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Whats goin on Zilvia? I have a few questions regarding a fuel pressure regulator for a SR20.

Alright first, here is my setup:
s13 blacktop
GT2871r .64 a/r
z32 maf
deatschwerks 700cc injectors (im guessing they are 740s, but the flowcharts that deatschwerks pakaged with them say 700cc)
FMIC
3" turboback exh
walbro 255


Now at the moment i dont have a FPR and i figure instead of just finding a stocker i would go ahead and grab a good adjustable FPR. Now im having trouble figuring out which to get. It seems like its a choice between either the Megan for ~$60~ or $200+ for an Aeromotive/SARD/etc.
Has anyone used the megan FPR? I really like the price and the fact that it comes with a gauge already, but im a little scared to grab it because im not too sure about the quality.
What aftermarket FPR's do all you guys run? At what power level do you NEED to upgrade the FPR?
Thanks guys.

steve shadows

you really shouldnt need an aftermarket FPR.

they shoud work to 500whp for most apps

Im going to be getting an aeromotive next

i wouldnt run megan crap for something like that

get an sard, ive seen them as cheap as 120 bucks

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RedtopTech

used meagan for 1 year, once a week or so the fuel pressure would drop a few pounds and i would have to stop the car, get out, and adjust it back up. No fun. also the gauge isnt very accurate

bigOdom1

nismo is so simple though

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MomentumGT

I'm with big....nismo is pretty simple.

-Jon

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RYAN_S-14

i have a nismo still in the box i dont see a piont to installing it yet at all (325 whp goal)

UNISA JECS

Actually they are good for much higher fuel pressure like you say but the problem is when you install high volume fuel pumps on a Nissan vehicle that doesn't run a Fuel Pressure Control Module (i.e. like all Nissan 4 cylinders models) the stock FPR cannot bleed off enough fuel volume to keep the numbers at 43psi @ zero vaccumm. So when we install high volume fuel pump on our S13/S14 they run at top speed even at idle, to counter the effects of a high volume fuel pump Nissan/Infiniti used a Fuel Pressure Control Module on all its 6 cylinder and 8 cylinder models which either ran a two stage voltage setup or 3 stage voltage setup, this would lower the amount of voltage the fuel pumps see at idle and part throttle cruise. I have been trying to figure a way to use the stock FPRCM but it looks like the ECU has to be programmed for this to work or your next best bet is to buy Fuel Pressure Controller (aftermarket).

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steve shadows

Its not supposed to be 43 at zero vacuum nissan wizard

its supposed to be at -43 at at vacuum of course this changes with cam profile so base idle fp will be different from car to car setup to setup.

If your using a crappy walbro this can be a problem if the pump can burn up over time. I still have not had a problem with this happening on s-chasis for the last 7 years even with walbro. If you are concerned and are truly building a race car then you should be using Waldon or a Aeromotive External in the first place. Pick up one of their catalogues.

If you want to insure your getting proper pressure, install a digital FP gauge and watch it from the cockpit. It’s redundant but you can make sure pressure is proper under load.

For drivability sake if your going with large fuel injectors and larger pump you should have an ems that can adjust things like cold start, and specific portions of the map in the first place.

Adjusting Fuel pressure is not going to make a night and day difference in pump life and performance or injector characteristics (it will affect fuel per ms of injector however depending on fp).


Where a FPR becomes useful is when you are tuning a car and getting close to using duty cycle you can draw more fuel from the fuel pump to stretch the usability of the injectors.

You can also use it to lower base fuel pressure BUT ONLY if you can adjust base Injector open time via EMS or other direct control of injection.

I understand what your saying, I’m just saying ive never had a problem burning pumps because of too much base fp due to stock fpr draw.

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UNISA JECS

I think you made a mistake because a fuel pump provides volume which results in pressure via the FPR, never would it provide a negative it doesn't work as a vacuum pump.

Fuel pressure at idle in a perfect situation (@ sea level) is 43psi with no vaccum.

If a car pulls 19-20in/hg (9.3psi @ sea level) of vacuum at idle you will see 33-34psi with vacuum.

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UNISA JECS

Lets leave out variables like cam profile, engine wear and elevation, everything im talking about is @ sea level its makes things less complicated for everyone reading this thread.

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srgabe

dude im using a sard fpr (with a walbro pump) and the thing works good and i only had to adjust the pressure once while i was tunning my car...sometimes its good to go with cheap stuff but dealing with fuel is important so spend the little extra money its worth it..oh phase2 has the sard fpr w/adapter for like 160

steve shadows

what the are you talking about?

edit*

thats a typo

Im talking about pressure at vaccum, your taking something completely wrong away from what I was trying to say.

FPR regulates the pressure at the rail, the Fuel Pump gives a constant volume under X voltage.

I dont know what world your living in but every SR I have tuned with a 255lt/hr or 295lt/hr pump is 38-40 psi at -19

The whole point of your explanation is reducing strain on the Fuel Pump by adjusting fuel pressure...

Your suggesting by adjusting voltage input the fuel pump can be controlled by the OEM Inifin NIssan devices you mentioned to allow longer pump life.

This has never been a problem for any of the cars or hundreds of cars Ive seen. And any real race car will be running a billet Waldon style external system with surge tank.

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steve shadows

BTW most SR's tuned for higher boost run a lot more happily at around 50 psi with no vaccum line connected.

This is about 43 or so connected.

Then put the car on the dyno

Another problem is draw off the pump.

On some SR's you will see a voltage drop at higher RPMS

where some of the in tank pumps will actually LOSE pressure off high rpm pulls.

To remedy this I suggest an additional inline draw pump or you can wire the power to the fuel pump (stock chasis wire from fuel pump for power) to a standard boshe relay to allow for a propper amprage pull up into higher ranges reducing pressure drop.

You can compensate with this with injectors as many unexperienced tuners do but watch the FP first.

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UNISA JECS

Fuel pressure at idle in a perfect situation (@ sea level) is 43psi with no vaccum.

If a car pulls 19-20in/hg (9.3psi @ sea level) of vacuum at idle you will see 33-34psi with vacuum.

lemme clear it up for you:
43psi no vacuum (this is actually a constant if you have a 3 bar FPR that isn't over worked by a high flowing fuel pump)
33psi with vacuum (this is different based on elevation, cam profile, engine wear)

End of story quit confusing the shit out of everyone

My argument was that high volume fuel pumps sometimes over work the stock FPR I know this becasue I have a fuel pressure gauge and have used Z32 TT pumps, Q45 pumps, Z32 NA pumps and stock pumps and yes they do raise the base fuel pressure with exception to the stock pump. On these cars at idle they see less than battery voltage (with exception to the stock S13/S14 pumps) in order to maintain base fuel pressure at vacuum ~33psi or 43psi with no vacuum.

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steve shadows

were the only people in this thread dont worry

ive always seen 38-40

sorry my atmosphere bust be different in long beach


how do you 'over work' a fuel pressure regulator?

im personally more concerned with pressure on boost than at idle.

Unless your having idle issues, setting base pressure to 43-45 with vaccum (50-53 without) is the way to go for a performance application.

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RYAN_S-14

whell when you have a FP gauge on a stock fuel system then install a 255 HPP it increases the pressure, then you need a FPR to adjust the Pressure down to 3 bar per FSM.

UNISA JECS

You over work one when you exceeds its exit flow capacity or better its ability to maintain 3 bar fuel pressure.

Well some people that run smaller injectors and want to get a lil more fuel flow from there injectors do raise there base fuel pressure such as 4 bar but without some fuel controller your gonan have a shitty idle and piss poor milage.

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UNISA JECS

Do this squeeze your return line and then tell me how your car idles, this raises your fuel pressure and you'll see it'll run rich and start to shake and run ruff, ineffect this is what running a high volume fuel pump can do, this is just an example.

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RYAN_S-14

JWT sells 370cc 3 bar ecus and 4 bar ECUS so you can make more power with less injector

RYAN_S-14

you might be able to get a smother idle at over 3 bar (stock) with higher fp, iu am running 850cc at 3 bar and it idles fine

UNISA JECS

This is an aftermarket version of basically what Nissan/Infiniti V6 and V8 comes with AKA FPCM (fuel pressure control module), this has probably never been discused on this forum (maybe once) but you can buy aftermarket ones from Aeromotive. If you didn't already know the fuel pump volume varies by the amount of voltage the fuel pump recieves and unlike walbro fuel pumps Nissan (Z32 TT fuel pump can output more volume with a fuel pump voltage booster.

http://www.jegs.com/webapp/wcs/store...50285_-1_10767

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steve shadows

no, you raise it, thats the point

the point of the bigger fuel pump is to provide more capacity/volume pressure.

your trying to take advantage of more pressure behind the injector.

even at 7 psi, stock config. That way your injectors arent overclocked.

I give up

yeah because it raises it shit high. Thats not a very good example

but even so

squeeze it closed

now adjust injector

now better power output

this is why so many "tuners" push giant oversized injectors for low outputs.

They run very low base FP and lots of injector.

In actuality its a balance of FP and Injector that makes the best power and throttle response.

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RYAN_S-14

read what i said, the HP fuel pump raises the pressure causing a rich condition, like your example above, stock FP should be 3 bar (FSM)

steve shadows

read what you said


My point is you want the increase in FP.

Even the stock SR runs better with an increase in stock fuel pressure at base.

Go check your afrs with a stock FPR and a 255lt/hr pump

They will not be overly rich, in fact they might still be lean.

The stock ECU is not designed for a modified SR, it's designed for a stock silvia in Japan.

If your car is idling and running like shit with piss poor gas milage because of your new upgraded fuel pump there is something else wrong.

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steve shadows

Here let me get this all back on topic for th OP.

I understand exactly what everyone is saying above and agree to some extent. I just think a FPR is useful for fine tuning for maximum output and will do little for driveabililty if your upgraded Pump is wired correctly and your tuned rom or stock ecu and engine components are working properly. If your stock FPR is trashed then I could see a problem with AFRs on light load areas.

oh and in regards to the nismo, they arent fond of frequent adjustments

the nut is made of soft metal and strips easy

if you do buy it be sure not to overtighten it.

Ive also had problems with it coming lose, or having to be readjusted down and then back up at random with no change i baro etc.

Im purchasing an Aeromotive, but the SARD is a great compromise and I loved my last one.

I have used all of the ones mentioned go with the SARD if you absolutly need to adjust FP.

FP adjustments can be useful if monitoring AFR, Fuel Pressue Under load and in conjunction with a Tuned Rom.

Otherwise set the fuel pressure to base 40 with vaccum line connected with a FPR and adjust fuel via a Standalone Unit.

If you don't have one as the OP mentioned, you still should not be having fuel efficency issues or driveablitiy hesitation etc, simply by replacing your stock pump with an aftermarket 255lt/hr'

If your absolutely sure that everything else is in proper order and your car is idling way too rich, your stock FPR is a pile of shit and per the nissan wizards advice above please purchase said cheap shiney FPR to adjust base, so your eyes dont burn out of your scull with your illegal motorswap when waiting at stop lights.

cheers

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RYAN_S-14

well this might be different, with a stand alone, it looks like you tune via standalone i always use the power fc

RYAN_S-14

all i learned was in japan

daryl337

For gods sake..

What steve is talking about is:

Fuel pumps try to flow a constant volume correct?
Fuel Pressure Regulators back that volume up into your fuel rails so the injectors have pressure correct?

There are two ways to increase your fuel. Because injectors have a given duty cycle, a certain cc of fuel can make it through the injector per pulse with a given pressure behind it.... so how do you increase the amount of fuel your motor gets?

You can A) increase your duty cycle, or B) increase the pressure behind the injectors.

Once you increase the duty cycle of an injector so far, it becomes not only unstable, but also un-reliable, so instead of overclocking the injectors you can increase the fuel pressure behind the injectors so you get a larger amount of fuel through the injectors for the same pulse time.

Fuel maps can be "tricked" using an aftermarket fuel pressure regulator.... but because you have 700CC injectors (which is more than you will need), there is no need for you to increase your fuel pressure because you will not need to increase your duty cycle enough to start worrying about injector failures. So in your case, the stock FPR may do just fine.

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discopotato03

The purpose for the FPR is to set fuel rail pressure at a constant above inlet manifold pressure . I think the only reason people worry about setting fuel pressure at atmospheric pressure ie hose off is because their mind can understand a figure above zero .
Problem is that atmospheric pressure isn't zero and if it was we'd all be dead .
Now , an "atmo" engine only runs between a low of idle manifold pressure up to atmospheric pressure . Also for the record there is no such nonsense as a negative pressure because EVERYTHING above a total vacuum is actually positive . Atmospheric pressure isn't the datum total vacuum is .

Hokay so lets also forget about inches of Mercury because that's ancient history . The relevant measures are psi or kpa or BAR/atmospheres .
Zero absolute is always zero with these three scales . Atmospheric pressure at sea level will be 14.7 psi/100 kpa/1 bar , same thing .
With fuel pressure the important thing is the pressure head or the difference that exists between manifold pressure and fuel pressure .
Through the 80s and into the 90s Nissan typically had a fuel pressure head of about 36-37 psi regardless of what manifold pressure is on a std car .
Lets just say your SR idles with a manifold absolute pressure of 5 psi , the FPR setting the "head" around 36 above this will give an absolute pressure of 41 psi . If there was atmospheric pressure in the manifold it would be 14.7 + 36 or 50.7 psi absolute .
In "gauge" pressure terms , which assumes atmospheric pressure is zero , the fuel pressure would be 36 .

Need more fuel . There is two sides to more fuel , first being volume and second pressure . To get volume means using a larger capacity fuel pump and larger injectors plus tuning . In theory all looks great but the simple and effective std FPR isn't setup to bypass the greater volume of fuel coming down the tube , so when it can't open up enough to bypass this extra fuel at idle/light loads the pressure is higher than std at those power levels .
Skylines from that era had a power dropping resistor in circuit so the fuel pump runs slower in those conditions . From light loads up their ECU signals a glorified relay connecting their pumps earth return wire direct to the body bypassing the dropping resistor . Full current , minus any wiring losses , to the pump so it can run at it's rated speed . The engine is passing enough fuel through the injectors for the std pump not to overwhelm the std FPRs ability to regulate the fuels pressure head .
What this all means is that if you markedly increase the pumps capacity you need to increase the FPRs bypassing ability if you want the system to run in regulation . Aftermarket regs generally do this and add adjustability as a bonus just remember that feature is only part of the increased functionality .

Also the next problem is fuel heating with so much more fuel going from the tank to the rail and returning at light cruise loads or idling/traffic driving for extended periods .
If you have some means of slowing the pump down at idle and light loads there is less fuel doing the roundies and carting heat back to the tank .
Obviously this depends on how much you overkill your pumps capacity so if you went from an OE S13 pump to a Walbro 460 and drive mostly at normal built up area speeds you could have dramas .

A .

waxball88

I prefer AEM fprs. I've heard more accounts of people having issues with nismo afprs, whether it be not fitting, not locking properly, etc. AEM gives me optional vacuum output where I can place it to where it is convenient. Can convert input and outputs to big 6-8an for more fuel capacity over nismo fprs.