45 replies to this topic

[Tmeranda]

I recently that some indy cars ran with a single turbo driven off one bank on the engine while the other bank had a normal exhaust. The logic was that the single turbo produced all the boost they could use and the other side with the open exhaust produced more power because of the less restrictive exhaust. Taken this concept further, would it be practical to have a seperate electric motor spin the turbo at a constant high speed and have both banks of the engine have open exahust? The boose could be fed into a manifold that had pop off valves linked to the throttle linkage to blow off boost during partial or closed throttle. Seems like turbo lag would be gone.

[OfficeLinebacker]

LOL when you drive the intake compression device off of something other than exhaust, it's called a supercharger!

And it's more efficient/simply to just drive that turbine with a belt off the crankshaft!

However, interesting that a turbo would be run off of one bank of a v-engine.

[SevenTwoSeven]

Didnt the lancia delta S4 have both a turbo and a supercharger?

[OfficeLinebacker]

Didnt the lancia delta S4 have both a turbo and a supercharger?

IIRC there are several examples of vehicles that have had both.

[zac510]

where would you get all of the electrical energy to spin this compressor at 100k rpm?

[robroy]

where would you get all of the electrical energy to spin this compressor at 100k rpm?

From the brakes?

[robroy]

IIRC there are several examples of vehicles that have had both.

Not many road cars available to the public did. I think there may also be a Japenese spec Micra with turbo and supercharger(?)

[kikiturbo2]

LOL when you drive the intake compression device off of something other than exhaust, it's called a supercharger!

And it's more efficient/simply to just drive that turbine with a belt off the crankshaft!

However, interesting that a turbo would be run off of one bank of a v-engine.

Saab had a V6 with a single turbo driven from a single cylinder bank...

supercharger - turbo combinations have been used to fill in the "turbo hole" in the old turbo instalations... however modern turbos in road car applications have very low lag, variable geometry turbos even more so, and in racing applications they use anti lag of various sorts so lag is mostly a non issue now..

[OfficeLinebacker]

Not many road cars available to the public did. I think there may also be a Japenese spec Micra with turbo and supercharger(?)

Oh I'm talking about ALL kinds of transport, and not street legal CARS at all, though that's interesting too.

[NRoshier]

Not much point really, lots of extra complication for little benefit.

[jgm]

I remember reading about a UK-based hillclimb / sprint car which carried a small auxilliary ic engine purely to drive the turbocharger. The turbo then blew into the main engine which drove the car. It seemed to work well.

Edited by jgm, 04 July 2009 - 07:14.

[Tony Matthews]

I remember reading about a UK-based hillclimb / sprint car which carried a small auxilliary ic engine purely to drive the turbocharger. The turbo then blew into the main engine which drove the car. It seemed to work well.

Many decades ago a friend connected the heater blower to the carburetter of his Triumph Mayflower and found that the acceleration was improved - almost imperceptibly - between 5 and 7 mph.

[gruntguru]

Many decades ago a friend connected the heater blower to the carburetter of his Triumph Mayflower and found that the acceleration was improved - almost imperceptibly - between 5 and 7 mph.

What do you mean "almost"?

[gordmac]

several Volvo boat diesel engines are both super and turbo charged.

[gruntguru]

several Volvo boat diesel engines are both super and turbo charged.

I don't know about the Volvos but usually when a diesel has both turbo and "super" chargers, it is a 2 stroke diesel and the blower is not supercharging the engine - it is pumping the fresh charge into the cylinders and driving the exhaust out - usually referred to as a "scavenge blower".

[Tony Matthews]

What do you mean "almost"?

It's a technical term, gg.

[Catalina Park]

where would you get all of the electrical energy to spin this compressor at 100k rpm?

You could run the alternator off the exhaust.

[NTSOS]

roots/screw Supercharger Optional

Edited by NTSOS, 04 July 2009 - 19:34.

[J. Edlund]

Not many road cars available to the public did. I think there may also be a Japenese spec Micra with turbo and supercharger(?)

VW offer their 1.4 liter TSI engine in several car models. The engine is supercharged by a turbo and a roots blower, producing 160 or 170 hp.

Saab had a V6 with a single turbo driven from a single cylinder bank...

supercharger - turbo combinations have been used to fill in the "turbo hole" in the old turbo instalations... however modern turbos in road car applications have very low lag, variable geometry turbos even more so, and in racing applications they use anti lag of various sorts so lag is mostly a non issue now..

Saabs 3 liter V6 engine from the late nineties is to my knowledge the only assymetric turbocharged engine. But it never became a success and later saw itself replaced by a turbocharged four cylinder engine. The engine used a turbocharger integrated to the exhaust manifold without a wastegate. The engine also produced 200 hp, the naturally aspiranted version of that engine produced 210 hp, although it did produce more torque at low engine speeds. From a control point of view it's difficult to handle such an engine since the exhaust backpressure on one of the bank will affect the VE of that bank and also it's fuel demand. The bank with the turbocharger also used some different hardware, like exhaust valves and valve springs if I remember correctly.

[venator]

Driving a turbocharger off the exhaust of one bank of cylinders is creating more problems than solving them. As for using both mechanical and exhaust-driven boost, the trick is to use a variable-speed drive for the supercharger, with boost falling off at higher RPMs, compensated for by the increased efficiency of the turbocharger.

[ray b]

there is E-bay junk that is just a fan and doesNOT work

and there are drag race ELECTRIC superchargers
one I saw used 3 starter motors geared together to drive a blower
and big truck batterys for power at high amp draw
but even that would not give boost for very long
OK for drags a 1/4 mile at a time but not much more
and the whole system was very heavy with the three motor battery and wires

http://www.turbomaga...r/photo_02.html

it is really hard to beat a turbo for lite cheap and simple
even with intercooler and blowoff ect

Edited by ray b, 04 July 2009 - 18:23.

[kikiturbo2]

I don't know about the Volvos but usually when a diesel has both turbo and "super" chargers, it is a 2 stroke diesel and the blower is not supercharging the engine - it is pumping the fresh charge into the cylinders and driving the exhaust out - usually referred to as a "scavenge blower".

Volvo KAD engines were 4 stroke diesels and use both roots supercharging and turbos to great effect... unlike the car aplications, such boat engines use the supercharger to provide greater power at low RPM where you need it to pull the boat trough the planing speed... after that the supercharger shuts down and you are left with turbos only..

[gruntguru]

From a control point of view it's difficult to handle such an engine since the exhaust backpressure on one of the bank will affect the VE of that bank and also it's fuel demand. The bank with the turbocharger also used some different hardware, like exhaust valves and valve springs if I remember correctly.

To fully optimise such an engine would require different valve timing bank to bank.

I am sure plumbing simplicity would have been a major motivation. Exhaust plumbing for a single turbo on "V" engines is always an efficiency compromise and often a packaging nightmare.

Edited by gruntguru, 04 July 2009 - 21:40.

[gruntguru]

Driving a turbocharger off the exhaust of one bank of cylinders is creating more problems than solving them. As for using both mechanical and exhaust-driven boost, the trick is to use a variable-speed drive for the supercharger, with boost falling off at higher RPMs, compensated for by the increased efficiency of the turbocharger.

Wow - talk about complexity. Turbo, blower, variable speed drive - sounds like a job for the Japanese.

Seriously - I don't know if its been done, but the simple solution is a Roots blowing into the turbo. The Roots would maintain essentially constant VE and boost for constant torque through the rev range (I can hear NTSOS getting excited). When the turbo comes on song it unloads the blower drive (in fact it will "drive" the blower via suction and put some power back into the crankshaft). Alternatively a simple check valve could let extra air into the turbo inlet and allow the boost to rise with rpm.

[gruntguru]

Volvo KAD engines were 4 stroke diesels and use both roots supercharging and turbos to great effect... unlike the car aplications, such boat engines use the supercharger to provide greater power at low RPM where you need it to pull the boat trough the planing speed... after that the supercharger shuts down and you are left with turbos only..

Interesting. I wonder if a modern variable entry turbine would meet the need with much lower cost and complexity?

[NTSOS]

Wow - talk about complexity. Turbo, blower, variable speed drive - sounds like a job for the Japanese.

Seriously - I don't know if its been done, but the simple solution is a Roots blowing into the turbo. The Roots would maintain essentially constant VE and boost for constant torque through the rev range (I can hear NTSOS getting excited). When the turbo comes on song it unloads the blower drive (in fact it will "drive" the blower via suction and put some power back into the crankshaft). Alternatively a simple check valve could let extra air into the turbo inlet and allow the boost to rise with rpm.

You mean the turbo blowing into the roots, right?

Hellion

John

[gruntguru]

You mean the turbo blowing into the roots, right?

No. I've seen it done that way. The effect is different to what I described. Roots into turbo would produce a flatter torque curve extending to lower revs than the Hellion system. More difficult to plumb though.

Edited by gruntguru, 05 July 2009 - 02:00.

[NTSOS]

No. I've seen it done that way. The effect is different to what I described. Roots into turbo would produce a flatter torque curve extending to lower revs than the Hellion system. More difficult to plumb though.

Interesting.....I have never seen a roots into a turbo setup. The Hellion system drives like a normally supercharged GT500 until the turbo kicks in.

John

[gruntguru]

Interesting.....I have never seen a roots into a turbo setup.

Neither have I. Apart from packaging, I can't see why not - it makes a lot of sense technically.

[cheapracer]

VT903T Cummins diesels are blown and turbo'ed.

If I recall the SAAB business was around the time of their low pressure philosiphy, not performance orientated.

[Bill S]

I had a two litre six-cylinder turbo & supercharged engine for my rally car many years ago, but never got around to fitting it or making it run.





There's no turbo on it there.
It was supposed to be about 500hp or so, from memory.

The engine was supercharged from the factory (1GG-ZE for the Toyota-sperts) and it had an HKS twincharger kit on it. They also made a similar kit for the 4AGZE's.

Edited by Bill S, 05 July 2009 - 09:48.

[kikiturbo2]

Interesting. I wonder if a modern variable entry turbine would meet the need with much lower cost and complexity?

probably would... as would a smaller turbo..

the problem with the turbos is to balance longevity with optimum size... usually the optimal size for greatest flexibility is to have the turbo on the smaller size which means high RPM and shorter life.. which might not be a goot thing in boat diesels..

I find that in modern petrol cars, all these interesting supercharger / turbo combos are not needed, as modern turbos (with or without variable geometry, in combination with variable valve timing) are good enough for really great engine flexibility.....

things get problematic when you get over 200 hp/litre, where you need big turbos...

[J. Edlund]

No. I've seen it done that way. The effect is different to what I described. Roots into turbo would produce a flatter torque curve extending to lower revs than the Hellion system. More difficult to plumb though.

VW TSI engines use roots into turbo while Lancia Delta S4 used the opposite, turbo into roots. There isn't really any big difference between the systems, in both cases a compressor bypass valve was used to 'disconnect' the roots blower and the VW engine also have a magnetic clutch. So when the pressure increase in the turbocharger is large enough and the flow through the roots is beginning to restrict the airflow to the engine the compressor bypass valve opens and the turbocharger alone supply the boost.

If I recall the SAAB business was around the time of their low pressure philosiphy, not performance orientated.

Early low pressure turbos were basically the same as their higher pressure versions but with a smaller turbo and the electronic boost control system. A cheap way to produce a mid range engine.

Back in the nineties GM decided that Saab should use their Opel designed 54 degree V6. The asymmetric charged V6 was a development of that engine with the purpose to produce more low end torque and offer a lower fuel consumption. The engine option was mainly for the U.S. market.

probably would... as would a smaller turbo..

the problem with the turbos is to balance longevity with optimum size... usually the optimal size for greatest flexibility is to have the turbo on the smaller size which means high RPM and shorter life.. which might not be a goot thing in boat diesels..

I find that in modern petrol cars, all these interesting supercharger / turbo combos are not needed, as modern turbos (with or without variable geometry, in combination with variable valve timing) are good enough for really great engine flexibility.....

things get problematic when you get over 200 hp/litre, where you need big turbos...

The trouble with turbo sizing is low speed boost (and torque) vs. high speed efficiency. If you use a smaller turbocharger you will improve low speed torque but the exhaust manifold pressure will be high at high speeds making engine efficiency and power to suffer. If you instead use a larger turbocharger, exhaust manifold pressure will be lower at high speeds (possibly even below the inlet manifold pressure) and engine efficiency and power at high speeds will benefit, but at the cost of low speed torque.

With modern petrol turbos manufacturers have chosen to go for low speed torque at the cost of higher engine speed efficiency since the latter rarely is an issue. To improve low speed torque further they also use a very compact exhaust manifold, sometimes with pulse split. Variable valve timing can also help improve low speed torque and it's probably only a question of time until we have the first gasoline engine with series sequential turbocharging.

With diesels a big reason to chose variable geometry is because it can be used to increase exhaust manifold pressure on demand, something that is useful for exhaust gas recirculation.

[gruntguru]

things get problematic when you get over 200 hp/litre, where you need big turbos...

The main problem in this area of operation is that compressor maps start to "pinch off" at the high boost levels required. That is to say the range of useful flow (and therefore useful engine RPM at full boost) drops to less than 50%. So for example, you might size a turbo to make full boost to say 10,000 rpm, then find you are unable to use full boost below 7,000 rpm (this would be a 30% FLOW RANGE). The useful flow range is governed by the distance between the compressor surge line on the left of the map and compressor efficiency limit or overspeed limit on the right of the map.

[gruntguru]

VW TSI engines use roots into turbo while Lancia Delta S4 used the opposite, turbo into roots. There isn't really any big difference between the systems, in both cases a compressor bypass valve was used to 'disconnect' the roots blower and the VW engine also have a magnetic clutch.

There is a lot of difference if you operate without bypassing. Turbo into roots has similar characteristics to any turbo engine - it just behaves like a larger capacity turbo engine. Roots into turbo behaves like a roots but with the potential for much higher efficiency and slightly better power at higher revs. Also potential to run much higher boost (at all revs) than normally possible with a Roots.

Interestingly the Hellion system looks like a Lysholm compressor - not a Roots blower.

[gruntguru]

it's probably only a question of time until we have the first gasoline engine with series sequential turbocharging.

Paralell sequential has already been used (Mazda rotary) to extend the useful flow range to low revs. Series sequential is normally only needed for very high boost applications
so I assume you are talking about an ultra-high-boost race application?

Edited by gruntguru, 06 July 2009 - 03:43.

[NTSOS]

Interestingly the Hellion system looks like a Lysholm compressor - not a Roots blower.

It is in fact an Eaton roots, not a Lysholm compressor!

John

[gruntguru]

It is in fact an Eaton roots, not a Lysholm compressor!

John

Thanks John.

[just me again]

Maybe J.Edlund meant turbocompound.

http://www.scania.co...ound/index.aspx

Bjørn

Paralell sequential has already been used (Mazda rotary) to extend the useful flow range to low revs. Series sequential is normally only needed for very hig boost applications
so I assume you are talking about an ultra-high boost race application?

[kikiturbo2]

The main problem in this area of operation is that compressor maps start to "pinch off" at the high boost levels required. That is to say the range of useful flow (and therefore useful engine RPM at full boost) drops to less than 50%. So for example, you might size a turbo to make full boost to say 10,000 rpm, then find you are unable to use full boost below 7,000 rpm (this would be a 30% FLOW RANGE). The useful flow range is governed by the distance between the compressor surge line on the left of the map and compressor efficiency limit or overspeed limit on the right of the map.

My Evo 9, which is stock apart from the exhaust, fuel pump, and a different boost control valve, develops close to 200 hp/litre (there are numeorus cars like mine running true 400 bhp), and I have positive boost from 1800 rpm, full boost at 3200 rpm, and is still at almost 1.6 bar at 7000 rpm... and those numbers are achieved on the road, not being artificially loaded up on the dyno..
the turbo is a twin scroll type, and there is variable timing on intake cam.. In my opinion, that is a really flexible engine, considering it's output.. In fact I do not see a need for anything more..

[gruntguru]

My Evo 9, which is stock apart from the exhaust, fuel pump, and a different boost control valve, develops close to 200 hp/litre (there are numeorus cars like mine running true 400 bhp), and I have positive boost from 1800 rpm, full boost at 3200 rpm, and is still at almost 1.6 bar at 7000 rpm... and those numbers are achieved on the road, not being artificially loaded up on the dyno..
the turbo is a twin scroll type, and there is variable timing on intake cam.. In my opinion, that is a really flexible engine, considering it's output.. In fact I do not see a need for anything more..

I agree - that is a very flexible engine. If the engine was more than just "close to" 200 hp/litre and we looked at say the 60% compressor efficiency and "full boost" point at high rpm, you would probably be around the 50% useful flow range. So I guess its above the 200hp/litre area where flow range starts to drop significantly below 50%. It drops pretty quickly above 2bar. My real point was - its no so much the big turbo causing the problem as the high boost.

[jatwarks]

Didn't Alan Mann enter a Ford Escort RS in the British Touring Car Championship with an electric supercharger?

Jim.

[kikiturbo2]

I agree - that is a very flexible engine. If the engine was more than just "close to" 200 hp/litre and we looked at say the 60% compressor efficiency and "full boost" point at high rpm, you would probably be around the 50% useful flow range. So I guess its above the 200hp/litre area where flow range starts to drop significantly below 50%. It drops pretty quickly above 2bar. My real point was - its no so much the big turbo causing the problem as the high boost.

agree.... once you get into high boost you start getting into all sorts of problems, esp. if you'd like to keep good driveability..

my point was that 15 years ago such performance in a race engine would have been stuff of dreams.. and those cars had much more turbo lag.. Modern turbo engines are so good, that all these eccentric combinations are not really needed anymore..

[SimonW]

VW have just won the International Engine of the Year award with 1.4l TSI Twincharger.

"The four-cylinder combines a turbocharger and supercharger in one compact unit. The result is power of up to 178bhp, but what’s most impressive is the engine’s specific power that attains 127.1bhp per litre of displacement. And with 240Nm of torque coming good at 1,500rpm, it’s easy to see why the jurors that look for performance and sporty characteristics were impressed.

But power is just part of the story for this year’s International Engine of the Year. The TSI derivative mated to VW’s DSG system emits 144g CO2/km, and in a Golf application, fuel consumption is rated at 6.2litres/100km (45.5mpg)."

Simon

[J. Edlund]

Paralell sequential has already been used (Mazda rotary) to extend the useful flow range to low revs. Series sequential is normally only needed for very high boost applications
so I assume you are talking about an ultra-high-boost race application?

Parallel sequential turbocharging was used by Porsche and Abarth back in the eighties, and later in the nineties by Mazda and Toyota. But now I'm talking about series sequential turbocharging, the same kind of turbocharging used by an increasing number of passenger car diesel engines such as the inline six found in BMW 535D since 2005.



Compared to single stage charging these systems can provide a high boost pressure over a very wide flow (and thus rpm) range. A boost pressure of 3.2 bar, as used by the Opel diesel engine in the description above might seem high at first for a gasoline engine, but remember that the VW TSI engine for instance use boost pressures of 2.5 bar and other high output SI turbos also use boost pressures in this region. Series sequential charging offer an performance advantage compared to variable geometry turbos and they use rather simple flap valves instead of complex variable vanes which usually have trouble to handle the high exhaust gas temperatures of a gasoline engine which today can be as high as 1050 degC.

Some more information
http://www1.eere.ene...r_sweetland.pdf

[gruntguru]

Parallel sequential turbocharging was used by Porsche and Abarth back in the eighties, and later in the nineties by Mazda and Toyota. But now I'm talking about series sequential turbocharging, the same kind of turbocharging used by an increasing number of passenger car diesel engines such as the inline six found in BMW 535D since 2005.

Compared to single stage charging these systems can provide a high boost pressure over a very wide flow (and thus rpm) range. A boost pressure of 3.2 bar, as used by the Opel diesel engine in the description above might seem high at first for a gasoline engine, but remember that the VW TSI engine for instance use boost pressures of 2.5 bar and other high output SI turbos also use boost pressures in this region. Series sequential charging offer an performance advantage compared to variable geometry turbos and they use rather simple flap valves instead of complex variable vanes which usually have trouble to handle the high exhaust gas temperatures of a gasoline engine which today can be as high as 1050 degC.

Some more information
http://www1.eere.ene...r_sweetland.pdf

An interesting system. Its benefit seems to be the same as the parallel systems - extension of the flow range, rather than extension of the pressure ratio (as in tractor pulling).

100% "series" operation occurs only in diagram 1 with the control valve closed and all exhaust gas flowing through both turbines. In this phase however, the large turbocharger is not contributing useful boost (according to the text) so pressure ratio extension is not ocurring.

Diagram 2 is a hybrid series/parallel operation, compressors in series and turbines series/parallel so extension of the pressure ratio (beyond what could be obtained with a single compressor) is possible but is this happening, since phases 1 and 3 are producing sufficient boost using one compressor only?

Diagram 3 is large turbo only - closer to a parallel system with one turbo disabled.

EDIT
Followed the link - nice.

Edited by gruntguru, 14 July 2009 - 02:03.