How much fuel pressure?

nasty 2005

nasty 2005

Cummins Tech.
Joined
Apr 25, 2011
Messages
301
I have been pulling my 95' and when ever I get on a tight track it acts like it runs out of fuel towards the end of the track, I was running 42-44 psi. I just turned it up to 62-64 psi. and was wondering what others were running? Haven't got a chance to hook since it has been turned up, hopefully friday night.
 
i ran into a similar problem but in normal driving....kinda

whats your pressure going down the track doing?
 
Not sure what it is doing going down the track just got the gauge put in, I checked it after I hooked up the gauge and turned the pressure up and at wot it goes down to 48-50 psi.
 
nasty 2005 said:
Not sure what it is doing going down the track just got the gauge put in, I checked it after I hooked up the gauge and turned the pressure up and at wot it goes down to 48-50 psi.
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That should be plenty of pressure. What kinda rpm does it go down the track at?
 
On a loose track 37-3900 on a tight track 27-3000 rpm thats in 4th gear low. I haven't tried 2nd high yet.
 
my pump builder told me 85psi......i dyno'd with an ADII200 set at 45psi and sucked it down to 0 half way through a dyno pull and low 8's hp wise and now i'm at 85psi and did 993hp with the same set up just fuel on the top end now

just say'n

sounds like your running out of fuel pressure...either the pump isnt large enough or is restricted some place
 
nasty 2005 said:
Not sure what it is doing going down the track just got the gauge put in, I checked it after I hooked up the gauge and turned the pressure up and at wot it goes down to 48-50 psi.
Click to expand...

Pressure is NOT the issue! 40psi is plenty. FLOW is what you want. In a sled pull application at the end of the pull the truck will consume way way more fuel than in a street WOT blast. Remember "pressure is a measurement of restriction", however we cant measure flow, we can measure pressure. you dont want your pressure to drop below 40psi EVER in my opinion. Generally the pressure drops off hard in the second half of a sled pull because of the mass consumtion of the engine when it is working the hardest. At that time the pump will drain the gallery and starve the engine if the P-pump isnt supplied with enough fuel. You can turn up your pressure all you want, but if your lift pump can not supply enough fuel to feed the engine and lubricate and cool the p-pump you will need to increase the flow capability of the lift pump.
I ran a belt drivin supply pump capable of 6gpm @ 60psi for my 13mm pump and it never fell below 60psi.
 
I am also running an Ad 200 I guess I will turn it up alittle more and see how it goes tonight.
 
I have the same pump and same pressure drop at 50-60 psi on my pull truck. On a test day day at the track, ran it at that pressure and it dropped to 40psi, so next run ran it at 70-80psi. It picked up almost 15ft and spun out with the higher fuel pressure and only dropped to 60psi. Alot say run 3/4 hose with the AD 200, helps with volume of flow. I haven't it done it yet but it is on my list.
 
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