"In our testing of the new set up in the manual transmission, pro-level drivers can run a full tank of fuel in temperatures of up to 100 degrees, a substantial improvement over prior years."
Tadge Juechter, Corvette Chief Engineer, Talks About Solving the Z06 Overheating Problem
by Ziva Allen
The current generation Corvette Z06 is a monster and has tremendous potential as a track day car. It has huge horsepower, huge torque, huge tires, huge brakes and huge grip. However, a small but very vocal group of owners alerted the world to a problem. On high ambient temperature days, the car was experiencing overheating issues on the track. Particularly with the automatic transmission version, the car would go into limp mode quickly. We recently talked with Tadge Juechter, Corvette Chief Engineer, about track day overheating issues with the new Corvette Z06. Here is what he had to say:
Q. There have been engineering changes to address the overheating issue. What are the adaptations which will help the 2017 Z06 edition to stay cool during hot HPDE days, other than shifting manually?
A. For the 2017 Z06, we have modified the intercooler geometry quite substantially to allow improved cooling of the intake charge to all cylinders in the LT4. This will reduce the likelihood of detonation and retarded spark timing which, in turn, reduces engine output. In prior years that was typically the first sign of thermal stress under heavy-duty track work in very hot ambient temperatures. In addition, for manual transmissions, we have adapted the horizontal, “lay down” cooler used to remove heat from the automatic transmission for additional cooling in the intercooler circuit. Unfortunately, the horizontal cooler is still needed to remove heat from the automatic transmission cars and so can’t be used for this purpose. In our testing of the new set up in the manual transmission, pro-level drivers can run a full tank of fuel in temperatures of up to 100 degrees, a substantial improvement over prior years. Obviously, performance is highly dependent on driver skill and style and most drivers will see no issues even at ambient temperatures well above 100 degrees. The automatic transmission car can be driven on the track and is improved for 2017. But, because we need the lay-down cooler for trans lube cooling, the automatic’s performance is not improved as much as cars with the manual trans. As a result, we are not claiming full-tank-of-fuel robustness above 85 degrees.
We will be working on continued improvement of the automatic transmission vehicles but, for now, the best choice for customers wanting durable performance in high temperature, hard-core track work is the manual transmission. Torque converter automatics have inherently more heat rejection and will always lag manuals in thermal robustness. Just be clear, neither transmission has an issue in street driving, auto cross, or road course work at lower temperatures.
Q. What has been done to help the new Grand Sport avoid overheating?
A. The Grand Sport has the additional lay down cooler like the Z06 and both manual and automatic can go full tank of fuel without overheating issues on track.
Q. What are the options going to be for current owners of the 2015 and 2016 to retrofit these adaptations to their cars? Will the parts be available through Chevrolet Performance? Are there any indications of the prices for these parts yet? There are some aftermarket kits available and they seem to range about $5,000.00. What do the Corvette engineers think about these aftermarket packages?
A. We are putting together plans for kits that would enable prior year owners to update their cars. More to follow on that. But, just to reiterate, those kits will do absolutely nothing for customers who drive their cars on the street. There is no horsepower change or other performance improvement.
Sum Up: Thus far, no aftermarket fix has been forthcoming from Chevy Performance. However, there are some aftermarket kit fixes that will run current owners around $5,000.00. These do not improve performance. They simply are designed to reduce the engine overheating problem. The bottom line is that the automatic transmission version of the Z06 is still not an option for track day enthusiasts who plan to run their cars at ambient temperatures above 85 degrees. Apparently, Chevy learned a lesson. The Camaro ZL1 has the same engine as the ZO6, but comes with eleven heat exchangers. The designers and engineers were taking no chances with their formidable new ZL1; perhaps the newest and greatest track monster from Chevrolet, and the better option for those who live in the hotter climates.