maniac719

Just got back from VIR with my street car (C5 race car is broken), and man what a track. It was a two day event where we had access to pro instructors and data analysis (amazingly valuable).

The good:

Amazingly great track for the Corvette! The track is FAST and technical. Car ran a best recorded PDR lap time of a 2:05.7, the AIM data from my SoloDL shows a slightly better rolling lap time but I was fighting traffic most sessions.

The bad:

In 93* heat, the car wouldnt last more than a few laps at full attack on a 2:05-2:06 second pace. I was down 3-4 MPH on the straights after the second or third lap and then I was into limp mode pretty soon after that. Toward the end of one of my sessions after hitting limp mode and taking a cooldown lap I came up on a new grandsport and while I was quite a bit faster in the corners I sure wasnt running away from him on the straight, I really suspect that car is quite a bit down on power after it gets hot. For the record I was running 100 octane all day long as an insurance policy against KR. In addition the car was popping out of third gear after a downshift and hard braking.

TL;DR:

2015 C7 Z06 runs 2:05s at VIR until it gets hot, falls off a little bit until it overheats into limp mode.

Conclusion:

Thinking about buying a C7 Grand Sport to avoid the overheating issues. Is there enought data out there to say that they dont overheat running at 10/10ths?

topmover

I hope to be able to answer that question in a couple of weeks as my new GS is planned for a trip to Sebring next month. I was just there with my ZR1 on a very hot week end so I'll be comparing my personal notes on temps between those two. I used to run my previous ZR1 4 or 5 years ago at VIR running between 2.02-2.04(on the old pavement layout) and it never over heated. I'm very curious to see how the GS does in the heat.

maniac719

I'd love to know how it compares, surprised you never overheated the ZR1 running at that pace. The Z06 was very hot all day long.

thebishman

Just get the secondary water radiator installed at the dealership. Problem solved and warranty intact. Plus a lot cheaper than trading the car in.
Bish

BEZ06

When you got the limp mode, what lights illuminated, or what messages did you get??

I have run VIR and Daytona in ambient temps similar to what you experienced, and my 2016 M7 Z06 hasn't had any overheating problems or limp mode at all. I did however just install last weekend the secondary radiator that comes standard on the 2017 Vettes with M7. It should cool down the engine coolant and oil temps 15° to 20°.

If you got the limp mode with no lights/messages, you probably had a CAC problem. If the intercooler pump cavitates it shuts down for 3 minutes, the IAT2 spikes, you get a limp with no messages/lights/codes at all.

.

maniac719

I did get a message "engine overheating idle engine". Also got a really weird behavior on day 1 where the motor wouldnt rev with no messages as if it was in limp mode. Was my last session of the day, felt like it wasn't opening the throttle body as quick as was commanded. After a bit of cool down and street driving it resolved but I cleaned the throttle body anyway and that problem didn't resurface.

Also looked at the data and it was down 6mph on the straights.

Poor-sha

Here's a video of me running a 1:59.2 at VIR in 95F heat. This is the full session video and as you can see I'm not really babying the car. Only cooling mods are the secondary radiator. Stock motor with DSC controller and Tractive shocks, Pirelli slicks, and AP Racing brakes. Non-Z07 car.

Poor-sha

Also, I do agree that the car loses power after being driven hard for a while. This video is earlier this year at VIR. If you skip to around the 15 min mark you can see me catch and eventually pass a C5Z race car. That was Randy Pobst driving another instructor's ST2 car.

While I was able to catch him you can see that he had to eventually lift on the back straight for me to complete the pass. The owner of the car says its a stock motor.

Bill Dearborn

I have had a drop off in power over the course of a day with top speeds dropping 5 to 6 mph. However, I never got close to overheating the coolant or oil. I do have the Secondary Radiator installed and from comparing data that BeZ06 took at the same event I was at the Secondary Radiator seems to knock off 10 to 15 degrees of oil and coolant temps. That might be worth looking at Vs trading cars.

One thing about the Z06 is it weighs a little more than the GS and it also has more downforce so it doesn't take a big drop in engine power to bring the car into line with C6Zs, C7 Z51s and GSs from a top speed standpoint.

I have had only one time where I had a significant drop in power and that was when I was at Watkins Glen last year. After the second session of the first day all 4 tires had slipped on the rims and the car was vibrating badly while on track. It was like being in one of those vibrating chairs with the vibration set to max. From that point on my top speed dropped around 15 mph and the car was performing similarly to what my 97 C5 with 345 HP used to run. There were no codes, no warnings, coolant and oil temps were in a good range with ambient temps in the low 90s but the car was sluggish. I suspect the knock sensors were picking up the vibration and reducing timing.

At VIR and CMP I have never had a drop off in power that was similar to that.

Bill

maniac719

Nice driving, secondary radiator for sure this season. How do you like the DSC and shock setup? I've been trying to avoid the rabbit hole of modding this car so I can always show up at the dealer without any questions, if my C5 racecar wasnt broken I wouldnt have driven the C7 at VIR.

I've also heard good things about the Pirelli slicks, stock wheels?

maniac719

Poor-sha, what tire was on your car? It looks like you were really wheeling.

Poor-sha

Absolutely love the DSC setup. That plus the AP Racing brake kit are all you need. In my experience the Pirelli scrubs seem to stick as well as Hoosier A's and last about twice as long at half the price. I'm running an 18" setup. 18x11F and 18x12 rear. I was running 18x13 rears but the slicks were stretched and they contact the UCA at full droop.

Those were Pirelli slicks. What was funny is that I didn't realize until later that the LF shock was unplugged and as a result was full soft all the time. I knew something was off with the handling that day but it took another day to finally figure it out.