CentralCoaster
Mechanical
- Sep 20, 2005
- 12
I'm surprised I couldn't find info on this in the archives, it's an ongoing debate over engine performance and oil & coolant operating temps. Can any of you in the automotive industry clarify some of these questions?
The old wives claims are:
Cooler is always better for horsepower
Engines are only run hot to reduce emissions
This specifically refers to the gen-1 Chevy small block V8, and the gen-2 Chevy LT1 (with reverse flow cooling), or any other relevant applications. The newer gen-1 motors use a 195F thermostat, regulates coolant flow leaving the engine (2-way valve). The LT1 uses a 180F thermostat, regulating coolant temp entering the engine (similar to a 3-way mixing valve).
I agree, I'm having trouble finding enough info on this, short of purchasing SAE papers. I hate relying on second hand information. There's advantages and disadvantages, the question is, where is the best compromise?
Facts...
Hotter heads promote detonation.
Hotter heads rob less heat energy from engine combustion, increasing combustion efficiency.
Hotter heads give higher cylinder pressures.
Hotter intake reduces density of intake air, reducing VE.
Hotter blocks reduce oil contamination.
Hotter/thinner oil reduces friction losses.
Piston/wall clearances are optimal at a certain temperature.
GM engineers care more about emissions effects than we do.
The questions are...
Which factors outweigh the others?
Is thicker oil viscosity the primary reason for claims of lost horsepower and increase wear on cooler engines? (easily fixed by running thinner oil), or is it due to temperature effects on piston-cylinder wall clearance?
The old wives claims are:
Cooler is always better for horsepower
Engines are only run hot to reduce emissions
This specifically refers to the gen-1 Chevy small block V8, and the gen-2 Chevy LT1 (with reverse flow cooling), or any other relevant applications. The newer gen-1 motors use a 195F thermostat, regulates coolant flow leaving the engine (2-way valve). The LT1 uses a 180F thermostat, regulating coolant temp entering the engine (similar to a 3-way mixing valve).
No one that I have seen yet has come in here with any evidence that your motor will suffer any undue harm by running it in the 180 range, by the same token that no one has shown that running at high temperatures will do any harm.
I agree, I'm having trouble finding enough info on this, short of purchasing SAE papers. I hate relying on second hand information. There's advantages and disadvantages, the question is, where is the best compromise?
Facts...
Hotter heads promote detonation.
Hotter heads rob less heat energy from engine combustion, increasing combustion efficiency.
Hotter heads give higher cylinder pressures.
Hotter intake reduces density of intake air, reducing VE.
Hotter blocks reduce oil contamination.
Hotter/thinner oil reduces friction losses.
Piston/wall clearances are optimal at a certain temperature.
GM engineers care more about emissions effects than we do.
The questions are...
Which factors outweigh the others?
Is thicker oil viscosity the primary reason for claims of lost horsepower and increase wear on cooler engines? (easily fixed by running thinner oil), or is it due to temperature effects on piston-cylinder wall clearance?