Well I initially purchased and installed the NISMO adjustable fuel pressure regulator along with a Walbro fuel pump (190L/hr)....Well the idle was loping in sync with the erratic fuel pressure. Had to adjust the fuel pressure to 60 psi in order to stabilize....Weirdest thing I've ever seen not being able to adjust the pressure down to 38-40 psi....I came to a conclusion after reading/searching a similar situation in the 5th Gen discussion with the same setup: NISMO AFR and Walbro fuel pump....The AFR is too dam small and can't handle the flow rate of this aftermarket high performance fuel pump!!!! So I upgraded to a larger AFR and hopefully I'm correct and right on track....If I need to I can flow thru the AFR in a 3 port setup or set it up as a 2 port setup....

 

You shouldnt be having problems with excess pressure with only a 190L/hr pump. Lots of turbo guys (including myself) use a 255L/hr high pressure Walbro pump and don't have any trouble (I am using an aeromotive AFPR though). Regardless, I thought you were ABLE to get your pressure down to 38psi but the car didnt run properly until 60psi right? Im guessing your gauge is way off or you hooked the send/return lines up backwards to the rail, cause 60psi at idle is way too high and shouldnt result in a properly running car.

 

You're not in the same situation....you didn't use the NISMO AFR and yes they were hooked up correctly it doesn't run hooked backwards....and as far as the gauge it's right on the money! Again the flowrate not pressure was to much for this stock sized AFR....Your Aeromotive is much bigger like my new Professional Products AFR, did you set yours up in the 2 port configuration or 3 port configuarion????

 

Maxpwer's comments are spot on. You shouldn't NEED that kind of pressure to keep the car running. sounds like you have clogged or bad injectors if it takes that much fuel pressure to feed the engine enough gas to run.

the flowrate through the Nismo AFR isn't the issue. I know lots of guys (including myself) that have used them in the past on Walbro 255 pumps and can get the proper pressure and everything works fine at normal pressures. it's not the AFR, unless it's damaged somehow.

Was your car running fine on the stock fuel regulator?
Why bother switching to an AFR anyway, since you don't need to change fuel pressure unless you're adding boost.

 

If you upgrade your fuel pump without getting an adjustable fuel pressure regulator, the fuel pressure will be too high. The factory fpr doesn't flow enough for a high flow fuel pump.

 

Wow, Really? B.S> Matt...I'm using it to tune my car during WOT (open Loop) with my Wideband....As for my issue the car runs smooth as silk but the pressure regulator starts to oscillate/fluncuate due too the poppet spring being to weak to control the return volume consistently at the desired fuel pressure 36-40 psi. It wasn't able to control the spring bounce/poppet valve opening until I cranked it up to 60 psi which hell we all know is too freaking high...DUH!!!! Search the org I found that 2 other folks using the exact setup I'm running had the same flunctuating idle and fuel pressure... using the Walbro 190 L/hr and a NISMO AFR which is what I'm stating....So I'll install these larger AFR that offers 2 configurations, unlike that fix configuration 2 port Nismo....Ican use the 2 port or 3 port configuration to cure the problem....More than likely the NISMO AFR prefers stock Fuel pumps or this part is Out of the box defective...it happens! Anyhow here's another thread I found with a relate problem:
http://forums.maxima.org/all-motor/5...my-walbro.html

You didn't read a thing ^ did you?

 

I'm always up for learning new things.

CMax: Help me understand what you are saying/describing. You stated that when using an upgraded fuel pump (or the one you're using) the stock FPR does not flow enough to keep the pressure down at stock levels. Okay, I can get that.

But, you state you have to install an external/aftermarket FPR and increase the pressure in order to allow the engine to run properly, right? However, if I understood FPR's function: First, they are installed on the return line after the stock FPR (or did you remove your stock FPR)? Second, FPR's act to restrict the flow of fuel back to the gas tank....so how does further restricting flow after the stock FPR (which you say is already too restrictive) fix the problem/symptoms you describe?

I'm just really confused. I'm also curious, did you hardwire the pump?

What I'm getting out of this (and maybe where some confusion is) this boils down to an issue regarding dynamics of flow versus pressure (ie: HV/LP versus LV/HP)? I'm not too familiar with the pump itself, but it sounds like the pump you are using is a High Volume - Low Pressure (HV/LP) pump, so you must compensate by increasing the pressure significantly above what a person typically sets thier fuel pressure to in order to achieve the injectors reading/obtaining the required amount of pressure to properly function/inject fuel into the cylinder?

I hope I made sense in my question. I just started thinking about it in terms of an air compressor and air tools/paint guns. If I do have it right, help me understand how having a high volume pump and having to jack your pressure up so high is benificial for your set up?

 

The problem is, if the pump is flowing a higher volume then pressure should be LOWER to match the old pump. Now I could go into a million examples and explanations of pressure vs flow but the bottom line is we all agree something is wrong. Lets fix the problem, and then if you care after that I'll explain what is going on.

The solution is simple, like Matt hinted at, just put the stock FPR back on there. When I first upgraded to a 255L/hr pump I had my stock FPR on there for a few months and I even passed emissions. If the stock FPR can handle the 255L/hr, it wont bat an eye at the 190L/hr. If the stock FPR fixes the problem, then you know where your problem is.

To answer your other question, I have mine setup in 2 port configuration. I believe 3 port is required around 800hp+ assuming the rails arent the restriction.

 

try adding a standalone fuel pressure gauge to see if the AFR is actually calibrated accurately. maybe its calibration is just way way off causing you to set it at Y psi when it actually is holding X psi.

 

That statement is all kinds of fail. Read up on how our fuel systems work again, bud.

CMax.. you're not making much sense either. Is your car pushing 350+hp? If no, then the stock fuel pump and AFR will do fine. jacking with open-loop numbers like that are only going to cause problems elsewhere in the system. do you really NEED more fuel?

even with ported heads and higher compression, my VE's stock injectors at stock fuel pressure are still only around 75-80% duty cycle. with JWT's rock-solid 12:1 AFR.
I think you've bitten off more than you can chew.

The injectors also don't give a damn about how much fuel is flowing through the rail. all they care about is pressure, since the volume of fuel leaving the injector is so much smaller than the volume of fuel flowing through the rail. that means the pressure in the rail is the same as what's seen at each injector. If the injectors were seeing a substantial percentage of the total flow and there was no restriction after them (not the case in a system like ours with the pressure regulated by restricting the return flow), then you might have an issue. but that's simply not the case on a Maxima with less than 400hp.

 

I think there's alot of ppl reading something else.....I'm sure my gauge is reading right...but I'll test it against another gauge. As far as someone mentioning something about injectors... my injectors are working fine....the Walbro pump is working fine....the problem is the combination. For some odd reason walbro fp and Nismo AFR doesn't work together....This is a high pressure, high volume fuel pump and no the OEM AFR isn't installed.....neither do I have any restriction in my fuel system....All I was simply saying was that there are 2 other orgers that had the same fuel pressure/idle flucuations when using this same exact combo..... That's all! The volume at idle causes the NISMO AFR relief valve/poppet valve inside the fuel pressure regulator to come off the seat, then on the seat, rapidly bouncing it back and forth due to it either being defective out the box (brand new) or cause it's to small physically....I'll be installing the bigger unit tonite or tomorrow nite....as for my Air to Fuel ratio @ WOT 12.5 -12.8 to 1 is my target for a few extra phonies to catch and pass that "BIG RED ONE".....LOL!!! Thanks for all your inputs guys....But I got this!

 

Actually, I read everything. My statement was in response to Matt.

Not true. I fully understand my fuel system. I have a walbro 255lph fuel pump and a afpr, installed by me. My fuel pressure is 37psi at idle and 43psi at wot. My afr is 14.7:1 at idle and around 12:1 at wot with a 150 shot. My fuel pressure was too high when I used the oem regulator with a walbro 255lph pump. The stock regulator does not flow as much as an aftermarket afpr. When the fuel pump flows more than the stock regulator can handle, fp will rise. If you search, you'll find that other .org people have had this problem as well.

I did some further reading and I realized that this shouldn't be the case with CMax03's walbro. He has a 190lph which should work with the oem fpr.

 

I bet that the nismo afpr is either defective or it's too small and doesn't flow enough.

 

Then why post?

My understanding of what you just said is that the FPR you are using is crap...period. That is not a "combination" problem, that is a QAULITY issue!

I've been running my same Stillen rising rate FPR for over 9 years. 4-5 of those years my engine was normally aspirated...I didn't need it, but I "wanted it." I'm still using it on my turbo and with the Walbro 255 now installed. Never a day of trouble out of the Stillen, and my stock FPR is blown. Just install something good and be done.

Maybe I've been on here too long, but stupid posts like this are really getting to me. Maybe I'm becoming hormonal?

 

My fuel pressure didn't change a lick when I installed my 255. Same with my 240SX which has a 255 Walbro in it too. Same for the other Maximas I've installed Walbros on for maintenance. Maybe your FPR or return line was clogged?

 

Someone finally heard me!!!!!!!!!!

Why is it getting to you....I was simply informing folks of the walbro 190 l/hr fuel pump and the NISMO AFPR combo incident on 2 other threads besides mine that were experiencing fluctuating idle and fuel pressure...as insight to this combo!
I'm happy that yours didn't, but your setup is not the exact setup that I'm using on the fuel pump side nor regulator side....So I'll see once it's connected into the fuel system....I'm fabricating a larger bracket for the AFPR....I'll keep yall informed with the results.....I sat a glass of water on the intake manifold cause it was running smooth as hell but of coarse the fuel pressure was out the ballpark.....again thanks for all the info....

 

just cuz it isn't "exact" doesn't mean that his results aren't relevant to your situation... they've already stated that the stock FPR very much CAN handle a 255lph pump (and therefore definitely a 190lph pump), meaning that upgrading the FPR in the first place was completely pointless... unless your stock one was somehow already broken.

What EXACTLY is different-from-stock about your motor anyways? Cams? Compression? Ported stuff?

 

Yeah it's not stock! Headers/CAI/Exhaust/Ignition/Cams/JWT ECU/ported and port matched....yeah it's not stock....so I'll be able to adjust me WOT air/fuel ratio to the sweet spot 12.5-12.8 to 1 and make a few more ponies safely!!!! Anymore questions???

 

You tell em buddy! LMAO!

 

As I'm reading through this post..I said the same thing Mr. C.Gregg..Why? Thanks for your you post..and I read no more!

 

Well GUYS......Drum roll please!....................................I just performed a bench pressure test using a media fluid called compressed air on both regulators!!!!
Well guys is really hard to admit it when you're wrong....................and I'm right on the money, the NISMO adjustable fuel pressure regulator is chattering/oscillating/buzzing like a ***** on a Friday night (payday of course) at any pressure below 50 psi......So I went on and set my new, larger, AFPR to 40 psi so it'll be pretty close during start up.....I guess I'll give COURTESY NISSAN a call to replace this NISMO since it was defective out of the box.....once I get the replacement regulator back, I'll install it on my nonturbo nor NO2 HB pick up 2.4L 4 banger so I can bite off more than I can chew on that one too....You gotta love it in Here!!! You Orgers never surprise me.....

 

Moreso due too the f**ked up post/replies like yours and the many like you....., Thanks for giving it your all guys......when all I needed was some listening ears not flapping lips......I was only trying to be informative......

 

Smokin a Marboro installin a Walbro on somthin like an N/A SHO goin hella slow with no flow.

Hope it works out though

 

the point is that your engine, even with the mods you've done, makes less power than a VQ30DEK whose stock regulator works just fine and is more or less the same as ours. so the reality is that you went and upgraded your fuel pump for no real performance reason, which then made you go and upgrade your FPR. If you'd just left both of them stock you wouldn't have had any trouble. but of course then your mod list wouldn't have been big enough

and for the money you wasted on JWT you could have gotten NISTUNE which would allow you to tune EVERYTHING yourself and get the exact AFR you wanted at every throttle position and RPM pairing instead of just turning the pressure up and down to 'roughly' compensate for this-or-that.

 

 

Honestly I upgraded the fuel pump and FPR at the same time....I just happened to get a defective(AFPR) new part,.... since that was important for you to (mis)quote....As for my mod list,..... you have any other ideas/parts that might make it longer.....since size matters!

 

Hey there Mister High and Mighty. go back and read my first response. who's wrong? http://forums.maxima.org/7423020-post4.html

You said the thing was chattering. That's because it's defective, not because it's the wrong part for the job. It would still do the job if it was in good working order.

It wasn't the new larger AFPR that fixed the idle, it was a WORKING AFPR that fixed your idle.

 

Go ahead.. post it up. Lemme see the FULL mod list. since size matters, whip that sumb!tch out.
then bring your car to the next road course event at MSR-Houston so you can be put in your place. I might even be tempted to bring the VE out of the retirement dungeon....

 

do it!
regardless of the outcome, it'll make matt 'member how much fun these can be to drive!

(if it happens, pics or it didn't happen)

 

First, nothing on here should be taken personally, regardless of even if someone intends it to be that way. Just not worth it (to all!). I do appreciate your posts CMAX in that I don't get the feeling you are taking anything personally, that is maturity (minus recent posts )which I don't see much anymore on this forum. Cudos to you!

However, you state there are some "f**ked up post/replies." Everything seemed to be on target with addressing your original post. You also say you were just being informative. But AGAIN, in your original posts you seemed to be making claims about things, why they were happening....which you were challenged on and is of course part of learning (and NOT personal!).

I guess I'm just asking you not insult anyone here by trying to make it out you were giving information when in reality you where asking for feedback about a problem you were having and your plans to handle it. Clearly no need for that 2 or 3 port set up you thought was the solution! I suppose that was my frustration is that I saw you going down that path early on, posting what seemed to be a question given your problem, then rejecting most of what was posted although it was on track. If you look at a lot of conveluded posts/threads here on the forum where you read and have no better understanding at the end of the resolution than you did at the beginning, that is frustrating. I fear the way you set up your initial post and your overall intentions for this thread essentially created just that, another thread where you read it and think/say, that was not helpful....or even worse, pointless. Just constructive criticism. I'll get off my soap box. VERY pleased you got it figured out!

 

Darn, I don't see any questions I asked in the original post...It was to be informative! So I see that my problem is cured now and beware of those NISMO AFPR cause it seems there has been more than my case of getting a defective new part from NISMO....I thought it was to small/ or the FP AFPR Combo when in reality it's again a defective new part....If I was asking questions there would have been (?????????) and I would've had a upgraded AFPR in my photo......But I knew it was the AFPR before I post this......As for Matt the Magnificant....Bring the "BIG RED ONE" out for a breather or two....I knew I could encourage you too bring it back to life.....Don't neglect it man....your mod list is longer than mine....it would hurt us all to know it rotted away seating in your garage/barn/whatever....along with all your hard work and mods......

 

It's not being neglected. it's just on the back burner until I finish getting my 240 ready to race and I have more time to work on the Maxima.
the suspension is worn- all joints and struts need replaced, the engine leaks and burns oil cause the moly rings never seated, there's some sort of gremlin electrical problem in the starting circuit, and I found out the other day that the radiator is cracked.

pretty much all of those issues are going to be addressed in some form or another when I finish the project, but I have no time, money, or motivation to mess with it right now. (all of that's going into the 240 that I'm trying to have ready to race this spring.)



My issue with this thread is that in your original post, you started talking about problems that weren't actually there. You were having a problem, yes. You found it, yes. but along the line you'd come to the conclusion that the NISMO AFPR was too small. In fact it wasn't too small- it's designed for cars capable of MUCH larger HP and fuel flow than the Maxima- it was broken straight out of the box.
If you weren't asking questions and trying to "teach us", then why not just say in the original post that you installed the thing, found the problem, and corrected it? Instead you drug it through 20+ posts of "yes it is, no it isn't. yes it is, no it isn't."

Let's move this forum past high school where boys are standing there in the locker room trying to pee the farthest. there's ALWAYS someone bigger, badder, faster, and smarter out there. maybe you run into them today, maybe tomorrow.

 

Ok.....A pissing contest, I doubt it.....I've been pointing toward this AFPR from the very beginning that's why I already had the new AFPR when this post was made......But anyway I would never win a pissing contest with any of yall....All in all it's a wrap so let's move on to the next thread you plan to dispute upon like so many in the past....different folks are gonna have different opinions in the real world guys!!! The End.......

 

It's not a pissing contest you effin moron, it's KNOWLEDGEABLE members trying to give you good info, that you refuse to listen to.

Fine, do what ever the hell you want to do to your car, just don't come in here trying to convince people that know what they are talking about that you are doing the right thing.