[1.2gees]

Now the second thing to modify for free/cheap on a 944 NA, for more power, that is the signal received from the engine temperature sensor.

The biggest reason emissions are worse with a cold engine (besides the fact that the cat isn't very effective), is because the engine is run a lot richer, with timing optimized towards more power as well. Ever notice how your car feels faster with a cold engine, part of the reason is this (the other part is lower intake temps, but I think the higher drag of a cold engine has a bigger effect than the low intake temps. However the power increase because of the modified air/mixture is even larger than that provided by the lower intake temperatures).

So in short, altering the signal from the engine temperature sensor, (making the DME think the engine is cold) will optimize both timing, and mixture for more power.

Keep in mind the most fuel efficient (besides producing theoretically the least amount of pollutants) air/fuel mixture, or the mixture for the most complete combustion, is also about 16% leaner than the theoretically ideal air/fuel mixture. This is on top of the extra cooling effect that running rich will cause! (I don't know about you, but by now I'm already thinking 'running rich' in the traditional sense is pretty much exactly what I want! Ofcourse not by too much, only about 10 to 15%)

So far the engine temperature sensor modification looks to be a very good thing to modify as well. Hope I don't need to mention it'll lower gas milage, and raise emissions! My idea is to put an adjustible resistance switch, with the ability to adjust for fuel economy/power as desired.

One thing however, if the signal is not within parameters, it will be ignored by the DME!

Also, the later cars (I believe starting with S2, but that's from memory) will start ignoring the signal, if say it looks like the engine hasn't warmed up in 600 hours of continious driving. They may even store a trouble code, but a trouble code for a broken engine temp sensor isn't exactly fatal.

I welcome comments, or ideas.

I'm surprised I could find the time to go through all the fuel injection/engine management books I recently purchased. I'll try to put some more time into this, and think it over/go through the comments before I actually proceed to perform either one of these mods on my own car.

PS: Finally got done with all the physics work I was missing from school, I've been up since 4:30 AM Sunday, my head is about to explode!
Ahmet

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It's all the driver...

[This message has been edited by 1.2gees (edited 04-22-2001).]