Afr reading

jaydog82

New member
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.
 

OutToWinPAHC

New member
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
 

RoAdbOy

New member
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 :)
 

jaydog82

New member
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.
 

RoAdbOy

New member
jaydog82":df5l9291 said:
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 :)
 

jaydog82

New member
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.
 

Mafix

New member
that already is far beyond the computers capability. the st165 just goes full dump past 1 bar of boost. fyi.
 

tubasteve

New member
A mbc can't "be set to", if you have consistent temps, then i could see this. When i ran mbc i would see 14 @ 85°, and 5 hours later @ 55° coos see as much as 16-17 psi. Bottom line watch/datalog your boost.

Aem gauges i believe can't read below 10:1.

Also didn't see a mls hg? Is be worried of blowing the head gasket around that boost.
 

jaydog82

New member
Still running the stock hg, that's why I'm not going above 16 psi. I watch my boost like a hawk and it never changes, I did some research and found a high quality mbc that does not very.

Ya my gauge reads from 10-1 to 20-1
 

tubasteve

New member
i would get an aem "true boost" it can shut down the boost kind of like the stock pcm if it sees over boost, and log your boost, and be used with the plug and play. i have one on my red car, and if i raced or wanted to trick out my black car she would have one already. it really saved my ass one night.

i also would not mess with the maf. find another way to tune it, like an adjustable fuel pressure regulator.
 

jaydog82

New member
I'm running a prosport electronic boost gauge with warning and prosport egt and prosport wide band.
Ya I'm not Gona mess with the maf, I might get a safc or just leave it better to be rich than lean.
 

tubasteve

New member
agreed, those are what i use in my black one. they are fine, but ive seen them tend to get off over time(boost gauges) my brother in law was messing around in his evo, never realized where the gaugue sat when off, it read "25psi"......the computer saw close to 35 when cyl #3 desided to take a detour out the side of the block.........then 20 mins later i met my wife for the first time :twisted:
 
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