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Diesels at Le Mans

Diesels at Le Mans

Diesels at Le Mans

(OP)

I see that the first diesel-engined car to qualify and race at the 24 hour race at Le Mans was a French entry in 1949, the first race held after the war.  The car was the Delettrez Diesel entered by brothers Jean and Jacques Delettrez and was of 4395 cc 6-cylinder.  It did not finish, running out of fuel about half way into the race.

Delettrez entered again in 1950, as did another diesel car, the MAP.  Again both cars DNF with engine problems, a cooling system leak in the case of the MAP.  The MAP was interesting in that it was the first mid-enginesd car to race at Le Mans, the engine was located immediately behind the driver, and was a two-cylinder opposed piston 2-stroke with rocking levers connected to a single crank, similar to the later Commer TS3 engine.  Many thanks to Aorangi for providing me with supporting information on this engine.

The Delettrez entered in 1951, for the last time, but again DNF due to the engine after only 4 hours.

My question(s):  Has anyone got more information on these pioneer racing diesels?  Have there been other diesel cars at Le Mans since then?  How long before we see diesel cars at Le Mans again; any guesses?

PJGD

RE: Diesels at Le Mans

On a slightly related note. Back in 1970 one of my neighbors was none other than George Cummins and he told me all kinds of stories about the Cummins Indy car but never said anything about Le Mans  His storys usually ended up with "Dad finally said it was too Da-- expensive to keep the dust down using race engine parts and diesel" One unknown tidbit was that George claimed he was allergic to diesel fumes.  Cummins may have some of the research data available
 Wish I could help.

RE: Diesels at Le Mans

(OP)
TChronos:
Yes. that worked well.  Thank you very much.  Do you by chance also have photos of the Jowett Jupiters that ran (and won the 1.5 Litre class each year) in 1950, '51, and '52?  If so, I would like to see those too!

PJGD

RE: Diesels at Le Mans

It’s unlikely that we shall see another diesel-powered racecar.

My opinion:  Because of the mechanics of the combustion processes, diesel engines can’t rev as high as gasoline- or alcohol-powered engines.  In the latter, the fuel is already vaporized and mixed with air when it enters the cylinder, plus the spark can be readily advanced in accordance with rpm.  In a diesel engine, it takes some finite time for the injected liquid fuel to spread across the cylinder, absorb heat, vaporize and then absorb some more heat to the point of self-ignition.  Of course, the injection can be advanced with rpm and the fuel pressure can be increased, but I have a strong hunch that diesels have a lower max. rpm and hence HP limit.

Anyone know what are the fastest-revving diesels?
Ken

RE: Diesels at Le Mans

I came across an interesting article discussing what would be required in a Le Mans Diesel engine, from a technical perspective:

http://www.totalmotorsport.com/Features/Technical/Display.asp?ID=1

Diesels are permitted under current ACO rules, in fact, there are special amendments to cover them. I think there was a privateer team in the last race that ran Diesel.

PGD:
Yes, I think I have photos of the Jowetts, I'll post them later if I find them.

RE: Diesels at Le Mans

Thanks, TChronos.

The Totalmotorsport article is very informative. It indicates 3 limiting factors to diesel engine rpm:
1) constant flame burning rate (as I posited above),
2) greater volume of air needed for same fuel energy (turbocharging was suggested),
3) heavier mass of engine parts due to 1.5x combustion pressure. Obviously a problem with reciprocating parts and bearings. One point of the article was that the winning required engine durability.

"Then again, the engine is heavier as the maximum power revs would be only around 5 000...6 000 per minute, whereas spark ignited engines can have it up to 10 000 rpm or so. So the load per cycle of a diesel engine is 10 000 / 6 000 = ..appr. 150% of that of a petrol engine of similar power. Therefore the components in a diesel need to be beefed up a lot = heavy engine. In a diesel, revs cannot be upped very easily as the constant pressure burning in the combustion chamber simply takes its time."
http://www.totalmotorsport.com/Features/Technical/Display.asp?ID=1

RE: Diesels at Le Mans

(OP)
An interesting analysis; thanks TChronos.

I cannot however agree with the comments suggesting that diesels are limited due to "constant pressure combustion" (the totalmotorsport.com article), or by "constant flame burning rate" (kenvlach above).  Constant pressure combustion was the theory back in the very early days of compression ignition engines, but it is not like that with the high speed engines we are contemplating here.  It is somewhere between that and constant volume combustion.  

Just as in SI engines, flame speed can be influenced by appropriate air motion (turbulence, tumble etc), so air motion (typically swirl) can be used in diesels to modulate the rate of air entrainment and thus the rate of heat release.  The rate of injection is another factor that has very strong influence on the rate of heat release, and this is achieved through raising (or lowering) the injection pressure.  Within limits, this is a tuneable feature with modern common rail and unit injector fuel systems.  As mentioned in the article, engine power is typically peak cylinder pressure limited in structural terms for CI engines, which corresponds to the detonation limit seen by SI engines.

While it may be that a BMW V8 diesel may appear at Le Mans in the near future, I am not convinced that it would be a good basis for a high performance engine.  With the availability of modern high pressure fuel injection systems, passenger car diesels moved from divided chamber IDI combustion systems (typically the Ricardo Comet Mk.V), to 4-valve central vertical injector bowl-in-piston DI combustion systems to pick up the benefit of better fuel consumption and higher thermal loading capability.  This translated into the sort of power outputs when turbocharged which made the engines comparable to current SI engines (on the order of 55 kW/litre).  But bowl-in-piston pistons are very heavy and not well suited to high engine speeds, and the combustion system is very dependant on escalation of injection pressure for future power growth.  My view is that there is still room for growth in divided chamber combustion systems if higher engine speeds are believed to be the way to go; the piston is much lighter, and the combustion system has more potential for rapid combustion.  I also think the thermal loading issues are solvable.  However, this is not the direction that the industry is moving in, so such an engine is not likely to be seen at the Sarthe.

PJGD

RE: Diesels at Le Mans

I would have thought the obvious choice for a le mans engine would be the VW V10 tdi,this develops over 300hp and 750nm of torque!! Why would you have to make a diesel high revving to be competitive? I dont think you do my own 1.9tdi Golf devolops 224hp flywheel and 204.5hp wheel and 480nm of torque with the right gear ratios it would do 160 mph!! If the engine doesnt rev but produce huge amounts of torque,then the right gear ratios would be the answer not making the engine rev beyond its design.

RE: Diesels at Le Mans

How do you work that out? Ballpark figure for hatches is 100 hp for 100 mph, and you are mostly fighting a cube law, ie you'd need in excess of 300 hp for 160 mph. My performance predictor for a Prius says it'd need 340 hp at the engine.

I mean, we are talking engineering here aren't we?

Cheers

Greg Locock

RE: Diesels at Le Mans

been following the discussion & remember seeing somethimg in Toronto Globe & Mail a few months ago about new diesel technology- may not apply to leMans but is interesting anyway- will certainly have many applications, especially in my field ( assuming it proves out- its about a company called Westport Innovations ( I have absolutely no connection to the company- no shares etc) - just thought you may be interested in the article ( if you look at Wesport's website the Globe & mail article is there)

RE: Diesels at Le Mans

(OP)
Direct injection of gaseous fuels is the way to go, if you can do it.  The Westport system is good, somewhat complex, and certainly expensive, but they are leaders in their field.  As applied to CI engines though, it is essentially a gaseous engine with diesel pilot, ie, under load 90% of the fuel burned is whatever gas you are using, and 10% is diesel fuel which acts as the ignition source for the gas.

I doubt that we will see an engine like this at Le Mans.

PJGD

RE: Diesels at Le Mans

Guess your predictor is for a petrol engine not a diesel!!

RE: Diesels at Le Mans

Audi are entering a diesel powered racecar at the next Le mans!!

RE: Diesels at Le Mans

(OP)
That is most interesting.  I will look forward to reading the articles about this initiative and how people "justify" using a diesel.  Personally, I think that this is good for the diesel industry; We need the product development that comes through competition on the race track.  SI engines have had the benefit of this for years; now perhaps the diesel can get a "boost" from it.  Will be interesting to see how it does relative to the Totalmotorsport article.

PJGD

RE: Diesels at Le Mans

PJGD,
Sorry I hadn't seen this interesting thread before !

Your paragraph...
"My view is that there is still room for growth in divided chamber combustion systems if higher engine speeds are believed to be the way to go; the piston is much lighter, and the combustion system has more potential for rapid combustion. "

...remained me of the SEMT-Pielstick PA 4 with variable geometry pre-chamber, a system which seems to combine the advantages of direct and indirect inject.

http://www.pielstick.com/frRail.html
 and then click on High speed diesel engines to find a picture of the combustion chamber.

What do you think of that ? I had some more documents about it, but I was unable to find them right now. Looks like I've lost them.

Cheers
Aorangi


RE: Diesels at Le Mans

It's off topic, but one of the most powerful piston aero engines was the Napier Lion.

This was a horizontally opposed, compounded diesel engine.

In development, they realised that more power would be available if the remaining oxygen in the exhaust was used to provide more thrust from an afterburner.

Eventually someone came to the conclusion that they would end up using the piston engine as a gas generator, essentially reinventing the jet engine with a lot of unnecessary complications.

RE: Diesels at Le Mans

Yes, the famous Napier Nomad (the Lion was a pre-war spark ignited W12 with 3 banks of 4 cylinders). It's been talked about on thread Thread71-63511 and Thread71-48738 in which the gas generator principle was also mentioned. I think the gas generator concept would have been more suitable for automotive then pure gas turbine since its efficiency can be somewhat higher in that size range, although not as good as that of a turbocharged diesel, especially under part and low load.

Perhaps a turbocompound 2-stroke opposed pistons diesel would be fine for racing. In the extreme case, when all the power of the diesel is used to drive the compressor, it becomes a gas generator. Any point in between the conventional diesel and the gas generator can be obtained with turbocompound differential supercharging such as in the Geislinger locomotives.

Cheers
Aorangi

RE: Diesels at Le Mans

Grovelling apology!

I've just found LJK Setright's book "Turbocharging and Supercharging for maximum torque and power".

Part of Chapter Eight describes the Napier Nomad, with cutaway diagram.

Complex is not the word for it!

rgds
Zeit.

RE: Diesels at Le Mans

(OP)
Aorangi:
I appreciate the link to the Pielstik PA-4 engine; I had not seen that before but can see that it has some valuable features.  

On the compression stroke, without the obturator (or piston poker) in the way, there is little restriction involved in pushing the air into the pre-chamber.  This is a significant advantage over the conventional fixed geometry pre-chamber designs which loose some efficiency to the pumping losses involved.  However, I do not see anything which would give the air a controlled motion once it is in the pre-chamber.  That is to say, it is a true pre-combustion chamber and not a swirl-chamber, since there is nothing to generate the (rotational) swirl.  This too is an energy savings, since it takes energy to create the rapid air motion.  It does however mean that the nozzle may have to be a bit special since instead of having the air presented to the single spray plume as is the case for a swirl-chamber, the fuel now has to find as much of the randomly turbulent air as it can - and this suggests a multi-hole nozzle?  Even though this design still has a large combustion chamber surface-to-volume ratio, similar to other divided chamber engines, the apparent lack of swirl will also help to reduce heat loss to the coolant and thus maintain high efficiencies.

After the start of injection, it is possible that the "uncooled" obturator now projecting into the pre-chamber, plays a role in initiating ignition.  But whatever: following ignition and as the pressure starts to rise in the pre-chamber, partially burned elements will be forced out of the pre-chamber and into the main chamber through a restricted annular orifice and, taking direction from the radiused profile on the obturator they will be directed across the chamber into the valve pocket areas above the piston where the remaining air is to be found.  This too seems like a relatively low energy loss geometry compared to a fixed geometry chamber, since as soon as the piston begins to descend, the orifice opens up once again.

I do however have concerns about the concept as it might be applied to automotive engines which must address stringent emission standards.  Such engines, to achieve reasonable engine-out NOx levels, are obliged to operate at relatively retarded injection timings very close to TDC, and with extended injection durations to keep bulk gas temperatures down.  This would likely require a much longer obturator (since the piston is now further down the bore) than the 1,500 rev/min rated Pielstik engine exhibits, and this might be a durability issue.  Nevertheless, on a first look, this chamber concept has much to commend it.

Thanks Aorangi!

PJGD

RE: Diesels at Le Mans

I have read two months ago that RICARDO Engineering has ready for the next 24 h of Le Mans an V10 Diesel sport engine with 600 hp.

RE: Diesels at Le Mans

framorgal, could you post a link or reference to where you read that?

RE: Diesels at Le Mans

I have read that in the RICARDO oficial magazine, which is sent every two or three monts to my company.
The article said -I remember- that RICARDO Engineering is planing to have a Diesel sport engine in the next 24 hour of le Mans, the engine has been developed by RICARDO, and now they are waiting for a company interested in the proyect, I think some kind of collaboration like the made with Audi in the developement of the Audi R8 gearbox.

Francisco

RE: Diesels at Le Mans

I was at the recent Performance-Racing Industry trade show in Indianapolis where Ricardo had one of their Lemans diesel prototype engines on display. It seems that the engine originated out of a very robust 3.5 L V10 F1 engine project that had been done some time ago. They are looking for a company to partner with to run this engine in the 2004 ran. Could be very interesting!

Dan

RE: Diesels at Le Mans

I read all the theorizing about limitations to diesel engined car racing.
How about being a lot more positive....
Isn t vwracing in europe been racing for a few years.
They have 1.9 l TDI diesels pumping out 450 lbs of torque, thats more than a 350 LTI vette engine....
All theory limited engineers should check: www.vwracing

They have fantastic V6 diesels in the european versions of the Passat ...

SPEED+++++

RE: Diesels at Le Mans

(OP)
I see that some information and a photo of the Ricardo mule engine is posted here:-

http://www.detnews.com/2004/motorsports/0401/11/e01-402...

I think that this report comes from the same Show that Dynodan above mentions.  Here's hoping that they find OEM support  and sponsorship!

PJGD

RE: Diesels at Le Mans

Would those glow plug model airplane engines qualify as 2-stroke Diesels?  up to 20,000 rpm for the littler ones.  18,000 rpm for the .4 CID with .7 inch stroke.

RE: Diesels at Le Mans

forget all the engineering arguments for not racing diesels.
They have twice the  torque and some .
There are guys who are stopped by arguments and those who do it. Its all in the attitude.

SPEED+++++

RE: Diesels at Le Mans

so, will monster torques win over HP ?

SPEED+++++

RE: Diesels at Le Mans

(OP)
I don't know, riktoo; however........
This graph came from the presentation that Dr. Shahed of Honeywell / Garrett Turbochargers gave at a recent SAE meeting in Detroit (Also available at: http://www.egarrett.com/about_garrett/pressreleases.jsp ).



It shows the specific power and torque of a representitive selection of modern engines, NA and TC SI, and TC CI.  You can see that the diesels are low on power but do OK on torque, although the turbocharged SI engines do impressively well too.  I suspect that the diesel point that is in among the TC-SI cluster is the high output unit injector VW 1.9L engine.

The interesting thing is that the power and torque projections for the Ricardo racing diesel engine place it just slightly beyond the best turbo SI spot.  That is a long way to move the rating of a diesel, and will represent a significant development of high speed diesel combustion technology.

PJGD

RE: Diesels at Le Mans

This thread has started to sound supiciously like a discussion in a hot rodder magazine - ie, importance of torque vs power, capacity specific outputs, etc.  Surely you can see past those.  

What does it matter what magintude of an engine's torque output is? I mean power is work rate.  So of course the engine with the largest power output wins - obviously provided other things are equal.

And what does it matter how much power an engine makes per capacity - except in capacity restricted racing.  As engineers, surely more useful metrics are things like brake thermal efficiency, mass specific power output, piston loadings, etc.

I'm not really trying to cause an argument, but as Greg posted on 31 july - we are talking about engineering aren't we?

RE: Diesels at Le Mans

Tmoose, no they wouldn't qualify. But the small adjustable compression diesel engines would. In a sense they are not a true diesel, because the fuel is not injected. But they are a compression ignition engine. A glow plug engine is just that. The ignition source is a glow plug. When I saw this thread I thought on the same lines you did.

RE: Diesels at Le Mans

Yes,

The fact is that more power always equals more torque...at the rear wheels that is.  All this is required is application of the proper gear ratio.

-Joest

RE: Diesels at Le Mans

I have some additional infos on the MAP.
MAP means Manufacture d'Armes de Paris.
The company was located in Paris's subburb (saint Denis).
MAP was manufacturing tractors (agricultural vehicules).
In 1950, the MAP raced with the N°1 plate and was driven by Ferdinand Lacour and Pierre Veyron.
My father was running a welding, hardfacing company and he welded together the tubular MAP chassis made of CrMo steel which was difficult to weld in the 50's !!!!
The company went bankrupt shortly after and my father never got paid.....
TChronos, I have not been able to find the photos at the given link, thank you to let me know where I can get them.
herve.leguellec@wanadoo.fr

RE: Diesels at Le Mans

A diesel is entered for Le Mans this year (2004). It has been in Autosport and Racecar Engineering. Backed by Catapillar, the team is using a Lola chassis and a production-based V10 disel engine. Who said it couldn't be done?

RE: Diesels at Le Mans

The engine they used in the le mans car backed by catapillar is the v10 tdi from a vw toureg.There were only a couple of big problems they encountered 1 being finding a 12v starter with enough power! and the other was the engines physical height with the sump so it was dry sumped,but the torque that was available is around 1000nm and 600hp.

RE: Diesels at Le Mans

Did anyone follow the race? Taking a quick look at the results, the Catepillar entry dropped out after 35 laps. If it had completed the race at it's initial pace, it would have finished around 8th in GTS class. Sounds like reliability was an issue...does anyone know why it dropped out?

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