fuel pressure

[dhen]

My car runs so rich on idle that black exhaust is getting my garage floor dirty. (This goes away once the car has been driving awhile.) I have a VPC, and even though I've leaned up the mixture, it's still too rich.

I'm beginning to think my fuel pressure is off. I saw this FPR on eBay:

http://cgi.ebay.com/ebaymotors...op:en

Any thoughts? It's probably a good idea to replace my FPR since the one I have probably sat in the rain in Japan for ten years.

Another question: I read that you should set the fuel pressure at 38 lbs. of boost. Do you set this on idle, does someone rev the engine and you set it, or what?

Sorry if this sounds stupid, but I really don't know.

Thanks,

Darian

[Ca_Silvia]

First off, get a buddies fuel pressure gauge, plumb it in and see what your fuel pressure really is. Then if the Regulator is f***ed buy the nismo unit from FR sport, not ebay crap. You will need the gauge if you have to buy the adjustable unit anyways so buying one wouldn't hurt either.

Stock fuel pressure is 37-38psi without vacuum attached

[sjbsuperman1425]

do NOT get the Nismo Type-A FPR from FRSport. get the same regulator from http://www.thenismoshop.com for cheaper ( $10?) its a good thing im a cheap a** haha

[Nali]

First off, get a buddies fuel pressure gauge, plumb it in and see what your fuel pressure really is. Then if the Regulator is f***ed buy the nismo unit from FR sport, not ebay crap. You will need the gauge if you have to buy the adjustable unit anyways so buying one wouldn't hurt either.

Stock fuel pressure is 37-38psi without vacuum attached

Whats wrong with the eBay regulators?

Most of them come with a gauge so you dont even need to buy a separate one.

Ive test mine and hit holds true even at full boost .Ive had it for months now and have had no issues? WHat makes the Nismo one better than an eBay one?

[sjbsuperman1425]

there are somethings you can buy off ebay, but important components like that are NOT on that list.. spend the $110 on the Nismo one and feel good you have a Nismo part on your car lol

[dhen]

Thanks. This give me something to think about.

Darian

[sjbsuperman1425]

and as for the fuel pressure itself, it should be set at 36psi no vacuum. there is a guide here and on driftopia on how to do it.

[RS12Turbo]

and as for the fuel pressure itself, it should be set at 36psi no vacuum.

I don't remember the write-up mentioning 36psi with no vac. Guess I need to go and re-read....lol

[sjbsuperman1425]

28psi at idle, 36psi static....i didn't no how else to word it until now haha

[RS12Turbo]

Well damn! No wonder i'm so rich....I've got mine set to 35 @ idle

[boost_boy]

Well damn! No wonder i'm so rich....I've got mine set to 35 @ idle

If you have an aftermarket pump, set the pressure to 37psi at idle and leave it be.

Dee

[sjbsuperman1425]

If you have an aftermarket pump, set the pressure to 37psi at idle and leave it be.

Dee

i was always under the impression the reason to get an adjustable FPR was to lower the FP back down to stock after upgrading the fuel pump..

[boost_boy]

i was always under the impression the reason to get an adjustable FPR was to lower the FP back down to stock after upgrading the fuel pump..

The volume is what increases more, but you control the pressure. 38psi for the stock injectors allows you to run you 12psi of boost on your T2 small hairdryers more effciently.

Dee

[sjbsuperman1425]

The volume is what increases more, but you control the pressure. 38psi for the stock injectors allows you to run you 12psi of boost on your T2 small hairdryers more effciently.

Dee

ahh i see..im only running 7...

[dhen]

This might sound stupid, but I really don't know. Can you lean up the mixture by reducing the fuel pressure or would the computer keep trying to compensate by adding more fuel?

Thanks,

Darian

[Ca_Silvia]

Sounds like a band-aid solution. Just get a tune done, best money you will ever spend on your car.

[Buddyworm]

In closed loop the ECU will regulate fuel, yes. In open loop the ECU starts reading off the fuel map and lowering the fuel pressure will, in fact, lean you out there.

Although one way or the other I think that's a bad idea.

Question: Have you measured your AFR's at all? On cold starts my car will get the floor a bit dirty too but my air fuels just reflect the expected warmup enrichment. The reason it goes away after a while is once the motor is warmed up the ecu leans the mixture out to normal.

[dhen]

In closed loop the ECU will regulate fuel, yes. In open loop the ECU starts reading off the fuel map and lowering the fuel pressure will, in fact, lean you out there.

What is open/closed loop. Do you have a link?

Question: Have you measured your AFR's at all? On cold starts my car will get the floor a bit dirty too but my air fuels just reflect the expected warmup enrichment. The reason it goes away after a while is once the motor is warmed up the ecu leans the mixture out to normal.

No, I haven't checked it yet, but it's good to see that your car is doing the same thing.

[Buddyworm]

Closed loop is when the ECU uses the O2 sensor readings to trim injector pulsewidths in order to reach the stoichiometric air/fuel ratio (14.7:1). On a CA this is from idle up to about 3000rpm depending on how much throttle you give it.

Open loop is when the ECU ignores the O2 sensor and calculates pulsewidths based on airflow measurements from the MAF. This is from ~3000rpm and up.

[dhen]

Thanks,

Darian

[Seishuku]

No offense, but I'm not paying $200 for nothing more than a modified STOCK pressure regulator.

Get the ebay unit, it's $20, if it doesn't work quite right, toss the stocker back on and you're only out $20. Just keep an eye on things, if you see it drop pressure or lean out too much, get out of it.

I see nothing wrong with the ebay regulators.

[Nali]

No offense, but I'm not paying $200 for nothing more than a modified STOCK pressure regulator.

Get the ebay unit, it's $20, if it doesn't work quite right, toss the stocker back on and you're only out $20. Just keep an eye on things, if you see it drop pressure or lean out too much, get out of it.

I see nothing wrong with the ebay regulators.

QFT!!!.

Theres nothing wrong with the eBay regulators ive been running mine for months, and it came with the gauge so no need to buy another.

[jynxtrix]

which one did you get? I'm curious, and until I start seriously tuning this thing, I'm fine with cheap.

[sjbsuperman1425]

No offense, but I'm not paying $200 for nothing more than a modified STOCK pressure regulator.

Get the ebay unit, it's $20, if it doesn't work quite right, toss the stocker back on and you're only out $20. Just keep an eye on things, if you see it drop pressure or lean out too much, get out of it.

I see nothing wrong with the ebay regulators.

yea but $20 is $20, and it adds up. Keeping an eye on a gauge under the hood is also fairly diffcult IMO. I can see buying things off ebay that are hard to get, but when it comes to something as important as FUEL, dont cheap out, please. The Nismo one is only $110 shipped from The Nismo Shop. Save yourself the headache please.

[Nali]

which one did you get? I'm curious, and until I start seriously tuning this thing, I'm fine with cheap.

Megan Universal.

http://cgi.ebay.com/ebaymotors...ories

No headaches yet.

[float_6969]

The ebay regulators are hit and miss, and they have a bad track record with the diaphragms crapping out on them after a year or so.

I've been running a NISMO on E85 for years with out one issue.

Also remember that the fuel pressure is 36psi with the motor OFF! If you start the car, pull the hose off, and set it to 36psi, you'll be putting in too much fuel.

Follow my guide in the FAQ.

[Seishuku]

When it comes down to it, the Nismo FPR could fail just as easily as a cheap-o ebay regulator. Both could pop the diaphragm, both could have spring failures. They have the same basic components, but the other thing is that the ebay units are actually rebuildable, you can't rebuild the Nismo unit.

What would the odds be that you'll actually run lean when something fails?If the diaphragm pops, you'll suck up fuel via vacuum line, you'll run rich.Though if the spring actually broke a coil, I guess you could drop pressure, but I doubt it would drop out quick enough to lean out and boom.

I donno, both could fail just the same IMO.

[sjbsuperman1425]

its basically the same eBay debate. OP, buy what you trust.