mikecl713

does the coolant temp factor in ecu created air/fuel mixtures?

xviper

Yes, it does. This is why most modern day engines use an auxillary air pump - to inject more air into the exhaust to help burn off the excess fuel during the engine warm-up phase, which can take several minutes. Until the engine reaches an "optimal" temp, it will run richer.

Slows2k

Yes cold engines require more fuel than allready warm ones. Ever start a lawnmower that has a choke? The choke provides a very rich mix so the engine will start.

The air pump is there to provide extra oxygen in the exhaust stream to bring the catalytic convertor up to temp faster. Cold start emmisions are much higher than on a warm engine.

Road Rage

I wonder if he is asking about closed-loop? The answer is still yes, but I do not think for example running a Mugen thermostat will cause too much richness, or else the car would lose power, which would be counter-productive. That might be, but I have soime confidence that Mugen knows what it is doing.

That is in contrast to some early "tuners" of the TPI Vettes and F-cars. They would use thermostats so low that the car stayed near open open loop values for richness, which gave a sense of squirt just off idle, but cost power way up the rpm scale, reducing peak power, and fouling plugs, causing engine oil to sludge, etc.

It is a matter of balance.

So between all of us, we have hopefully answered his question.

mikecl713

i have spoon cooling mods which are slightly more agressive than mugen. i recently lose 20 hp and i tried everything i could think of. whack the map sensor...
switch out intakes.. and now i just switched back to stock cooling mods.... i hope that solves the problem
but on my first dyno i had the cooling mods and on top of that it was during dec and it was raining. i dynoed out 206.
i put in toda header with comptech intake with spugen exhaust as oppose to aem intake and dc sports with the spugen.. i dynoed out at 187 i lost power throughout the powerband. wheni look at the air/fuel mixtures they were completely different when the old sheets start to lean out the new sheets start to richen up. the avg a/f was 13.5. while now it leans out at 13.2 and averages 12.0 throughtout. the tuners thought it might have been the intake so i switched out the intakes with the stock and still about the same

Road Rage

Somehow I knew you were not asking about warmup. i really think it would have been better if you had stated your question clearly from the beginning, because xviper spent time answering a question which was not being asked because of the way you put the question - it's a copurtesy thing.

I would attach my scanner to ensure the car is in closed loop, but my statements that too cool a thermostat could lead to richer condition and loss of power stand. Now, Spoon may stand by their mods, and unless the conditions of the dyno runs were nearly identical, you can infer nothing from your dyno runs. UL has often stated the variances that IAT, etc have on dyno runs in general, and the S2000 specifically, which will pull timing/change A/F very quickly.