lower temp thermostats

Road & Track Febuaray 2005 Page 140

Cold Performance

"Do lower-temp thermostats really improve performance? My car's OEM thermostat is rated at 195 degrees Fahrenheit. I am currently using a 180-degree thermostat.
Some of my friends are using 160-degree thermostats. I have read that they improve performance because they keep the engine cooler and more resistant to detonation (therefore you can advance the timing) and by increasing the density of the incoming air into the engine. Is all this snake oil?
Will the car's computer be confused by the lower temperatures?"




"Engine-management computers rely on the as-designed coolant temperature (typically 193 degrees F) to better atomize fuel, maintaine heat exchanger efficiency, provide lower emissions, optimize fuel economy and other factors, so running the engine in colder than designed can have multiple ill effects. These are the sort of effects that are not immediately apparent, so such issues are more long-term durability concerns.
Tuners often fit 180-degree F thermostats to give hot-rodded engines a larger cooling margin for when they're making tons of heat (horsepower) at full throttle. This is a bona fide need on an engbine that has sprouted a supercharger, but simply fitting a cooler thermostat to a stock engine will not lower the intake air temperature enought to matter and will not support a meanginful timing increase.
Cooler than 180-degree thermostats are not recommended on modern cars. Most domestic automakers' engine-management systems go into open loop at 168 degrees F. Meaning that the engine is operating in its warm-up mode with perhaps and overly rich mixture and un-optimized ignition timing. Eventually the computer will consider such long warm-up times abnormal and could trip the Check Engine Light.
Furthermore, higher coolant temperatures promote engine efficiecy, especially for fuel economy and emissions, and reduce cylinder wear(a cold block wears faster than a warm block), and the engine internal dimension shave been set for the designed operating tempeorature. If you're really beating on you car in the summer and figure it's overheating, then a 180-degree thermostat could be the answer to return youn coolant temps the the as-designed levels, but anything coolers is counterproductive."





I personally changed my thermostat on my Impala SS from 180 deg-160 deg and am worried about longterm affects. though i'd post the heads-up.