Rising Rate Fuel Pressure Reg

[SXY_33]

Hey,

just got my 33 tuned n dyno'd 2day. made 230.3 at the rears with:

hypergear hi-flowed turbo

3" turbo back

FMIC

bosch 040

POD filter

boost spikes at 14.5 n goes down to 10psi

so im smiling.

But was told i need a rising rate fuel reg if i wana b able to hold 15psi, as it is leaning out a bit and hitting boost limiter.

my question is are they all rising rate??? is there a way of tellin which r or rnt.

ive been lookin at either a Nismo one or this one off ebay(below)

http://cgi.ebay.com.au/SARD-Fuel-Pressure-...id=p3286.c0.m14

are they both rising rate??? is one just as good as the other???

thanks

[2LV8ETR]

Most modern fuel injected cars run a fuel pump in the tank and run much more fuel than is needed to the fuel rail. A regulator keeps a certain amount of fuel pressure in the rail and then sends the rest back to the tank.

Your car as well as most fuel injected cars have a one to one fuel regulator. It varies the fuel pressure by watching manifold pressure. It uses a diaphragm to control pressure. Most Nissans at idle (vacuum) fuel pressure is 34psi and at full throttle (No vacuum in theory) 43psi. If you further put pressure (turbo or super charger) to the manifold, it further increases fuel pressure. In factory regulators, for every pound of boost, it adds a pound of fuel psi. Hence 1 to 1.

Most adjustable regulators are still one to one or close to that, however you can adjust the pressure at idle or full throttle for fine tuning. There is one other type of regulator that is used with aftermarket forced induction, these are rising rate regulators. These regulators increase fuel pressure at a multiplication factor of boost. So instead of messing with complicated computers and injection duty cycles, these systems just increase fuel pressure to add fuel. They go inline down from the factory regulators and only start to add pressure under boost. So when you are off boost, you maintain factory tuning and drivability. Only as you get boost does the regulator begin to increase fuel pressure.

Rising rate regulators have a vacuum/boost line hose connector on them.

[SXY_33]

thanks for the info.

now that i know the difference how do i know which is a rising rate. ppl that sell them just say fuel pressure reg??? or does the rising rate have 2 inlets and one outlet as opposed to one in n one outlet on a normal one??

wat brands do ppl use??

[R34GT-t_07]

not sure if they are all rising rate but am using a TOMMI which is a rising rate, am verry happy with it my tuner recomended it to me, he also said that the nismo ones are very good as well.

hope this helps.

[2LV8ETR]

Rising rate regulators have a vacuum/boost line hose connector on them.

wat brands do ppl use??

I use a Malpassi.

[R31Nismoid]

You don't necessarily need a rising rate.

If you only need 5-6psi increase and you can apply that from the base, then you just need one that is adjustable.

[Moodles2]

I'm guessing the FPR was recommended by the tuner because the current injectors are being maxed out? I think a set of 2nd hand GTR injectors is a better choice than using the FPR to get more out the current injectors, at least then you've got a ~60kw bufferzone till you max out the GTR injectors.

[heller44]

Pity he has a 33 gtst then, eh? No gtr injectors for him. Top feed ≠ side feed.

[Beer Baron]

forget all the confusion between rising rate and 1:1 fuel pressure regulators most people do not understand what they are talking about so just leave it at that. all fuel pressure regulator will have a vacuum hose connection so that they can regulate fuel pressure in line with manifold pressure/vacuum.

a couple of key points.

1. no one uses anything other than a 1:1 adjustable fuel pressure regulator on 99% of turbo applications.

2. people using regulators that have a rate other than 1:1 are usually used on NA cars as they do not produce any boost. so at full throttle they are at 0 boost/vacuum. so people sometimes change their rate to get more fuel in.

3. tomei, nismo, sard, all the japanese regulators will do the job and all are around the same money. they all need to be set-up by someone who knows what they are doing and has a fuel pressure guage.

4. malpassi regulators are rubbish. very popular on NA applications but I have seen failure after failure on turbo cars. hence their nicknames of malpissi or malcrappi. use one if you want to enjoy some inconsistent fuel pressure and be scratching your head in a few months time wondering why the hell your car sometimes doesn't run very well.

5. the other cheap ebay regulators are just as bad. yes they are no complex devices but they still need to be up to a certain standard of quality to dampen any pulses and to properly regulate fuel pressure without spiking and without failure.

6. easiest solution is the nismo reg. if fits in the factory location and requires no extra plumbing. the tuner will just need to install a fuel pressure guage for set-up, then once set remove it. if you want a permanent fuel pressure gauge set-up (it's not a bad idea, fuel pressure is important and can tell you a lot of things) then go for something like Sard which has a port to add a pressure sensor easily.

7. increasing fuel pressure to get more fuel flow is ok if you just need a tiny bit more. but generally if you need a tiny bit more than means your current pump and/or injectors are giving 100% of their fuel just to keep things as you want them at full power. so you have no headroom. and in some circumstances you could have problems. so generally I'd say just get a bigger set of injectors or a fuel pump or even better, get both. raising fuel pressure is a band-aid solution. it's the cheap way out.

[2LV8ETR]

The only thing I have found with the Malpassi is that you can't put them anywhere near a high heat source, this is generally when they fail.

Mine has been on for about 18 months now and I haven't had any issues whatsoever with pressure fluctuations (gauge installed). The only reason I have it because I am at the limit of my injectors and I wanted a little bit of insurance. I know I should get larger injectors, but at the moment I'm happy with what I have.

[SXY_33]

thanks guy, info definatly helped.

i think ill go with SARD. yeah its prob my injectors, but i dont hav to money atm, guess fpr will hav to do for now.

[discopotato03]

IMO rising rate FPR's in turbo engine apps is a failed concept . The fact that the fuel rail pressure rises out of proportion to manifold pressure means it's going to create tuning problems for sure .

The other thing is that they force the fuel pump to work harder when you can least afford to have them let you down .

EFI pumps generally trade volume for pressure so pushing the pressure up isn't a terribly successful way to gain greater volume at high pressure .

The people I know that play with adjustable FPR's use 1 to 1 or linear rate ones and raise the pressure right across the board . They also insist on changing EVERY rubber hose that sees pressure upstream of the reg because you can't afford major leaks from old hose and higher than std fuel rail pressure .

Anyway to each their own , cheers A .

[SXY_33]

for some reason i always thought that the fpr makes it easier for the pump?

[BADR33]

factory fuel pressure regulator is rising rate of 1:1 so the same as aftermarket sard etc. the only thing it lacks is the base fuel pressure ajustment.

there is only a small window of pressure increase that is benificial before the increase in injector dead time actually costs fuel flow. as fuel pressure increases it becomes hard to open the injector.

all the sard regs we install at cars at my work, we just set to the same as factory reg.

in your case bumping the pressure up a few psi will help. although i don't know how long your factory turbo will last on 14-15psi as the exhuast wheels like to fall off.

230kw is the limit of the factory 370s, you can get v5 sti 440 injectors that drop right in, you just have to change the plug. im running them in my rb25 skyline and iv got 277kw with more fueling to go for when i up the boost

[bozodos]

mine was tuned at 245rwkw no FPR or other mods, standard RB25 injectors, and I've seen it hit max duty on my display several times at WOT in 4th, so I turned the boost down, however, everyone I've spoken to (ie mechanics) has said that adjustable FPR aren't worth bothering about and to just get new injectors / retune.

Wouldn't that be safer than trying to stretch the limits of your current injectors?

[SXY_33]

My problem is that my standard fuel pressure reg has prob stuffed up, as my injectors arnt the problem, its the fact that i have low pressure in my fuel rail, so when the injectors open less fuel then normal goes through. Ive just ordered one from Nengun, and apparently its gonna take them a month just to post it out

[wolverine]

do you want a stocker FPR for cheap? pm me. i have one or two lying around.

[gtr fan]

I was under the impression if you have bigger injectors and fuel pump, don't worry about an adjustable fuel pressure regulator on a turbo car. Anyone agree?

[R31Nismoid]

Agreed, at least on RB's that is 100% correct