countzero

Hi,
I'm a longtime lurker, and thought I'd finally make a contribution to the group.

I took my street ZR1 to the NASA weekend at VIR the past 3 days. I am a relatively new NASA and SCCA racer, with a Corvette Grand Sport prepared by Phoenix Performance for Touring 1 and ST-2, but my race car is finishing some repairs, so I brought my street car instead, and ran Open Practice and HPDE 3 instead of racing.

I put fresh Michelin Cup tires on the car before the weekend, and bled the brakes. After I drove to the track with cold tire pressures of 30 all around, before my first track session, I reduced cold tire pressures to 25 front and 21 rear, which gave hot pressures of about 34 front and 28 rear. This seemed to give excellent grip front and rear. I ran the car in Performance Traction Mode 5, which turns Active Handling Control and Traction Control off.

I have some prior experience driving a Skip Barber MX-5 at VIR, but not a Corvette, so I know the line, and some technique for each turn. With this background, I was quickly able to get my lap time on a very hot track (air temps ranging from 80's to mid-90's) down to 2:07.5 . For comparison, this time is better than the best race lap times recorded by many cars in NASA ST-2, American Iron, ITC Caymans, and GTS-3. The cars that were consistently faster were Super Unlimited and GTS-4. All of these race cars were of course on slicks, and have prepared and tuned suspensions, often are lighter weight, etc.

Overall, I was very impressed with how easy the ZR1 is to drive on the track, and with the performance of the carbon-ceramic brakes, which were extremely fade resistant, even with repeated braking from 155-160 on the front and back straights. The car is well-balanced, with some tendency toward understeer, which can be overcome by braking and turning technique, and throttle as needed. The car is very stable at high speed (with only its minimal aero aids of splitter, lip spoiler and side skirts), and is stable under hard braking. The Cup tires are excellent for track use for street legal tires, but they don't last long when pushing hard. My fronts are toast after about 7 sessions on track, with the rears holding up much better. The main limitation of the car for track use is engine and transmission cooling, as in these ambient temperatures the car was prone to oil and coolant overheating, as well as trans overheating, which led to significant performance degradation. If the car is to be used for extended track sessions in these conditions, it would need improved cooling of at least these systems.

The ZR1 is a serious track day weapon. The main thing I had to continually remind myself was that it is not a full race car, and has no roll cage, race seat, or safety harness. It is as capable as some of the fastest cars in amateur competition, but you have to be careful how you use it on the track, so as not to foolishly endanger yourself in what is just a street car. Also, the absence of a race seat and harness means bracing yourself with the dead pedal and with your left knee against the driver's door, which can cause a contusion or abrasion, as I now have from the weekend's activity .

Hope this is helpful to others.

X25

I'm glad to hear you had fun! Corvettes are truly amazing machines out of the box.

Compared to what Michelin recommends for cup tires (25F / 28R cold), you're putting much more pressure up front, and much less at the rear. I am not trying to suggest that you had wrong pressures, but I'd love to hear your insight on why you chose to go with those pressures. I also wonder if the high front pressure is what might have made your fronts toast and caused the understeer

countzero

You may be right. I set the cold track pressures similarly to how I set my Hoosier A6 pressures on my race car. I'm used to ignoring the recommended pressures from Hoosier, which are completely wrong for the Corvette. I did have a lot of understeer at the exit of turns 1 and at Oak Tree, and I wondered about lowering the front pressures a bit to help that. I'll try the Michelin recommended pressures with the next set of Cup tires, next time I take the ZR1 to the track.
Thanks!

911/Q45

5 gives you lots of leeway, but not quite all the way off. If you hold the T/C button down for about 8 seconds, then everything is off. Great write up, sounds like you had a lot of fun.

QUIKAG

Great write-up! I've been tracking my '10 ZR1 for about 2.5 years now and it really is an incredible track machine. If you ever get the urge, get some slicks and a race seat/harness plus a few other goodies and you'll really see how capable a car it is on the track.

OnPoint

Now come on Quik, all the anti-ZR, anti FI guys would have you believe you can't pull the ZR out of the garage without heat soaking. . . . j/k

I really am just kidding, as I know how well they run.

3LZZ06

Sounds like a great time. You really put it through it's paces and it seems the ZR1 did what it was designed to do!!!

Thanks for the great write up...

BEZ06

Excellent report!!

I put a link to this thread in the AutoX/Roadrace section. I think some of the track hounds that don't read this ZR1 section will enjoy your info.

Bob

ZZ

Thanks. Enjoyed your post and useful information.

jvp

One hundred percent of the Stabilitrak system is off in Modes 4 and 5. It sounds to me like he knew that and wanted the advantage that PTM gives without the yaw control bothering him.

jvp

...yeah... in a straight line. Right?

OnPoint

Hey now, I've counted at least 3, maybe 4 curves in the state of Ks.

Kinda neat when you come upon one. . .

countzero

Thanks for that info. I know about the long double push to shut it all down in other C6 Corvettes, but didn't know it was an option in the ZR1. I noticed some intervention to limit use of the throttle steer at slow corner exits, which I would love to have been able to use. Thanks again!

911/Q45

Mode 5 and shuffle steering, can't we all just get along?

countzero

Here's a nice link that others may have posted previously on the actual difference in performance among the modes and with PTM completely off, with Tommy Milner at the wheel: http://www.roadandtrack.com/go/news/...t-how-it-works

jvp

I don't think he was referencing the actual Performance Traction Management when he said "Traction Control" was off. Good odds he meant the traction control part of Stabilitrak.

AU N EGL

Hooked another one

cflm3

I am getting oil temps as high as 260 F at the track. I plan on putting in a larger radiator and inter-cooler.

X25

I think 260 degrees F is acceptable. As a precaution, you should run a higher grade oil like Mobil1 0W-40, though. At Bobstheoilguy, there was a test conducted on oils and they found Mobil1 5W-30 starting to break down at around 265 degrees F, but it was still lubricating well.

cflm3

I run redline 10-40 at the track now. I change it before I go on the track.