sr20det is running lean.

[S13NismoStyle]

Hi, i just recently installed a aem uego wideband into my s13 blacktop sr which ive only had for about 3 months. Its just about completely stock. I just have a full exhaust, z23 tt fuel filter and a fmic and im using a 180sx fuel pump. Ive been running it at about 10lbs with the stock t25 for the past couple of weeks with no problems really. But now, after installing the wideband i have noticed that my afr's have been running about 13.5-14.0 at wot. so i went and disconnected my mbc and was running vac straight to my wastegate. so now underfull boost it creeps to 8-9psi, but my afrs are still around 13.5 or so. I know this is way lean and im wondering what the possible causes could be. also my car is always running lean when crusing and not under boost. is this normal? i thought that the factory tune would be rich if anything. thanks for the help.

im also wondering that if my car has been running that lean for a while, what is the chance of severe engine damage. i havent been driving it i found out about it leaning out.

[srdub-t]

lean out of boost and not under load is ok.... but 13 at WOT is baad, i dont know what could be the cause of this, check your fuel pressure

[S13NismoStyle]

yeah thats what i was thinking. what afrs does a stock sr usually run. man i hope i havent hurt my sr, it only has about 35k on it.

anyone else have any other ideas.

[Emperor_Tha]

180sx fuel pump is the same as 240sx fuel pump as I recall. I would recommend getting a walboro. I was getting 16.0 at wot, bog at 4k rpmon a bad fuel pumpJust a little helpalso check for exhaust leak before the wideband sensor

Stock maf, psi at 7, safc untuneidle 14.7cruise at 2-5% throttIle 14.5-15.2wot 10.6

Z32 maf, 7 psi, safc tuneIdle 13.2-14.2. I run a little richer to keep the engine coolercruise. 14.7-15.6. Mwanahah close to 30mpg 16.0 at 0% throttle while in gearwot 12.0. On 93 octane, 12.2 is safe to run cuz it is low boost.

[IanS]

Stock tune I see around 12.5 WOT, anywhere from 13 to 17 while cruising, depending on load. 13 to 15 at idle, depending on engine temp.

[uberkillerz240]

yea. i agree. the stock fuel system gets maxed out fast. i heard some even say it does at around 10 psi, but not sure about that number. getting a walbro fuel pump and a regulator will definitely help. Are u runnin @ 10 psi all day everyday? does any1 know when the injectors get maxed out? cuz that would help us both.

[S13NismoStyle]

Im not running 10 psi anymore. When i was running 10-11 psi, i was getting the EXACT same afrs that i am getting at 8 psi.

also, my afrs at idle and while cruising seem to be consistent with everyone elses, but mine at WOT are still lean. I will check for a exhaust leak today.

im pretty sure that im not maxing out the injectors. what fpr does everyone recommend? ive read mixed things about the nismo ones.

also, does anyone know how to check the stock fpr to make sure it is working properly?

thanks

[IanS]

im pretty sure that im not maxing out the injectors. what fpr does everyone recommend? ive read mixed things about the nismo ones.

also, does anyone know how to check the stock fpr to make sure it is working properly?

thanks

Ive been running the Nismo FPR paired with a Walbro pump for 3+ years now. The stock regulators tend to run too high of pressure when the high flow pump is introduced. Check your fuel pressure to see if the regulator is failing.

With a walbro pump, the stock 370cc injectors reach maximum duty cycle around 14 psi with the T25. The stock MAFs is also reaching its limits at this boost level.

I have been running 12 PSI for over a year now, before that I ran 10, this all on stock injectors, MAFs, and a T25.

If your AFRs are normal everywhere accept at wide open throttle, I would check for an exhaust leak, or a small leak in your intake pipe, after the MAFs but before the turbo.

[S13NismoStyle]

thanks for the suggestions. I swapped out fprs and mafs with a friend and i didnt change anything.

there werent anyone exhaust leaks or vacuum leaks on the intake.

I have no idea what it could be. thanks again

[Tulsa_S-13]

"The book also works as a hat"
Modified by Tulsa_S-13 at 2:30 PM 3/17/2008

[S13NismoStyle]

i just got this from the garrett turbo website.."Leaner AFR results in higher temperatures as the mixture is combusted. Generally, normally-aspirated spark-ignition (SI) gasoline engines produce maximum power just slightly rich of stoichiometric. However, in practice it is kept between 12:1 and 13:1 in order to keep exhaust gas temperatures in check and to account for variances in fuel quality. This is a realistic full-load AFR on a normally-aspirated engine but can be dangerously lean with a highly-boosted engine.

The turbocharger increases the density of the air resulting in a denser mixture. The denser mixture raises the peak cylinder pressure, therefore increasing the probability of knock. As the AFR is leaned out, the temperature of the burning gases increases, which also increases the probability of knock. This is why it is imperative to run richer AFR on a boosted engine at full load. Doing so will reduce the likelihood of knock, and will also keep temperatures under control. "

found this too Mixtures leaner that stoich (15:1 ~ 18:1) provide better fuel economy (unsurprisingly, since they contain less fuel!) and sometimes we do want our fuelling to be this way, especially during deceleration, or light throttle openings (cruising). But put your foot down at the strip, and if you're running 18:1 you ain't going anywhere. Acceleration needs richer than stoic, 14:1 ~ 13:1, sometimes even 12.5:1. A turbo under low boost needs to be around 13:1 minimum, and under full boost richer than that. HOW MUCH richer depends on chargecooling, ignition mapping and other factors.

i know that i am running richer than stoich, but 13.5-14.1 is still consider lean for a turbo car. or so i have been told

[Emperor_Tha]

try pinching the return line and see if the the afr drops down richer under wot. Possibly bad fpr, or weak fuel pump under a load. My problem was the walboro fuel pump crap out on me after 1500miles.

[S13NismoStyle]

i already swapped out the fpr.im getting ready to try the fuel pump. I just dont understand why the afr would be the same at higher boost as it would at lower boost if the fuel pump was bad.

could timing affect afrs

[uberkillerz240]

im not exactly sure, any help from some1 else? cuz this is benefitting me 2.

[IanS]

This whole time we have been troubleshooting with the beliefe that the engine is running lean, but what if its not, what if you only think its running lean, because that is what the gauge tells you. What if the gauge is wrong?

Where did you mount the new wideband o2 sensor?

Are you using the factory o2 sensor to feed the ECU, or are you using the analog output from the UEGO?If you are using the analog output, what setting do you have it on?

[S13NismoStyle]

my uego is mounted about 20 inches down my downpipe from where it bolts to the 02 housing. i am using the factory O2 sensor in the O2 housing as well. Ive tried a friends innovate wideband with the same result. so i dont know.

Im almost just going to get some type of engine management and just increase my fuel. i know that is just like putting a band-aid over the problem, but im running out of options.

thanks again for all the advice.

[Emperor_Tha]

Check your fuel pump. When I first install my fuel pump in my gsx I was running lean. Problem was the fuel pump was not secure to the post. It moved to the side so the hose and the pump nipple werent proberly line up in a striaght line

[S13NismoStyle]

yeah im going to swap out fuel pumps to see if that helps.

could i be getting voltage drop to the fuel pump at wot?

and ive checked my timing. its perfect.

what do you guys think about just running a safc and adding more fuel?