fast as the piston, so a vavle can not operate at peak velocity at all revs.

[Melbourne Park]

Dear palmas,

You quoted the efficiency of three engine types:
>"
typical values would be:
Diesel engines 38 to 42% eficiency
Otto engines 35 t0 40% efficiency
turbines 28 to 38% eff. ">

I am confused, because in for instance SUVs and European cars, the fuel efficiency of diesel engines in much greater than for Otto engines even though typical deisels accellerate slower. Similar cars like Peugots or VWs for instance can be bought either as Otto or diesel with similar accelleration, and in these cases the diesel is much more than a few percent more fuel efficient.

So does effieciency not relate to the real world?

[Melbourne Park]

DangerMouse, you said several excellant things about F1, and I would like to ad a little:

<" F1 is (was) supposed to explore new technologies - shame it's so hamstrung. ">

I agree, but then its become such a money game that its inevitable that this would be the case...

<" I still think F1 rules should comprise of the current saftey and ride height regs plus a given bucket of fuel to run a race on - how you burn that fuel is entirely up to you, and the amount of fuel is reduced on a yearly bases - this will A) keep speeds down to a reasonable level and B) make the emphasis on ecomony and efficiency which helps everyone. ">

These are golden words and even the greenies would have to approve. Maybe add in a sound restriction rule etc.

But I comment because I feel if your formula was adopted, as the fuel became more of an issue, the cars would enevitably have to forgo grip for straightline speed. With less grip, there would be less turbulence issues, and, wonder of wonders, overtaking might re appear (for those young ones who have not seen it, overtaking is the old fashioned way of gaining racing places, by moving past a car whilst actually being on the racing track).

[Melbourne Park]

bleakuzs
:
" I must be in my alter ego today, Homer Simpson. DOH!

BTW, a valve can only open as fast as the piston, so a vavle can not operate at peak velocity at all revs.
__________________
No matter how wrong I am, I will always be correct. :"

Not so. It depends on the shape of the piston, and the shape of the valve. DOH...

[koenda]

Originally posted by Melbourne Park
I am confused, because in for instance SUVs and European cars, the fuel efficiency of diesel engines in much greater than for Otto engines even though typical deisels accellerate slower. Similar cars like Peugots or VWs for instance can be bought either as Otto or diesel with similar accelleration, and in these cases the diesel is much more than a few percent more fuel efficient.

So does effieciency not relate to the real world?
[/B]

The efficiency which Palmas quotes are the maximum efficiencies. A Diesel engine has a much higher efficiency at part-load then an otto engine because of the losses caused by the butterfly valve.

Efficiency does not relate to acceleration, Power does. Power does not equal efficiency ;)

That's why the fuel consumption is described in a certain cyclus (in Europe) so the comparison between vehicles can be made.
For truck engines specific fuel consumption is used to compare the engines (gr/kWh) and also for the emissions (e.g. NOx = .. g/kWh).

Marco> 4 stroke, divide by 2 ;) 18.000/60/2 = 150 cycli a second.

[Melbourne Park]

I think now I understand:

" The efficiency which Palmas quotes are the maximum efficiencies. A Diesel engine has a much higher efficiency at part-load then an otto engine because of the losses caused by the butterfly valve. "

OK. Say the Palma's effeciency must have been related to stationary engines. Although trains for instance have diesel power electrical generators but I have not heard of a petrolium version, and such engines tend to run at a limited range of engine speeds.

Should I be more circumspect of efficiency ratings then? Is there an average efficiency rating for diesel car engines compared to Otto car engines? And are there average efficiency reatings available? (by average I mean the averaged efficiencies of an engine that would include a city cycle and some country cycle usage, which would be predominantly part load).

I wonder if these efficiencies include configurations such as valve train and injection systems as well (ie four valve VTEC versus 2 valve non VTEC, and for the diesels direction injection diesel verses non direct injection and common rail injection?

[Marco94]

koenda> Oh well, I admit I am not without error. 80

Marco.

[palmas]

Originally posted by Melbourne Park
Dear palmas,

You quoted the efficiency of three engine types:
>"
typical values would be:
Diesel engines 38 to 42% eficiency
Otto engines 35 t0 40% efficiency
turbines 28 to 38% eff. ">

I am confused, because in for instance SUVs and European cars, the fuel efficiency of diesel engines in much greater than for Otto engines even though typical deisels accellerate slower. Similar cars like Peugots or VWs for instance can be bought either as Otto or diesel with similar accelleration, and in these cases the diesel is much more than a few percent more fuel efficient.

So does effieciency not relate to the real world?

Efficiency as stated is the relation kWh(pci)out/kWh(pci)in
, not liter/100km or miles/galon.
So you will have to check the enegy content in the gas and diesel oil and then have the correct engine energy (kWh) output. Also the efficiency changes with the engine speed, and throtle position. Do not forget to relate engines with similar technology (f.i. both with direct injection...)
In the end you will probably agree that diesel engines are a little more efficients than the others.

If you require more specifica data, maybe it is available.

[Melbourne Park]

[/B][/QUOTE]

Efficiency ...
In the end you will probably agree that diesel engines are a little more efficients than the others.

If you require more specifica data, maybe it is available.
[/B][/QUOTE]

In the Australian at least, diesels engines are significantly more efficient.

In England, even Mercedes Benz seem to think so.

I have enclosed three E Class Mercedes sedans below. In short, the diesel version has higher performance yet uses significantly less fuel.

While an academic viewpoint may argue that there is little difference in efficiency, the real world has great differences between engine set ups and actual efficiency.

I remain disturbed that the quoted 5% difference in efficiency between diesel and petrol does not reflect actual engine behaviours...

Manufacturer: Mercedes-Benz
Model: E-Class 4-door
Type of car: Saloon
Engine capacity: 2.4
Trim: E240 Avantgarde
Fuel type: Petrol
Width: 1799
Length: 4818
Insurance group: 15
Mechanical: 3 years
Corrosion: 30 years
Paintwork: 1 year
Miles per gallon: 27
Engine power: 168 Bhp
Acceleration: 0-60 in 10.8 secs
Max. speed: 139 mph


Manufacturer: Mercedes-Benz
Model: E-Class 4-door
Type of car: Saloon
Engine capacity: 2.8
Trim: E280 Avantgarde
Fuel type: Petrol
List price: £30540
Width: 1799
Length: 4818
Insurance group: 15
Mechanical: 3 years
Corrosion: 30 years
Paintwork: 1 year
Miles per gallon: 28
Engine power: 202 Bhp
Acceleration: 0-60 in 9.1 secs
Max. speed: 143 mph


Manufacturer: Mercedes-Benz
Model: E-Class 4-door
Type of car: Saloon
Engine capacity: 320 CDI
Trim: E320 Avantgarde
Fuel type: Diesel
List price: £31040
Width: 1799
Length: 4818
Insurance group: 16
Miles per gallon: 36
Engine power: 195 Bhp
Acceleration: 0-60 in 8.3 secs
Max. speed: 143 mph

[marion5drsn]

I’ve been working on the hydraulic operation of the closing of the valve and it certainly doesn’t appear to be a big problem as long as one gets the pistons in the proper position in respect to the actual opening point of the valve by the cam lobe.
The desmo system shown in the diagram in Desmodromology is incorrect as the closing cam and the opening cam are not in time. It shows it in a 90-degree position and it should be somewhat less and in relation to the actual opening and closing of the valve. As you know the properties of any hydraulic fluid are that the liquid is considered to be non-compressible and you can’t have the opening and closing cams in opposition. The one that I drew is 148.53 degrees camshaft, 297.06 crankshaft. In the layout of the lobe I started out with a 306-degree duration crankshaft, 153 camshaft but the actual duration ended up with the aforementioned degrees. It makes me wonder why there haven’t been any hydraulic systems as simple as the one mentioned. In that system the camshaft in mechanical fashion opens the valve and the closing of the valve is by cam-actuated hydraulics. It also seems to be that the valve lash is done in the fashion of hydraulic automatic adjustment. M.L. Anderson