Quote:
Originally Posted by Arragonis
What was the difference between the messing about with the TPS and just pressing the pedal less ?
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When he says that less TPS% gives him more spark advance, I can deduce that his ECM uses TPS% in the load calculation. The calculated load is used by the main fueling table and main spark table to determine which calibration value to use. Naturally, if he's running closed-loop mode, then the adaptive fueling algorithm will adjust (usually up to plus or minus 25%) fuel-trims to maintain a 14.6:1 AFR. However, if there is no knock retard in effect, the different load value will result in a different spark advance calibration. Generally in the spark advance table the advance calibrations increase as load decreases.
With a TPS tricker this function is independent of actual throttle position and actual VE of the engine.
There are also other tables based on calculated load value that control other functions such as AE - Acceleration Enrichment, transmission shift points (in newer vehicles), and TCC lock-up in automatics. TPS% is also one of the main thresholds for PE - Power Enrichment activation.
How much a TPS tricker can affect engine operation depends on exactly how much the TPS% is factored into the load calculation.
Some algorithms base load factor more heavily on input from the MAP or MAF sensor. In those cases a TPS tricker would prove to be less effective in some functions, and not effective at all in others.
For example, the 1991 Chevy truck listed under my name uses only the delta-MAP input to skew the AFR from my base calibration (VE table) when in open-loop mode. The TPS% is almost a non-factor for calculating VE in that particular ECM. TPS% does determine PE activation, and in the calibration I have my choice of heavily basing the AE on either delta-TPS% or delta-MAP.
Every car model is a little different.
Assuming no change in calculated VE, opening the throttle more will result in an increase in actual VE, which will increase cylinder pressure, burn temperature, and burn speed. Most things being equal, the efficiency will go up, at least for the engine. Whether it helps your MPG or not can depend entirely on how you drive it to take advantage of the situation. For example, If you try to accelerate heavily with increased spark timing, a locked torque converter, and no down-shift, then you're likely to get bad results.
I tried to be thorough.