Your afr's, not just threw boost but before and after also - Boost Forum

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Your afr's, not just threw boost but before and after also
Saturday, November 17, 2007 4:39 PM
Im getting ready to install my Megasquirt, but I just realised I dont know what my crusie idel decel and mild pull afr's should be. I plan on keeping my WOT set to 12:1 Im thinking 11:1 for idle 13.5 for crusie and 12 for decel. I figure Im not really woried about the crisp response that comes with the leaner AFR's becuase I can just make up for it with timing not to mention the richer fuel is safer


But I curious as to what the rest of you guys are seeing.


"Kick azz is my boost hero!!! "
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Re: Your afr's, not just threw boost but before and after also
Saturday, November 17, 2007 4:45 PM
do you not pay attention to what people post ?

idle and cruise should be around 14.7 decel will go up near 20 , accell off bost mid to low 13






Re: Your afr's, not just threw boost but before and after also
Saturday, November 17, 2007 4:48 PM
11:1 at idle is way too rich... You'll most like see black smoke for sure. I have mine idling at 13.5:1. Under full boost it's at 11.8:1, cruising at 12.5-13:1, and decel at 15.5:1. Car runs excellent and is very responsive.



Re: Your afr's, not just threw boost but before and after also
Sunday, November 18, 2007 10:32 AM
I didnt know your decel was supposed to be lean? Ive been rumageing threw my megasquirt and there is a decel inrechment table that I have yet to tackel.

thanks man.


"Kick azz is my boost hero!!! "
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Re: Your afr's, not just threw boost but before and after also
Sunday, November 18, 2007 10:49 AM
Yes you do want the decel lean. You won't be in boost or have any demands for fuel. It's mostly just to increase fuel milage. But where my car is mostly just a track car i don't worry about fuel milage to much. But you will want it lean, probably even more lean than i run mine at.



Re: Your afr's, not just threw boost but before and after also
Sunday, November 18, 2007 12:04 PM
ecotec
s see knock in boost at anything above 12:1 afr under wot. I'd suggest 11.5 - 11.8 afr under full boost



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Re: Your afr's, not just threw boost but before and after also
Sunday, November 18, 2007 3:53 PM
[quote=97cavie24ls(™)]do you not pay attention to what people post ?

idle and cruise should be around 14.7 decel will go up near 20 , accell off bost mid to low 13

Agreed, although maybe a tiny bit richer on decel- 17or 18:1 would be good.
Decel enrichment (not sure why they call it that) is a percentage reduction when TPS and MAP are decreasing. They actuallyrecommend starting with a cruise AFR of 16.5 and adjusting it from there- don't think i would try that though.
Curiosity- are you running MS1 or MS2, and what version processor? Also have you printed off all the megamanuals, its a lot off printing, but its worth it for being able to highlight important things for easy reference.

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Now with northstar V8, IRS, 20's n 22's
Re: Your afr's, not just threw boost but before and after also
Sunday, November 18, 2007 5:01 PM
ms1 v 2.2 I read and read and read. but I can assure you theres always more. I kinda just wonder where most stock cars run.


"Kick azz is my boost hero!!! "
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Re: Your afr's, not just threw boost but before and after also
Sunday, November 18, 2007 5:58 PM
Well then these are pretty good numbers to start with, if something doesnt seem to work for you then you can tweak it from there. Under cruise my wideband showed mid 14's, decel was 17 or leaner and under boost is all a matter of opinion. Does MS1 have a knock sensor reading? if not get yourself a gauge (i have seen them, never looked into where to get them) And i dont believe MS1 has ignition retard for knock, so thats something to be very careful with

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Now with northstar V8, IRS, 20's n 22's
Re: Your afr's, not just threw boost but before and after also
Monday, November 19, 2007 12:09 PM
03-05 eco run 14.7 or there abouts constanly , except decel which should end up close to 20

most stock tunes will go close to off scale lean on decel , alot depends where your measuring at , GM shuts the injectors off on long decel in attempts to save gas , and provides some engine braking to slow you down , give the piston some time to cool down

id try and keep the cruise ratio in the 14's , lower than 14 and youll loose some mileage









Re: Your afr's, not just threw boost but before and after also
Monday, November 19, 2007 1:24 PM
I would start off at 11.5 under boost tapering into the 13s everywhere else.

After its running fine I would begin to lean the idle and cruise operation to 14.6.

As far as decel goes, factory PCMs totally cut off fuel during decels. It is not a requirement to do that though, the factory does it for economy.
Totally cutting fuel can be a pain if not spec'd out correctly. It dries out the manifold and can cause huge tip-in spikes and surges when you want the power back on.

If you want it, it has to be a fuel cut, not a lean shift. Simply shifting lean to 15-18 range will cause exhaust backfiring. The 20:1 that was posted came from the limits of the readout unit and is not the actual A/F during decel. Its much leaner.

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