axr6

Finally a nice warm day to try out the GM secondary radiator. Just got back from a 24 miles canyon run with the ambient temps right at 80F.

Previously at these temps (80F) my engine oil temperatures got to 280-290 very quickly while the coolant temps never exceeded 225F (due to me shutting it down when the oil reached 290) and the A8 transmission temps were near 200F.

Used the first, downhill portion of the drive to warm up the car and its tires. Turned around an climbed back about 6 - 700 feet in elevation gain in dozen miles with mostly 2nd and 3rd gear cornering speeds, holding the engine over 4000 most of the time, all the way to the redline when the roads allowed.

Conclusion: The Secondary Radiator seems nicely effective for the coolant and for the oil temperatures. Highest coolant temps were 201F, highest oil temps were 262F and the highest A8 temps were exactly on 200F. I am happy with the coolant temps, would still prefer to see the oil not higher than 250F even though I am running the 15W-50 Mobil 1 full time. But, what GM promised appears to be quite close (25F reduction in coolant and 15F reduction in engine oil temps.)

So, looks like the oil temps might still be near 280-290 on those near 100F days but, the coolant issues seem to be fixed, at least for my NA car. Take into account that in my driving I had no straights of any kind where speeds could have contributed to increased air flows into the radiator. My highest speeds achieved were right at redline in 3rd gear.

Changes on my car:
DEI heat shield on cat converter.
GM secondary radiator.
ZO6 front grill.
30/70 coolant mix
15W-50 Mobil 1
Removed duct between top of radiator and hood vent. Also removed plastic piece mounted under the hood vent.
Vitesse Throttle controller.
Brake ducts.
Z51 shocks
aFe swaybars
fully lowered on factory bolts
aFe CAI

Now, the car handles beautifully and is a TON OF FUN tossing it around those narrow, winding roads. I'd like to believe that my heat issues are fixed as I can probably live with the oil temps over 260F.

SBC_and_a_stick

Superb review! I haven't had a chance to test mine out on a hot day. It rained heavily when I tracked last time with the second radiator and the ambients were only in the 50s.

Mad Dog 24

AXR6 I didn't realize till now you have a non Z. Those were some high temps coming from a non supercharged engine. Kind of says our superchargers are not adding a lot more towards the heat issues.

You should be fine with temps now even on a track although you appear to run dam hard on the street. Here in NY if you get caught doing that one would end up in jail for a week and car towed away!

Great review, you could probably drop our water mix more, we run 10/90. Enjoy your 80's still 40's around here, sucks!

foreverfuelie

The OP's ride is obviously not a Z06, why is this post on this thread? The NA issue has no direct value to FI folks. Just sayin'.

axr6

Yes, the NA engine overheats just about as quickly as the SC engine in the C7. Have to say, however, that I do not have any of the same heating issues in my 5.0, SC Jaguar XKR. I frequent the ZO6 forums because there seem to be a lot more hardcore racers and performance people here as opposed to the NA forums.

I purchased the 3" duct setup that you pioneered but, ran out of time in putting the car back together so, all the parts are still there, waiting. As it seems, I may not need it. I also have a 170F thermostat but, given what I had seen today, I may not install that, either.

As far as hard driving vs. speeds; yes, I used to do banzai road racing in the Bay Area hills, many years ago. It was intense and surprisingly open, as far as the LE was concerned. There were often police cars at the gathering spots but, I'd never seen them make an attempt to stop anyone from racing. Seem like they were there to document and pick up the pieces of mostly superbikers that lost it and ran off the canyon roads. :-). In my lightweight (500HP, 2600 lbs) twin-turbo 3rd gen RX-7 never lost a single race to anyone, bike or car!

These days I live in the Sierra Foothills, surrounded by nearly deserted, beautiful but, tight, winding canyon roads. Mostly 2nd, 3rd gear stuff, which means that I am not exceeding the 55 speed limits by truly prohibitive measures. Given all the electronics that the LE have these days it is truly foolish to open up these cars to anything over 100 MPH. Lose licence, car and go to jail. Not worth it. If I do come to a straight section that could accommodate 100+ MPH speeds, I simply lift and back off. A local Sheriff friend once said: "You're the only person I know that slows down on straights and speeds up into the corners".

I used to race in SCCA successfully for decades, AFTER crashing two expensive street cars on racetracks. Following the crashes, no street cars for me on the tracks. Race cars were much less hassle to repair following those (for me) inevitable crashes.

axr6

If you do not see the value in my post about the new secondary radiator, you're truly missing something. Do you think I should ask for permission to post-in and follow this forum?

BTW - looks like we're only a few miles away from each other near Folsom. Perhaps you could come up the hills for a nice drive and show me how your ZO6 would be superior to my NA car over my local roads :-). Who knows, you may actually learn some things by looking at a well setup NA car...?

Bill Dearborn

The issue is engine overheating when under full power. The base engine can be as good of a demonstrator of improvements as a Z06. The temperature drop from the OPs baseline is good to know whether or not you are driving a car with an LT1, LT4 or some other combination. Don't confuse the major problem of overheating with the minor problem of heat soak in the intake which could be a difference between the LT1 and the LT4. Heat soak you lose a little power and have to back out of the throttle for a minute or so while overheating takes you to the garage.

Bill

5thGear

Good for you! Thanks for sharing

SBC_and_a_stick

You are... a madman. I love it.

descartesfool

Did you know the GMPP secondary radiator was developed by GMPP for the normally aspirated Z51 to be used in a new race series called the Corvette Challenge as well as for SCCA racing of the Z51 in the T1 class, and only the Z51 was highlighted at the GMPP booth at SEMA this year where they introduced the secondary radiator, s shown on 2 Z51's. I don't know GM has ever shown the secondary radiator in a Z06, although it will fit and will help, but no claim that it is a full and final solution for the Z06. All of the new cooling solutions at the GMPP booth were targeted at the NA car with manual transmissions.

Poor-sha

I saw a roughly 10 degree drop in coolant temps last weekend with the secondary radiator. This is compared to a slightly cooler day at the same track last November.

The real test won't come until we get some warm weather but mine never went critical on temp when stock.

axr6

Likely you did not see as much improvement as I have because you already had the ZO6 front grill, which, per GM, allows 17 percent more air flows. I've just replaced my stock C7 grill with the ZO6 the same time as I added the radiator. I believe that GM claimed the 25F improvement as the result of adding both the secondary radiator AND the ZO6 grill to the Z51.

Chets LS3

Thanks for sharing.

The z51 cars can get as hot as the z06 cars. Minus heat soak and whatnot. Typically the z06 cars might get to those temps a little faster. But regardless both can get there.

And to see a drop in the z51 will make me
Believe a z06 will see a drop as well.

I am subscribed for warmer temps as well.

Poor-sha

At this point it's just a data point. My max temp went from 217F without to 210F with and all but one session it was a max of 205F. You really don't want to cool the car more than that.

I'll have better data once we get some actual warm weather to compare to last year.

truth.b

subscribed

J.R.

Simple answer - YES