Fuel pressure
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Fuel pressure
I have an 89 f250 460 5speed manual 4x4. In time I am looking at doing the maf conversion with larger injectors and adjustable fuel pressure regulator. I just replaced both of my lowpressure in tank sending units and pumps. However my high pressure pump is getting weak as well.
My question is, will the factory high pressure pump be enough pressure for the larger injectors and adjustable regulator, or do I need to get an aftermarket pump for higher pressure?
My question is, will the factory high pressure pump be enough pressure for the larger injectors and adjustable regulator, or do I need to get an aftermarket pump for higher pressure?
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Does the engine have upgrades that will require bigger injector? Simply plugging in larger injectors is probably not going to do what you think, the computer is programmed to use 24lbers and anything else will have it continually counteracting what it percieves as a rich condition.
The stock squirters are more than enough for a stock or lightly modified motor and the computer will add more fuel if the engine needs it, so what you need to know is if the motor is running lean at rpms and if so is that because the injectors are maxed out or because the fuel pumps can't keep up. To figure this out you need a fuel pressure gauge and a wideband O2 sensor to monitor these system while you are driving and working the motor to it's limits. What you should see is that fuel pressure stays at 40-45psi all the time at WOT and that A/F ratios are maintained at about 12.5-13:1 for best power. If pressure drops or the motor goes lean(14-15:1) then you know what system to upgrade next. With the stock SD EFI system a simple adjustable FPR may be all that's needed to keep the motor fat under load, but you won't know that until you have some data to look at.
The stock squirters are more than enough for a stock or lightly modified motor and the computer will add more fuel if the engine needs it, so what you need to know is if the motor is running lean at rpms and if so is that because the injectors are maxed out or because the fuel pumps can't keep up. To figure this out you need a fuel pressure gauge and a wideband O2 sensor to monitor these system while you are driving and working the motor to it's limits. What you should see is that fuel pressure stays at 40-45psi all the time at WOT and that A/F ratios are maintained at about 12.5-13:1 for best power. If pressure drops or the motor goes lean(14-15:1) then you know what system to upgrade next. With the stock SD EFI system a simple adjustable FPR may be all that's needed to keep the motor fat under load, but you won't know that until you have some data to look at.
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Well for the moment the motor is all stock, however I have the original motor sitting on an engine stand that I am getting ready to bore, port, shave the head, headers, slightly larger cam ect. I know that as stock I dont need anything different however why buy a stock pump now if in a few months or maybe a year I would have to get an aftermarket pump anyways? The rebuild is when I get rid of the sd system and go to the maf system which will alow me to program the computer to my specs and not factory specs.
I have never heard of a wideband 02 sensor, ill have to look into that.
I have never heard of a wideband 02 sensor, ill have to look into that.
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Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
I guess I forgot to answer your original question. The stock pump will supply the full capacity of the stock injectors(300hp at 43psi) but that's about it so an upgraded pump is a good idea. Note that you can get as much as 350hp from the stock injectors by raising fuel pressure and extending the dutycycle.
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