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, Wed, 20 Jun 2001 09:50:19
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The new production with the T7 ECU's have air mass meters. And better fuel economy too.
The T5 is a speed density system. The air mass flow is computed by the manifold pressure, intake temperature and engine RPM's. The formula has a few constants in it, one of which is a fudge factor determined by the O2 sensor's feedback. So this works quite well. The ECU should be able to use the O2 sensor to calibrate the engine volumetric efficiency and thus be able to accomodate changes to the exhaust system automatically. This also allows for accomodation of changing fuels with changing energy of combustion properties. So when they added alchohol to gasoline, your ECU automatically adapted to use 1% or 2% more fuel. I could get into a long fuel rant, but I won't.
When under boost, the O2 sensor is ignored and the fuel is mapped in an open loop as far as O2 feedback is concerned. The mapping objectives are to run richer, which increases knock resistance, and keeps temperatures lower. The ECU will play with timing and mixture and boost pressure to avoid knocking. If you fit an MBC and isolate the BPC valve, the ECU will manage knock with mixture and timing alone. (However, that may not be the case if the engine, plugs, injectors and fuel system are in a severly poor state of maintenance.)
Don't get too obsessed with measurements. Your seat of pants dynometer will work very well. And technical measurements don't have a seat of pants impact. The obvious stuff will have obvious effects. Silicone hoses and tinted windows won't.
, Wed, 20 Jun 2001 09:50:19
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