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Discussion Starter #1
It seems Ive got the dreaded dead thermostat. I need to drive it about 30 min to where I work on it. Any issues with that?
Also I have the Moroso baffled oil pan so have a 6qt capacity. I was thinking of going to a 170deg thermostat but I was wondering if 180 would be more suitable.
Thanks much
 

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A 30 minute drive should be fine, just keep the rev's down.

Why do you want to go to a lower temperature thermostat? A lower temperature thermostat does not provide any extra cooling system capacity. With the car's propensity to wipe cams, apparently due to cold oil, I don't know why anyone would want to run these engines cooler.
 

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2005 Elise LSS Saffron Yellow
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The only reason to run a colder thermostat than stock is if you are trying to get 'extreme performance' and want to be able to run more spark advance/lower octane fuel/more boost. With older/dumber EFI systems, it was popular to run a colder thermostat because it could be used to fool the ECU into richening the mixture. With really old (carbureted V8) engines, it was a way to deal with uneven mixture distribution because of cruddy manifolds, uneven coolant circulation, and poor cylinder matching - you ran the engine colder so that lean cylinders would be at an acceptable mixture and not have ping or detonation. All the engines in modern Lotuses have excellent coolant circulation, so no reason to mess with this.

On any post-2000 model year car with the stock ECU on the street you want to run the car at the stock thermostat temperature. Running a colder coolant temperature will get you:
  1. Slower oil warm up. This is already a problem on the 2ZZ-GE Elige
  2. More oil dilution with fuel and water. This is always a bad thing
  3. Worse fuel economy - due to higher engine internal friction, among other things
  4. No measurable performance change - the ECU is already dynamically managing the quantity of fuel injected in open loop control at any coolant temperature above 160F.
So I'd recommend going with the stock temperature until at very least you put in a tune that capitalizes on the potential of a lower managed coolant temperature.
 

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Whatever the thermostat temperature, on big load, you will reach around 185-190, close to oem thermostat temp, which is good. Replace the thermostat by a oem, jobber do not give stable temp.
 

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2006 Exige
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Does a dead thermostat mean stuck closed?If so you will overheat in less
than 5 min let alone 1/2hr
 
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