be unaffected, because I don't think any changes were made to the timing values used at those speeds. Nearly all of the timing came from engine speeds of less than 2000 rpm, and load factors less than 12 TTP. Not having a Labjack at the time, I was unable to identify those specific cells that were active while driving at a given speed and load. However even if I had that capability; my primary objective was to alter the timing in a way that resulted in the smoothest transitions within the lower ranges of engine performance.
Having since acquired a Labjack, I will now be able to target specific cells; and should it be advantageous to add some timing to preserve mileage, I think it would be possible to do that, and keep the on/off throttle modulation smooth.The most significant gains in drivability came from making timing changes at levels of 800 to 1200 rpm. This is the point where timing abruptly shifts from 15' to 40', without any kind of step-down, or buffer, to smooth the jump. It would be interesting to know if other EPROMs have this same major shift in timing at such low rpm and loads.... Or maybe somehow my chip was simply burned with the wrong values. Regardless of the causes, the improvements made to the car's overall drivability are remarkable. The aforementioned timing issues resulted an unwanted lump early in the off-idle section of the lower powerband. This has now been shaved off and smoothed over. The power-on sequence is a now smooth linear progression without any of the on-throttle surge previously experienced. Conversely, when backing out of the throttle, the engine slows and brakes in a steady controlled and linear fashion. Also fixed was a pronounced 'clunking' sound heard whenever the accelerator pedal was lifted quickly. This clunking noise was previously thought to have been caused by driveline slop, and it was the primary reason for a complete driveline rebuild from clutch face to rear wheel contact patch. The same backlash between rotating parts still exists; but since the sudden shift in engine braking between on and off idle engine status has been modulated, the noise has been almost completely eliminated. Furthermore, the bucking and jerking formerly associated with parking lot maneuvers has given way to a smooth tractor-like pull from idle. The engine can now lug from 750 rpm in second gear, and pull straight through its rpm range without so much as a hiccup. So I might be giving up some low or mid range power; or even around the town mileage (but I doubt it!). But I will gladly make that tradeoff for the tractability and sheer pleasure of driving with a smooth and seamless powerband.
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