Keeping T/C off
05-29-2012, 03:55 PM
#21
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Let me just clarify here, I was under the impression, possibly mistaken, that the newedge and S197(at least earlier 05-09s anyhow) used a round robin approach, but that a step involved cut fuel in such a way as it could still cause catastrophic detonation should you be FI. From what I interpret you're saying, this is not the case?
How can NO fuel cause detonation? What it does do is unevenly cool the exhaust valves, and possibly damage the cats, the "round robin" routine is specifically incorporated to deal with that as stated in the code snippet.
The specifics as to how it was doing so was not previously researched by myself, so that's good to know. But you're talking(well, writing anyhow) to a programmer, general IT guy, and former electrical engineering student. I've only tried starting to be a gear head in the past few years, so many of the finite ins and outs put me in the "special" section here still.. Hence my scouring of different sections, and even forums, although this one is of course home.
Implementing a 2-step limiter in the tune, by intelligent disabling of injectors, produces less smooth engine operation during the limiting action; this is and the "wive's tale" about cutting fueling are the basis for the objections raised by the "MSD/ignition cut-off" crowd. However the downsides of not cutting fuel delivery while cutting ignition make that less smooth limiting action a viable trade-off.
You can hold a fuel cut-off engine at the limit indefinitely, you would not want to do that with an ignition system cut-off system; MSD specifically warns against it in their literature.
Are you familiar with C? PM me...
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