Snorman

Ran the car at Sebring this weekend with Chin Motorsports. I wish I could say it was a good track weekend, but three oil-downs, a rain session and lots of slower traffic sort of ruined the weekend.
Only decent session was the last session on Sunday. I followed my buddy out in his '15 GT3 for some fun lead-follow. But notwithstanding any cooling issues, the Z06 is faster.


About 23 minutes in I got an over-temp shutdown accompanied by a power steering warning (note: the PS felt normal, contrary to other reports of varying levels of resistance). This was basically the entire session...we pitted out a minute or two after the track went green and the GT3 passed me while I was on the hot pit and got checkered. Ambient temps were 92-93*, windy and dry. I am on the last of the brake pads in this session (fresh pads) and it reflects in some early braking, particularly in T7, T10 (where I have had a few previous occurrences) and T17. I 'think' there may be a difference in the pad compound GM is installing during assembly and that which is offered by AC Delco/GM parts. Max water temp was 262*, max oil temp 302*, max trans oil temp 235*. The car was driven in manual mode.






Pretty confident I could have pushed the car to a ~:25-26 today, and probably a :23-24 in cooler weather...maybe a tad quicker. But first time out at Sebring with it and happy to put in on the trailer as it came off two days ago. I'm not very fast at Sebring, but Roebling in two weeks.
S.

Movie Muscle

Nice post and with full real world data. Coolant and oil temp certainly got up there on 7 and 8. How much pressure is the cooling system under? Haven't taken a boo at a manual or cap on anyone's cZ as of yet. Cap has to be better than 15lbs ...265 is pop for a 15lbder. Guessing a 20?

lawdogg149

Nice driving. Haven driven sebring quite a bit I found my self bouncing in my office chair over the bumps with you. Love that place. Looks as if you had the same results as me when I chased a GT3 around Rd atl. The cars are close in performance with the slight edge going to the Zo6.

Snorman

It is a pretty rough track. My buddy could tell that I was holding back in a number of places around the track and giving him room. There was a particularly well driven black 991 GT3 out there that was probably 2-3 seconds faster than I was.
While it was a crappy couple of days, a crappy couple of track days is better than no track days at all. But the damn heat. It was about 8-10* above average and windy as heck yesterday. I'm sure in better weather the car will pick up a couple seconds. Won't be back to Sebring until Oct or Nov.
S.

C7_Z06

Sean what do you think about the high-temp shutdown now? i.e. GM failed to address in maintaining consistent performance... or just too darn hot and the C7 can't handle it lap after lap? Were there any other cars that same day which experienced the same issue?

Snorman

It was really hot, and pretty much my personal limit for a track weekend. The temps were in excess of GM's 86* claim, but only ~6-8* (saw 94* on the display and in my truck yesterday afternoon). That being said, I'm not sure it would have fared much better at 86*. Also consider the fact that if I was driving the car harder, that 23 minutes might have been shorter.

I think GM could solve with some modest adjustments to the cooling system. I can't fathom that a more efficient radiator core would not solve much of this and a revised/upgraded/external oil cooler would do the rest. My buddy's GT3 was running 235* coolant temps, so ~25-30* cooler than the Z06. From a cooling perspective GM should be able to address this. But they didn't with the C6 either. You don't have to look very far to see people who had coolant and oil temp issues with C6 Z06's while on-track.

Personally, it is yet to be determined if this is a huge issue for me. I'll run the car at Roebling and the temps will likely be low-mid 80's. After that I'm taking much of the summer off (RR will be days 11-12 on-track this year), so the car won't come back out until September.

I would like to see GM offer a few upgraded components, but can see the logistical fallout from trying to retrofit 5000+ 2015 cars with it.
S.

NineBall

Sean,

I appreciate the solid data you share, and nice driving on that video. I've been looking for a another track car to split time with my others, and was waiting on these high temp results from the C7Z06. I'm not liking what I'm seeing on their temperature management. The cars do appear phenomenal with potential, but durability and consistency also matter to me. I've had a few GT-R driving friends that could only do half sessions before pitting, rather frustrating. As it gets hotter outside, it seems that this Corvette will be similar.

At this point, I'm comparing the C7Z, C6Z w/ Z07, ZR1, and Gen 4 ACR. I'm leaning C6Z with the carbon package, in terms of bang for the buck. I like the removable roof on the C7Z though, and think it looks better than the C6. First world problems.

Are you having any regrets about not getting an M7? Or do you still prefer the drag racing advantage over the road course overheat issues?

Tony

soulsea

fify

On a serious note ... that's some great driving Sean!

Checkmate1

Damn shame about the C7 Z06.

Germans seems to manage temps a whole lot better consistently. As someone who tracks regularly, my M3 has never seen Oil Temps above 250'. This is with a DCT Transmission. (Knock on wood).

So much for putting a deposit down on the C7 Z06. Damn shame. I really wanted to get the car this year.

Redc8z06

Has anyone that tracked changed to coolant ratio? Antifreeze vs water? Water dispenses heat better than antifreeze and I know the owners manual says to change the ratio if tracking. I believe our cars come 50/50 and GM recommends 70/30.

georgehitch18

I noticed you said the track was rough. Did you try sport mode to see if a tad softer mag ride would perform better?

king awesome!

I live in Arizona and after tracking the car once i had the dealer change the water/antifreeze ratio to 90/10. They also added an anticorrosive agent. BIG difference! Obviously conditions were different and i can't give you an exact, detailed, side by side comparison, but the car ran about 15 to 20 degrees cooler in similar temperatures. I drove the car hard on a twisty 1.2 mile track, two thirds in second gear, the rest in third and my max temperature was 286. It is an M7 with headers, intake, tune and cat-less x-pipe. For some perspective, there was a new A8 at the track and he overheated after six laps on the first session. he overheated again on the second and third and called it a day. he was running a stock car with a 50/50 mix.

thebishman

The stock mix is 40/60 antifreeze/water iirc.

thebishman

Sean,

What approximate rpms were you changing up at if you remember?

MavsAK

For sure I'd get a Dewitts then.

Seems about like that's the first thing anyone who drives their cars hard, should do with a Corvette, gen to gen. (4 gens running now of GM putting inadequately sized/not enough cored radiators in their cars!)

Snorman

Yeah...the GT-R trans and oil cooling issues are well documented and the fixes are not cheap.

Of the options you listed, only the Gen 4 ACR would be a consideration for me and in fact, was for a period last year. Not only because I think they are the best looking of all the Vipers produced to date, but they are a simple and solid track car. However, I started weighing the availability of parts, and costs to repair/replace and if there was ever an off-track that caused even modest damage to the car, it likely would be a total loss. As you know, value of a Gen 4 ACR is probably ~$70-80k+. You can very easily do $35-40k damage to one. That's likely why you do see so many Corvettes, older 911's, etc. on-track.

The A8 and the water/oil temps are issues that are independent of each other. I am pleased that the A8 seemingly is very solid on-track with temps only hitting 235*. Both the M7 and A8 cars seem to have somewhat marginal water and oil cooling. I've always tracked a manual transmission car, and was somewhat hesitant to get the A8. But after four track days no regrets. It's actually kind of neat. And as I said, it seems like lots of the GT3 guys are running those cars in automatic mode. It's where things are headed. I have no predispositions about what trans somebody runs on-track as I think effective shifting techniques should be requisite to include heel-toe downshifting.
S.

Snorman

It really depends. I would stretch out the shifts a little heading into T1, Bishop's and T17 but typically kept them in the ~6k range. I would also run 4th to ~6k heading into T2 rather than upshift to 5th. But I'd shift at 5500 through T6 toward T7 and through T8/T9 heading to T10. Of course, if there was traffic (and that was much of the weekend) those might change because I might not need the extra rpm. But if you look at the :27 and :28 laps those shift points are pretty accurate.
S.

Cyclone09Z06

Sean, very nice lines, your buddy with the GT3, well not so much lol. The A8 sounds great and the trans temps are fantastic! I'm running this Saturday and I will be short shifting and staying in 3rd, grrrrr. I would like to bring my temps down and it looks like this is the best way. I may even try running without the chimney to see if it lets the heat out. Thoughts? Frank

dvandentop

so you think the Delco pads are better or worse then the stock factory pads? didnt see much explanation on that.

OnPoint

Given low to mid 90s ambient temps, not a bad as I feared it might be.

That's fairly damned hot, for the driver let alone the rig.