Subaru Impreza GC8 & RS Forum & Community banner

1 - 7 of 7 Posts

·
Registered
2004 Forester XTi
Joined
·
1,005 Posts
Discussion Starter #1
I was just wondering after what type of mods will the stock fuel pump need to be replaced with a higher flowing one. ...or when it will start improving performance from small mods. I would assume getting a faster flowing pump will make the engine eat loads more fuel. Will the ECU learn that a faster 'and more furious' (I had to type it :p ) fuel pump is now in place of the stock one? My mind is jumbled.
 

·
Registered
Joined
·
852 Posts
Uprated fuel pumps are important when you start adding major components to the car, or anything that is going to require more fuel to efficiently run. An intake, not necessary at all, as your atmospheric pressure level is still below zero. Intake and cams, no, still not enough air. Turbo, YES. This is so because you are now adding atmospheric pressure in the cylinders above a level of zero, and this extra air needs more fuel flow.

If you are N/A, you will probably feel a slight increase in power with an uprated fuel pump, probably something around 255 lph.
The main reason that stock pumps are replaced its simply because they cannot keep up and/or maintain a good ratio with air.

Graham
 

·
Registered
2004 Forester XTi
Joined
·
1,005 Posts
Discussion Starter #3
I came upon this question by snooping around on JoeT's (Toronto's Subaru Impreza Club) thread talking about Brullen headers "requiring" a faster flowing fuel pump for full efficiency of the headers. It is a long thread that talks about, both, the presale and sale of the headers. That's why I'm thinking if I were to get the Cobb header-cat or the MRT system, I may be needing one. I don't have the link, sorry.
 

·
Registered
Joined
·
852 Posts
I'm not too familiar with the Brullen headers, though they very well my require an uprated fuel pump.


Graham
 

·
Registered
No Subie to see here, carry on
Joined
·
109 Posts
The first thing you might try figuring out is how much fuel the stock fuel pump flows. From there, you can figure out how much hp it will support.

Then figure how much power you are making or at least want to be making and follow these steps. You'll need to change some numbers around.

Total Fuel Flow (lb/hr) = Injector Size (lb/hr) X number of injectors

To convert lb/hr to gallons-per-hour divide by 6.25.

To convert from pounds-per-hour to liters-per-hour divide by 1.64.

To convert from gallons-per-hour to liters-per-hour, multiply by 3.8.

OK, now that this is out of the way lets figure out what I need for my 200 hp 1.8L.

The injector size we figured on is 29.4 pounds/hr

Total Fuel Flow (lb/hr) = 29.4 X 4

Total Fuel Flow (lb/hr) = 117.6

Now we have to convert it to Liters-per-hour since that's what most pumps are measured by.

117.6 / 1.64 = 71.7

so about 72LPH for 200hp

Chad
93 1.8T
 

·
Registered
2004 Forester XTi
Joined
·
1,005 Posts
Discussion Starter #6
Ahh, more math for me to do.

Subachad, I'm guessing your 200 hp Scooby is bhp and not whp, correct?
 

·
Registered
No Subie to see here, carry on
Joined
·
109 Posts
200 is actually a goal for my 1.8L, the actual BHP is probably about 170. This is based on a JC Sports dyno run where they got 142 at the Wheels with 5psi, no intercooler, and no engine management. I have 7-8 psi, rx7TT fuel pump, and an intercooler.

Chad
93 1.8T
 
1 - 7 of 7 Posts
Top