High performance thermostats

[Daves]

My first thought is that the streetbike engines are high performance right out of the box (or wrecking yard), so why would a different thermostat be beneficial?

We at LeTourneau have just lost an F4i engine due to overheating that may have been caused by a faulty thermostat. This engine's compression had been raised by a shop in Dallas milling the head. Is the stock thermostat adequate for this type of racing? Is more coolant flow needed, or does the thermostat need to open at a lower temperature? Do motorcycle racers use the stock thermostat?

After Googling and going to DennisKirk.com, I have not been able to find any aftermarket thermostats for streetbikes. Has anyone else had any luck?

[Daves]

My first thought is that the streetbike engines are high performance right out of the box (or wrecking yard), so why would a different thermostat be beneficial?

We at LeTourneau have just lost an F4i engine due to overheating that may have been caused by a faulty thermostat. This engine's compression had been raised by a shop in Dallas milling the head. Is the stock thermostat adequate for this type of racing? Is more coolant flow needed, or does the thermostat need to open at a lower temperature? Do motorcycle racers use the stock thermostat?

After Googling and going to DennisKirk.com, I have not been able to find any aftermarket thermostats for streetbikes. Has anyone else had any luck?

[woollymoof]

We have an after market thermostat (not running it though), opens a couple of degrees C earlier. But unless you have an efficient enough cooling system to bring the temperature down below that of the stock opening temp there is no point in running an aftermarket thermostat.

Perhaps the problem with your thermostat is that it didn't open at all rather than not early enough.

Off the top of my head I think we got our aftermarket thermostat through Gates. Not sure what brand it is.

[DanO]

We used the stock t-stat and ended up winning the visteon cooling award.

I dont think you need an aftermarket one unless you can verify 'exactly' why you need it to open a few C cooler.

[BryanH]

Dave, you should regard the ignition map as main suspect, not the much maligned thermostat
Small cap engine running hi comp needs not much taken of the head to lift comp into the stratosphere. might be rooted
Bryan H.

[Chris Boyden]

Anybody yank the thermostat and run an electric water pump and a controller for the pump and fan? That may be a good way to get more flow out of the system ....

[jonno]

yeah we eliminated the stock thermostat: there's a small temp transducer in the flow just after the head. electric water pump is permanently on (otherwise you'd end up with a red hot head and cool pipes because of no flow: ecu thinks the head is cold). The ecu then turns the fan on & off to increase / reduce cooling. We get very stable temps.

Regards,

[Chris Boyden]

That's cool...

I guess that I was thinking of a system that would act in a similar way to t-stat system, where the flow through the engine during warm up would be reduced by lowering pump voltage.
That way you could avoid the problem just mentioned, hot head - cold pipes. Getting rid of that t-stat housing and replacing it with a high flow fitting/adapter would probably help flow.

Has anybody flow tested the stock F4i pump? It sure looks like a piece of junk with that stamped impeller. Although, It seems to do the job on a stock bike. Sure seems inefficient....needs to be tested!

[woollymoof]

We've tested it in the engine. Flow varies linearly from 0.17kg/s at 3100 RPM to 0.69kg/s at 9700 RPM