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Afr reading

PostPosted: Tue Apr 17, 2012 12:48 pm
by jaydog82
I just finished rebuilding mt st165, I finally got my prosport wideband installed and I am trying to understand my afr readings. I have q jdm engine, stock ct26 running 15 psi, New everything on the motor prosport boost gauge, walbro 255lph fuel pump, straight intake and a 3" Aussie Dp. When I'm cruzing it reads around 14.7 under max boost around 10.0 and when I let off to slow down its reading 20.0. I did have some problems with my last maf, maybe I need to adjust the new one.

Re: Afr reading

PostPosted: Tue Apr 17, 2012 1:04 pm
by OutToWinPAHC
Off throttle does cause this, 14.7 isnt bad I like a 14.5 idle, but when do you see 10.0? That's a bit rich at certain areas on the throttle map

Re: Afr reading

PostPosted: Tue Apr 17, 2012 1:36 pm
by jaydog82
I am seeing 10.0 at wot at 15psi boost

Re: Afr reading

PostPosted: Tue Apr 17, 2012 2:05 pm
by RoAdbOy
it seems ok, but like the OutToWinPAHC said 10:1 is a bit at the rich side.
no problem to run it, but your car will be faster if you can adjust it to the 11:1 - 11.5:1 mark with a SAFC or another simple piggyback :)

Re: Afr reading

PostPosted: Tue Apr 17, 2012 3:09 pm
by jaydog82
Ya that's what I was thinking, what about adjusting the maf? I read that you can lean it out by adjusting the spring inside the maf.

Re: Afr reading

PostPosted: Tue Apr 17, 2012 3:19 pm
by RoAdbOy
jaydog82 wrote:Ya that's what I was thinking, what about adjusting the maf? I read that you can lean it out by adjusting the spring inside the maf.


yes of course you can :) but i wouldn't touch the maf.
i myself use SAFC too :) very simple and helpful unit when you can use it.
but watch out; do not set it more lean than %10
only small touches :)

Re: Afr reading

PostPosted: Thu Apr 26, 2012 6:20 pm
by Mafix
your conditions are completely normal for a stock ecu

Re: Afr reading

PostPosted: Thu Apr 26, 2012 8:30 pm
by jaydog82
Ok, is 15 psi the max I should run?

Re: Afr reading

PostPosted: Thu Apr 26, 2012 9:09 pm
by RoAdbOy
jaydog82 wrote:Ok, is 15 psi the max I should run?


i think 15-16psi is enough for a stock ct26 :) more than 18psi will increase hot air like hair dryer.

Re: Afr reading

PostPosted: Mon Apr 30, 2012 12:11 am
by Mafix
i'm not familiar with your car. generally on a stock gen 1 no more than 1 bar.

Re: Afr reading

PostPosted: Tue May 01, 2012 2:21 pm
by jaydog82
I have a 1st gen jdm motor, low mile ct26 with very little shaft play, all new gaskets seals hoses ext, New fuel pressure reg and damp, walbro 255 lph pump, cleaned and ballenced injectors, OEM spark plugs, New cap and rotor, magnacor wires, spec stage 2 clutch, rebuilt drive shaft and cv shafts, redline lightweight shockproof gear oil in the trans and diff, redline syn oil in the engine, ate super blue brake fluid, wta ic pump constant run mod with a 10" fan on the heat exchanger, 3" Aussie Dp, mbc set to 16 psi, straight intake with a arm dry flow filter and a shadow special catch can, battery relocation to the trunk, pro sport egt- boost and wideband gauges, all aluminum asi radiator from the c tech group buy, New Toyota thermostat, braided steel clutch line, ebc red stuff brake pads.

I plan on installing a water/meth injection and a 2.5" full exhaust, then start going through my suspension.

That's all I can think of for now for my mod list.

Re: Afr reading

PostPosted: Wed May 02, 2012 5:24 pm
by Mafix
that already is far beyond the computers capability. the st165 just goes full dump past 1 bar of boost. fyi.

Re: Afr reading

PostPosted: Wed May 02, 2012 5:29 pm
by underscore
^ but if he isn't hitting fuel cut then does the ecu even know?

Re: Afr reading

PostPosted: Thu May 03, 2012 12:14 am
by jaydog82
^ I have the stock boost sensor unpluged for now, untill I can get my dyi FCD installed.

Re: Afr reading

PostPosted: Thu May 03, 2012 12:18 am
by jaydog82
Mafix Do you have any input on my set up?