Questions about my SR20det AFR's

[jerryscherry]

So installed my wideband today and went for a short drive to the market.

-when i come to a stop/idle initially it will be at about 14.6-15.. then after a few seconds it will be like 13-13.5 and stay there.

-partial throttle 0-4psi boost will give me 15 to mid 16's (lean or okay?)

-WOT from 1-4krpm it will be about 12-13ish then taper down to mid 11's in higher rpms

-Cruising is around 14.6 to low 15's

-i'm concerned about my partial throttle/boost AFR'S (15 to mid 16's??) since i have been trying to figure out my hesitation problem that occurs on partial throttle from like 3500-4000 rpm.

And also im worried about my 12-13 on low rpm WOT.

Stock sr20det redtop t25, stock boost, stock sr 370cc injectors,stock FPR, walbro 255, FMIC, 3in from the turbo back, stock ecu.

Are my partial throttle AFR and Low RPM WOT AFR's okay? It seems a bit lean based on some articles I read online.


Update 02/03/2014

i tried to pinpoint my hesitation problem, it occurs at 0-2psi around 3800rpm ish, AFR at 17.5 from my knowledge

Idle should be like 13-14, cruise 13-14 , partial accel boost 12-13s and 11s at full boost , somebody correct me if im wrong?

Update 02/08/2014

ordered a DC sports aluminium intake to replace my crappy oem rubber one, that was leaking a little from the re circulation port. (maybe sucking in a lot of unmetered air, going lean)

seems fine now, hesitation is gone, afrs no longer ever hit 17, the partial boost is more like 13-14 now. Car gets on boost a lot smoother now

i hope this was the fix to my problems, its only been one day, crossing my fingers!

[Seraphim38]

Yes, more rhan 14.7 is too lean. Below 11 is too rich.

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[jerryscherry]

Yes, more rhan 14.7 is too lean. Below 11 is too rich.

Sent from my SGH-T999 using Tapatalk


so what is ideal afr for low boost/partial throttle? 12-13? and for WOT is it supposed to be around 11 the whole power band including low rpm?

and what could cause the lean conditions? I just changed my fuel pump for a walbro 255, cus my previous walbro died...

FPR?

[Seraphim38]

Naturally aspirated optimal afr is 14.7 ish, if not just a little less. Boost is 12.5. At 11 there is too much fuel, which can "wash down the cylinders" and reduce the oil on the cylinder walls. Above 14.7 the engine start to generate heat and can melt pistons under load.

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[Seraphim38]

Stock fprs can creep with lots of fuel pressure. With a lot of stock components, your ability to tune is limited.

Martin at rs enthalpy comes to mind as a good option...

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[Kingtal0n]

Your problem is the maf. Grab a different SOHC KA maf, actually grab a few of them. Or try cleaning yours. I see this ALL the time on redtops;

everything else you describe is normal. The dropping down at idle, the wot a/f etc.. is all fine.
You don't need a rom tune on any stock engine.

[jerryscherry]

Stock fprs can creep with lots of fuel pressure. With a lot of stock components, your ability to tune is limited.

Martin at rs enthalpy comes to mind as a good option...

Sent from my SGH-T999 using Tapatalk

im not worried about fpr giving too much fuel, but too less fuel if thats possible x.x weak
diaphragm or something
Your problem is the maf. Grab a different SOHC KA maf, actually grab a few of them. Or try cleaning yours. I see this ALL the time on redtops;

everything else you describe is normal. The dropping down at idle, the wot a/f etc.. is all fine.
You don't need a rom tune on any stock engine.

thank you, i cleaned my maf last month trying to fix the hesitation problem at partial throttle, didn't change much, sprayed the shit out of the sensor with maf cleaner

you think this could be fpr related? i will swap some different Mafs to make sure mine isn't bad. i was driving today trying to pinpoint my hesitation, its at about 0-2psi 3800ish rpms, AFR at 17.5!!!! :O thats wayy too lean even under partial throttle right?

[Kingtal0n]

Yeah. its either the maf or the TPS. If it goes that lean suddenly then maybe you should also try a different tps. Dont bother adjusting them or recording the output voltage; usually even bad ones will read proper most of the time. The reason they are "bad" is because, faster than a voltage meter will show, the voltage spikes or fluctuates down or up, but you do not notice because it happens too fast. So just swap it out. Swap the maf and tps out, one at a time, 99% that is your problem.

The fuel pressure would only be an issue if the pressure rise is delayed. In other words, when you stab the gas pedal, the pressure should shoot up. This is because you have a vacuum source on the FPR that feeds off the intake manifold. If this source is poor, or if it is tapped off into something else, response will be delayed and the result will be what you are experiencing. So make sure your FPR has a good DEDICATED vacuum source, with a very short small tube connecting to the intake manifold (usually through the throttle body).

See my thread here for more info about the maf:
http://www.freshalloy.com/showthread.php/169975-More-random-observations-about-OEM-SR20DET-S13-engines

[jerryscherry]

Yeah. its either the maf or the TPS. If it goes that lean suddenly then maybe you should also try a different tps. Dont bother adjusting them or recording the output voltage; usually even bad ones will read proper most of the time. The reason they are "bad" is because, faster than a voltage meter will show, the voltage spikes or fluctuates down or up, but you do not notice because it happens too fast. So just swap it out. Swap the maf and tps out, one at a time, 99% that is your problem.

The fuel pressure would only be an issue if the pressure rise is delayed. In other words, when you stab the gas pedal, the pressure should shoot up. This is because you have a vacuum source on the FPR that feeds off the intake manifold. If this source is poor, or if it is tapped off into something else, response will be delayed and the result will be what you are experiencing. So make sure your FPR has a good DEDICATED vacuum source, with a very short small tube connecting to the intake manifold (usually through the throttle body).

See my thread here for more info about the maf:
</title> <link rel="shortcut icon" href=/images/"favicon.ico" > <link rel="icon" type="image/gif" href=/images/"animated_favicon1.gif" > <script type="text/javascript"> </script> <script type="text/javascript" src="http://www.freshalloy.com/clientscr (http://www.freshalloy.com/showthread.php/169975-More-random-observations-about-OEM-SR20DET-S13-engines)

Thank you for your information, I will try the TPS and MAF, and it seems im pretty much lean on all partial throttle, no really sudden jump, but when I had the hesitation, it gradually was showing 17.5ish ,

I will try those and let you know! , my FPR vacuum is T off to my boost gauge, isn't this what everyone uses it for? i've had the problem before my boost gauge though, so might not be a weak vacuum problem

[jerryscherry]

bump i think i may have fixed my problem, see updates in original post :)