HOT UNDER THE HOOD
Q:I'm about at the end of my rope trying to understand the cooling issues with my '89 Chevy TPI. I'm at the point where I'll be making purchases and I want to make informed ones, but there is a lot of misinformation out there.As I understand it, the stock thermostat is 195 degrees F. If I buy an aftermarket radiator and water pump and add a product like Redline's WaterWetter, the thermostat will still keep the coolant temp at 195 degrees, won't it? So what is the point of these products?
If I switch to a 180-degree thermostat, will that throw the computer off and cause the performance to suffer? Truthfully, how much performance is there to be gained by lowering coolant temp on computer-controlled vehicles? The car is primarily driven on weekends and occasionally raced in SCCA Solo II events. Thanks.
Mark Roth
Via e-mail
A:Most Tuned Port engines of your era didn't run below 195 degrees. The cooling systems were designed to keep those engines well above 200 degrees F. Lowering the coolant temps will affect the performance in many ways. The cooler you can keep the engine temps the less heat transfer you'll have into the incoming air throughout the induction system. Also, the cooler the engine runs the further away the engine is from the threshold of spark knock. You may be running in knock retard quite a bit of the time while performance-driving your car. Also, the blast of hot air coming from the radiator going across the intake air ducting raises the inlet air temperature. As the computer sees this increase in air temp, it retards the spark advance to prevent spark knock. As you can see, the lower (within reason) we keep the engine overall temperature the better the engine may perform.
Yes, if your cooling system can keep the engine temp below 195 degrees, the thermostat will regulate the water flow to maintain 195 degrees. Lowering the thermostat to 180 degrees will give you some relief from the high engine temps as long as your cooling system can suck that much heat out of the water while you're beating on your car. As for the computer squashing all your gains, it takes a much greater reduction in coolant temps to mess with the factory program.
Lowering coolant temps gives you the ability to recalibrate the engine to take advantage of reduced temp. Commonly, you can increase the spark advance if you're always going to run premium unleaded fuel. Check out Hypertech's ThermoMaster chip and Powerstat 160-degree thermostat. The ThermoMaster chip is programmed to take advantage of this cooler, more powerful air/fuel mixture produced by the Powerstat. All temperature-sensitive functions controlled by the ThermoMaster chip (such as a minimum temperature for torque-converter lockup, closed-loop operation, and in some cars, early fan turn-on) are adjusted for a cooler-temp thermostat.
Source: hypertech.com CHP