I have a question regarding low-temp thermostats, like the Mishimoto unit. This thermostat opens at 60C (140F). Will this lower opening temperature negatively effect the fuel trim/map? In other words, will the ECU misinterpret this lowered operating temperature? I understand that the motor will eventually run warmer than 140F despite the thermostat opening at 140F but I am just curious. Any info is appreciated. Thanks.

 

The tstat just starts circulating the coolant sooner during engine warm-up, which extends the warm-up period. There's nothing for the ECU to "misinterpret" -- the engine is, in fact, taking longer to warm up, and the ECU will do just what it needs to do. It's no different than starting the engine on a very cold winter day vs. starting it on a hot summer day.

 

Technically when the tstat opens up, the engine is in fact "warmed" up as it is the tstats job to regulate the coolant temp. Assuming normal use, the coolant temp won't climb much at that point.

 

Isn't the full open position lower as well?

 

Not with a low-temp tstat! My experience with the Mugen part (fully open at 68C, stock is 78C) was that it would open up so early that, during warmup, my temp gauge would initially hit 3 bars (AP1), then drop *back* to 2 bars as the tstat allowed a rush of cold coolant into the block. Only after another minute or two would it get back up to 3 bars. Presumably the effect of the 60C Mishimoto part would be even more pronounced.

For the OP: A warm engine is a happy engine, so the quicker it gets to operating temp the better. For this car, low-temp tstats are most useful for FI applications where the block can potentially heat up so fast (during warm-up or upon a sudden surge in load/power) that it creates "hot spots", boiling the coolant before the tstat has opened up enough to compensate.

 

The only real thing that I see to improve in a thermostat is the flow rate.

For cooling issues, look at:

Using a fluid with a higher specific heat capacity (Use a larger ratio of water in your coolant mixture, or use all water if you run a race car)
Use a larger heat exhanger or a heat exchanger with a more effective heat transfer rate as a core.
Duct your heat exchanger better and vent the exit side sufficiently.

The S is actually ducted very well from the factory [thank god] in my opinion. I'd guess that a vented hood, a coolant mixture with a healthy amount of water, and a Koyo [or equivalent] should be more than sufficient. Although, I have never had a problem with the stock cooling system even in Florida.

Oil cooling can also make a difference.

 

This is good information, thanks guys. Does anyone know at what temp the f22 makes the most power? Having been able to motor-dyno some of my non-honda builds, I've found that there is a 10 degree window where motors make max power.