SR20DET stock fuel pressure??

[Zaxx84]

Hey, I'm working on passing emissions at the moment, and I seem to be running a little, or actually, a lot rich. On stock FPR with my Walbro 255 LPH high pressure, I was pushing about 35 PSI, it backfires quite a bit, mostly when I'm downshifting. And by the way, I had bad sputtering at high RPM's, as if I was flooding slightly.

So today I got my Nismo adjustable FPR, just got it hooked up, and tried it in increments, I have not set it to lower than 25 PSI at idle, and it runs a LOT better, but I still heard SMALL backfires.

I guess my question is this: what is it supposed to be at on stock boost at idle? How low can I safely go?

[SWIFT_DRIFT]

On stock boost at idle with a Walbro you should actually be in the 40-50 psi range (I've heard 40-45psi and some as high as 49psi). Also make sure you are testing pressure on the fuel SUPPLY line (duh, but just in case).

The fuel pressure on the stock FPR sounded about right. Should be between 35-36 psi. So sounds like something else is the culprit and not the FPR. Are you running an atmospheric BOV? Have you replaced the plugs, check the O2 sensor, etc? Also the sputter at high rpms to me sounds like a running lean problem, not rich. A good indication of running rich would be a LOT of black smoke out the exhaust at full boost and poor gas mileage. How long was your car backfiring and sputtering when you were using the stock fpr?

Hope this helps a little more info would be appreciated to help diagnose the problems.

[Zaxx84]

Yes, I am running an atmospheric blow off valve, but when I wen to emissions, my hydrocarbons were EXTREMELY high, so I fugured I was running rich.

[SWIFT_DRIFT]

Well I asked 5 questions and you only answered 1...

[Zaxx84]

Sorry man, I answered that last one really late last night, I was a little out of it....My plugs are all good (condition anyway) they are NGK R's, what are they supposed to be gapped to, just incase?? I have not checked my O2 sensor yet, however. I puff a little black smoke at high rev's, and a bit more in between shifts....people that drive behind me at night say that when I rev high and shift hard, I spit some flames out my exhaust and it clearly lights up the back of my car....this wouldn't be a result of running lean, right?

I only had the stock FPR on there for less than a month, and it only sputtered on hot days. At night when it was 75 degrees or cooler, it ran pretty good. My gas mileage, however, is HORRIBLE. I was getting MAYBE 150 miles to the full tank, even when driving it nicely (another reason the FPR popped into my head). Does this help you out at all?

[BaliLover]

Flames = rich

Flames are a result of unburned fuel leaving the combustion chamber and igniting in the exhast, If you were running lean there'd be no unburned fuel to ignite.

[SWIFT_DRIFT]

Stock plugs should be gapped to .9mm or .035"

A little black smoke in between shifts and during acceleration is normal on a turbo motor, especially if you are running a gutted cat or test pipe. Are you running an safc with your bov setup?

Well your stock FPR numbers seem to be normal and if it's running differently on only hot days it makes me think something else is to blame. However it's weird you are getting such terrible gas mileage. I would definitely check or replace the O2 sensor and check your Mafs.

BaliLover, thanks for the Initial D info...

[BaliLover]

Swift, he described flames out of his exhaust and asked "this wouldn't be a result of running lean, right?" I gave him an answer and a basic explianation of why he was correct. I'm aware its basic info but he asked a question and I answered it.

[SWIFT_DRIFT]

Backfire does not always mean flames dude. Turbo motors run slightly rich anyways and that, again, is not always bad. Trust me, with a full turbo back exhaust and a bov you will spark flames even if you aren't running rich.

[BaliLover]

... I spit some flames out my exhaust and it clearly lights up the back of my car....this wouldn't be a result of running lean, right?

He said flames, not just backfire... Thats where I got it from.

[Zaxx84]

I got the FPR tuned down to 25PSI now, does that sound safe? It's running much better now.

[Zaxx84]

I am not running an SAFC as of yet either, atmospherically vented BOV, stock ECU.

[MojoMan]

I got the FPR tuned down to 25PSI now, does that sound safe? It's running much better now.

This is No where near safe. Turn it back up. Your FPR is not the problem. Have you checked your whole ignition setup? Was it doing this before your walbro was put in? How is your timing? You said your ecu is stock, but do youknow for a fact that your ecu was never reprogrammed? It could be remapped. You can always open it up and look for a daughter board. What injectors are you using? Have you gone over your vacuum and made sure it is correctly routed. What about your tps? These are just some Ideas.....

[SWIFT_DRIFT]

Zaxx, like I said in my original response to your question:

On stock boost at idle with a Walbro you should actually be in the 40-50 psi range (I've heard 40-45psi and some as high as 49psi). Also make sure you are testing pressure on the fuel SUPPLY line (duh, but just in case).

[Zaxx84]

I have never run any pump other than the Walbro, so I don't have a base for comparison with fuel pumps.

Of course I don't know for a fact that my computer was not reprogrammed, but I got my setup from Heavy Throttle, so I guess I just assumed it was ready to go...

Vaccuum lines all appear to be good, and I am running stock 370cc injectors as of yet.

How do you "check" the throttle position sensor?

I tapped my Fuel Pressure gauge directly after the fuel filter, so I know for a fact its on the supply side. What about the MAFS, my plugs clip is broken, but it stays snugly connected, think this could have something to do with it?

[Zaxx84]

By the way, I tried setting fuel pressure to 45PSI at idle, and it runs like complete garbage. Sputtering, backfiring, and black smoke out the tailpipe.

[MojoMan]

The problem is that if you change the fuel pressure to the incorrect pressure you will never figure out what is wrong. Was this happening before your walbro? How long have you had this setup from H.T.? Try and get ahold of another maf. And even try someones ecu. Have you checked for any leaky injector o-rings? One lower o-ring and thats all it takes. Oh yeah and about the tps, you have to losen it up and moniter the voltage and set it at (x) amount of voltage. I cant remember what it is right off the top of my head but I think its supposed to be around .5 volts at idle and all the way up to 4 volts at WOT. Its in the manual so dont quote me but Im close. You have to swivle the tps to obtain the correct voltage at idle and set it. Real easy. I dont think its your problem though.

[droptopsilvia]

as far as passing emissions what kind of shape is you cat in...or do you have a test pipe? a larger downpipe also hurts for emissions. lowering your fuel pressure usually doesn't lower your emissions it just lowers the supply of fuel coming into the engine not whats leaving your exhaust (you'd think so but it doesn't work like that)have you checked the o2 sensor yet? like two others have said this could very well be the answer to your problem. thats what it sounds like to me, ecu thinks your cars running lean and dumping more fuel so turning the FPR down is kind of like you overriding the ecu. conflict

[Zaxx84]

I've only been driving it for a little over a month, and I haven't changed anything as of yet, I'm still waitin on my cat to arrive in the mail....I bought a brand new one, so I'm hopin it should run clean once I get all this shiznit figured out. Currently I am still running my 80mm Project Silvia test pipe, however.

How do I know for sure if the O2 sensor is bad or not?

[droptopsilvia]

VOM- dont know what it should read but if it reads 0 its bad...the catco cat should clean it up a lot my car failed miserably before it and almost passed after it..#%#$@now I need to check the EGR valve and PCV valve I need to get my car to pass before I drop in the SR