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Old Nov 22, 2011, 08:12 AM
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Fuel pressure on idle?

Hi,

I have Detschwerks 300 fuel pump and stock fuel regulator. I have 35 psi (~2.4 bar) on idle (850 rpm). Shouldn't I have something like 43 psi???

Thanks!

Anton
Old Nov 22, 2011, 11:07 AM
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You are right ! you shuld run 3 bar of fule pressure , Without vacum house attaced to the regulator when you dile it in , thats about 3 bar -- 43 psi ,, if im right !
Old Nov 22, 2011, 07:39 PM
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This isn't the place to post this but yes. It's supposed to be at 43.5 PSI. You're going to need an AFPR to control it.
Old Nov 23, 2011, 08:37 AM
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It's 43.5psi with the vacuum line disconnected from the FPR although it will have less fuel pressure when vacuum is present and the vacuum line is still connected. I generally see 39-40psi with decent vacuum at idle. In theory, -17in/hg of vacuum (stock cams vacuum usually) is roughly -8.5 "PSI" of vacuum. Since it is a 1:1 ratio FPR, it technically can see as low as 35.5psi of fuel pressure with that much vacuum applied.

To measure it correctly, just do it with the vacuum line disconnected and see what reading you get.

-Jamie
Old Nov 23, 2011, 01:49 PM
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Originally Posted by Dynotech Tuning
It's 43.5psi with the vacuum line disconnected from the FPR although it will have less fuel pressure when vacuum is present and the vacuum line is still connected. I generally see 39-40psi with decent vacuum at idle. In theory, -17in/hg of vacuum (stock cams vacuum usually) is roughly -8.5 "PSI" of vacuum. Since it is a 1:1 ratio FPR, it technically can see as low as 35.5psi of fuel pressure with that much vacuum applied.

To measure it correctly, just do it with the vacuum line disconnected and see what reading you get.

-Jamie
Don't forget to plug the vacuum line when taking the reading! I.E. finger over the end of the line.
Old Nov 23, 2011, 03:30 PM
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Everything works as expected! Thanks a lot guys!
Old Nov 23, 2011, 05:18 PM
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make shure you have a fuild filld fule pressure gauage ,fore better acuasy,
my gauage needle wanna to wobbel , som times made it hard to set the fule pressure precie right , on the dot..f just at good tip anayway
Old Nov 27, 2011, 02:16 PM
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Translated for you
Originally Posted by Fastone_evo6
make sure you have a fluid filled fule pressure gauge better accuracy. My gauge needle wanted to wobble, sometimes making it hard to set the fuel pressure precisely on the dot. It's just at good tip anayway
I personally have never had an issue with the bouncing needle when using a quality FPR and non-filled fuel pressure gauge.

-Jamie
Old Nov 27, 2011, 02:33 PM
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LOL

You guys are something )
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