1red5 wrote:With all your track-work though, you wouldn't consider a Mishimoto one?
At the moment I'm using a 72deg thing that was meant for something like a Bedford truck. It was the biggest low temp thermostat I could find. Cost about $8 and I ground down the mounting disk until it fitted in the MX5 housing. It's good for track but low temp thermostats (including Mishimotos) do have some downsides. Using the OEM ECU I can tune the mixtures for fuel in open loop but can't do anything about fuel in closed loop, so it runs a bit rich as a daily driver. To get better daily economy I can either run a resistor across the ECT sensor or go back to a standard thermostat. It's easier to do the latter.
Previous aftermarket ones have given me issues with slow opening rates. On a really hot day at the track the temp can rise 30-40deg in the course of a single lap, even on my fairly stock motor. Some of the cheaper thermostats can take over 2 minutes to open when dropped in boiling water. So on lap 1 the coolant can boil inside the head before the thermostat opens.
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