Coolant Temperature Discussion
Optimal Engine Coolant Temperature for Performance and Longevity
It turns out that engine coolant temperature (ECT) is an important topic for balancing performance and longevity. There are downsides to running the engines too hot OR too cold and I wanted to type this page up as a quick summary for folks looking for a starting point.
For reference, I run a supercharged 5.3L iron block LM7 that redlines at 7K and sees up to 11psi of boost on stock internals. It uses a stock W210 radiator with a custom shroud and 2x SPAL 30102038 1640 CFM fans. It is common to run 160F thermostats in performance LS applications, but that alone will not manage for the desired temperature range.
I ended up with an ECU-switched set of 40A relays that turn the fans on at 190F and turn them off at 180F. I want to give you an idea of side-effects of running the engine too far outside of the intended operating temperature range.
On the bottom end, we're trying to be high enough to:
For reference, I run a supercharged 5.3L iron block LM7 that redlines at 7K and sees up to 11psi of boost on stock internals. It uses a stock W210 radiator with a custom shroud and 2x SPAL 30102038 1640 CFM fans. It is common to run 160F thermostats in performance LS applications, but that alone will not manage for the desired temperature range.
I ended up with an ECU-switched set of 40A relays that turn the fans on at 190F and turn them off at 180F. I want to give you an idea of side-effects of running the engine too far outside of the intended operating temperature range.
On the bottom end, we're trying to be high enough to:
- reduce energy loss due to radiation to cold piston/cylinders
- have oil be at high lubricity and prevent frictional losses
- boil off contaminants and water + fuel (!!)
- account for factory designed tolerances at the intended operating range
On the top end:
- don't want to boil coolant
- don't want to risk warping heads
- don't want to contribute to knock
- leave plenty of room for temps to climb during back to back runs past the 190F mark and have that safety net until say 230F
In settling down on a starting location, I reviewed this video by HP Academy: