base pressure for fuel regulator

[renxun]

what does the above mean..? issit the pressure when our key clicks to on but havent start the car ..?

OR

does it mean pressure when the car was started...?

basically what is the fuel pressure of a car during idling...? im using a 1jz... just bought a sard regulator... duno what pressure should i set.. now i just put it at 2.1bar during idle and drive for the time being.... can anyone enlighten me?

 

[speedchaser]

Base fuel pressure is set when your car is idling. Unplug the vacuum hose from your fuel pressure reg and then you set you base pressure from there. For a 1JZ-GTE, the stock base pressure should be set at 45psi (3 bar).

 

[renxun]

thanks alot bro....very much appreciate.

 

[markii]

what is the suitable pressure to set to for 1jz?

 

[renxun]

was mentioned above.... 3bar base pressure.... in my case i up it a little bit pass 3 bar.... around 46psi

 

[Joeker]

Base fuel pressure is set when your car is idling. Unplug the vacuum hose from your fuel pressure reg and then you set you base pressure from there.

Yes, base presure is set during idling.

But when the vacumn hose is unpluged from the regulator, the regulator is reading WOT.

So my query is, how is it possible to set iddling base pressure when the regulator is reading WOT?

 

[renxun]

but then my car is turbo ... how could it be wide throttle if unplug the vacuum?
do enlight me... so what you mean is i should set 3 bar when my car is idling wid vacuum plug on?

 

[Joeker]

Fuel pressure regulator controls how much fuel goes back to the fuel tank.

When engine is iddle, vacumn is strongest ie. negative manifold pressure.

When the vacumn hose is disconnected, there will be no vacumn, thus simulating a situation similar to WOT.

Therefore I'm surpsie how could base fuel pressure (iddling fuel presssure) can be dial-in under WOT? Hope speedchaser would enlighten us.

 

[ART///SPEED]

all engine is 3bar

 

[renxun]

all engine is 3bar

3 bar in what condition? during idling with vacuum hose plugged in ?
3 bar when the key is click to on before starting the car?
3 bar during idling WITHOUT vacuum hose plugged in?

lets discuss this

 

[speedchaser]

On a "stock" regulator with vac unplug, that's the WOT (base) pressure for an NA. "Idle pressure" is what you should be getting when you plug in the vac. It determines not only how much fuel goes back to the fuel tank, it also determines how much and how fine the fuel goes into the cylinders.

On an adjustable FPR, we need to set it with the vac unplug cos we need to get the same WOT pressure or more (modded cars) for safety or performance issues, and sometimes the "idle" pressure could be affected with different FPR even if you set the base pressure correctly. Most of the time it's negligible. Some aftermarket FPRs might have different rising and ramp rates and we might have to compensate it by tuning it out on the ECUs if it cannot be compensated with the engine's stock close loop operation on idle.

On a turbo, the FPR is control not only by vac but also by the rising rate of the pressure in the manifold and it will go beyond what is set on atmospheric. That is why setting the FPR on idle without the vac (atmo) is the middle point.

Fuel pump is another issue that must to be factor in for it is the heart of the fuel operations.

Hope this helps.

 

[speedchaser]

all engine is 3bar

Sorry, I beg to differ on this! Not all cars are the same. This is completely wrong info.

 

[Joeker]

On a turbo, the FPR is control not only by vac but also by the rising rate of the pressure in the manifold and it will go beyond what is set on atmospheric. That is why setting the FPR on idle without the vac (atmo) is the middle point.

DO you mean, at positive pressure (pressurized manifold condition) the AFPR will supply more fuel?

Please do not take any aftermarket engine management or fuel pump into consideration.

 

[jinkl]

DO you mean, at positive pressure (pressurized manifold condition) the AFPR will supply more fuel?

Please do not take any aftermarket engine management or fuel pump into consideration.

if its a sard regulator or aftermarket fuel regulator it will bro
1:1 for sard small , means, 1psi of boost will increase 1psi fuel pressure

if FSE 1.7:1 is diffrent, 1psi boost will increase 1.7psi fuel pressure

 

[kruger]

Sorry, I beg to differ on this! Not all cars are the same. This is completely wrong info.

Agree with speedchaser... You must tune your FPR based on your Air Fuel Ratio. Basically you must use wideband.

 

[markii]

renxun, mind sharing what setting u using for your 1jz? and hows the results? im using 1jz too

 

[renxun]

i just set it based on logic... as my max boost setting is at 27psi which is roughly at 1.9bar. so my fuel line pressure shouldnt go max more than 73psi during full boost... at which for base pressure, a max of 73psi - 29psi which will make a suitable base pressure of 3bar or 44psi or somewhere around there... why 73 psi is because the fuel pump im using... which is the bosch 910 flowrate will drop pass 73psi and since im running on twin bosch 910 pumps, n my total max flow is 260l/hr so i still can push another 2 psi upwards on base pressure... so my base pressure now is actually 46psi... (without vacuum hose plugged in)

im runnning such high pressure because my 550 injectors are running out... at that level of booost my af ratio is just around 12.2. and thats with the pressure pushed up...

 

[ecupro]

i just set it based on logic... as my max boost setting is at 27psi which is roughly at 1.9bar. so my fuel line pressure shouldnt go max more than 73psi during full boost... at which for base pressure, a max of 73psi - 29psi which will make a suitable base pressure of 3bar or 44psi or somewhere around there... why 73 psi is because the fuel pump im using... which is the bosch 910 flowrate will drop pass 73psi and since im running on twin bosch 910 pumps, n my total max flow is 260l/hr so i still can push another 2 psi upwards on base pressure... so my base pressure now is actually 46psi... (without vacuum hose plugged in)

im runnning such high pressure because my 550 injectors are running out... at that level of booost my af ratio is just around 12.2. and thats with the pressure pushed up...

Hello,
Let say you using stock ecu, and let say injection timing is at 2.2ms and using stock injector and set at 45 psi for for fuel pressure regulator.
At this time, let say A/F show 14.5.
Now, you change your injectors to 550c.c.,your A/F should show at RISH side say, 12.9 ( by the way, the stock ecu still inject at 2.2ms )
Althought the ecu have build in feed back loop ( ecu try to adjust to 1.9ms ),you A/F will show 13.2
So, in order to kept A/F 14.5, you should reduce the fuel pressure and NOT rise the fuel pressure.
Bye.

 

[FatAssRubber]

Hmmmm.. very interesting comments all around. Some are true.. some are not so correct and some are commendable logic.

Again.. speaking like a old fart, the whole flow of fuel from fuel rail into injector and then manifold is depending on the pressure differential between the components. Let this be the fundamentals. This is material and law of dynamics. the higher the pressure difference, the more flow. Fluid flow from High Pressure to low pressure. Ok.. onto next step.

Does higher pressure always deliver more fuel?? Yes.. but only if your fuel pump is strong enough. As Volume is a function inversion of pressure. m=p/v.

So, what does Fuel Regulator Do?? it relieves excessive fuel pressure in the fuel rail to maintain a constant pressure, therefore you get a constant flow. it doesnt give you anymore fuel that what the pump can do by itself. Now.. i know this is getting a little more confusing and still do not answer your question of what is the correct fuel pressure to set.

Point one.... idling.. NA or Turbo.... same old same old... unplug the vacuum hose... i would say normally we want the pressure about 1.5 bar atmospheric (or 2 bar absolute). Note that on all engines, at idling, you will have -0.5 bar atmosperic. Some more.. some less. So what we are creating here is a 2 bar absolute between fuel rail and mainfold.

When you throttle and rpm goes up, the engine consume more fuel, thus less fuel being let off by the regulator back to tank.. in some cases the drop is significant that the pressure drop.. this is not the fault of the regulator.. the pump is working its heart out but still cannot fulfill the consumption..

In a good fuel regulator and we assume pump capacity is well enough, it will maintain this 2 bar pressure differential accross the rpm and power band. Meaning at -0.1 bar manifold pressure, the fuel rail pressure will be +1.9bar (approx) and at 0.8 bar manifold pressure.. fuel rail goes up proportionately to 2.0+0.8bar= 2.8 bar ... most cases of the power addict here..boosting 1.8 bar... then it should read 3.8 bar... Faham tak ooiii!!

The vacuum hose function is to maintain base pressure.. and then whatever manifold pressure add on to it to create a constant different between the two side of pressure differential..

well.. if still cannot understand.. but me a teh tarik.. some afternoon in sunway.. i am more than happy to share.. as long as i am in town..

ciao..

 

[ecupro]

Hello,
"This is material and law of dynamics. the higher the pressure difference, the more flow".
So, if you increase the c.c. of your injectors, you will have more flow and so the A/F also raise when engine idle.
So, you have to reduce the fuel pressure and NOT RAISE.

IF you use stand alone ecu or piggy pack, you can reduce the figure in your FUEL MAP in order to get back your A/F without adjust your fuel pressure regulator or stock fuel pressure regulator.
Bye.