[MEDISIN]

Originally Posted by BaylorCamaro

It's a known issue...

Originally Posted by RLHMARINES

Automatics are the only ones that I'm aware of that have this issue.

Originally Posted by Scott@Bjorn3D

The auto has been having overheating problems at the track. Several reviewers commented the Z06 was fast but the auto shot craps and broke down in several track review test.

Never been a problem for the manual.

Let's keep this "overheating" in perspective. I assume you're referring to Pobst's hot laps at Road Atlanta earlier this summer? This was brought up in a Q&A with Tadge Juechter.

Question was asked:

Could you describe what occurred to the car that the media ran at road atlanta back in November 2014. It seems several magazines have quoted having the over heating issue but no one clarified if it was the trans or the engine oil. I know from my personal experience that my car did get pretty warm on a cold 40 degree day there a few weeks back. I and many people are concerned we will see issues come this summer without mods.

Tadge answered:

There are lots of interesting back stories behind recent media tests, but the question asks about Road Atlanta so for the purposes of this thread I will focus on our long lead media event last November. We spent a week there with journalists from around the world. We had pro drivers Tommy Milner, Randy Pobst, and Andy Pilgrim behind the wheel along with many other very capable drivers. They were permitted to run consecutive laps with minimal or no traffic, so essentially "qualifying laps". Over the course of the week we had 2 cars come into the pits with a hot warning messages. The first was due to the loss of an accessory drive belt. We had a pre-production tensioner on that car which failed, throwing the belt and we lost the water pump. We have had no issues with production tensioners. The second car was an automatic. I believe it was being driven by Randy on the hottest day there which was right around our design performance target of 86 degrees (more on that below). After multiple laps at speed he came in with a hot warning message. Although the car had been out on track all week, that was the first and only incident. In Corvette's 60 year history, we have never put automatics on track for media and never encouraged people interested in track usage to buy automatics. The new 8 speed automatic gives us a chance to put more automatic transmission customers on the track. Since there is some lack of clarity around the true capability of each of the transmissions, this question gives us the opportunity to publish some guidelines.

The Z06 Manual is designed to keep engine oil, coolant, transmission and differential fluids below the hot warning targets when driven by a professional on a 30C day (86F) on a "typical" racetrack for an indefinite period of time (effectively the time to burn through a full tank of fuel). Our team validates the durability of the Z06 cooling systems with a 24hr accumulated track test to simulate the most aggressive track-day usage by our customers.
We designate our track: the Milford Road Course, as the "typical" standard, but recognize that there are tracks around the world which are easier on a cooling system and some which are harder on a cooling system. Generally speaking, tighter tracks with lower average speed and higher sustained RPM, will drive higher fluid system temperatures.
Higher temperature ambient conditions affects all car's abilities to run sustained laps at ten-tenths.

The Z06 Automatic transmission put in "Drive" selects the lowest possible gear ratio for best acceleration, and because it has 8 closely-spaced ratios typically runs higher average RPM than the manual. This optimizes lap time performance, but also taxes the engine oil and coolant more for any given track. So the automatic has the capability to run faster laps than the manual, but thermal limitations are reached more quickly. Customers who are planning to run extended track-day sessions at 'professional' speeds, are advised to go with the manual transmission, or to paddle shift the automatic and select higher gears when conditions warrant it.
Any time the maximum recommended temperatures are reached in any condition, the DIC will give warnings at the appropriate time for coolant, oil, or transmission fluid. A cool-down lap or two will bring operating temperatures back to a reasonable level and aggressive track driving can be resumed.

Some may wonder why don't we design to higher temperatures, say 110 degrees, to accommodate southern tracks in the Summer. We have used the "pro driver at 86 degrees" criteria for generations of Corvettes and for the vast majority of customers, it has resulted in excellent performance for their usage. If we designed to higher temperature criteria, we would have to add a lot of cooling hardware which drives mass up and perhaps more importantly, you have to feed the system with more air which has a huge impact on appearance and aerodynamic drag. Like most aspects of car design, the challenge is in finding the best balance of conflicting requirements.

During testing (vs the GT-R) at Willow Springs, Randy Pobst commented on the Z06 automatic and heat production.

As in previous tests, the Z06 got very hot during lapping and pulled power. Per Pobst: "The power starts to fall off significantly after the first lap. It was nearly pegging the oil temp gauge after a few laps. 320 degrees. I did a cool-off lap and it came right back down." We checked the data, and lap times and peak speeds did fall off by a few tenths of a second and 1 or 2 mph on each subsequent lap , though these could also be attributed to tire wear and other factors. Although Pobst has consistently complained of reduced engine power when lapping C7 Z06s, the problem does not appear to be especially great (in terms of lap times) and only seems to affect drivers of Pobst's incredibly high skill, suggesting that most customers won't encounter it.

Read more: http://www.motortrend.com/roadtests/...#ixzz3lLGKqs26

Note: the CTS-V in this years Lighting Lap also combines the LT4 + 8L90 and did not experience heat-related issues in 100F weather. The authors note both Mustangs suffered from the heat.