setting fuel pressure

Hello
Past little while iv been working on a formula libre race car for a guy.
Car makes 200ish hp its a stock ford DOHC 2.0L focus motor in it.

Has 220cc injectors a areomotive FPR and a walbro inline 255 pump.
saw his fuel pressure was set to 84psi!

I know a stock focus system runs 45PSI

now my car fully built evo 3 street tune makes 419whp I have a walbro 255 and 1000cc injectors and FPR set to 42psi.

what i dont seem to understand is how do you pick what your PSI should be set to on the FPR ... or the LPH that you need ..

could some one please clear this up for me ..

thank you

Wish I could help better but your text gets me confused...



Is that car modified??? Was this vehicle modified with some kind of forced induction (power adder)???

What is "libre" means???

Ghislain

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Injectors will squirt Xcc/min @ Ypsi fuel pressure. I can't remember but think they are rated at 45psi.. You need enough pump L/hr to cover the squirt at the max duty cycle % and fuel pressure that you run. Consider that we use 1:1 rising rate regulators.

I guess to idle with double the stock fuel pressure on stock injectors, there must be a fuel control program running the injectors at half. Seems like that would be a tall order to control, does it idle like sh!t?

On picking the correct base fuel pressure, you would want one that allows the fuel to atomize and burn well in your setup under all loads. Typically it's set the same as stock but there is some room to play.

Hence my WTF???

Ghislain

the car has Individual throttle bodys and tube exhaust, runs full standalone. its still NA

formula Libre is a class of race cars where any thing goes pretty much .. car we are running is a British F2000 formula ford looks like a small indy car.

car idles not to bad, but cracks and pops when you rev it up

When I see 200ish hp out of 220cc injectors on a 4 banger with unusually high fuel pressure, my first impression is that they are bumping fuel pressure up to compensate for the fact that the injectors are too small.

Agreed. And now that we learn it's not boosted, it makes a little more sense because they aren't going to have the pressure rise to something rediculous with load. Maybe huge compression and flow making the power? It's still funny with a standalone because they can control larger injectors. I guess a regulator setup is a bit cheaper than injectors and they had to run lines for more fuel anyways.. Is the plan to boost it later?

Most Fuel Pump have a Pressure Relief Valve that opens when Fuel Pressure is above a certain amount. Walbro 255's Relief Valve normally open around 75 psi.

As stated above I would suggest running larger Injectors and reducing the Fuel Pressure.

Ghilsain

Rob .. the goal is to at some point turbo it .. from what i read that motor can handle 350hp boosted.

Ghislain .. thats what i had suggested aswell to run larger injectors and get the fuel pressure around 40-50psi

the walbros he keeps putting in are blowing after a few races i assumed its due to the high pressure .

I remember hearing something about the Focus SVT engines and their fuel setups. Not sure how much you're using from the Focus, but I remember hearing that the stock system does not use a regulator; the stock fuel pump is a variable-flow pump that is controlled by the ECU. If you replace it with a Walbro (or any other standard electric fuel pump) it will not last very long.

Considering that this car has a standalone ECU, I doubt this is the issue.. just a coincidence. But I thought I'd mention it.