Nismo FPR = Shitty???

[jspaeth]

I haven't had any real problems with this FPR yet, but prior to purchasing it, I heard they could be a bit touchy.

So, I just got back from the dragstrip....4 runs in a row, I noticed my PFC was registering a maximum knock of 58-60!!!!

Now, I 've been driving the car about a month since it got tuned, and never once had the knock go above 20.

Finally, after 3 runs like this, I decided maybe it's the fuel pressure. Sure enough, I get out, and with the car idling, it's at like 27-28 psi. However, it was tuned with the pressure around 32 psi at idle or so.

So, I raise it up to 33 or so, do a run, and when I get back, it's at 36 psi...


Anyone else having issues with this FPR randomly deciding to be jumpy?

[hotlavaflow]

Wow I hadn't heard this. That is def not good though. I was thinking of getting one of those.

***Posting to see the responses when they come in***

[s13drob]

try and get ahold of where you got it and refund that bitch. get a new 1. nismo shouldnt be havin that problem. ITS NISMO. its defected and they should replace it HOPEFULLY.

[GSXRJJordan]

I was looking for an adjustable FPR and got lucky - I found a Supra guy parting out his fuel system and got a huge Aeromotive dual AN-8 input w/boost ref (vacuum source) for $100. Its rock solid.

That being said, I've never heard that they're 'bad', only the typical rising-rate vs static FP discussion...

[jspaeth]

I understand what you are saying^.

You would agree, though, that if the vacuum at idle is essentially constant, then the fuel pressure at idle should stay roughly constant. Mine was all of a sudden 4 psi or so lower than before.

Yikes!

[UNISA JECS]

Well first off you set your base fuel pressure incorrectly, to do it the right way you start your engine and disconnect the vacuum to the FPR and adjust until you get 43psi......period end of story.

The reason you do not adjust FP by vacuum is because there are to many possible varibles in respect to vacuum, i.e. cams, state of tune, timing, worn rings, elevation are all things that can make your vacuum lower.

[jspaeth]

Well first off you set your base fuel pressure incorrectly, to do it the right way you start your engine and disconnect the vacuum to the FPR and adjust until you get 43psi......period end of story.

The reason you do not adjust FP by vacuum is because there are to many possible varibles in respect to vacuum, i.e. cams, state of tune, timing, worn rings, elevation are all things that can make your vacuum lower.


I agree with you completely on this....when I initially set the fuel pressure, I set it out of vacuum to 43 psi.....

However, it is worrisome that with the vacuum at idle essentially constant, the f.p. was 3-4 psi low. Again, vacuum at idle is maybe -20...any deviations I've seen are very, very tiny....not enough to cause a 3-4 psi change in fuel pressure.

[UNISA JECS]

Well then what I would have done with out making anyfurther adjustments to the FPR I would have disconnected vacuum and checked to see if FP was still at 43psi.....If it was not I wouldn't write the FPR off as bad yet, just readjust it without vacuum to 43psi and monitor it.

[jspaeth]

You are COMPLETELY correct.....I wish I had checked the base fuel pressure while I was having it tuned....that was a severe dumbass move on my part.

[dorkidori_s13]

nismo fpr = shit

ive seen tons of em go bad in 2-4 months after install...they dont hold proper psi for shit

do it right...hks -6an adaptor, steel braided lines and a aeromotive fpr w/gauge...worth every penny

[UNISA JECS]

To bad you didn't that sucks....but the FPR and gauge are also good tunning tools, you can actual loose about 2-3 in/hg (with incorrectly gaped sparks plugs, overly retarded ignition timing, even a misfire will upset your vacuum, and driving to different elevations will make a difference for about ever 1,000ft or so) so its a good little indicator as well.

[jspaeth]

I've got a Marshall gauge, which I am really happy with, but you are right, maybe I will have to switch over to a different FPR.


I just think it's amazing that with all of the high tech stuff that goes into cars, a simple little spring-valve that regulates fuel pressure can be the difference between your car running great and running lean and blowing up.

booo

[UNISA JECS]

nismo fpr = shit

ive seen tons of em go bad in 2-4 months after install...they dont hold proper psi for shit

do it right...hks -6an adaptor, steel braided lines and a aeromotive fpr w/gauge...worth every penny

I dont know I used one before for about 3 years I didn't once have a problem with it ever, maybe the locknut wasn't properly tightend and it caused a leak I dunno.

[916S14]

Just gonna let you know better FPR possibilities for the future, i got a sumit racing FRP and it works great. And UNISA JECS knows his stuff.

[jspaeth]

I dont know I used one before for about 3 years I didn't once have a problem with it ever, maybe the locknut wasn't properly tightend and it caused a leak I dunno.


That's possible, but I don't see the locknut not being tight causing the threaded adjustment bolt to "back out"

However, you sound like you know better than I

[efrain240sx]

I'm having kind of the same problem. My fuel pressure is very low 26-28 psi with nismo fpr. So I took it off and put on my stock one which I know that works fine. but even with the stock fpr the pressure still at 26-28 psi. So I'm guessing that it's going to be my fuel pump thats going bad.

[jspaeth]

I wouldn't necessarily say that^

[bmx22]

i have a nismo fpr it changed on me in the begining because the car was not hot when i set it. After pownding the car around i re set it making sure the lock nut is tyte and its been fine for a year.

[nismostate]

bringing this thread back.

anyone have problems with nismo fpr leaking AIR? retuned the car and it ran great at 15psi. next day started it back up and it idled like crap, vac went from 15 to 8-6, and would not boost more than 10psi. did a boost leak test and noticed leaks everywhere in the system. fixed all of them and then i noticed air coming out of the nismo fpr. how i know? sprayed soapy water on their and it was bubbling on the back side of the fpr. i also noticed the head part can rotate unlike the stock fpr. looks like it is holding the fuel pressure i want but just leaking air. anyone have input on this?

gt2871
BC stage 2
FAST ems; GM 3 bar sensor
blitz dsbc

[nismostate]

bump
anyone?

[Dream240]

you're talking about air coming from the backside of the metal casing of the fpr? Could the air be coming from a faulty vaccuum hose?

The onl yI could think you would just all of a sudden get a vaccuum leak like that would be from a faulty hose. Or maybe your FPR got damaged somehow (something whacked it, or rubbed against it, etc.)

Good luck.

[WoolyS14DET]

Nismo FPR yes are very touchy and I have also herard of them going bad.
I suspect that they go bad due to the shitty rubber diaphram inside that gets a hole or corroded due to the shitty gas and then starts rotting/corroding the spring which will cause the fuel pressure to change.
Dump it and get a external FPR !!! IMO:bigok:

[nismostate]

you're talking about air coming from the backside of the metal casing of the fpr? Could the air be coming from a faulty vaccuum hose?

The onl yI could think you would just all of a sudden get a vaccuum leak like that would be from a faulty hose. Or maybe your FPR got damaged somehow (something whacked it, or rubbed against it, etc.)

Good luck.

yea air is coming from the backside. its not coming from the vaccum hose because i replaced the fpr with a stock one and no leaks. there's really nothing to rub/whack it so thats odd too.. it is keeping my fuel pressure at 50psi so im not complaining about the pressure changing, just leaking air. now at wot i dont know if theres any problem because gauge is under the hood. i guess i can log my runs and see if theres a dip in a/f but i doubt it. sucks cause i dynoed the car on 50psi but now im dropping it back to stock pressure. can someone confirm that the nismo fpr "head" can rotate? if so, couldn't i just braze the backside so there's no leaks? or is that going to effect the adjustability of the fpr?

wooly, an aeromotive fpr is probably the way to go but damn i really dont want to spend money on something i have already replaced!! trying to get other things done and this is making me take steps backward.. again.

[GSXRJJordan]

I feel ya there... I've worked on a car that had one, but I honestly don't remember if it's supposed to rotate/whatever. My intuition says that's not the problem, but if you're not holding boost, it may be.

[fliprayzin240sx]

Ive had a nismo FPR do this, it leaked where the top part clamps down to the bottom part. My guess is when you installed it, you twisted the top a bit and loosened the clamp. What I had to do is got a pair of pliers and clamped it back down, that made it stop leaking...

[nismostate]

hell yea that's exactly what i wanted to hear. Im gonna try clamping it down and see if it stops the leak. if not, im welding/brazing that bitch. for the love of god i just want to drift!

[Bigsyke]

I really hate to bump this, however I seem to be having the same issue. I drove from one gas station to the next, popped the hood, and the pressure had changed. Slightly however. Does this mean the start of a FPR going bad? had it less than a month.

[RBSilvia1406]

Ya ive heard that the nismo fpr are very touchy n inconsistant from NICO. i, myself am going with an areomotive fpr.

[fliprayzin240sx]

Check it if its leaking, pressurize the vacuum source on it and see if its leaking. You'll hear it leak at the cap section if it is. I clamped mine down and you could probably JB weld the seem too if it is leaking.

[rc1honda]

I had a similar problem with my SARD. It was not upping the pressure at a 1:1 ratio with boost and the base pressure was fluxuating . I never noticed it until i had it on the dyno. I just bought a Aeromotive w/ some
-6 line and haven't had a problem since.

[jspaeth]

Okay....I replaced it with an Aeromotive big boy status, and STILL occasionally have slightly low fuel pressure at idle...

Should be 35-36 psi, sometimes i see 30 psi at idle.

Going to start trying to pinpoint the problem.

Given the quality of Aeromotive, I am leaning towards fuel pump not working perfectly all the time, possibly needing rewiring.

This is the worst problem ever, in my opinion, as a sudden unexpected fp decrease can cause your motor to go byebyes

[UNISA JECS]

What fuel pump are you running by the way? Sounds like a fuel pump going south.

[jspaeth]

I am running a Walbro 255 pump.....I really doubt it's the FPR, as Aeromotive makes top of the line shit, and this happened with BOTH the Nismo FPR and Aeromotive now.....

I would say probably 90% of the time, at idle it reads 36 psi.

The other 10 % of the time it reads 30 psi.


When I BEAT on the car hard, my knock sensor on my PFC is almost always below 20.

Maybe 1 out of every 100 (or maybe even 200) times that I floor it and get full boost and full load, I see the knock sensor go up to 40+.

....and that is with my boost pressure being pefectly controlled with AVCR.

That only leaves inadequate fuel supply (relative to what the map is telling it to feed) as the cause.


1) I need to run my FP gauge into the car to make sure that my FP is going up 1:1 with boost.

2) I need to check voltages at the fuel pump when I see low FP at idle (which is tough, bc it happens so INTERMITTENTLY).


This is just a pain, bc the problem is so intermittent.....I am guessing fuel pump or voltage drop due to wiring.....may try wiring it on it's on power wire or whatever that mod is.

[UNISA JECS]

You know it is possibly that its your tune, its very possibly and highly likely you'll loose a few in/hg (inches of mercury) if yoru to rich or to lean or to much or not enough timing at idle.

Whats the consistancy of you max fuel psi @ max boost psi? Thats whats gonna tell you what the condition of yoru pump is in?

[jspaeth]

You know it is possibly that its your tune, its very possibly and highly likely you'll loose a few in/hg (inches of mercury) if yoru to rich or to lean or to much or not enough timing at idle.

Whats the consistancy of you max fuel psi @ max boost psi? Thats whats gonna tell you what the condition of yoru pump is in?


I do see what you are saying, but I can't see that being the case.

When the FP drops to 30 PSI at idle, the car is idling fine and the vaccum is identical to what it is when it is at 36 psi.

Furthermore, when the FP drops to 30 PSI at idle, I pull off the vacuum line, and the FP gauge reads 39 PSI (again 6 psi too low).

This indicates that the idle/vacuum is NOT the reason the FP is down, but that is an actual supply problem with the pump not giving enough PSI to the FPR (regardless of vacuum).



Yes, you are right, I need to take a look at how the FP is at max boost under full load.

But then 3-5 times EVER that I have had my knock sensor go high (like 40+), I have then pulled over and checked the FP at idle, and sure as shit, it was like 30 or so, rather than 43.

All the other times I do pulls, I have no problems.....again we are talking like <1% of the time that this problem occurs.....


EDIT:

Also, to other people having this problem:

At idle, there is no reason for your FP to go DOWN due to vacuum/idle/etc. problems......if your car is not running right (i.e. not pulling ENOUGH vacuum) or there is a blockage or pressure leak, this will pull LESS vacuum on the FPR and cause your FP to go UP!

Same problems under boost will cause your FP to go down

[om3ga]

Yeah ive been hearing alot of bad things about the Nismo FPR, Ill be going with the tomei or sard unit when i upgrade mine.

[steve shadows]

Yeah I would suggest the stock one or the SARD unit

[Bigsyke]

has anybody measured the PSI of a walbro 255, on a stock FPR? is it nearly the same?

[usdm180sx]

I got a sard one for $14.95 at the more-japan.com sale ftw

[steve shadows]

has anybody measured the PSI of a walbro 255, on a stock FPR? is it nearly the same?

usually its 40-42 psi which is fine if not better. having a tiny bit more FP on injectors under 850 cc size is fine

[Bigsyke]

Well the nismo only fluctuates about 5psi between stops, never gets below 31psi. I would assume this could do for now.

[jspaeth]

If you put the numbers into a calculator.....17 psi boost would give you ~60 psi FP under full boost.

Calculate the fuel flow at 60 psi compared to 55 psi of back pressure, and you find about a 3% reduction in fuel flow.

[UNISA JECS]

has anybody measured the PSI of a walbro 255, on a stock FPR? is it nearly the same?

Yea it over runs the stock fuel pressure regulator return system by a good amount ~6-8psi depending the voltage your fuel pump gets (some people gotta shitty wiring and the pump see's less voltage) so results will vary.

[cbh148]

**********

[codyace]

Check the vacuum lines for the FPR to make sure they secure/not ripped. If they are known good, and the FPR has a good strong vacuum signal from the intake, then I'd suspect the FPR.

[hOngsterr]

check the FPR, nismo's leak at the half, mine did that...

[steve shadows]

Just use a good stock one. I used one up to 500 whp with track time.

If you want to upgrade get an aeromotive 1:1 Rising rate off-rail.