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I now have 4 track days (3 different track) under my belt on the Z51 A8.
Track 1: Air temp 60F, gears used 3, 4, 5, going easy on the transmission 4 shifts per lap (6 would be faster). Lap time 1:17, average speed 85MPH.
Track 2: Air temp 50F, gears used 3,4,5 also going easy on transmission 4 shifts per lap (6 or 8 would be faster). Lap time 1:27, average speed 66MPH, a bit tight in places.
Track 3: Air temp 40F (cloudy, mist), gears used 3,4,5, going easy on the transmission 6 shifts/lap (10 would be much faster). Lap time 2:24, average speed 85MPH.
Manual mode, track, TCS off were used on all tracks.
Almost all upshifts were done at 5,500-6,000 RPM, with only one per lap near redline. All down shifts were done at the very last possible moment in the braking zone to minimize down gear RPM.
On all tracks transmission temperature shot up quickly (by lap 5-8) to 275-279, at which point both I and the computer started fighting to try to cool the transmission. Shift commands became unpredictable and I ended up doing a cooling lap and pitting in.
Water temps were fine, never exceeding 225.
Here are a couple of typical sessions - they all look very similar, and air temperature didn't seem to make much of a difference (first one was at 65F track 1, second one was a bit below 50F, track 2). Please note that the out lap is missing from the first screen cap, don't want anyone to think the car entered the track already hot - it was sitting off for over an hour.
The transmission overheating issue is presently the only issue preventing me from fully enjoying the Z51 on track. Everything else, braking, handling, PDR, tire temps/wear, has been great.
Solutions I am considering, but waiting for someone to post actual before/after temp drops:
1 - C7 Vent Enhancer add on scoop to the side air vents.
2 - Replacing side vents with Z06 style.
3 - Exhaust wrap around the transmission area.
Out of the 3, the only one that I would not mind doing myself is #1. The other 2 seem to be a lot of effort.
If anyone has actual before/after data on what has worked to reduced either A6 or A8 on track temps, please post here.
If you can tell me where to get the data in your table I will see what my temps were a few days ago when I ran at the Track. Ambient temps were around 83 F. I ran on auto mode and let the computer do its thing. I have wrapped my exhaust with volcano wrap. I was watching the data on the screen and oil temps got to about 270 and stayed there and trans temps were about 270 also and did not climb any higher. Water temp was steady at 210.
If you can tell me where to get the data in your table I will see what my temps were a few days ago when I ran at the Track.
Download the Cosworth Corvette tool to your PC. Copy the PDR video file to your PC. On the Cosworth open the file. On the top you will see various parameter tabs. Choose Vehicle Health.
It would be great if you had before wrap and after wrap files to compare.
It would be good if you could also look and post your tire temperatures as well (different tab).
With the transmission in Auto mode, you may be masking the problem, because the transmission will start to stay on a taller gear, not downshift aggressively, etc once it hits high temps.
But any data would be welcome. Also, could you tell us how long it took to do the exhaust wrap? Did you put the car on a lift to do it? Is that something that a Performance shop would do?
Thanks for the heads up on the Cosworth data. I never knew about that. What a sweet data package. I will play around with it and see what I can view. I attached a pic of my temp data. What's interesting is that even though my air temp was much higher than the days you tracked my highs are about the same as yours. I don't have a baseline before I installed the exhaust wrap. It is surely something a speed shop can do. I did mine on my own on ramps and wheel stands in the back to get me 10" off the ground. I don't know if being in auto restricted anything but it did not seem like it did to me. It held gears and rev'd to redline every lap.
What's interesting is that even though my air temp was much higher than the days you tracked my highs are about the same as yours.
Yes, that is the one thing that gives me hope that things won't get much worse once we are into high summer temperatures. The temps seem to be relatively independent of air temp.
Which makes some sense. When the transmission oil is near 300F, the difference in the cooling air being 80F or 50F is only 10% of the fluid temperature. Shouldn't make that huge a difference.
Yes, that is the one thing that gives me hope that things won't get much worse once we are into high summer temperatures. The temps seem to be relatively independent of air temp.
Which makes some sense. When the transmission oil is near 300F, the difference in the cooling air being 80F or 50F is only 10% of the fluid temperature. Shouldn't make that huge a difference.
i read a post thaf said that the Z06 scoops did not make a big difference. Is it worth a $250 and a few hours of work experiment is the question I have. I think I will first pull the inner fender liner and check the fitment of the duct to the cooler first and seal that up good. I have another track day scheduled for the end of the month and I will see if this makes a difference before I buy the scoops
I think it is interesting that GM seems to have solved the A8 track temperature issues in the Z06. There is a thread where the Z06/A8 was driven hard at Daytona/Sebring at high temps and transmission fluid never got above 235F.
I'm babying the transmission on the Z51 and even at 39F air temp got the transmission to 280F.
But given that the Z06 has the different cooling scoops, bigger transmission cooling radiator, and additional transmission cooler, it is hard to tell if the scoops alone will make a difference.
Running stock EXCEPT DEI Exhaust wrap near tranny and rear diff. My first outing in C7 so was taking easy but have done Watkins Glen 10 times- Group 3. Ran both Auto and Paddle- not much difference in temps. Ambient both days 40-50F (cold) Baron at same event.
Cosworth:
Water 196-210F range, start was ~ 185 F each session
Oil P- 35-53 PSI again pretty consistent this range both days
Oil T- 196-266 F , start ~ 150F A8 Tranny- 150-262 F, Start ~ 127 F, in lap peaked 270 F
25 minutes sessions, Ave Speed ~ 83-85 MPH, Max 142 MPH back straight/ 130 MPH front straight.
Threw CEL day 2- "misfiring".
First outing was taking it easy but I think the DEI exhaust wrap does aid in control A8 overheating
I am sure you guys heard by now that the 2016 Z51 will come with front mounted secondary transmission cooler similar to the Z06 setup. The Z06 A8 doesn't overheat on the track (the Z06 engine is a different story). I am seriously looking into adding a secondary cooler option.
So are you saying Chevrolet is not gonna do anything about this on the 2015's?
Originally Posted by AliZ51
I am sure you guys heard by now that the 2016 Z51 will come with front mounted secondary transmission cooler similar to the Z06 setup. The Z06 A8 doesn't overheat on the track (the Z06 engine is a different story). I am seriously looking into adding a secondary cooler option.
Ok I had a track day yesterday. I had previously added thermal wrap to the exhaust next to the trans and had a max trans temp of 277. I added the Z06 fender scoops before my event yesterday and I don't think they made a big difference. Same track, but ambient temps were a bit higher yesterday, about 90 F compared to mid 80's before. I did get the dreaded "high transmission temp, Idle engine" at the very end of one of the sessions. I had been leaving the trans in Drive and let the programming shift for me, but the programming is so aggessive it drives the trans temps up quicker. I ended up using the manual shift mode and short shifted a bit and it helped keep the trans temps from climbing so fast. Reviewing the the data this morning a couple of observations.
1) the programming in the transmission when it's in drive is awesome, but it holds the gears real long and keeps rpm way up. When I manually shifted I could keep the trans temps from climbing as quick by keeping Rpm's lower
2) if you look at the data the trans temps continuously climb. They never flatten out. That tells me that airflow across the trans cooler is not the issue. The z06 scoops may add airflow, but if the cooler does not have enough surface area to transfer the heat then increasing airflow will not help. I think that's what I am seeing. Only way to fix that is to add more cooler area with a bigger cooler , or a second cooler which sounds like the 2016 will have. I guess I will wait until I can get those parts and add it to my 2015.
3) manually shifting and keeping Rpm down helped slow the climb of the temps and will be what I do going forward.
A couple of data shots from Cosworth.
Session with the car in Drive.
Session manually shifting
As a side note there was a 2015 Z06/Z07 there and he was bad fast...... For 4 laps, then his engine temps got high and he went into limp mode and came off the track while others continued on. A lot of attention from folks at the track on that car. Good because they loved the look and performance, but bad because it could not run a full session.
Thanks for the info and damn that transmission gets hot quickly. I really want an A8 but the overheating on the track has me wondering should I get the M7 for those 2 - 3 track days a year to avoid issues. If it was mainly a track vehicle then yes definitely get the M7 but I only do a few track days a year. And it seems that the DEI wrap really helps.
For 2 - 3 track days a year if you want the A8 and dont wanna shift gears get it. You will love it. It will be fine at the track. You need to be OK with making a few mods to keep the temps in check, or pull off early in a session if the temps get to high. 2-3 times a year its clear you are just out for grins and you will get plenty of those. Dont get a M7 just for those few track days if you mainly drive street and dont want to row gears. I track my A8 twice that and make it work.
Originally Posted by vader03
Thanks for the info and damn that transmission gets hot quickly. I really want an A8 but the overheating on the track has me wondering should I get the M7 for those 2 - 3 track days a year to avoid issues. If it was mainly a track vehicle then yes definitely get the M7 but I only do a few track days a year. And it seems that the DEI wrap really helps.
I voted - has the question been submitted? I can't get passed 12-14 min on track, even though I keep it in manual mode, shift way before redline, and restrict shifts to as little a 4 shifts per lap. Outside air temperature seems to make no difference from 39F to 85F it always overheats at about the same time. Runs a bit longer on tracks with long straights where you spend several seconds per lap in 5th gear - but even that only buys you a couple of minutes.
If I tried to rung aggressive laps with redline shifts and optimum shift, I'm afraid I would never even get to the 10 min mark.
From other owners attempted fixes, we know:
1 - Adding the Z06 scoops and even a giant home made one didn't help much or at all.
2 - Wrapping the exhaust with DEI tape didn't solve the problem.
3 - A6 and A8 both overheat.
4 - Adding the Z06 front cooler is a major undertaking with unknown results (?)
5 - Shifting manual before redline and minimizing shifts only buy a couple of minutes.
I voted - has the question been submitted? I can't get passed 12-14 min on track, even though I keep it in manual mode, shift way before redline, and restrict shifts to as little a 4 shifts per lap. Outside air temperature seems to make no difference from 39F to 85F it always overheats at about the same time. Runs a bit longer on tracks with long straights where you spend several seconds per lap in 5th gear - but even that only buys you a couple of minutes.
If I tried to rung aggressive laps with redline shifts and optimum shift, I'm afraid I would never even get to the 10 min mark.
From other owners attempted fixes, we know:
1 - Adding the Z06 scoops and even a giant home made one didn't help much or at all.
2 - Wrapping the exhaust with DEI tape didn't solve the problem.
3 - A6 and A8 both overheat.
4 - Adding the Z06 front cooler is a major undertaking with unknown results (?)
5 - Shifting manual before redline and minimizing shifts only buy a couple of minutes.
If we have enough votes, the question will be submitted on June 14th
05-09-2015, 03:50 PM
My Z51 A8 Transmission and Engine Temps on Track
