jc052685 Posted December 21, 2008 Share Posted December 21, 2008 the car just started to ??afr walk?? last night while tunning. I niticed the duty cycle is doing the same. But I am not seeing the cause of it. This is my first time using the datalog so I am not sure but I thought the RPM signal was rather noisy. Maybe not. There is only so much the ECU uses to control fuel delivery so I am sort of at a loss. Thanks Jeff http://i217.photobucket.com/albums/cc114/jc052685/screeenshotAFRsearching.jpg Quote Link to comment Share on other sites More sharing options...
jc052685 Posted December 22, 2008 Author Share Posted December 22, 2008 ok, I have figured out that the wideband o2 is also being read as the fuel pressure. So it gets this rich lean/ low high fuel pressure wave form going on. How do I get Megasquirt to ignore fuel pressure or just turn it off completely? Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted December 22, 2008 Share Posted December 22, 2008 Megasquirt normally ignores the fuel pressure; it's just used for logging. Do you have a data log and MSQ that you could post? These will provide more information than a screen shot. However, my gut feeling is this is a combination of a somewhat out of tune VE table with a large amount of O2 correction: This will produce the sort of bouncing behavior you're looking at as the system overcorrects and swings back and forth. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted December 24, 2008 Author Share Posted December 24, 2008 is this better? notice the AFR and the fuel presssure are the same wave form Quote Link to comment Share on other sites More sharing options...
jc052685 Posted December 24, 2008 Author Share Posted December 24, 2008 little bigger here http://i217.photobucket.com/albums/cc114/jc052685/Untitled-2.jpg Quote Link to comment Share on other sites More sharing options...
mobythevan Posted December 29, 2008 Share Posted December 29, 2008 What are your EGO settings for steps between corrections, authority and correction amount? Maybe changing those a little will help EGO ignore the pressure fluctuation. Do you have any kind of damper on the fuel system? Also, do fire all injectors simultaneous or alternating? These are all things that can lead to pressure oscillations which will cuase some trouble trying to get a stable idle and stop AFR oscillation. Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted December 29, 2008 Share Posted December 29, 2008 Please, I need the data log itself, not a screen capture. There's information in the data log that the screen capture doesn't show. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted December 30, 2008 Author Share Posted December 30, 2008 What are your EGO settings for steps between corrections, authority and correction amount? Maybe changing those a little will help EGO ignore the pressure fluctuation. Do you have any kind of damper on the fuel system? Also, do fire all injectors simultaneous or alternating? These are all things that can lead to pressure oscillations which will cuase some trouble trying to get a stable idle and stop AFR oscillation. I think you are missing that I have no Fuel pressure sensor to even connect to the megasqirt box. Injectors fire in 2 sets. no dampner, my fuel pressure has no oscillation. It is the setup seeing the O2 sensor as a fuel pressure sensor also. MATT, How would I upload this file for everyone to see? Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted December 30, 2008 Share Posted December 30, 2008 I think you are missing that I have no Fuel pressure sensor to even connect to the megasqirt box. Injectors fire in 2 sets. no dampner, my fuel pressure has no oscillation. It is the setup seeing the O2 sensor as a fuel pressure sensor also. MATT, How would I upload this file for everyone to see? If you want to upload it here, put it in a ZIP file along with your MSQ, make a post in Advanced Mode, and click the Manage Attachments button to post it. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted December 30, 2008 Share Posted December 30, 2008 Even though you don't use fuel pressure at all, the EGO settings are relevant since that will directly affect the searching. What size injector are you running? Quote Link to comment Share on other sites More sharing options...
jc052685 Posted December 31, 2008 Author Share Posted December 31, 2008 Even though you don't use fuel pressure at all, the EGO settings are relevant since that will directly affect the searching. What size injector are you running? ok, file should be attached. runnning 440cc. Also, I think I said it already but, with the wideband disconected from the ecu then there is no afr searching. Both gauges go dead. Fuel Pressure & O2 jeff 12-19-09 afr hunt.zip Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted December 31, 2008 Share Posted December 31, 2008 Ok, try decreasing the Controller Authority percentage to zero, and get the AFR in the 2500 to 3000 RPM / 45 to 50 kPa range to match your target. This data log shows that you've got a case of a somewhat aggressive O2 correction and a VE table that's just a little bit out of tune. You can turn the controller authority back on once the VE table is fixed, though I wouldn't go over 10%. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted January 1, 2009 Author Share Posted January 1, 2009 Ok, try decreasing the Controller Authority percentage to zero, and get the AFR in the 2500 to 3000 RPM / 45 to 50 kPa range to match your target. This data log shows that you've got a case of a somewhat aggressive O2 correction and a VE table that's just a little bit out of tune. You can turn the controller authority back on once the VE table is fixed, though I wouldn't go over 10%. This is a great but why am I seeing an identical waveform from my fuel pressure? I dont want megasquirt to even recognize fuel pressure as something thaat even exists. I basicaly want to see the waveform as a solid line. But yes, that makes sense and I will give it a shot. Thanks Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted January 2, 2009 Share Posted January 2, 2009 Unless you have wired up a fuel pressure sending unit, the reading from the fuel pressure log is going to be something random. Could be reading electrical interference from the O2 input, even. The Megasquirt doesn't use this reading for any of its calculations. You could ground the spare ADC port through a 1K resistor if it bothers you, but really, there's no need to look at the fuel pressure log anyway. Quote Link to comment Share on other sites More sharing options...
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