Bdburton32@msn.com

I have a C7 Grand Sport (automatic transmission) that has had overheating issues on hotter track days (probably high 80's-90's) at Dominion Raceway (VA) and Summit Point (WV).

Overall, I love the car, but I am really disappointed with the overheating issue (which I thought was just a Z06 issue). On my second 30 minute session at Dominion Raceway in June my car completely overheated, systems shut down (power steering..etc) and pretty much all the coolant overflowed. I know hardcore track guys usually go for the manual, but a Grand Sport automatic should be able to handle 4-5 track days a year. I think GM has a design flaw here because there are plenty of other cars on the track with automatics (Dodge Hellcasts, porsches...etc), with no overheating issue. So far, my dealership said this is a known issue, but there is not fix.

Has anyone made progress getting their Chevy dealership/GM to fix/address this overheating issue (which I think is ridiculous as the Grand Sport is marketed as a track car)? If not, any suggested solutions?

Thanks,

Brett

WhiteSands

dfkruger

Dewitt radiator . heat shield the front cats and get rid of the stupid plastic duct above the radiator ,Corsa extreme mid pipe . these mods worked for me . Corvettes for ever . dk

Donatella

You didn't mention if If you're letting the car shift automatically. If you are you will have a problem. If you use the paddles and short shift at around 5,000 in warm weather you should not have a problem.. The auto in track mode will hold the RPMs until redline putting a real strain on the car. I have a GS A8 that is a dedicated track car and I have never had any kind of over heating problems...

rb185afm

Bdburton32@msn.com

Thanks for the helpful info. Wow - bit of a scam marketing this car as "track ready." I can understand the need to make mods if you heavily track the car, but the cooling system should be able to handle a few track days a year without overheating. I think Chevy really blew it on this one. Anyways, thanks for th solution.

Bdburton32@msn.com

At times I let the auto shift (usually in Sport mode), when I'm on a new track and trying to learn the lines. Thanks for the info. about short shifting in hot weather.

It is what it is, but I am still disappointed in the car. Heavily marketed as "track ready," but the cooling system was clearly poorly designed if it can't handle two 30 minute track sessions. I saw other stock sports cars with automatics without this issue. Anyways, thanks and at least now I have a solution.

Thanks again!

malexand123

Dealing with same issue on my stingray. watching many of these threads for ideas.

nmbsun

It's not just C7's that run hot. My C5 has run hot since day one when I bought it new. The car has never been on the track, just on the public roads at normal start and stop traffic speeds. Had it checked out by dealer under warranty and their response was " the fans come on as they are suppose to". This running hot happens in heavy start and stop traffic in the summer at 85 dg and up. I have tried to get GM to address this but to no avail. I still have the car and after reading the posts about the new C7s and their problems I would never spend my money on a new Corvette again. I do not think that Corvette can build a sports car that will work proper in any situation. LIVE AND LEARN !!!!!!

The HACK

JMII

Does the Porsche PDK count as an automatic? My brother has one in his Boxster GTS and so far no issues. Granted in south FL we avoid tracking our cars during the summer since its just too hot for the driver.

BrunoTheMellow

You should provide details. There's no way coolant spewed before the car going into limp mode or warning you. My supercharged z51 overheats but I can handle it by short shifting. Ive never hearded of a GS even getting past 230. Let's see some data. Some videos. Cooling systems that handle 1 hot track day will handle 20 track days a year. That doesn't matter. So give us some details and we can help. Otherwise you're just complaining. Whats your oil temp? Coolant temp? Transmission temp? How many laps in. Are you shifting or just holding in gear?

Bill Dearborn

Don't remove the duct from the upper radiator to the hood. That will reduce cooling capacity. The duct empties into a low pressure area on the hood thus helps pull air through the radiator. Removing the hood lets air from all over the engine compartment exit through the hood and that air may not have gone through the radiator thus didn't provide any cooling. GM didn't pay money to put that part in there for no benefit. If it didn't benefit the car it wouldn't be there.

Experiments with the DeWitts Radiator have been inconclusive and it seems like increasing the radiator cooling capacity which worked so well on the C5s and C6s doesn't provide as much benefit as expected. Some people theorize the added resistance to air flow caused by the thicker radiator reduces the effectiveness of the radiator with a net result near zero.

I suggest you drive the car like a person driving an M7 GS would drive it. Use whatever gear is comparable to third in the Z51 M7 gear set, 4th which is 1:1 and 5th. Fifth, gear usage on M7s is more than likely limited just as much as it is limited with C7Zs. I don't know if the Z51/GS A8 has the same gear ratios as the Z06 but I recommend only using 4th, 5th and 6th gears in an A8 Z06 while running rpms up to above 6K in those gears. It isn't so much about avoiding going over 5K rpms as it is not running high rpms in the lower gears where speed is lower and air flow through the cooling system is lower. For example 90 mph in 3rd gear might be well over 6K rpm but 90 mph in 4th gear would be below 6K. I regularly run my C7Z M7 to red line in 3rd and 4th gears where the track permits with no temp issues.

At the last NCM VIR event I instructed a Novice driver in an A8 GS, her husband was co driving the car in another session and he and his instructor would come in from 20 minutes of track time and she and I hopped into the car and hit the track for another 15 minutes. She drove in Auto Mode. I don't know what mode he used. I saw no problems with over heating during the first day of the event. The second day was a wash out. The net is the car was seeing almost 35 minutes of on track at speed operation with no overheating.

Bill

archfarseer

I have a 2018 GS A8 and tracked 3 days at COTA (fast track) and 5+ days at MSRH (slow track). No overheating, not even close. However I never auto-shifted.

BrunoTheMellow

Eh sort of... Remember that while exhausting out the radiator is a good thing, manufacturers have to engineer for worst case scenario too. What if the customer drives in heavy snowfall, what about heavy rainfall, can I shoot a hose at the vents and hit something I shouldn't if I didn't have the duct, does it affect paint quality, on and on. The duct actually blocks quite a bit of air from the radiator.

I am going to test this with actual data on track in 3 weeks. 1 session with both parts of the duct and 1 session without.

Also, a random question I can't find the answer to. Does the radiator fan turn off past 35 mph if the car is above X degrees? I know it turns off under normal temps but does it come back on even while driving fast? If it doesn't come back on, then I am building up the courage to trim the excess plastic on the radiator fan shroud to help with flow at the track.

jaybar

RF School is in Los Vegas. I was there last August don't think anyplace could be any hotter. And none of the cars in my class including z06 had any overheating problems.

The HACK

PDK is a double clutch "manual-matic." Automatic transmission with torque converters and planetary gears generate significantly more heat than the traditional gear based manuals and manual-matics like BMW's DCT or Porsche's PDK. While these transmission still generate heat and some may require aux cooler, nothing requires cooling like traditional autos because the torque converter generates heat via fluid friction, and the planetary gears generate heat because all the planetary gears are all spinning at the same time, unlike a manual, a DCT, or PDK where only the engaged gear is spinning along with the input and output shafts.

In order to keep an automatic's gear oil, same fluid that the torque converter uses to transfer friction across fluid couplings, cool, most modern cars use MULTIPLE heat exchange cores for automatics, sometimes a dedicated cooler, a coolant to gear oil heat exchange, and a engine oil to gear oil heat exchange to keep automatic fluid operating at a reasonable range. For any sort of oil based lubricant, any 20 degrees above operating temp of 210º basically HALVES its usable life, up to about 315º where most motor oil "flashes" and boils. So for automatics that does not have ways to shed heat fast enough, most ECUs that monitor transmission temp will cut power past 285º as continued operation for gear oil at this temp dramatically shortens its usable life.

In cars with coolant and motor oil heat exchangers, using the radiator or aux oil cooler to add cooling to transmission fluid, this adds heat and strain to either the coolant or engine oil temp. Most modern engines will start cutting power to engine once engine oil temp goes past 290º, as any sustained operation above 300º you run a high risk of oil flashing and engine losing lubrication, and I believe engine power will be cut at about 270-275º for coolant temp (at that point the pressurized coolant can no longer evacuate heat fast enough through the radiator).

Autos require a lot of creative ways to keep the transmission and transmission fluid cool for track use. Where as the traditional 4 or 5 speed autos have fewer planetary gear sets and do not generate heat as much, the new 8 and 10 speed autos are just a freakin' oven for gear oil.

The HACK

I've never done Ron Fellows events, but I've done a few drive and follow events in very similar format with BMW ///M school. The amount of "pushing" and heat generated at a solo'ed HPDE vs how lead follow events generate heat is entirely DIFFERENT.

Anecdotally, few club racing/HPDE instructing friends and I attended a BMW ///M school once. We didn't tell the organizers who we are, as we were just there to enjoy a hot and fun track day. As we went out for our first orientation laps, you can tell the "lead" instructor kept his pace down in the turns and floors it on the straights, so your average driver who hasn't gone through a ton of DEs would think they're pushing these mighty M cars HARD, when in reality they're not driving past what we considered 5/10th in the twisty part. But even at 5/10th and leaving a ton on the table, it feels fast for most people. But at that corning pace, you're not really pushing the car close to what it's designed to do.

Anyway. After the first lap the "lead" instructor quickly realized he's got people who knows what they're doing behind him, as all 3 cars remained GLUED to each other's bumper as he floored it on the straights. By lap 3, we were all driving at about HPDE pace, maybe 8/10th and still all glued within inches to each other's bumpers, but at that point, we were basically lapping slower traffic (they put 2-3 groups on track at the same time) every 3-4 laps.

Needless to say, when we pulled back into the pits, the lead instructor for our group had a huge sh*t eating grin on his face. Said to us, and I'm paraphrasing, that he doesn't often get to "push" and thanked us for the opportunity.

Having done enough of these type of events in almost 20 years on track, I can tell you that any of the Ron Fellows instructors know well enough how to control the speed through the turns to not overheat these cars, and still give the participants the "drive" of their lives. Trust me.

Dane@LGmotorsports

There are a lot of opinions and conjecture on the topic, but we can help resolve this issue. Give us a call 972-429-1963.

Thanks!

Dane

Deepdiver

Looking forward to your findings...