Let me just reiterate:
Cold start = cold engine = cold coolant. Since that great mystery is solved, I will go on w/ the chlorophyll.
The cooling system is at STP when cold. To allow the engine to warm up to operating temperature and pressure, the thermostat doesn't start to open until about 190 F. The electric fan doesn't spin up until about 212 F.
Myth #1: Engines have better performance cold. Nope. The engine management system is designed to get the vehicle up to operating temperature quickly so it can run more efficiently and cleaner. The reactions in the converter are catalyzed best at real high temps - one good reason not to do that exhaust mod right after you get back from Canada, eh? At op. temps, the air/fuel mixture is a stoichiometric ratio: roughly 14:1 - this is for economy, not performance. To warm up quicker, the EEC-IV enriches the mixture and advances ignition timing.
Myth #2 A cooler running engine is a happier engine. Nope. Those guys in the thermostat thread are morons. A 160 or 180 F stat will not only make your defrost about as useful as your a/c in the arctic, but does worse to your motor. Engines are designed to run with clearances at op. temp. Running cooler will cause undue wear, cause the computer to think the engine is still warming up - killing economy, and may even trigger your CEL (since it can never warm up).
The only good cold thing is air. Cold air more dense - there4 more O2. Would you like to swallow 150F+ air on the Marine Corps Marathon?
For those driving stop+go whining about the "My temp gauge reads in the AL of NORMAL," go drink some antifreeze. Your car is hot because you are torturing it. Run it on the highway, and your radiator will run its convection magic. Anyway, the gauge takes a reading off of a different sensor than that of the computer, so it may not be a true indication for starters. 2nd, your car running on the hot side is better than on the cold side. In fact, the hotter it can run w/out overheating, the better for econ. emissions and engine life.
Now for the part dear to us all, performance. First, as stated above by others who have it screwed on right, NEVER run hard without warming her up. Second, never try to run cooler to take advantage of the performance oriented air/fuel mixture and ignition timing offered by the EEC during warm-up.
If you want to take advantage of this however, you need to provide cues to the computer that it is warming up, even though it is already warm. Design a circuit that will alter the resistance of the IAT and ECT sensors (inverted thermistors - increased temperature = decreased resistance). Increase the resistance to 35k-40k ohms which will be about room temp. 68 F. Want to see some great ideas? Try
http://pub34.ezboard.com/fzx2racingfrm22.showMessage?topicID=2.topic Don't email me yet - my circuit will include throttle position based activation and is currently on the drawing board. I am also working on a circuit for external mirror turn signal LED's. More to come (performance and aesthetics forums).
