fuel pressure and timing questions

94gtslow · Sep 4, 2004

my car has 30# injectors what should i set my fuel pressure at?

right now i think its at 38 vacum disconected form the fp regulator, and with it connected its at like 32.

my timing is at 14, and I run 93 octane but it detonate in 4th gear.

the question is my last rip to the track I ran a 13.8 at 101 with a 2.2 60ft time, I lost 5mph somehow, only thing ive changed is the fp, and I cant remeber what it was set at before.

I am just looking fo rsimular combos to help me try to figure out were my timing and fp should be.

yes ive searched.

SlowGT · Sep 4, 2004

Any dyno numbers? 30# injectors are overkill for a 320hp motor. My motor ran ~320hp on 21# Accels @ 37psi. I can email you the dyno sheet with A/F graph if you're interested. Best run of 13.5 @ 104 with terrible traction. Timing at 16 degrees. I'd get some smaller injectors and go from there.

mo_dingo · Sep 4, 2004

Smaller injectors???? Qua????

Your injectors are fine. Keep them.

Did you have the AFPR when you FIRST went to the track? What was your fuel pressure set at then?

If you increased your fuel pressure, and you lost ET, then I say back it down. It's easy to adjust, so I would say go back out to the track, get a couple baseline runs, and then remove some fuel pressure & see what happens.

If you are pinging in 4th gear, then I suggest running less timing. Try 12*. You can do all of these things at the track, and it's a great way to test the changes.

A dyno would be another solution.
Scott

94gtslow · Sep 4, 2004

the thing is i dont know were to start fomr were should my base fp setting be with the vacum on and with it off?

SlowGT · Sep 4, 2004

mo_dingo said:
Smaller injectors???? Qua????

Your injectors are fine. Keep them.

Any useful information to back that up or is that just some magazine tech talk? I'm not flaming you because I'm aware that most people don't fully understand fuel requirements and the only source of information that a lot of folks get is what they read in magazines or catch on HorsepowerTV.

Did I miss 5-7psi of boost somewhere in the setup

A lot of places advertise injectors for a given HP and offer a very conservative HP rating. If you'd do the math, you'd find that 30s for his application are uncalled for. I'm not going to have a big discussion about injector design because you're probably not interested anyway.

Sure, you can run the 30s at 28psi and 55% duty cycle. Or you can size the injectors for the application. Guess it depends on how heavy your wallet is.

SlowGT · Sep 4, 2004

94gtslow said:
the thing is i dont know were to start fomr were should my base fp setting be with the vacum on and with it off?

You always set the fuel pressure at idle with the vacuum removed from the regulator. Since you don't have any dyno #s, I'd use the 320HP that the motor is advertised at and do the math. Figure out how much fuel is required for 320hp. Then figure out what pressure your 30s need to be at to deliver that much fuel.

Change of injector flow for a given change in pressure

Just guessing, you're 30s N/A should be good up to around 440hp (flywheel). I've done all the math for 19s,21s & 24s for my old setup. 21s fit the bill for mine just fine. I'm not at home, so I can't find the links for all the fuel calculations. If you have any trouble finding them, I can try to find them for you tomorrow. Just FYI, I'm putting 42s in my new 408 and John Bennet guarantees me that it'll make 630hp (flywheel) with no trouble at all.

fuel pressure and timing questions

94gtslow

SlowGT

mo_dingo

94gtslow

SlowGT

SlowGT

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