Fuel pump questions.

Topic: Fuel pump questions. (Read 1942 times) previous topic - next topic

Fuel pump questions.

July 20, 2005, 08:23:43 PM

1. First what is the flow rate on a stock fuel pump?
2. What kind of fuel pump are you runnig?
3. What flow rate fuel pump should I look at for my car?
(possible power adder(s) being added soon)
4. Do I need a pressure regulator for an aftermarket high flow pump?

My car Is an 88 Cougar XR7, 302, mass air, 19lb injectors, HO upper and HO throttle body.

The reason I am asking is because my fuel pump took a on me and I need to replace it.

Re: Fuel pump questions.

Reply #1 – July 20, 2005, 08:57:29 PM

The stock V8 pump in your car is rated at 66lph. The 5.0 HO pump is rated at 88.

66LPH = 17.36 Gallons per hour
88LPH = 23.16 Gallons per Hour

For a rough estimate lets use 1 Gallon of gas = 7 pounds.

So the stock pump then puts out 121.52 Pounds of gas per hour
The HO pump puts out 162.12 Pounds of gas per hour

By those numbers you can see what size injectors the pumps can handle. Just divide by number of injectors:
121.52 / 8 = 15.19 pounds per hour
162.12 / 8 = 20.27 pounds per hour

Keep in mind that the stock injector is rated at 39 PSI and increasing the fuel rail pressure if you should so wish to do so makes the injector act as a larger one. A 14 pounder at 62 PSI is equal to a 19 pounder at 39 PSI. They will flow the same provided they have a pump that can support them.

Raising Fuel rail pressure will have the reverse effect on your pump. The rail and line pressure actually work against it lowering the actual output. This is why a lot of people (including myself) go for overkill on their pumps.

I'm running 52 PSI with a 255 pump. The pump is WAY overkill, but I got it cheap :D Mine's a Walbro unit. As far as needing an adjustable fuel pressure regulator with a Higher flowing pump it is not necessary.

You did not have enough pump for your injectors, but it was enough gas for your engine. HO's have been run on the dyno with 14 pound injectors at stock pressure and made full HP/torque. It's nice to have the safety factor of a biger injector to keep the A/f ratio from goin south on you though.

Since you're gonna go power adder I would go with nothing smaller than a 155 LPH pum AND an adjustable regulator. An injector upgrade may be needed as well depending on your boost levels.
Remember it's better to have a bigger injector at low pressure than a smaller one at high pressure

Re: Fuel pump questions.

Reply #2 – July 20, 2005, 09:01:25 PM

Quote from: Paul Flockhart

Since you're gonna go power adder I would go with nothing smaller than a 155 LPH pum AND an adjustable regulator. An injector upgrade may be needed as well depending on your boost levels.
Remember it's better to have a bigger injector at low pressure than a smaller one at high pressure

Ya we can add that question also. What size injectors? I was looking at running no more than 10psi. I was thinking of trying and finding a set of brown tops from a Merker or TC. Got any opinions on that?

Re: Fuel pump questions.

Reply #3 – July 20, 2005, 09:55:58 PM

Quote from: slamedcat

Ya we can add that question also. What size injectors? I was looking at running no more than 10psi. I was thinking of trying and finding a set of brown tops from a Merker or TC. Got any opinions on that?

Can't use the turbo 2.3 brown tops. They are a peak and hold type that have only 2.5 ohms resistance vs our saturate system that uses 14 ohm injectors. You can use the 30lb(red) or 36lb(dark blue) SC inj as they are the correct impedance.

Re: Fuel pump questions.

Reply #4 – July 23, 2005, 04:39:51 PM

Well I went to get my new fuel pump today and left without it. I found some other things to spend the money on.

http://www.foxtbirdcougarforums.com/showthread.php?t=4053

So I started swaping fuel tanks from the Mark to the Cougar.

Re: Fuel pump questions.

Reply #5 – July 23, 2005, 07:11:11 PM

So which one you gonna carb?

Re: Fuel pump questions.

Reply #6 – July 23, 2005, 08:41:26 PM

I was thinking the 91 Mark and putting a T5 into it. Does that sound wrong to anyone else.

Re: Fuel pump questions.

Reply #7 – July 23, 2005, 08:41:33 PM

I was thinking the 91 Mark and putting a T5 into it. Does that sound wrong to anyone else?

Re: Fuel pump questions.

Reply #8 – July 24, 2005, 12:58:26 AM

in your situation, power adder and fuel injection, id go with no less than a 190lph

im running a 255lph high pressure pump in my car, but thats only because it is able to provide fuel pressure more consistantly at higher pressure/boost levels, i can run 90psi of a fuel pressure total, and the pump wont flinch, but since youre looking at 10psi, a 190 should do you good