Air leaks, pressure loss and fuel filters
01-16-2007, 09:57 AM
#1
Registered User
Thread Starter
Air leaks, pressure loss and fuel filters
Ive been tracking down air leaks in my fuel system for awhile now, as well as this weird phenomenon where my fuel pressure dips as low as 12psi at WOT. Right now Im suspecting my filter assembly doesnt flow enough fuel and its creating a vacuum on the feed side of the pump. Looks like the air Im seeing might be the vacuum pulling the air out of the fuel. Would explain why most of it clears after the lift pump too. I know this sounds a lot like a bad overflow valve, so I picked up a new one from cummins as well as tried stretching the spring in a cummins part to 12mm with no real improvement.
I read someplace .18 * HP is a good rule of thumb for figuring out flow in GPH, so if I was at my goal of 500HP Id need a filter that flowed 90gph. I picked up a racor 500FG filter that does only 60gph before I came across that info though
Any folks with 12v's running 500+ HP care to tell me what your experiences have been with fuel pressure at WOT with the stock filter and heater setup? Did you upgrade? Have you ever installed clear filters or lines to look for air?
Another thing Im trying to find is some kind of diesel / vacuum proof line that I can see through.
I have 1/2" feed and 3/8" return from the tank but Im currently running the stock filter until the weather improves. It was probably overkill but I wanted to eliminate the stock fuel lines as air sources.
I read someplace .18 * HP is a good rule of thumb for figuring out flow in GPH, so if I was at my goal of 500HP Id need a filter that flowed 90gph. I picked up a racor 500FG filter that does only 60gph before I came across that info though
Any folks with 12v's running 500+ HP care to tell me what your experiences have been with fuel pressure at WOT with the stock filter and heater setup? Did you upgrade? Have you ever installed clear filters or lines to look for air?
Another thing Im trying to find is some kind of diesel / vacuum proof line that I can see through.
I have 1/2" feed and 3/8" return from the tank but Im currently running the stock filter until the weather improves. It was probably overkill but I wanted to eliminate the stock fuel lines as air sources.
01-16-2007, 10:33 AM
#2
Registered User
Ive been tracking down air leaks in my fuel system for awhile now, as well as this weird phenomenon where my fuel pressure dips as low as 12psi at WOT. Right now Im suspecting my filter assembly doesnt flow enough fuel and its creating a vacuum on the feed side of the pump. Looks like the air Im seeing might be the vacuum pulling the air out of the fuel. Would explain why most of it clears after the lift pump too. I know this sounds a lot like a bad overflow valve, so I picked up a new one from cummins as well as tried stretching the spring in a cummins part to 12mm with no real improvement.
I read someplace .18 * HP is a good rule of thumb for figuring out flow in GPH, so if I was at my goal of 500HP Id need a filter that flowed 90gph. I picked up a racor 500FG filter that does only 60gph before I came across that info though
Any folks with 12v's running 500+ HP care to tell me what your experiences have been with fuel pressure at WOT with the stock filter and heater setup? Did you upgrade? Have you ever installed clear filters or lines to look for air?
Another thing Im trying to find is some kind of diesel / vacuum proof line that I can see through.
I have 1/2" feed and 3/8" return from the tank but Im currently running the stock filter until the weather improves. It was probably overkill but I wanted to eliminate the stock fuel lines as air sources.
I read someplace .18 * HP is a good rule of thumb for figuring out flow in GPH, so if I was at my goal of 500HP Id need a filter that flowed 90gph. I picked up a racor 500FG filter that does only 60gph before I came across that info though
Any folks with 12v's running 500+ HP care to tell me what your experiences have been with fuel pressure at WOT with the stock filter and heater setup? Did you upgrade? Have you ever installed clear filters or lines to look for air?
Another thing Im trying to find is some kind of diesel / vacuum proof line that I can see through.
I have 1/2" feed and 3/8" return from the tank but Im currently running the stock filter until the weather improves. It was probably overkill but I wanted to eliminate the stock fuel lines as air sources.
Runnin stock Fuel filter setup
and heater assembly. I got lucky, all that I did was stretch my OFV spring and Put in another spring from a bic pen and got fuel pressure into the 40 psi range at idle, and with the new LP, cleaned prefilter, blown out tank, a massive dose of power service, and clean fuel it would drop to 25 or so PSI at WOT...
Rick
01-16-2007, 03:02 PM
#3
Registered User
Thread Starter
It would pass the no-load 2000rpm test no problem, so the measurements are in spec. Its just that the pressure would dip so much at WOT that had me wondering. Im thinking Ive got a restriction someplace thats overpowering the lift pump and the only thing left is that filter. My tuner took a spin and told me that reading was abnormal for the fueling in it. 
Anyone want to buy a racor 500FG if I upgrade to a 900FG?
If Im seeing air in the fuel pre-lift pump, makes me wonder what others are getting with the stock fuel plumbing and if thats killing performance.
I know after I did the fuel lines and bypassed the fuel heater my seat of the pants dyno gained a few HP.
Anyone want to buy a racor 500FG if I upgrade to a 900FG?
If Im seeing air in the fuel pre-lift pump, makes me wonder what others are getting with the stock fuel plumbing and if thats killing performance.
I know after I did the fuel lines and bypassed the fuel heater my seat of the pants dyno gained a few HP.
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