Quote:
Originally Posted by matt demaria
I just had the opportunity to check a 2000 996 yesterday. Yes the dash gauge was inaccurate on the left side of 180. About 10 degrees worth. It seemed to get accurate about 190 and above. But the curious thing that I noticed is that the pulse width for the injectors didn't stabilize untill it reached 190. At 150 pulse width was 3.2 ms. At 190 it dropped to 2.9ms and remained at this value while temp was increasing. Does this not imply that it is tapering off the cold start network untill the thermostat opens. This would result in a perceived power increase (richer mixture) if the fuel trims didn't kick in.
So the bottom line question is if you put in a lower stat would the DME think that the engine is still cold and not fully warmed up for the fuel control?
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The DME has the flexibility to deal with the car running slightly cooler without issue, plus the injector pulse at those temps is varying in response to the mixture delta across the three way cats as their temperature varies more than the coolant temp; plus we have had a number of customers that commented their fuel mileage increased very slightly after we installed a 160F stat, just as we have seen on the dyno. While the difference's in mileage and power are not very great, they seem for the most part to be reproducible, which could imply a very small improvement in the engine's efficiency with lower coolant temps.