SimonR Posted December 27, 2007 Share Posted December 27, 2007 Hi Folks, I’m a little confused about some fuelling behaviour during auto gear changes and wonder if anyone can shed any light. In the attached log sample (from the Pod – 12.5@118) I’ve noticed that my AFR goes peculiar during gear shifts. My car is an auto so there’s no backing off the throttle, so the butterfly stays open and fact that the boost remains fairly constant seems to confirm this. Injector duty cycle and pulse width also don’t change drastically but the AFR during the shifts (in this case 2-3) goes super-lean. The only other variable that I can think of is retarded timing from the ECU to make the shifts smoother. Timing changes wouldn’t account for those lean AFRs, would they? And no – my map isn’t pulling fuel in the relevant cells! Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 27, 2007 Share Posted December 27, 2007 It's probably actually going very rich, but the wideband is confused due to the unburnt fuel in the exhaust during gear changes. Quote Link to comment Share on other sites More sharing options...
SimonR Posted December 27, 2007 Author Share Posted December 27, 2007 Why do you think that Chris? The injector duty cycles don't appear to be increasing drastically. I can't think where else the additional fuel would come from to make it run rich. Mind you, I don't see why it would run lean either Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 27, 2007 Share Posted December 27, 2007 It's not the AMOUNT of fuel that varies, it's how it's burnt (or not, in this case). Quote Link to comment Share on other sites More sharing options...
SimonR Posted December 27, 2007 Author Share Posted December 27, 2007 Many thanks for that. Any idea how I would diagnose this? Presumably the same limitation to the funcitonality that you describe on my Wideband would also apply to other Wideband sensors? Is it time for a proper gas analyser? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 27, 2007 Share Posted December 27, 2007 Many thanks for that. Any idea how I would diagnose this? Presumably the same limitation to the funcitonality that you describe on my Wideband would also apply to other Wideband sensors? Is it time for a proper gas analyser? It's not a problem, it's something all cars will do. Quote Link to comment Share on other sites More sharing options...
paul mac Posted January 7, 2008 Share Posted January 7, 2008 My car is an auto so there’s no backing off the throttle, so the butterfly stays open unless you have modded the car the trac butterfly closes on full throttle gear changes, the ecu does this as well as retarding ignition to protect the auto box, sorry if you allready know this Quote Link to comment Share on other sites More sharing options...
SimonR Posted January 7, 2008 Author Share Posted January 7, 2008 unless you have modded the car the trac butterfly closes on full throttle gear changes, the ecu does this as well as retarding ignition to protect the auto box, sorry if you allready know thisNo probs, thanks for the input. TRAC only on the decent cars - I got the poverty version No ABS either Quote Link to comment Share on other sites More sharing options...
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