How to Determine Fuel Pressure?

[packman]

How does one determine fuel pressure on a non-stock engine? i.e. 351W with aftermarket EFI. Just curious. Thanks guys



Packman

[turbo2256b]

How does one determine fuel pressure on a non-stock engine? i.e. 351W with aftermarket EFI. Just curious. Thanks guys



Packman

Should be able to do it the same way just need the valve and a gage. Some asian cars needed to adapt some stuff to do it as they didnt have the valve. Just need to know what they deem thier system pressure to be

[packman]

Should be able to do it the same way just need the valve and a gage. Some asian cars needed to adapt some stuff to do it as they didnt have the valve. Just need to know what they deem thier system pressure to be

Do you mean the supplier of the aftermarket parts (i.e. Trick Flow with their cylinder head and intake packages) recommends a fuel pressure? Or is there a formula for determining fuel pressure? Or do you build an engine and after you get it running, have a tuner set it up?



Packman

[1990LTD]

adjustable fuel pressure regulator

[packman]

Okay, perhaps I asked teh question the wrong way. How do you determine the fuel pressure value? i.e. 30 psi etc..... How do you determine that psi value for a given engine combination?


Packman

[1987cp]

Isn't fuel pressure just part of the tuning process?

[packman]

That's what I was asking. So when the time comes, I will just guesstimate (adjust the pressure among other things) and make the car driveable so I can get it to the place where it will be tuned. Kinda like rebuilding the front suspension; you get it as close as you can get to the original set up and then you bring the vehicle out to be aligned at a shop.



Packman

[turbo2256b]

Are you using a aftermarket ECM?

[mrltd]

Fuel injectors are designed to be run at a specific pressure. If you are running ford injectors, 39 psi..... and most aftermarkets are all rated at as certain psi, which is around 39 psi.... Changing the pressure to tune for a combo is the wrong way to tune.

What do you mean "aftermarket" efi? Holley pro-jection? EZ-EFI? Those all have specific pressures the system is designed for.

[turbo2256b]

Changing the pressure to tune for a combo is the wrong way to tune.

That depends on the system. A returnless system it wont as the ecm knowss the pressure and will work around raising it. Most of the return style systems with conversion to an adjustable pressure regulator it can help up to 40% duty cycle on the street possibly 60 on the strip. If you have 19#injectors and realy need 30s it isnt going to work

[packman]

I was thinking of running Trick Flow 185cc street heads and the R-series intake (not the box intake rated for 7000+rpm) for the 351W. 30-32# Bosch or Accel injectors. Comp Cams 270HR cam. It's not a wild combination by any means, so I think a Mustang A9L should run it, unless told otherwise.



Packman

[gadget73]

you'd need to tune it but the A9L should be able to cope with that. Generally speaking you want to run stock fuel pressure and increase fuel to the engine with tuning and possibly bigger injectors. You'd really need to put it on the dyno with a wideband to find out what its doing and what it needs. Wideband gives you the A/F numbers, and you use that data to adjust the fuel so its right.

[turbo2256b]

If your planning on using Fords factory fuel lines and rails a 75mm TB and proper sized MAF you will never be able to supply enough fuel to the injectors. I have some slightly used 30# FMS injectors and some flow tested (for calibration perposes) Ford ones would sell.

[mrltd]

I was thinking of running Trick Flow 185cc street heads and the R-series intake (not the box intake rated for 7000+rpm) for the 351W. 30-32# Bosch or Accel injectors. Comp Cams 270HR cam. It's not a wild combination by any means, so I think a Mustang A9L should run it, unless told otherwise.



Packman

That's not aftermarket EFI. That's FORD EEC-IV. It will need a tune to get the most power and drivability out of it.


Dave, sure you can boost the pressure, it's still a band aid for improperly sized injectors. It will change a lot more than just the delivery amount of fuel per hour.

[turbo2256b]

Dave, sure you can boost the pressure, it's still a band aid for improperly sized injectors. It will change a lot more than just the delivery amount of fuel per hour.

It works if you have 30# injectors and realy need 32.87 lb ones to maintain as designed system pressure.