IMSA DPi Discussion

[FormulaFox]

Originally Posted by RWill2073

Wouldn't it be better to do the bodywork to style it like an nsx instead of a Honda?

Not necessarily. They have to balance aero efficiency in the mix as well - BoP can only do so much, particularly when there's a specific yardstick to be balanced to. Screwing up the aero can snowball into a bigger problem and ruin the whole package.

There's a reason GM didn't do roadcar-derived aero for the Caddy DPi.

[Makaze]

The rumor is...a new Honda S2000 will debut this October at the Tokyo Motor Show.So that or a CTR bodywork for the Dpi.

[MagVanisher]

If HPD wanted to base their DPi car on the NSX, then go for it! Just hoping that it'll stay competitive after some adjustments from IMSA.

On the other hand, any news of ACO allowing DPi in Le Mans, racing in LMP1-P?

[knighty]

Originally Posted by MagVanisher

If HPD wanted to base their DPi car on the NSX, then go for it! Just hoping that it'll stay competitive after some adjustments from IMSA.

On the other hand, any news of ACO allowing DPi in Le Mans, racing in LMP1-P?

the NSX Super-GT racer in Japan uses the 2.0L I4 engine used in Japanese SuperFormula dallara single seaters, yes its 600bhp, but it will not be capable of producing the torque that Cadillarc and Nissan are with far bigger engines, it will just be another Mazda style of fragile 2.0L turbo engine which BBQ's itself regularly.......they will need to either get a V6 with about 3.0-3.5 Litres capacity, such as the previous LMP2 engine would be ideal, I believe currently used by Shank in 3.5L guise......or they will need to increase the 2.0L I4 out to something like 2.5L and this might help bridge the gap......its a tough call, as the V6 is probably too heavy, but the I4 is too low on capacity, but would allow ideal weight distribution, either way Honda have 2 reasonable engine DPi starting points........I think its only a matter of time before a manufacturer realizes a big capacity I4 or I5 Turbo gasoline motor with 2.5 to 3.0 litres of capacity is the ideal tool for both the IMSA DPi job and LMP1 in WEC

[Jonerz]

Originally Posted by chernaudi

The current Audi R8 GT3 is quoted as making 580bhp. The Cadillac DPI is quoted as making 600bhp. I don't see why it'd be hard for Audi for example to coax an extra 20bhp out of the GT3 engine--a simple air restrictor change can make up that difference.

However, I have no quotes for how much power the NSX GT3 is making in full GT3 spec. The road car on engine power alone makes 500.

Quite right, I meant the opposite, though. I don't think IMSA GTD cars are significantly tuned down. GTLM received a significant power boost with the "new" rules in 2016, so its not like the days when 430 battled RSR and each was making 480-500hp.

Originally Posted by chernaudi

I do see a DPI program from HPD is being a lot more likely right now than one from Volkswagen Group. People have tried to tie Audi Sport, Bentley Motorsport and Lamborghini to a DPI program. That's not to say that it won't happen. But I don't see a VAG DPI program happening soon, not unless someone's helping to foot the bill. Audi Sport will probably be back in LMP1 before we see a VAG DPI program for all I know.

But HPD don't have VAG or Toyota sized motorsports budgets, and probably don't want to spend that level of money even if they did, and they do have a GT3 car that they can take the engine out of and probably have a competitive DPI effort in short order. Not to mention that the NSX Earth Dreams engine is more race ready than the old LMP2 engine, which was a sedan/minivan engine modified as little as possible. Granted, until BOP came in, it was about useless against the Nissan VK45, which is about as removed from a stock block engine as one can get and still claim it was a stock block engine (it was basically a de-tuned Super GT GT500 engine).

While I think VAG will return to Le Mans very soon, I think the DPi program may even debut next year.

Also, to defend Honda's old P2 engine, re-homologating it as the beefier 3.5L is what turned it on here in North America. It never really got a chance in Europe to shine.

Originally Posted by FormulaFox

Not necessarily. They have to balance aero efficiency in the mix as well - BoP can only do so much, particularly when there's a specific yardstick to be balanced to. Screwing up the aero can snowball into a bigger problem and ruin the whole package.

There's a reason GM didn't do roadcar-derived aero for the Caddy DPi.

They didn't make a CTS-V Coupe DPi or anything of the like, but the detail changes GM and Dallara made to the DPi-V.R were road car derived or inspired. Caddy's road car engineers got to participate in the design work.

Chris

[knighty]

erm, everyone keeps talking about just power figures in bhp, sorry but Cadillacs advantage is in the colossal amount of low down torque it makes, hence the air restrictors hardly made any change to its on-track performance .......power and torque characteristics are just as important as each other in a heavy car such as a GT or prototype.......you cant just talk about power in isolation

[canaglia]

Originally Posted by knighty

the NSX Super-GT racer in Japan uses the 2.0L I4 engine used in Japanese SuperFormula dallara single seaters, yes its 600bhp, but it will not be capable of producing the torque that Cadillarc and Nissan are with far bigger engines, it will just be another Mazda style of fragile 2.0L turbo engine which BBQ's itself regularly.......they will need to either get a V6 with about 3.0-3.5 Litres capacity, such as the previous LMP2 engine would be ideal, I believe currently used by Shank in 3.5L guise......or they will need to increase the 2.0L I4 out to something like 2.5L and this might help bridge the gap......its a tough call, as the V6 is probably too heavy, but the I4 is too low on capacity, but would allow ideal weight distribution, either way Honda have 2 reasonable engine DPi starting points........I think its only a matter of time before a manufacturer realizes a big capacity I4 or I5 Turbo gasoline motor with 2.5 to 3.0 litres of capacity is the ideal tool for both the IMSA DPi job and LMP1 in WEC

Actually don't know if nissan/honda/toyota 2.0 L4 turbo engines could be more or less reliable than the poor reliable mazda engine in a 24h race, but trust me, fuel flow GT500 engines are much better hot stuff than mazda motor.
As far I know, in GT500 cars fuel flows triggers at 7000rpm or 7500rpm, where max output is released. Redline in those engine is at about 8000rpm. To reach 600hp @8000rpm are required 535Nm!!! so those engines run not less than 600Nm for almost the whole rpm range. Basically GT500 engine torque figure is comparable to the one of road mp4-12c, despite being 1/2 large.

High power - high rev - DI - high torque release = state of art.

If only could be found a way to make it the last 24 hour, it would be the ultimate sportscars engine.

[chernaudi]

Originally Posted by knighty

erm, everyone keeps talking about just power figures in bhp, sorry but Cadillacs advantage is in the colossal amount of low down torque it makes, hence the air restrictors hardly made any change to its on-track performance .......power and torque characteristics are just as important as each other in a heavy car such as a GT or prototype.......you cant just talk about power in isolation

You do seem to be forgetting to a degree that's why cars with small engines run turbochargers or superchargers. They're torque multipliers. That's why Audi had some big advantages in the R8 LMP900 days, is that they were the only ones with a forced induction engine that worked well. You don't get a 3.6 liter V8 to make the torque of a big block V8 and red line at 7000 rpm by it being a NA engine.

The problem with the 2.0 four bangers, though, is can they handle the boost to get the power and torque needed. Toyota managed it in the IMSA GTP days, but they destroyed a lot of engines and at least one or two engine dynos to do it. So far, Mazda hasn't.

I do think that a four cylinder is a poor choice for endurance racing, but not for power or torque reasons if forced induction. I think that most four cylinders have rigidity issues that hamper their durability in high boost applications. A V block is much more torsionally strong. That's why Porsche's four banger in the 919 is a V4. That's why Audi went with a V6 in the R18 series, as well as a V8 in the R8, a V12 in the R10, and a V10 in the R15. All Toyota LMP engines have been V engines, be it V8s or the current V6 family.

Not to mention that V engines can be easily designed to be stress mounted to the cars tub. Not of huge importance in DPI (where stock block engines are the common rule), but even in a semi-stressed mount, I feel that a V engine still has some advantages. Only VAG designed a successful stress mounted inline four for their F3 cars, and that was designed by Audi engine man Ulrich Baretzky. And no one's figured out how they did it.

[TF110]

I think the Mazda (actually an AER) engine is a bad example of the competitiveness of a small turbo. I don't think Honda or Acura will use that type in a dpi though. Most likely something already used in lmp or the NSX GT3 engine (which works as a mid-engine already unlike the ESM Nissan).

[schmidder]

Sorry, missed the quote..but to chris a ways up...VAG is at lemans this year in p1 with porsche...you mean audi?

Sent from my SAMSUNG-SGH-I337 using Tapatalk

[Matt]

Originally Posted by chernaudi

You do seem to be forgetting to a degree that's why cars with small engines run turbochargers or superchargers. They're torque multipliers. That's why Audi had some big advantages in the R8 LMP900 days, is that they were the only ones with a forced induction engine that worked well. You don't get a 3.6 liter V8 to make the torque of a big block V8 and red line at 7000 rpm by it being a NA engine.

The problem with the 2.0 four bangers, though, is can they handle the boost to get the power and torque needed. Toyota managed it in the IMSA GTP days, but they destroyed a lot of engines and at least one or two engine dynos to do it. So far, Mazda hasn't.

I do think that a four cylinder is a poor choice for endurance racing, but not for power or torque reasons if forced induction. I think that most four cylinders have rigidity issues that hamper their durability in high boost applications. A V block is much more torsionally strong. That's why Porsche's four banger in the 919 is a V4. That's why Audi went with a V6 in the R18 series, as well as a V8 in the R8, a V12 in the R10, and a V10 in the R15. All Toyota LMP engines have been V engines, be it V8s or the current V6 family.

Not to mention that V engines can be easily designed to be stress mounted to the cars tub. Not of huge importance in DPI (where stock block engines are the common rule), but even in a semi-stressed mount, I feel that a V engine still has some advantages. Only VAG designed a successful stress mounted inline four for their F3 cars, and that was designed by Audi engine man Ulrich Baretzky. And no one's figured out how they did it.

Toyota's 1.9l turbocharged-out-the-ass four cylinder would like some words with you re: poor choices for endurance applications.

[chernaudi]

You seem to be forgetting that the Toyota engine initially wasn't that reliable, and, above all else, Toyota were dumping $25 million dollars a year into their IMSA GTP program by the time the Eagle Mk III came out. Even allowing for inflation, Mazda are spending a small fraction of that, and AER's engines have never been known to be rock solid.

[Jonerz]

Originally Posted by schmidder

Sorry, missed the quote..but to chris a ways up...VAG is at lemans this year in p1 with porsche...you mean audi?

Sent from my SAMSUNG-SGH-I337 using Tapatalk

Yes, I meant Audi. I had been discussing VAG generally and the terms became interchangeable in my head.

Chris

[YZFrider]

Originally Posted by canaglia

Actually don't know if nissan/honda/toyota 2.0 L4 turbo engines could be more or less reliable than the poor reliable mazda engine in a 24h race, but trust me, fuel flow GT500 engines are much better hot stuff than mazda motor.
As far I know, in GT500 cars fuel flows triggers at 7000rpm or 7500rpm, where max output is released. Redline in those engine is at about 8000rpm. To reach 600hp @8000rpm are required 535Nm!!! so those engines run not less than 600Nm for almost the whole rpm range. Basically GT500 engine torque figure is comparable to the one of road mp4-12c, despite being 1/2 large.

High power - high rev - DI - high torque release = state of art.

If only could be found a way to make it the last 24 hour, it would be the ultimate sportscars engine.

This! As Chernaudi said too Toyota IMSA GTP engine was very successful. To add World rally cars also were making around 500-530 nm of torque at 2000 rpm with 2.0 turbo fours and a 34 mm restrictor. They then tuned the engine to pull those torque numbwr all the way to 7000 rpm!!! Seeing as the restrictor choked off peak power it then became a game of broad powerband. That's why I've always said in a good BoP small forced induction motors can match and/or be better than large displacement motors. Funny how Mazda just received more midrange boost in the latest round of BoP. As much as speedsource/AER are to blame for results, is this adjustment an indictment of wrong BoP to begin with?

[canaglia]

Originally Posted by YZFrider

This! As Chernaudi said too Toyota IMSA GTP engine was very successful. To add World rally cars also were making around 500-530 nm of torque at 2000 rpm with 2.0 turbo fours and a 34 mm restrictor. They then tuned the engine to pull those torque numbwr all the way to 7000 rpm!!! Seeing as the restrictor choked off peak power it then became a game of broad powerband. That's why I've always said in a good BoP small forced induction motors can match and/or be better than large displacement motors. Funny how Mazda just received more midrange boost in the latest round of BoP. As much as speedsource/AER are to blame for results, is this adjustment an indictment of wrong BoP to begin with?

mazda-AER engine is simply weak as hell... according to bop sheet it revs up to 8800 (at 8900 no boost). Considering that in 2016 it had 2.5 boost for the whole range, while this year is in the range of 2.5-2.7, it didn't gain a lot of power at all, guess in the range of 550hp in the most optimist scenario. It was just wrong to compare state of art engines to a not so great motor, just because of the same layout and displacement.
Agree 2.0 L4 WRC engines were beasts, just 300hp but costantly pushing over 500Nm.
Guess only porsche and toyota lmp1 engines are better than GT500 engines, for the simple reason that are in the same performances range but consuming less fuel.

[TF110]

If Mazda had one of those Super GT engines, they'd be whooping some butt! Well, maybe not. The car (chassis, downforce) doesn't seem like it's fully up to snuff with the likes of the Dallara Caddy.

[FormulaFox]

Originally Posted by MagVanisher

On the other hand, any news of ACO allowing DPi in Le Mans, racing in LMP1-P?

There isn't likely to be any news on that before the rules meetings at Le Mans. There's a lot of rumor about what's being planned and some of them would likely kill DPi in LMP1 if true. Others would make it absolutely ridiculous not to allow it.

All we can do is wait and see. The withdrawal of Audi has clearly made the ACO realize that something needs to change NOW. DPi in LMP1 may or may not be answer, but the current status quo is approaching endgame, so plan for it or face a real problem.

[knighty]

Originally Posted by chernaudi

You do seem to be forgetting to a degree that's why cars with small engines run turbochargers or superchargers. They're torque multipliers. That's why Audi had some big advantages in the R8 LMP900 days, is that they were the only ones with a forced induction engine that worked well. You don't get a 3.6 liter V8 to make the torque of a big block V8 and red line at 7000 rpm by it being a NA engine.

The problem with the 2.0 four bangers, though, is can they handle the boost to get the power and torque needed. Toyota managed it in the IMSA GTP days, but they destroyed a lot of engines and at least one or two engine dynos to do it. So far, Mazda hasn't.

I do think that a four cylinder is a poor choice for endurance racing, but not for power or torque reasons if forced induction. I think that most four cylinders have rigidity issues that hamper their durability in high boost applications. A V block is much more torsionally strong. That's why Porsche's four banger in the 919 is a V4. That's why Audi went with a V6 in the R18 series, as well as a V8 in the R8, a V12 in the R10, and a V10 in the R15. All Toyota LMP engines have been V engines, be it V8s or the current V6 family.

Not to mention that V engines can be easily designed to be stress mounted to the cars tub. Not of huge importance in DPI (where stock block engines are the common rule), but even in a semi-stressed mount, I feel that a V engine still has some advantages. Only VAG designed a successful stress mounted inline four for their F3 cars, and that was designed by Audi engine man Ulrich Baretzky. And no one's figured out how they did it.

Chernaidi, please rest assured I'm not forgetting anything so basic and trivial, as I design high-performance engines for a living for the past 20 years, as a guide, gone are the days that I take an engine design lecture from the majority of people, for sure there are a minority that know a bit more than me, as nobody knows everything, but I dont see them anywhere on this forum ;-)

[Scorchess]

Originally Posted by MagVanisher

On the other hand, any news of ACO allowing DPi in Le Mans, racing in LMP1-P?

At the moment that is allowed, as far as the ACO is concerned ESM can enter their car without any problem while only changing a few minor things related to the ECU. WTR could enter too but they can't call it a Caddilac.

The better question is why would anyone want to enter a slightly beefed up LMP2 car against bespoke LMP1 prototypes?

[Matt]

Originally Posted by Scorchess

At the moment that is allowed, as far as the ACO is concerned ESM can enter their car without any problem while only changing a few minor things related to the ECU. WTR could enter too but they can't call it a Caddilac.

The better question is why would anyone want to enter a slightly beefed up LMP2 car against bespoke LMP1 prototypes?

because the CLM is a pile.

[Scorchess]

It handily beat the LMP2s at Spa. Perhaps the LMP1 regulations would allow for example ESM to turn up the boost a bit but I still would be curious if that would be enough to keep up with the CLM.

And for next year there will be quite a few more cars in the class it seems.

[TF110]

Originally Posted by Matt

because the AER was a pile.

Changed it a bit The Nissan engine seemingly breathed some life in the old dog.

[chernaudi]

The problem with Mazda is that Toyota made a turbocharged 4 cylinder work. But Toyota had a huge budget for IMSA GTP back then, and they also used a steel engine block. I think that a lightweight aluminum block (at least how Mazda/AER designed it) just isn't up to snuff to handle huge boost pressures/compression ratios. Increasing turbo boost will increase power, but for how long until the engine turns more into roman candle than race engine?

I'd think that maybe Mazda would be well served, if they want to keep with the four banger route, to use a production derived block and head if it's beefier. Yeah, weight will undoubtedly go up a bit, but the Toyota GTP engine used a cast iron/steel engine block slightly modified from production (the Mazda Skyactiv gasoline and diesel engines use aluminum blocks for the record). Even VAG still use steel blocks on most of their three, four or five cylinder inline engines, even gasoline engines, for durability. And I doubt that they're much heavier than most aluminum block engines of similar size. A Ford Windsor small block in steel/cast iron is only marginally heavier than GM's all aluminum LS/LT engine, for example, when both are fully assembled.

And even most aluminum V engines, be it road or race, are probably heavily reinforced to give them the strength and durability desired, mostly through bracing/strengthening webs.

[carbsmith]

It's not like Dyson was grenading the previous version of the engine every weekend.

Worth noting there is the possibility of more LMP1-P cars than DPi next year.

[MagVanisher]

That's true, but the question is how long these privateers would last? One season or beyond that?

But let's go back to DPi regulations. Since they can't run in Le Mans in their current guise, would it be better if they bend the rules a bit like allowing a fifth chassis manufacturer or something?