IMSA DPi Discussion

[MoMedic9019]

Originally Posted by HORNDAWG

No it's not. It may get bumpy and a schism may develop at the prototype level, but, the OEMs are to important for both sanctioning bodies in GT for there to be a 'cutting of ties

It's not going to happen on either side. But, IMSA is less than thrilled with the ACO right now.

[skycafe]

Originally Posted by Chiana

Yeah, the very well preserved identity of Petit Le Mans, thank god we still have the world class LMP1 cars going for 1000 mile distance and all the class winners earning Le Mans invites, after whole week of Road Atlanta testing in their preparations for the event! Right, right?

(DPi zzzz)

The changes in the cars now running is not lost on me at all, and I am not ignoring that, but I am also being realistic. Something that no longer exists is not coming back, no matter how much wishful thinking is involved. Porsche 962's aren't coming back, but that is no reason to change Daytona or Sebring formats to something else, although a short sportscar race at Sebring and then stadium trucks might play for the Green Park crowd (apologies in advance-it just made an easy target to enhance the absurd).

Just how many changes in car type have occurred at Sebring and Daytona over the decades, yet they still function with the 12 or 24 hour format (I know about 1972), don't they? Right?

[MoMedic9019]

Originally Posted by FormulaFox

False. The closeness of GT3/GTE performance was the primary reason there was an effort to combine the two a few years back.

No. It's not false. The GT Convergence was being attempted to remove multiple cars built by the same manufacturer. I can assure you that a GT3 car would get destroyed by an unrestricted GTE car. I've seen laps run under IMSA BoP P2 times whilst unrestricted. A GT3 car in GT3 trim isn't going to keep pace.

[FormulaFox]

Originally Posted by MoMedic9019

A GT3 car in GT3 trim isn't going to keep pace.

Yeah. You go right ahead and keep telling yourself that.

[MoMedic9019]

Originally Posted by FormulaFox

Yeah. You go right ahead and keep telling yourself that.

I have no issues. I know what the differences are. I've seen it. I know what the data says.

[FormulaFox]

Originally Posted by MoMedic9019

I have no issues. I know what the differences are. I've seen it. I know what the data says.

You're trying to say that with no BoP restrictions, the class with fewer restrictions on aerodynamics, weight, engine type, AND which allows driver aids will be slower than the far more restrictive rulebook.

Sorry, not buying it for a second.

[Maelochs]

No, he is saying the purpose-built chassis and suspension, body and aero of the GT2/GTE/GTLM will outperform the modified street cars in GT3.

DPi.

[FormulaFox]

Originally Posted by Maelochs

No, he is saying the purpose-built chassis and suspension, body and aero of the GT2/GTE/GTLM will outperform the modified street cars in GT3.

If you think GT3 cars are merely modified street cars, you're fooling yourself.

First off, NEITHER class requires the use of any component of the roadgoing car EXCEPT the chassis - and even then, only the most basic pieces thereof. Some roadcar engines are actually ILLEGAL under GTE rules(Corvette C7.R has to use a smaller engine than the roadcar uses, for example) without a special waiver, whereas any gas engine the manufacturer has can be used in GT3(BMW Z4 took big advantage of that rule).

Neither class are merely "modified street cars." You don't get the type of widebody aerodynamics that dominate both classes(especially noticeable in GT3) just by modifying a street car's bodywork and suspension.

Manufacturers aren't flocking to GT3 because the cars aren't heavily modified, they're going there because they can do almost anything to the cars.

[Maelochs]

Originally Posted by FormulaFox

Manufacturers aren't flocking to GT3 because the cars aren't heavily modified, they're going there because they can do almost anything to the cars.

Last I heard GT3 was popular with manufacturers because they could run just about anything, with the much looser restrictions (everything gets BoP'd down anyway) and also the cars could be built more cheaply and easily, with no need to apply for waivers.

Why try to build to exacting GTE standards (or apply for waivers and maybe not get all of them (unless you are BMW)) when you can take any car available and any engine and make it work as well as any other car in the pack (come on ... a Bentley running on even terms with a Ferrari 488 and a McLaren?) In GT3 anyone can play with any toy they happen to find, buy, or build ... GTE rules are much more restrictive.

Currently GTE tends to have more downforce---and more drag---and turn in faster laps times. Of course, Both classes are heavily restricted by BoP. Hard to say what would beat what if all restrictions were removed ... but then, neither class would still be that class.

Anyway ... you have numbers to back up your assertion?

What does this have to do with DPis?

[FormulaFox]

Originally Posted by Maelochs

Last I heard GT3 was popular with manufacturers because they could run just about anything, with the much looser restrictions (everything gets BoP'd down anyway) and also the cars could be built more cheaply and easily, with no need to apply for waivers.

Why try to build to exacting GTE standards (or apply for waivers and maybe not get all of them (unless you are BMW)) when you can take any car available and any engine and make it work as well as any other car in the pack (come on ... a Bentley running on even terms with a Ferrari 488 and a McLaren?) In GT3 anyone can play with any toy they happen to find, buy, or build ... GTE rules are much more restrictive.

Correct on all accounts. Like I said, the appeal of GT3 is that anyone can do anything so long as they can get permission to build the car(from the original manufacturer if they're independent tuners and form the executives for the original manufacturers).

You can go crazy like with the McLaren 650S, or apply KISS like the Bentley.

Currently GTE tends to have more downforce---and more drag---and turn in faster laps times. Of course, Both classes are heavily restricted by BoP. Hard to say what would beat what if all restrictions were removed ... but then, neither class would still be that class.

That was kind of the point I'm getting at - completely unrestricted GTE would simply not outrun GT3 in a general sense. SOME GT3 cars -ones built to the minimal possible changes- would certainly be outpaced, but there's no way a car as excessively modified as, say, the McLaren 650S, would be outpaced by a car from a class that has as many restrictions as GTE.

GT3 allows for the creation of faster machines than GTE.

Anyway ... you have numbers to back up your assertion?

I would, but truly unrestricted numbers simply don't exist. Or more accurately, the only people who may have them(the car builders) don't publish them. The cars are always running under some level of BoP restraint in any arena where numbers are readily available.

What does this have to do with DPis

More than you think, actually. GT3 engines ARE expected to be the basis for the DPi entries, and this whole debate has come up from discussing the notion of alternatives to DPi.

[carbsmith]

While last year's GTE cars were significantly more restricted in design than a typical GT3 car, I wouldn't say that's really the case anymore. The restrictions on diveplanes, fender shape, etc. have been heavily relaxed and the cars can run very considerable diffusers without the shape restrictions of prior years. GT3 cars only tend to have slightly bigger rear wings still but GTE cars no longer lack for height or distance set back anymore. On the engine side a GTE motor tends to be much more heavily modified because there's a displacement based restrictor formula they occasionally look at rather than just BoP'ing purely by performance. The Viper GT3R for example is listed at only 680hp unrestricted, while the production Viper makes 645hp with emissions equipment and street exhaust. Remember the hilarious restrictor spec the GTE version had with its presumably similarly underdeveloped engine? Still with some of the larger displacement/turbocharged GT3 cars that might not be much of a handicap.

The major performance difference is going to be that GTE is an open tire category with top secret car specific tires while GT3 tires are all customer even in the few series with tire competition. GT3 cars don't really have anything that will beat that.

The Bentley is by far the most heavily modified car in GT3 by the way. The 650S is probably one of the least modified cars behind the Audis.

[Speed-King]

The major performance difference is going to be that GTE is an open tire category with top secret car specific tires while GT3 tires are all customer even in the few series with tire competition. GT3 cars don't really have anything that will beat that.

*cough* 24h Nürburgring *cough*

[FormulaFox]

Originally Posted by carbsmith

On the engine side a GTE motor tends to be much more heavily modified because there's a displacement based restrictor formula they occasionally look at rather than just BoP'ing purely by performance.

The thing with GT3 cars is that there are only two restrictions to what goes in the engine bay - no hybrids, and must run on gasoline. They don't need to modify the engines - they can literally drop in anything that will fit.

The Bentley is by far the most heavily modified car in GT3 by the way. The 650S is probably one of the least modified cars behind the Audis.

You don't SERIOUSLY believe that, do you? The car with the least visible aerodynamic changes is the most modified and the one with the msot visible aero changes is the least?

I'm not gonna like neither are heavily modified - there's a lot that gets changed underneath the skin even when there's no visible change after all. But let's be honest, when a car has been widened so much that it's starting to look like a pre-DTM-merger GT500 car, you can rest assured it's far more heavily modified than the car that looks like they just slapped a few aero pieces on the road car.

[wdave0]

Originally Posted by FormulaFox

The thing with GT3 cars is that there are only two restrictions to what goes in the engine bay - no hybrids, and must run on gasoline. They don't need to modify the engines - they can literally drop in anything that will fit.



You don't SERIOUSLY believe that, do you? The car with the least visible aerodynamic changes is the most modified and the one with the msot visible aero changes is the least?

I'm not gonna like neither are heavily modified - there's a lot that gets changed underneath the skin even when there's no visible change after all. But let's be honest, when a car has been widened so much that it's starting to look like a pre-DTM-merger GT500 car, you can rest assured it's far more heavily modified than the car that looks like they just slapped a few aero pieces on the road car.

You don't seriously believe that do you?

The car that looks most modified must be so?? Take a road car that weighs about 2.5 tons and has the aero of a brick ,front engine, designed for luxury and make it competitive with mid-engine exotic sports cars of half that weight and say the result is less modified?

[Maelochs]

Originally Posted by wdave0

The car that looks most modified must be so?? Take a road car that weighs about 2.5 tons and has the aero of a brick ,front engine, designed for luxury and make it competitive with mid-engine exotic sports cars of half that weight and say the result is less modified?

I cannot supply proof, but that is certainly my opinion.

Anything that looks like a 5000-lb Bentley but corners like a 3000-lb Ferrari has been modified in way more than just the aero. In fact, a brick can be made a little more aero with subtle shaping differences---look at NASCAR cars. Fender flares are not the only mods needed to make a whale of a luxury car keep up with some of the quickest generally available production sports cars in history.

But anyway ... this is a debate about which imaginary car is faster. The answer is, whichever one you imagine.

As for which engines will end up in DPis, so far the answer is Chevy, Mazda/AER, or Gibson. Until another manufacturer steps up and makes the investment in an engine, bodywork, and whatever the series charges for letting them play, that's all we get.

Theoretically anyone could put any engine n the back of any chassis but the rules say a manufacturer has to be involved. Otherwise we could see Any sports car or GT3 engine---except the V12 Vantage motor---in any of the four accepted chassis .... which would be a good thing, until those little teams which made their own cars started winning, so they will never get the chance.

[wdave0]

Originally Posted by FormulaFox

You don't SERIOUSLY believe that, do you? The car with the least visible aerodynamic changes is the most modified and the one with the msot visible aero changes is the least?

I'm not gonna like neither are heavily modified - there's a lot that gets changed underneath the skin even when there's no visible change after all. But let's be honest, when a car has been widened so much that it's starting to look like a pre-DTM-merger GT500 car, you can rest assured it's far more heavily modified than the car that looks like they just slapped a few aero pieces on the road car.

Sorry - The above was the quote I was referring to - didn't notice the auto edit. Absolutely the Bentley must be most modified and I suspect the M6 is next.
<<
You don't seriously believe that do you?

The car that looks most modified must be so?? Take a road car that weighs about 2.5 tons and has the aero of a brick ,front engine, designed for luxury and make it competitive with mid-engine exotic sports cars of half that weight and say the result is less modified?
<<

[HORNDAWG]

None of this *sh it* is about the 2017 DPi.
Just adding ... DPi... to the end of a sentence is very telling.
There are literally dozens of threads that this subject matter fits in.









L.P.

[carbsmith]

The McLaren has aggressive aero but that's a result of the street car. The Bentley has just as many aerodynamic modifications and heavy, heavy mechanical changes to improve weight distribution

[FormulaFox]

Originally Posted by wdave0

You don't seriously believe that do you?

The car that looks most modified must be so?? Take a road car that weighs about 2.5 tons and has the aero of a brick ,front engine, designed for luxury and make it competitive with mid-engine exotic sports cars of half that weight and say the result is less modified?

I believe both cars are heavily modified. I also not only believe -but know from experience- you have to modify a car a lot more to produce widebody aero than a simpler setup. It's a lot more than just slapping wider bodywork onto it.

Also, the Bentley's base aero isn't as brick-like as you think, and the car is also designed to perform pretty well despite it's weight. Additionally, the BoP addresses many disadvantages the car has.

[FormulaFox]

Originally Posted by carbsmith

The McLaren has aggressive aero but that's a result of the street car.

Incorrect. The 650S GT3 has been widened considerably over the street car for both improved aerodynamic AND mechanical grip. There's a lot more to it than just the road car's design.

Let me reiterate: I am NOT saying the Bentley is not heavily modified. I'm saying it's LESS modified relative to the roadcar than the McLaren.

[wdave0]

Originally Posted by FormulaFox

Incorrect.

Let me reiterate: I am NOT saying the Bentley is not heavily modified. I'm saying it's LESS modified relative to the roadcar than the McLaren.

Balderdash!
But, to get back on topic, there has been a fair bit of scuttlebut concerning Bently GT3 engine in DPi. It will certainly have lots of development behind it. The grille could be a bit of a problem though.

[FormulaFox]

Originally Posted by wdave0

But, to get back on topic, there has been a fair bit of scuttlebut concerning Bently GT3 engine in DPi. It will certainly have lots of development behind it. The grille could be a bit of a problem though.

Bentley isn't going anywhere near DPi. GM, however, is planning to use the Cadillac GT3 engine for DPi.

[Rcz]

BoP to me is interesting concept.

BoP has existed since most off auto racing existence. In the older days, Big engine cars were heavier but had fatter tires. Small engine car had lighter weight but skinnier tires.

But the biggest difference between those older era and today, is that in the old era they changed rules before the the next season started. But today, they are basically changing the rules after every race. At least with GT car and Jr. Prototypes.


My problem is even with BoP, there's no guarantee you can stop a really good car.

Sure you can effect top speed but not handling, right. It makes wonder, can you develop a DPi with really good handling with aero? That what I would do.

And what if car has a terrible under steer, how would you bop it back in contention? You can't just bop down everyone else.

[Maelochs]

Originally Posted by Rcz

And what if car has a terrible under steer, how would you bop it back in contention? You can't just bop down everyone else.

IMSA will balance all the aero beforehand, so understeer and similar issues would be more the result of shock and spring choices, and could be modified through aero with dive planes and gurneys all withing the existing regs.

If certain chassis just seem to work better ... well, as was pointed out above, Riley was the chassis to win with in Rolex. If a single chassis seems to be superior out of the four offered for 2017, everyone will flock to that, too. But that has nothing to do with BoP or aero ... that is maybe some slight differences in geometry or adjustability or stiffness or stuff I admittedly don't understand, except to see that some things work better than others.

BoP will mostly be applied to engines; I don't see how cars with spec chassis could be made to carry more weight, or aero could be BoP'd after the series spent so much time in the wind tunnel reducing all the chassis down to the level of the worst design, before the season started.

[Rcz]

Would it be better if they first tried making everyone the same before Daytona but as the season goes on, BoP up the slower cars but never nerf the faster ones.

Because it is prototypes and they should have some development.