jond

Anyone know why the diesel le mans prototypes are faster than the gas prototypes?

I'm thinking the compression ratio is higher, the strokes are probably longer, etc. But still, power is power right? Regardless of the RPM, regardless of whether it's termed torque or horsepower, it's power. As long as the power curve is where you need it, it seems like it wouldn't make a difference.

Anyone know for sure? Any theories?

Micha

Way more torque? (completely a guess)

chris_c

diesel technology is really being pushed to the limit these days. i wonder if it is as simple as more resources [time/money, etc] are being allocated to diesel development.



outside of that i have no idea...

Micha

It would be kinda cool if they make a racer that runs on biodiesel.

AWDstylez

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jond &raquo;</TD></TR><TR><TD CLASS="quote"> As long as the power curve is where you need it, it seems like it wouldn't make a difference.
</TD></TR></TABLE>

SO glad you understand that, because not many people do.

According to some interview I read in a magazine with someone from Audi, the diesels actually have a much broader powerband. They don't make much more power, but the power curve is almost flat, so full power is available at all usable RPMs. As opposed to the gas engines with normal looking, up sloping power curves.

Or maybe it's just another year's worth of chassis developement. Maybe it's the aerodynamics and handling that actually making them faster.

That's about all I can think of...

Farmer Brown

Because Audi has been kicking *** and taking names in Le Mans for years.

.Chris.

They have advantages everywhere.

If you're talking strictly about lap times, I would suggest that more use-able power would be one part of the answer to that question. Audi also usually has a very well sorted chassis overall.

In terms of advantages over the course of a 24 hour race - Reliability and fuel consumption. I've also head that due to that broad torque curve they're easier to drive. That's a huge advantage when the driver is trying to stay on rhythm for a 4 hr stint.

theSQad

because Audi has the $$$$ for R&D

Mr.E.G.

it's simply an issue of torque. now before i get flamed for talking out of my ***, i'll remind you that this is straight from the horses mouth., racecar engineering magazine that is.

its the same reason that big engine cars kick *** in Super GT (formerly jgtc). in these series they limit horsepower and try to keep all of the vehicles making the same power through various restrictors and whatnot.

however, this only applies to peak numbers. they dont entirely address overall acceleration, just peak power. the transient numbers of the deisels kick the crap out of the peaky na petrol engines.

now that explains why the cars accelerate faster. the reason they are front runners is due to many factors. the primary difference between a privateer team and a factory backed team is the amount of money. this pays huge dividends in terms of aerodynamics.

aerodynamic r&d is the trickiest and most expensive aspect of a modern le mans prototype.

in a sport where the difference between the winner and second place is extremely marginal, money goes a long way.

heres an interesting fact. during the design of the c6-r (which just in case you dont know isnt based on the road going c6 chassis. its a full tube frame car that is wider, longer, has a different suspension arrangement, etc etc. it just happens to be wrapped in skin that looks like a corvette) the industry took several giant steps forward in terms of computational fluid dynamics software and the c6r design team was able to use this software to design the body work in considerably less time than they had on the c5r. with the c5r they had to actually build the parts from carbon fiber, take them into the windtunnel and test them and do this over and over until they found the best combination of parts. needless to say this took a ton of time and there were more than a few parts that were not sutiable and therefore scrapped.

when they designed the c6r it was all done in the software. they tweaked it until they got several versions that they liked and then they had the parts made from these computer renderings.

one of thier engineers was talking about this and he said that thanks to the cfd programs they were able to save 2million dollars in aerodynamic research. :-O

thats just one part of the car. now the prototype cars are cheaper to make than gt1 cars but they are still million dollar cars audi and peugeot can throw money at it. not everyone can do that.

Lan

I can't wait to do aerodynamics on race cars. Great post :goes back to studying math:

Mr.E.G.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lan &raquo;</TD></TR><TR><TD CLASS="quote">I can't wait to do aerodynamics on race cars. Great post :goes back to studying math:</TD></TR></TABLE>

is that what you are going to school for?

have you read any mcbeath or katz?

Lan

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.E.G. &raquo;</TD></TR><TR><TD CLASS="quote">

is that what you are going to school for?

have you read any mcbeath or katz?</TD></TR></TABLE>

Mechanical Engineering. I have not, I just got back into school haha. Right now I am taking simple Algebra.

Brandon

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lan &raquo;</TD></TR><TR><TD CLASS="quote">

Mechanical Engineering. I have not, I just got back into school haha. Right now I am taking simple Algebra.</TD></TR></TABLE>

Mech Eng's won't be doing aero work, sorry.

Diesel motors at LeMans don't have the same rules as petrol cars, which is part of the reason Porsche refused to run their LMP2 cars this year.

Mr.E.G.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Brandon &raquo;</TD></TR><TR><TD CLASS="quote">

Mech Eng's won't be doing aero work, sorry.

Diesel motors at LeMans don't have the same rules as petrol cars, which is part of the reason Porsche refused to run their LMP2 cars this year.</TD></TR></TABLE>

are there any diesel LMP2 cars? i thought all of the diesels were LMP1.

Mr.E.G.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.E.G. &raquo;</TD></TR><TR><TD CLASS="quote">

are there any diesel LMP2 cars? i thought all of the diesels were LMP1.</TD></TR></TABLE>

edit. it just occured to me what i just said. lol

Brandon

I'm so confused... but to answer your question I believe only Pug and Audi are using oil burners.

ucb

hp under the curve (a true measure of a cars power/speed potential). Peak hp numbers are for poopra and turbo honda owners

/thread

Brandon

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ucb &raquo;</TD></TR><TR><TD CLASS="quote">hp under the curve (a true measure of a cars power/speed potential). Peak hp numbers are for poopra and turbo honda owners

/thread

</TD></TR></TABLE>

Not true, narrow powerbands have won LeMans more than you think. The 787B had one of the narrowest powerbands you've ever seen but even with it's 5spd transmission they geared it well enough to where it doesn't matter. Proper gearing can overcome any potential powerband issues.

ucb

Agreed, but if you can make 700whp flat for 3k rpm spurts, you are in much better shape than a car making 600-700whp for that same 3k rpm spurt

More hp at lower rpms is only going to make the car faster (not to mention more predictable). Fewer shifts per lap is only going to help as well

Mr.E.G.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Brandon &raquo;</TD></TR><TR><TD CLASS="quote">I'm so confused... but to answer your question I believe only Pug and Audi are using oil burners.</TD></TR></TABLE>

thats what i was saying. originally, i was thinking, why would porsche care since they are in a different class, but if forgot that in the alms the lmp1 and lmp2 classes compete with one another unlike the gt classes which are seperate. it occured to me what i said right after i said it.

Brandon

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ucb &raquo;</TD></TR><TR><TD CLASS="quote">Agreed, but if you can make 700whp flat for 3k rpm spurts, you are in much better shape than a car making 600-7000whp for that same 3k rpm spurt

More hp at lower rpms is only going to make the car faster (not to mention more predictable). Fewer shifts per lap is only going to help as well </TD></TR></TABLE>

More torque will put more strain on the box than more shifts will on modern sequential transmissions and computerized engine control, especially when you are coming from a stop.

Brandon

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.E.G. &raquo;</TD></TR><TR><TD CLASS="quote">

thats what i was saying. originally, i was thinking, why would porsche care since they are in a different class, but if forgot that in the alms the lmp1 and lmp2 classes compete with one another unlike the gt classes which are seperate. it occured to me what i said right after i said it.</TD></TR></TABLE>

Well the other reason Porsche wouldn't run is that the current LMP2 rules penalize the LMP1 cars more to keep the LMP1 cars on top. If they were level then you'd see Porsche win LeMans with an "inferior" car.

ucb

I dont see how either of those facts have anything to do with speed

Brandon

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ucb &raquo;</TD></TR><TR><TD CLASS="quote">I dont see how either of those facts have anything to do with speed </TD></TR></TABLE>

Broken 'box means you're not going anywhere. I thought that was what you were referring to. Shifting doesn't really hurt acceleration on the LMP cars which use sequentials, it's only marginally less strain on the drivers.

ucb

Last time I checked the audi le mans cars weren't having any gear box issues

Yes the cars already shift fast, but if each shift still takes a few tenths, and you can save a few shifts per lap, thats going to add up over a 24hr period