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change for 10:1 to 11.5:1 using datalogs

Old 06-11-2009, 08:52 AM
0.5 BAR
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Join Date: Jul 2006
Posts: 55
Default change for 10:1 to 11.5:1 using datalogs

At the moment I have no one to drive the car for me to datalog so I have a really rich map right now to go out and datalog.

I've always done live mapped and removed duty cycle on as the driver holds the revs.

I've got a datalog and I want to change the a/f ratio by upto 2 points in some places, how would i calcualte the difference in duty cycle % to add/remove on the map?

for exmaple i am at 2000 rpm , duty cycle 5.5%, a/f 12.36:1. I want 13.5:1. I have 1000cc injectors if it makes a difference.

at the moment I am sort of doing it be my instinct lol but I don't wanna upload it and then drive to find its meag rich or lean.

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Old 06-11-2009, 09:53 AM
0.5 BAR
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Join Date: Jul 2006
Posts: 55

figured it out in the end.

say you get a value in the cell which is 14(%) (dutycycle) and has an a/f 12.5 and you want 14.5

you divide 12.5/14.5=0.86 so now multiply your cell value by this 14*0.86= 12.06. You may have to round up depending on software.

I'm sure a lot of you guys know this already but I'll put it up for the noobs like me lol.
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Old 06-12-2009, 10:47 PM
1.5 BAR
Join Date: Nov 2005
Posts: 829

Holy crap thats a complicated way of tuning especially while driving, lol.

Rule of thumb is 1 AFR point =about 8%, so if your ar 12.5 and your target is 14 you would subtract 12% and it should get you close, just remember that the math isn't perfect because the ECU is actually interpolating the data from 4 different cells on the map at once and averaging them to find the correct pulse width.

Why are you watching duty cycle as a point of reference? using crome?
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Old 06-13-2009, 06:41 AM
3.0 BAR
Join Date: Oct 2005
Location: St. Augustine FL
Posts: 3,938

----, thats complicated. i guess i have just gotten a feel for it and do it.
Scott-EP is offline  
Old 06-15-2009, 12:14 PM
0.5 BAR
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Join Date: Jul 2006
Posts: 55

I can do live mapping pretty easily as thats the only way I have ever done it but I don't have anyone else that I trust to drive it so I gotta datalog it and then make my changes and try again another day.
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