quick fuel pressure question

BlackVert

15 Year Member

Oct 3, 2003

5,589

9

98

Bethesda, MD

Apr 23, 2010

#1

• Apr 23, 2010

• #1

what is the stock pressure at the rail with the vacuum on again?

my injectors were flow tested for 30.1 lbs/hr at 43.5 psi but i know that our pressure is lower than that. i need to lower that number for my tune.

i should know this, but my memory has gone to hell. i did a search but did not see the answer in the first 10 threads of the results

i'm sure you guys know this off the top of your head ... :SNSign:

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

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Apr 23, 2010

#2

• Apr 23, 2010

• #2

It will vary. Anything above 30 PSI is acceptable though most folks are in the 32-34 PSI range at idle with a stock-ish vacuum signal.

 

BlackVert

15 Year Member

Oct 3, 2003

5,589

9

98

Bethesda, MD

Apr 27, 2010

#3

• Apr 27, 2010

• #3

what i actually need is the number ford expects it to be with the vacuum off. since i am doing math with it to determine my injector flow rate, a difference of 1 psi makes a difference in the tune.

30.1*(39/43.5) = 26.98
30.1*(40/43.5) = 27.68

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

34

129

Apr 27, 2010

#4

• Apr 27, 2010

• #4

I see what you mean. I believe I have the spec for a fox III but not CBAZA. Bump for you.

 

G

grngt50

Member

Apr 26, 2004

250

0

16

Los Angeles

Apr 30, 2010

#5

• Apr 30, 2010

• #5

i believe it's 32 with the vacuum hooked up, and around 39 without

 

Grn92LX

Fidanza Man!

Founding Member

Jan 14, 2001

6,819

64

129

New York

Apr 30, 2010

#6

• Apr 30, 2010

• #6

39-40 psi no vacuum. With vacuum, it will vary depending on the camshaft. Camshafts that produce less vacuum will result in higher pressure at idle.