Time for a Pro? or do I go?




Ok so I am having a problem.  I can set up the car just fine, part throttle, full throttle, cruise is just fine.  When I come off the throttle,  the revs will drop, and either catch at about 800 rpm stumbles or almost stalls to 100 RPM then recovers. 


When I take my foot off the gas, it pins full lean, even if I force the system to still pump fuel. So it is one of two things


1) My spark control is bad or something with the ignition that I can't figure out.  Everything has been gone through, there is one thing I need to check with Holley tech support.  I have an adapter to run the tach.  I am not sure if it should be on the MSD now that the Sniper is in or run off the "Tach out" on the Holley. From all that I can read, it doesn't matter.  Losing spark on the way down would cause a false lean. 


If anyone knows if something that will fool the Holley, please let me know.  The Holley can control the timing but I would have to heavily modify a Holley dual-sync dizzy to fit   It needs a 12V square wave output, not sure If I can get there with a trigger wheel.  I am looking at the megajolt software tonight.  


2) The other thing is it is registering a false lean for another unknown reason, be it a combination of head, header, intake etc... that will require an engineer to diagnose, and expertise far beyond mine. New intake gaskets, header,and a new O2 sensor after the Holley one broke (will get replaced under warranty), cap rotor, plugs just to make sure that it isn't something simple, has been done. Voltages look fine, worked with my NA setup. 


The problem, as far as I can tell, is that the false lean, causes the EFI to dump fuel, then it dumps too much, on the way down to idle.,  floods it and causes it to stall and stumble.  Can this be tuned out? I am not sure.  


Maybe I am reading this all wrong, but it is the only thing that makes sense based on the fuel flow and the data and what I can cobble together.  Any other theories are welcome.  


It does idle nice, if I am out of closed loop, it is just every time I come to a stop, the stalling is just too annoying to overlook. 



Below is the data. 


On the left side, I forced open loop so the Closed loop comp stops trying to fix this.   On the right, I have closed loop, and you can see the idle peak then drop.  The red is RPM.  





Below you can see how CL comp chases the spike lean in the AFR. 













Sniper Log hunting idle.dl

BMW2002 v 14 Reboot.sniper.info.txt


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Yes the 02 sensor fixed the massive waffling of the 02 readings.  Now for the first time, it appears to be actually measuring the AFR correctly and consistently.



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17 hours ago, Dudeland said:

Yes the 02 sensor fixed the massive waffling of the 02 readings.  Now for the first time, it appears to be actually measuring the AFR correctly and consistently.



Dudeland, I apologize for the hiatus.  For some reason I am still not getting notifications.  Any new updates since you've gotten it running better?  Also, if you don't hear from me, the best way to reach me is via telephone.  -Luke @ Holley Tech

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Hey glad to hear you've made some good progress on getting things running correctly!  Hope your starting to have fun with things and can't wait to see how the next datalog looks!

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It is really getting dialled in.  I am in an intensive Data Science Bootcamp for the next 12 weeks.  I am driving the car more than normal, as a result, I have more feedback on the tune.  


Cold starts are much better.  The only tiny glitch I have is after the startup hold starts to decay, there is a slight stumble for 2-5 seconds, then back to smooth running.   It is by no means a game stopper, and I doubt anybody but me would really notice it. 


BTW how do I get the old 02 sensor covered under warranty.  It is through Summit?, or do I go straight to Holley?






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Just a quick update,  I am going to post a wrap-up on the install to this point.   


When I was tuning I took out the vacuum advance, just to make it a little easier to find the base tune.   I got around to smoothing out the advance curve a bit and put in the Vac advance again.    I have to say it made a big difference in terms of accelerating at low speed+RPM.  It detects the load and responds, I never quite understood it untill now. 


The change would normally dictate some futzing around with jets et al, but with the EFI, I let it get a much fuel as it likes, and boom, instant performance, nice and easy.   A really nice ( and unexpected)  upside to having this sort of system.  It gets the best performance out of any change you make. 






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