Nissan 200SX Club - South Africa

ok, There seems to be a bit of confusion going around with static fuel pressure and rising rate regulators.

Ok, 1st. Static fuel pressure meens the fuel pressure stays the same, most of them have a regulator in the tank or is not connected to the intake manifold. The fuel pressure stays the same, if it's 3bar it's always 3 bar, under vacuum or boost.

2nd, constant rate regulators means it changes the fuel pressure to accomodate what the engine needs, if it's set to 3 bar with the motor of and you start is and the vacuum is then -0.5bar then the pressure drop by 0.5 bar. This is a 1:1 ratio rising rate regulators. Yip, they call it that too by some.

3rd then you get rising rate regulators with other ratios, like 1:1.7. They are mostly used in racing applications. They increase pressure on a higher ratio, they're also mostly found on cars with small injectors or on modified cars that don't want to run massive injectors, the bigger the injector the more difficult it is to get it to run cleanly on idle or low RPM.

The SX has gor a 1:1 ratio regulator on as standard.

You will also some guys talk about regulators with "boost reference".

Static regulators are mostly found on NA carburatored cars.

Static regulators are mostly found on NA carburatored cars.

Above is Hennies quote.
Then I quote the Aussie again:"

In answer to your questions, no, the stock FPR isn't a rising rate, and you don't want a rising rate. They use rising rate FPR's on NA cars that have been converted to forced induction (turbo/supercharger). Since our ECU already has all of the info it needs to add the correct amount of fuel based on the input it's receiving from it's various sensors, all you need to do is give the fuel injectors 36psi static pressure and everything should be OK. If you use a rising rate FPR, your AFR's will get horribly rich as boost pressure increases. As for the 90° hardline, yea, you can remove it.

Static fuel pressure is the fuel pressure that is in the rail relative to the vac/pressure in the manifold. The purpose of a fuel pressure regulator is to give the injectors a relatively constant amount of fuel pressure so that the ECU is easier to program. Here is what I mean; under vacuum, with out a fuel pressure regulator, MORE fuel would be injected than normal since the manifold is "sucking" the fuel into the rail. To compensate for this, the FPR drops the pressure in the rail so that not as much fuel is available to be injectors. The opposite happens under boost. The pressure in the manifold pushes back on the fuel trying to come out of the injectors. With out a fuel pressure regulator, you would have to keep the injectors open longer, or use bigger injectors, which can make having a smooth idle difficult. With the FPR installed, when the boost pressure in the manifold increases the regulator increases the pressure in the fuel rail in a linear proportion so that the same relative amount of fuel is injected. AKA, with vac fuel pressure goes down, with boost, fuel pressure goes up.

Hennie , I am still no with you:Static on NA and this guy says rising on NA converted to forced induction?? So, please dont get pissed off of me, and I appreciate all yours ppls knowledge. But we are still not there.

Or Hennie - will the above FPR pic of Phinx do the job on my sx? 1:1 rising?. Shi....

The SX has gor a 1:1 ratio regulator on as standard.

This Aussie says no? Am I right? May be I read not good enough?

let me try and help.
Some modern cars have the regulator at the pump without a return line.
these are NOT referenced to manifold pressure.
Most cars have a regulator that is referenced to manifold pressure this is to compensate for the fact that at light throttle the vacuum in the manifold helps suck fuel out of the injector.

These regulators are 1:1 which means that the fuel pressure will increase by whatever the boost is stock FP of 3 bar plus 0.5 bar boost = 3.5 bar fuel pressure.
HOWEVER the pressure at the injector nozzle is still 3 bar because you have the 0.5 boost trying to push the fuel back through the injector.

Rising rate regulators raise the fuel pressure more than the boost increase these are normally fitted to compensate for injectors that are to small.

HOWEVER as fuel pressure goes up fuel delivery dimishes so you cant just whack up your fuel pressure to compensate.

OK, its all coming together now.

Calibrator and Hennie thank you.
From this I understand no go for rising type on the sx?
And the sx stock FPR is then static?
And can I use then 1:1 FPR pic at top of this thread. Pic rom Phinx. The chrome jobby?
Thanks again.
Freddie

The Calibrator wrote:HOWEVER the pressure at the injector nozzle is still 3 bar because you have the 0.5 boost trying to push the fuel back through the injector.

.

I actually don't agree, If you've got a 3 bar pressure from one side and 3 bar from the other side, it doesn't mean that the pressure becomes 0bar, all it means is that the fuelflow will become 0, not the pressure, the 1.1 ratio is there to keep fuelflow(volume) constant by by changing the fuel pressure to compensate for vacuum or boost.

Do not confuse fuelflow volume with fuel pressure.

ChemCool wrote:Calibrator and Hennie thank you.
From this I understand no go for rising type on the sx?
And the sx stock FPR is then static?
And can I use then 1:1 FPR pic at top of this thread. Pic rom Phinx. The chrome jobby?
Thanks again.
Freddie

i think you're getting confused.

there are 3 types mentioned in this thread.

1.static - once the pump is running then there is always 3 bar fuel pressure for example.

2. 1:1 - there will be a specific fuel pressure (3bar for example) when manifold pressure is at atmosphere. the fuel pressure will then increase/decrease on a 1 to 1 ratio with either boost or vacuum.

3. 1:1.7 - the same as number 2, but the ratio is higher. so if manifold pressure increases by 1 bar, then fuel pressure increases by 1.7 bar.

sx's have FPR's that work like number 2 above as far as i know!

exactly, atleast one that has the same answer as me. Thanks Veecee.

Hennie Marais wrote:exactly, atleast one that has the same answer as me. Thanks Veecee.

NP - you know me - i never say anything that hasn't been said before!!!!

sx's have FPR's that work like number 2 above as far as i know!

Ok, I think I follow that. Can I buy the FPR 1:1 from Phinx then?

if it's a 1:1 ratio, then ye, it will work perfectly.

or you can buy one from me if you'd like!!!

sorry phinx!

if it's a 1:1 ratio, then ye, it will work perfectly.

Phinx, we got a deal. I take that FPR. Hennies head is on the block.

PM please to arrange .Freddie

damn - nearly snaked that from phinx!!! oh well!!!