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Closed loop lamba, variable AFR's.

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Closed loop lamba, variable AFR's.

Posted by bazzasti at January 24. 2008

Due to big cams my car likes to idle at 13.5 AFR. However cruise it's fine at 14.7. Having the ability to have the ECU switch between the two dependant on rpm, tps or vehicle speed would be cool :)

Re: Closed loop lamba, variable AFR's.

Posted by Ashley Duncan at January 24. 2008

In a  car running big cams you should not be running CLL at idle.  Especially if you are using a narrow band sensor as they are only useful at 14.7.  You should set the lower RPM lockout for your CLL above idle... 

Re: Closed loop lamba, variable AFR's.

Posted by bazzasti at January 25. 2008

It's a wideband :)

What is there any reason why you shouldn't be running CLL at idle with bigger than stock cams?

Re: Closed loop lamba, variable AFR's.

Posted by Ashley Duncan at January 26. 2008

As a general rule AFR's are usually too unstable at idle when big cams are used.  Note that our definitions of BIG cams may not be exactly the same.  If your engine can idle with a steady 13.5 then the cams may not be that wild and using CLL would probably be OK.  We plan to release an AFR table soem time in the future (no date set yet) that would allow you to do what you want, so for now set the lockout above idle...

Re: Closed loop lamba, variable AFR's.

Posted by bazzasti at January 28. 2008

Yeah they're only 272/272 with 11 mm lift so not to big and idle is quite easy to control but it loves to idle at 13.5. At 14.7 it sounds lumpy :)

That AFR table will be awesome when it arrives.

Something else I've noticed is the voltage effects the wideband dither. Voltage to low and it will cause the dither to run lean. Voltage to high and the dither is rich. I am using the injector voltage compensation to adjust but not sure if this is the correct way as when CLL is turned off the AFR's are fine again. Maybe a dither for different voltages would work? I've used an innovate and turboxs wideband and both had the voltage compensation issue.hmmmm

Re: Closed loop lamba, variable AFR's.

Posted by Ashley Duncan at January 29. 2008

The dither voltage effectively sets the AFR target.  You set the dither voltage to the voltage that your WB controller outputs at 14.7:1.  You will also need to invert your WB controllers output so it goes from 5-0V with low to high AFR, not 0-5V with low to high AFR.  You can intentionally try to make your CLL run lean or rich by adjusting the target voltage...


Do not use injector voltage compensation to change any AFR's!!!  That compensation is there to allow for battery voltage effects on injector deadtime.  It should be setup once at the start of tuning for a particular set of injectors and never adjusted again...
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