| Re: [GMCnet] EFI Question [message #349766 is a reply to message #349764] |
Tue, 29 October 2019 19:32   |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
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James Hupy wrote on Tue, 29 October 2019 19:25This might get into reaction time for O2 sensor response to rapid pulsations of different concentrations of air/fuel. I have not got a clue how rapidly the sensor can read changes like we are discussing. But, I bet Matt can shed some light on it.
I do know from 1st hand experience that when the system is in closed loop, that very tiny changes, like a misfiring plug or an injector that sprays odd patterns occasionally due to foreign stuff in the fuel stream, will cause fluctuations in rpm. So, is the computer playing catch-up with erratic information from sensors? I dunno.
Jim Hupy
Salem, Oregon
Jim is very right (not any big surprise here), his experience is well founded.
Ready, Long story follows.....
The reaction time of O2 sensors is fast enough that back in the 80s, we were doing a development program for the 302. The OE was having a hard time getting the power that they though should be there without other problems. We did a two fold distribution study. This was a study of first mixture and then charge pressure (just after the intake closes). We could see the variations in mixture by cylinder, but even flow matched injectors could not fix it. This lead to the charge pressure study. Because the intake is a dynamic system, it is also crankshaft speed dependent. We looked at the maps we developed and then went back to watching the O2 signals. Things didn't make sense until we built "stereo EGO" exhaust. Then we used high speed analysis instruments to watch both banks individually. Whoa, we could isolate the individual cylinders! This was not a passcar production ECU, so we were able to adjust the cycle time of injectors by cylinder and then pull up to WOT and configure the individual timing to match. All this from the output of the "stock" (no special part number) O2 sensors. We were able to map and modify the controls to the individual cylinders and not just let the poor ones rule.
Customer was introducing a new and more capable ECU. When we passed the reports along, BOOM. We were in the middle of an unexpected (but very profitable) amazing development program. This was before internet, we tried to Modem the days data to their group. In a month, we had the first ISDN line I had seen installed to pass the days data to them in almost real time.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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