r/USCR PFAFF Motorsports 911 GT3 #9 Nov 17 '20

History 12h Sebring — Fastest Lap Evolution (1999-2020)

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u/DismalMode7 Nov 17 '20 edited Nov 17 '20

who marked the overall best time in 2008? R10 or rs spyder?anyway guess this graph is wrong because last year (2019) the best Q laptime was 105.8 due new michelin instead of shitty continental. Is a bit strange find out that dpi after 4 years of development are just a bit quicker than 2011 peugeot 908 at debuting race

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u/MidnightMulsanne PFAFF Motorsports 911 GT3 #9 Nov 18 '20 edited Nov 18 '20

It is a typo, the time was 105.865, indeed. About the cars performance, it is pretty simple: a racing car is as fast as its allowed to be by its regulations. For example, Super GT's GT500 cars are still seconds slower than the Jaguar XJR-14 while being nearly as fast as the Toyota TS030. Using Road America as an example, look how long it takes to beat the Eagle Mk.III time from 1992. And nowadays we don't have much a development, either. Wathever you do you won't go much faster because the series have their BOP and target times.

EDIT: And the 2008 time was done by Sarrazin with Peugeot.

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u/DismalMode7 Nov 18 '20

sorry but to me you're wrong in all examples you did...
xjr-14 in 1991 scored suzuka pole in 1.48, gt500 cars run in 1.44-1.45... suzuka layout dind't change during the years, so how can you say that gt500 are slower than xjr-14? lol it's totally a nosense comparison considering how poor was group C aero while actual gt500 cars have state of art aero/tires and are in same range of power of xjr-14 in racetrim.
Also your road america example is wrong in its concept because you're taking as reference cars with extremely different specs, while my example is more pertinent because nowadays dpi are however related to peugeot 908 since have both lmp spec and basically are in the same weight/power range (about 930kg x 600hp).
And it isn't even 100% true your first statement as well, 2014-2016 dp3.5 performances are some kind of "artificial " because were arbitrarily made to let silly and cavemen old steelframed cars like dp to be faster than much more advanced lmp2 cars....
until 2013 dp3 (about 1100kg x 500hp, and basically almost zero aero) were just about 1 second faster than ALMS gtlm and about 5 seconds slower of ALMS lmp2 of the same year... for 2014 TUSC (grand-am and ALMS merge) dp got bigger engines to get more torque and >550hp, some weight break and a spec diffuser/rear wing to improve aero... results? suddenly slow cars like dp3.5 became faster than lmp2!
it's not about dp3.5 were fast as allowed to be, it was a deliberate power-up to let dp3.5 faster than lmp2!

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u/MidnightMulsanne PFAFF Motorsports 911 GT3 #9 Nov 18 '20

Suzuka changed quite a bit.
Also, you totally missed the point of my argument. I will keep it simple and straight forward, as usual: cars will go as fast as its regulations allows it to be. If a front-runner current car doesn't go faster than a previous generation car, it is mostly down the regulations preventing it to do so.

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u/DismalMode7 Nov 18 '20

suzuka main change was the position of last chicane moved a bit forward, but this and dunlop corner that kept the same fast radius simply don't confirm that xjr-14 was faster than gt500 as you said.
I got your argument, it was simply wrong.... as said 2011 peugeot 908 and 2017-2020 dpi have common lmp base platform and share similiar weight-power ratio (about 930x600hp)... we are not comparing a f1 car with a gt3.
I can't see any big regulations restrictions in dpi actually... oreca based cars like acura dpi could actually be a bit lighter than 930-950kg maybe but that reference min.weight is set by bop reason, same about power that is kept at about 600-620hp because of reliability reasons.
Big difference is that dpi have almost 10 years of extra aero/chassis development that 908 could not have and despite that, are still in the same performance window. That's a bit disappointing to me.

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u/MidnightMulsanne PFAFF Motorsports 911 GT3 #9 Nov 18 '20

How much of those extra aero and chassis development is neutered by the BoP, though?
Comparing then directly, the 908 had bigger air restrictors than DPi and had slightly bigger underbody tunnels as the car was a bit wider. Can't tell about DPi's turbo, but for the 908 they were limited to 3.6 bar.

And the GT500 hasn't reached XJR-14 pole time from 1991 at Autopolis, which is a track that hasn't really changed.

EDIT: Somebody is downvoting for some reason. It is not like you insulted me at any point. Or at least I didn't feel like it.

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u/DismalMode7 Nov 18 '20

in IMSA there is some mandatory bop only for rear wings profile heights and inclination in a range of values for each dpi model.... overall body aero created by bodywork and undercar aero crated by splitter+diffuser can't be bopped because you know... it's what the car is made of lol.
Here is another example you are basically writing about things you don't know... do you know why 908 had a so high pressure boost? because it was a turbodiesel car, in a turbo diesel engine ignition/combustion is given by pressure and not by sparks as happens in petrol engines! all turbo diesel engines from the one of the cheapest citycar to the one of racing prototypes need higher turbo pressures to work.
Dpi have bop mandatory turbo boost, the more the engine is larger, the lowest pressure boost it gets and reverse, but since all of them are petrol engine, turbo pressure is however lower otherwise they would get close to 1000hp with 3.6bar... mazda dpi has a small 2L and turbo boost is about 2bar for most of rpm range and revlimited at about 8800-9000rpm, acura dpi has a 3.5L V6 and turbo boost across the rpms given by bop is lower with mandatory revlitmiter at about 7000-7200rpm.
I checked also about autopolis, the track has a shorter layout as you can check in the track map of this site
https://apexonlineracing.com/community/threads/aor-gt-sport-league-pre-season-5-gr-4-ford-mustang-social-autopolis.53213/

seriously you can't really believe that xjr-14 of 1991 runs with the same times of nowadays superformula lol... and the reason is simple.

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u/MidnightMulsanne PFAFF Motorsports 911 GT3 #9 Nov 19 '20

Now you're being condescending, to say the least. I know the basic principle of those engines. I was just pointing out what was going on for the 908 at the time. But you kind of anwered yourself here, so now I believe we can move on.

And, as you can see here, they were using the full layout in 1991. Other user have made a more in dept analysis between sportscars classes here: https://www.reddit.com/r/wec/comments/i00z1y/historic_sports_car_prototypes_lap_time/

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u/DismalMode7 Nov 19 '20

It's not being condescending, it's you who wrote about 908 turbo pressure like if it was a bop factor, totally ignoring real dpi turbo petrol pressure values and the fact that a turbodiesel car needs that kind of turbo boost to actually have a working engine. You can't blame on me for your lack of knowledge.
The video you posted barely can see a thing actually, while the other link just tells that groupC cars were potentially able to qualify inside the 107% rule of f1 qualifying of the same time period, a thing that every motorsport fan knows.... also 2014 TS040 silverstone pole position would had let the car qualify for F1 Q1 of the same year....