The highest value anywhere in my FN2200 spark table is 43, but for some reason, after moderate accel to 4000 rpm, followed by a closed throttle decel I have logged as high as 49 dbTDC, generally about 2 secs after releasing the go pedal.
Just wondering why this happens?
Sean
Why does spark exceed spark table value (sometimes) on decel?
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- Posts: 67
- Joined: 2021 Mar 31, 17:29
- Location: Victoria, BC CANADA
- Vehicle Information: QH, TunerPro RT 5, GUFX_220418.xdf, A9L2_220405, DECIPHA_220505.ADX, 395w, AFR 195CC Renegade heads, Comp XE274HR cam, Siemens-Deka V 80lb/hr (shorties), Mass-Flo-EFI style 4bbl throttle body with GM maf on top. Custom long tube headers, sidepipes, 5 spd manual.
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- Posts: 67
- Joined: 2021 Mar 31, 17:29
- Location: Victoria, BC CANADA
- Vehicle Information: QH, TunerPro RT 5, GUFX_220418.xdf, A9L2_220405, DECIPHA_220505.ADX, 395w, AFR 195CC Renegade heads, Comp XE274HR cam, Siemens-Deka V 80lb/hr (shorties), Mass-Flo-EFI style 4bbl throttle body with GM maf on top. Custom long tube headers, sidepipes, 5 spd manual.
Re: Why does spark exceed spark table value (sometimes) on decel?
OK, looks like FN389 Dashpot CT spark multiplier is the culprit! the actual dbTDC value made me nervous but checking it against FN389 x SAFTOT, I can see it's adding timing to try and more quickly stabilize idle speed from closed throttle transition.
Sean
Sean