Ever wonder how fast Trans Am/GT1 car is Vs a WC Vette? Options

[FASTFATBOY]

Mike Skeen at the wheel, those two Stangs are making some grits under the hood.

http://youtu.be/FKpWiT0A_9A

[Beach Cruiser]

Mike Skeen at the wheel, those two Stangs are making some grits under the hood.

http://youtu.be/FKpWiT0A_9A

Thats an awesume vid and great timing! I'm headed to VIR on Friday and now I know the line better! Wonder what happened to the red mustang over the hill? That is a scary place because you can't see what's over the hump, and to be fast you have to be to the left on the gas over the hill and drift out to the right and hit the gators there. My best time there is a 2:14 in a full weight, bolt on only car. I'm sure he was running under 2 min laps.

[FASTFATBOY]

Mike Skeen at the wheel, those two Stangs are making some grits under the hood.

http://youtu.be/FKpWiT0A_9A

Thats an awesume vid and great timing! I'm headed to VIR on Friday and now I know the line better! Wonder what happened to the red mustang over the hill? That is a scary place because you can't see what's over the hump, and to be fast you have to be to the left on the gas over the hill and drift out to the right and hit the gators there. My best time there is a 2:14 in a full weight, bolt on only car. I'm sure he was running under 2 min laps.

He lost a wheel, watch it again.

[JACE323]

Holy hell. those mustang were moving on the straights. I know the world challenge cars arent to crazy in the horsepower department but that was rediculous.

[198esp]

Talking to some of the vintage trans-am guy at njmp,even most of them were north of 800hp

[StanIROCZ]

those two Stangs are making some grits under the hood.

thats no joke

[Beach Cruiser]

Wonder if the white mustang got as much damage? Looks like he also went off track. The red one looked like it rolled after he lost the wheel. Since Mike had a clean restart and clear track, I'm guessing so. And yeah, they both had some balls!

[StanIROCZ]

That White Stang had a bunch of grunt but it is interesting how much of that time Mike gained back in the braking zone. I'm guessing a big part of that is ABS versus non?

[dailydriver]

Talking to some of the vintage trans-am guy at njmp,even most of them were north of 800hp

Yes, forget about WC spec cars, it would take a TOTALLY UNRESTRICTED C5/6R (the 7 liter ones, of course) to compete with a Trans Am/GT-1 ride, on anything larger than a Miata/S2000/Elite autocross course! (IMG:http://www.frrax.com/rrforum/style_emoticons/default/wink.gif)

This post has been edited by dailydriver: Oct 9 2012, 10:23 PM

[Beach Cruiser]

That White Stang had a bunch of grunt but it is interesting how much of that time Mike gained back in the braking zone. I'm guessing a big part of that is ABS versus non?

I noticed that too, and Mike has so much seat time at VIR which could also be a factor.

[mr.beachcomber]

Actually, I would say that it was the result of better threshold braking by Mike given equal braking capabilities between the two cars.

As a driver, you want to use your brakes to the threshold of lock-up and not activate ABS (which will result in longer, not a shorter, braking distance).

Once you've activated ABS, all you can do is stay on the brakes until the car slows down to the point where you re-gain control and by lifting off the brakes.

[StanIROCZ]

As a driver, you want to use your brakes to the threshold of lock-up and not activate ABS (which will result in longer, not a shorter, braking distance).

I suppose it depends on how good of ABS system you have and how good of a driver you are. When I talk to the new Vette and Mustang drivers they basically use the brakes as an on off switch and let the ABS do all the modulation. They also go twice as deep into the braking zone as I.

Without ABS you are limited by the tire with the least amout of traction (assuming your front to rear bias is optimized). If one wheel goes into a dip or goes over a smooth patch of tar it is going to lock up before the others which means you have to let up on the pedal. With a good 4 channel ABS it will pull pressure only from that one wheel while still maintaining the pressure to the others. Basically it acts as a 4 wheel LSD. I don't see how even the best driver can do better than that.

It is also very possible that Skeen knows his way around that track very well,.

[mr.beachcomber]

I suppose it depends on how good of ABS system you have and how good of a driver you are. When I talk to the new Vette and Mustang drivers they basically use the brakes as an on off switch and let the ABS do all the modulation. They also go twice as deep into the braking zone as I.

It sounds as if the Corvette and Mustang drivers you've talked with are making the same mistake the C4 Corvette drivers made when ABS became standard equipment back in the mid 80's. We thought that we could dive into a corner at higher speeds, brake later, and that ABS would take care of the rest. Didn't happen that way as once ABS kicks in one or more wheels is alternating between lock-up/free wheeling and braking thereby increasing the braking distance needed to whoa down the vehicle. Still, for the average driver, ABS will pay for itself the first time that it save's the driver from a nasty accident either on the street or track. That's why there's an ABS system on the 2012 ZR-1 for us street/track drivers while the Corvette C.6R race car doesn't have an ABS. (Nor do F1 cars, buts that's because I'm sure that there are systems out there like what you described below that can perform faster than a driver can react to locking brakes.)

Without ABS you are limited by the tire with the least amount of traction (assuming your front to rear bias is optimized). If one wheel goes into a dip or goes over a smooth patch of tar it is going to lock up before the others which means you have to let up on the pedal. With a good 4 channel ABS it will pull pressure only from that one wheel while still maintaining the pressure to the others. Basically it acts as a 4 wheel LSD. I don't see how even the best driver can do better than that.

Good write up and explanation of how a good system should work. I'm sure that there are ABS for racing that do just what you described, but I just haven't had experience with one that good on a street car yet; although I would like to try out either the 2012 Z06 or ZR-1 ABS just to see how well they function. (The 2012 Vette's Performance Traction Management system will allow the driver to turn everything off except the ABS.) Just based upon my own driving experience in a Z51 C4 and a C5 Z06, a good driver will always out brake an ABS using threshold braking. Still, would like to hear from any other auto-x/track drivers that rely upon ABS for their shortest/fastest braking performance.

It is also very possible that Skeen knows his way around that track very well,.

That's a distinct possibility too as Mike definitely knows his braking points at VIR very well!

[StanIROCZ]

It sounds as if the Corvette and Mustang drivers you've talked with are making the same mistake the C4 Corvette drivers made when ABS became standard equipment back in the mid 80's.

I don't think they are. I don’t claim to be the best driver and I know that I have a lot of time left in the braking and corner entry areas of the track. But one thing that is for sure is the C5’s and new Stangs are braking significantly later than I would ever dare. My limiting factor is a wheel locking up and I haven’t pinpointed if it is consistently the same one or not so it could be a mechanical issue.

American Iron racers will tell you that the new Stangs go ~100 feet deeper in the braking zones than they can. Because of this American Iron has put a weight penalty for ABS.

A friend of mine is an engineer for an ABS supplier has told me that the ABS does targets individual wheels. I know old ABS systems can be a POS and may not do this but I think the modern systems are very good.

Alan retrofitted a C5 ABS system on Ken Kurtz Formula and I believe they have noticed a big improvement. Maybe one of them will read this and confirm.

[nape]

American Iron racers will tell you that the new Stangs go ~100 feet deeper in the braking zones than they can. Because of this American Iron has put a weight penalty for ABS.

A friend of mine is an engineer for an ABS supplier has told me that the ABS does targets individual wheels. I know old ABS systems can be a POS and may not do this but I think the modern systems are very good.

Alan retrofitted a C5 ABS system on Ken Kurtz Formula and I believe they have noticed a big improvement. Maybe one of them will read this and confirm.

It depends on the corner, but the biggest advantage to ABS is that it will let you brake through turn in and you won't have one-wheel lockup like you might without it. Sometimes, that will let you go in deeper, but it won't save you if you go in way hot. It will save you if you are only moderately stupid though.

It's not an end all, beat all, but it does help a mediocre driver look better.

[matt f]

From what I hear, the Ford Racing ABS is better than a good, or even great driver. This is why there is the weight penalty, to let everyone else catch up.

[mr.beachcomber]

Sounds like the Ford has managed to build (and program) an ABS much like Stan was referring to in one his posts above. A computerized system can always react faster than a human to changing, variable inputs. The C4 Vette's ABS is pretty much an all or nothing type of system on the road or track. The C5's ABS is much more adaptable to individual wheel conditions. (It's fully integrated into the traction control system.) The C6's ABS is supposed to be awesome period. Maintains vehicle stablity in the wet (which is hard when you're constantly hydroplaning)!

Here's a link to Dennis Grant's page on ABS. (For those of you that aren't SCCA auto-xers, Dennis is a Chrysler Engineer and one of the primogenitors of the popular Street Modified class which allows just about every mod you can think of except slicks and a stripped interior.) Notice that Dennis describes a peak in braking just prior to activating ABS. Hitting that peak is the target and is extremely hard to do consistently. Still on a dry surface, it's faster braking than activating ABS in my experience. However, ABS in the wet is an absolute requirement when running w-i-d-e tires either on the street or track. (Drove a friend's 2007 Z06 on the back roads of NC, and that Vette would activate ABS for dew on the road! Very Impressive.)

[STFU racing]

Very impressive...I could never road race because once I did, I would be broke as hell because I have a feeling I would enjoy it too much.