Has anybody experimented with fuel pressure on a stock motor?

JJFIVEOH

Member

Jun 10, 2003

263

0

16

Boca Raton, FL

Feb 19, 2008

#1

• Feb 19, 2008

• #1

I have found myself in a situation where I need to find just under .2 seconds with my bracket car. It used to be the footbrake class we have around here was just one class with all cars run and a fast ET limit. Now we have sportsman and pro classes with pro class using a 13.99 ET cutoff on the slow end. After a new converter install last week, I was running low 14.0s. I cannot make an engine mods, and I also want to stay away from weight reduction if at all possible. Since I run brackets, I never really messed around with fuel pressure. However, I am trying to squeak out as much as possible. Currently I am running 50PSI with a Holley regulator. When I had my car dynoed, the A/F ratio was just about 12.0 averaged out over 4000-5500 RPMs. Has anybody experimented with adjusting the fuel pressure and how much did it change your ET? Thanks in advance!!!!

PS-Please don't suggest weight reduction and/or engine mods. I don't have time for engine mods, and I like to keep my car looking streetable even though it is a trailer car.

 

2000xp8

SN Certified Technician

Aug 8, 2003

8,036

1,625

194

NJ

Feb 19, 2008

#2

• Feb 19, 2008

• #2

You'll need some test and tune time at the track, but there is a couple tenths in fuel pressure adjustment.
I forgot the increment you should adjust by, but i think it was .5 lbs at a time.

 

millhouse

Founding Member

May 14, 2002

1,985

0

46

Simpsonville, SC

Feb 20, 2008

#3

• Feb 20, 2008

• #3

Adjusting the fuel pressure will only work short term….unless you throw the car in continuous open loop mode (disconnecting the 02's will accomplish this), the computer will tune out any fuel pressure adjustments by altering the fuel table trim. While the WOT open loop uses it's own multiplier…it's still using the main fuel table as a base…so the fuel pressure changes will eventually affect both.

 

JKidd

Member

Aug 21, 2007

164

3

19

Suffield, CT

Feb 20, 2008

#4

• Feb 20, 2008

• #4

What Millhouse said.

 

JJFIVEOH

Member

Jun 10, 2003

263

0

16

Boca Raton, FL

Feb 20, 2008

#5

• Feb 20, 2008

• #5

Millhouse, that totally never dawned on me. I guess I'm thinking too old school, lol. Doesn't 12.0 A/F seem a bit fat? That 12.0 number is what caught my attention when I was brainstorming about ideas to get some ET. If I could lean it out a bit, that would get me some ET. But does 12.0 sound right for stock? I use VP Motorsport 103 fuel (aka Street Blaze) which might make the A/F results a bit off.

 

black87ttop

Member

Oct 29, 2007

43

2

8

burlington,new jersey

Feb 20, 2008

#6

• Feb 20, 2008

• #6

I think there is something going on if your only running 14.0 with that car, seems like there is alot left on the table.

 

JJFIVEOH

Member

Jun 10, 2003

263

0

16

Boca Raton, FL

Feb 20, 2008

#7

• Feb 20, 2008

• #7

Well, it has stock H/C/I, MAF, TB, original motor, no rebuilds, 15 years old, almost 2,000 passes, 107,000 miles...... all @ just under 3,500 pounds. Still runs like it did when I bought it though. The car is quite an overkill for the motor, but I plan on changing that eventually. Since I go to the track probably 40-45 weekends a year, I really don't have a chance or the room at home to step it up.

Keep in mind, down here the air isn't that great, even at sea level.

 

millhouse

Founding Member

May 14, 2002

1,985

0

46

Simpsonville, SC

Feb 21, 2008

#8

• Feb 21, 2008

• #8

Here is the stock WOT AFR table...

 

cleanLX

Founding Member

Jan 17, 2001

976

537

144

Feb 21, 2008

#9

• Feb 21, 2008

• #9

12.0 is wayy fat for a n/a stocker, and 50psi is crazy talk.
I always found running stock fuel pressure would pump 13.2-13.6 a/f between 3000-5500rpm... and is where my car ran strongest.
Are you running u/d pullies or a aftermarket MAM?

 

tmoss

Gettin Wired

Founding Member

Jun 28, 2001

7,153

32

128

Saint Louis, MO

Feb 21, 2008

#10

• Feb 21, 2008

• #10

good to see you back, Mike - 4 wheelin isn't takin all your time I guess.............

 

JJFIVEOH

Member

Jun 10, 2003

263

0

16

Boca Raton, FL

Feb 21, 2008

#11

• Feb 21, 2008

• #11

cleanLX said:

12.0 is wayy fat for a n/a stocker, and 50psi is crazy talk.
I always found running stock fuel pressure would pump 13.2-13.6 a/f between 3000-5500rpm... and is where my car ran strongest.
Are you running u/d pullies or a aftermarket MAM?

Click to expand...

Stock MAM and no U/D pullies. In fact, I have an O/D water pump pulley (93 Cobra pulley). The fuel I run is oxygenated, maybe that has something to do with it.

 

5.0Droptop

...all those nights we shared, and you're a dude??

Special Agent Mukity-Muck Whats in Charge Round Here

May 15, 2002

1,785

1,130

233

Indiana

Feb 22, 2008

#12

• Feb 22, 2008

• #12

tmoss said:

good to see you back, Mike - 4 wheelin isn't takin all your time I guess.............

Click to expand...

Wow just like the old days.

Hi mike!!

Hi Tom!!

Oh I was always told Leaner is Meaner.

 

enyawix

Member

Dec 18, 2005

507

0

19

127.0.0.1

Apr 3, 2008

#13

• Apr 3, 2008

• #13

cleanLX said:

12.0 is wayy fat for a n/a stocker, and 50psi is crazy talk.
I always found running stock fuel pressure would pump 13.2-13.6 a/f between 3000-5500rpm... and is where my car ran strongest.
Are you running u/d pullies or a aftermarket MAM?

Click to expand...

What is so crazy about 50psi? I am tuning for E85 and need more flow to reach stoich I have 2 fuel pumps and bigger fuel lines. What can the injectors handle?