Return Style fuel system question.....Fuel Pressure

[xtremekustomz]

I have lethals budget return system on my car with the 2.9 whipple. We have tuned the car at at 50lbs static pressure. The vaccum line is tied into the FRPS but the vaccum line is capped off on the regulator. My tuner says it tuned with a constant 50lbs of fuel pressure going through the return setup. According to what i have read should it not be set at 58 -60 psi according to 1psi to every 1lbs of boost then running 18lbs of boost should make the fuel pressure 58psi.

Sorry if this sounds confusing, what i want to no is should i not sent the regulator to 58lbs as that is what the highest amount of pressure the car should have at 18lbs.???? Im alittle confused about this setting of static pressure??

 

[Blown38]

You need to reference vacuum/boost to the return style fuel pressure regulator. So when it is in boost it will raise the fuel pressure. When you set the static pressure have the car running and unhook the vacuum line from the Fuel pressure regulator and set it to your 50psi then hook the vacuum line back up to the regulator. When you hook the vacuum line back up with the engine idleing the fuel pressure will be lower than your static setting, which is perfectly normal.

And for reference ford calibrates injectors at 39.15 psi base pressure.

Here is a video

http://www.youtube.com/watch?v=tmKoAVKRY7g

 

[xtremekustomz]

You need to reference vacuum/boost to the return style fuel pressure regulator. So when it is in boost it will raise the fuel pressure. When you set the static pressure have the car running and unhook the vacuum line from the Fuel pressure regulator and set it to your 50psi then hook the vacuum line back up to the regulator. When you hook the vacuum line back up with the engine idleing the fuel pressure will be lower than your static setting, which is perfectly normal.

I uderstand that but he was setting the regulator to feed the fuel lines at a steady pressure as opposed to the pressure changing via vaccumm. So therefore using static pressure as a constant. Thats why i was saying if the make pressure is 58lbs then should it not be set to the max it would draw threw the 63's?

 

[xtremekustomz]

Ya base pressure should be around 40psi. It is confusing for me too but the car seems to run well with the base set to 50lbs and only drops by 2-3 psi at wide open throttle.

 

[Blown38]

You need to have the pressure raised when boost is in the manifold or your injectors will act as smaller injectors as the fuel pressure will be the same but you now have 18 psi working against the tip of the injector.

You want to keep the delta pressure at the 39.15 psi. Which is the pressure in the manifold and the pressure in the rail working against each other to where the the fuel pressure at the injector tip is always 39.15 psi.

I'm not very good at explaining things so if you don't understand what I am saying hopefully someone better will chime in.

 

[xtremekustomz]

So if the rail pressure is always at 58psi then the injectors have enough pressure/fuel to compansate the delta pressure???

 

[Blown38]

If FP is always 58 psi the injectors will flow like 63lb injectors at 18 psi boost. And flow more at low/no boost or especially vacuum. Your injector flow rate will not be linear. And your MAF curve will probably have big steps in it to keep the AFR correct.

It is not the correct way to do it. And its not hard to set it up the correct way.

The most common reason to raise base pressure is to make your injectors act bigger. If they are on the border for the HP you are making. But if you raise base pressure and reference vacuum/boost to the regulator like you should, you better have enough fuel pump/line capacity to flow the extra fuel in the upper rpm/boost range where you really need it.

 

[xtremekustomz]

Thats what i am confused about.... I thought you would use the regulator for what it is ment to be used for and not cap it off. I am not a tuner so i try to have faith but it didnt make sense to me. So he tuned the car at 50psi on the regulator and that never changes because the regulator is capped off and the vaccumm line only runs to the FRPS, like stock. Now if i jump the vaccum line from the FRPS back to the regulator and set the pressure back at 40psi will the tune still work or do i need a retune? I just went out to the car and did that and the pressure jumps from 40 to 55 when i blip the throttle so it is building pressure under throttle.

 

[xtremekustomz]

No one else has any imput??

 

[Blown38]

It would need a retune I would think. It never made sense to me either when you explained it. On The stock returnless system if you log fuel pressure you will see the computer trying to keep the pressure at 39 psi which is delta pressure(psid) and if you hooked up an external gauge you would see your 58 psi guage(psig) at 18 psi boost. It kinda sounds like he was trying to tune it like the returnless setup.

 

[Blown38]

Did you install the blower and fuel system yourself? Does your pumps run constantly with the key on?

 

[xtremekustomz]

Ya all installed bye myself. Pumps run full time with key on. Ya I think he is used to running returnless. The car does run alright but should be better. At WOT it does stay around 11.5 AFR. It just bothers me that I have this return setup and Im not using it properley.

 

[xtremekustomz]

During full pull on the dyno fuel pressure dropped 5 psi from 50 to 45psi but still had a good afr.