Restricted Exhaust Systems - Tech Corner

James Berry Nov 26, 2009 0 Comment(s)
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Question: I own an '08 Z06 and would like to reprogram the Electronic Control Unit (ECU) with aftermarket calibrations. Is it possible for the dealership to tell if this has been done? What portions of the warranty are voided if you have an aftermarket calibration?

We were talking about this at a Corvette club meeting, and some of the guys suggested I swap the original ECU with an aftermarket one. That way, I could swap the original one back for warranty service or reflash the ECU with the stock tune before taking it in to the dealer for service. Do you think the dealership will be able to detect a reflash or an ECU exchange? Tony Via the Internet

Answer: Yes, there are always signs of calibration changes. In fact, there are several Technical Service Bulletins (TSBs) that assist technicians in determining if a reflash or an ECU swap has taken place. The detection of any aftermarket calibration will void your powertrain warranty, including the engine, transmission, transfer case, and driveline. Many dealerships are cracking down on this! GM engineers take great care in programming new-car ECUs. Their goal is to put the best possible combination of performance, reliability, durability, fuel economy, and emissions into each calibration.

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While an aftermarket unit or program may give you increased performance, you'll run the risk of damaging or reducing the life span of your engine, transmission, drivetrain, and exhaust system. It may also cause your car to fall out of compliance with federal emissions standards.

I suggest that you wait until your Corvette is out of warranty before making any modifications. But if you really do want to "play," don't expect your dealership to pay.

Question: I have a C6 Z06 with 20,000 miles. It's completely stock, but I think it runs hotter than it should. I live in Miami and drive in high-traffic areas. The coolant temperature in stop-and-go traffic runs between 240-250 degrees Fahrenheit. The oil temp ranges between 220-230 degrees Fahrenheit. After talking to some friends in my local Corvette club, I was thinking of lowering my fan settings. It appears that the fan can be altered to come on at 192 degrees and stay on all the time. Do you think this is a good idea? Bob Via the Internet

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Answer: First, do not alter the factory setting! Running the fans all the time will cause the fan-control module to overheat and fail. The guys in your Corvette club must own C5s, which use a totally different operation system for fan control.

The C6 fans run off of a duty cycle and are capable of running at variable speeds depending on demand. The maximum duty cycle is defined as the percentage of time in a 10-minute period that a system can be operated continuously before overheating. The C6 system is not designed to run the fans continually. Try the following steps to determine why your Corvette is running so hot:

1. Check to make sure the cooling system is full and that there are no air pockets.
2. Check to make sure there isn't too much coolant in your system. A high concentration of antifreeze does not transfer heat as well as pure water or a 50/50 mix of antifreeze and water.
3. Check to make sure there is no debris in front of the radiator.
4. Check your thermostat to make sure it's working correctly and the cooling system is circulating coolant. You can use an infrared thermometer to check coolant temperature at the thermostat housing.
5. Perform a visual inspection for any kinked hoses.
6. Check to make sure the oil level is full.
7. Confirm that the fans are coming on when the car reaches operating temperature, and that the control module is responding to correct commands.
8. Check to see if there are any diagnostic trouble codes.
9. I've seen some people cut the center out of the thermostat to make the coolant flow faster. This is a bad idea because moving the water too fast through the radiator will keep the radiator from absorbing the heat from the fluid.


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