TBI Throttle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.

fuel pressure info

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Old Mar 26, 2011 | 06:55 PM
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one92rs's Avatar
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fuel pressure info

ok i have searched numerous times.

1. what is the lowest psi that a 305 tbi will run on
2. what is the max fuel pressure a 305 tbi will handle
3. what is the best fuel pressure for a stock internal 305 tbi engine
4. what fuel pressure do you run and why
5. do you have ultimate tbi mods?
6. what thermostat
7. did you do tuning?
8. do you have open air element

Last edited by one92rs; Mar 26, 2011 at 08:12 PM.
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Old Mar 26, 2011 | 07:43 PM
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: fuel pressure info

1) 11psi maybe
2) 14psi maybe
3) 12psi is stock
4) 12psi, because it's stock
5) what's the question?
6) 180 minumum, lower will make car run rich maybe, and you'll never feel any heat from heater/defroster - 195 is factory spec
7) No tuning on staock motor other than new plugs, wires, cap, rotor, filter, and setting timing (which is 0 factory, can be bumped up to about 4*BTDC).

Some folks with mods will do a vacuum adjusted fuel pressure regulator - I never noticed any difference when I did mine.
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Old Mar 26, 2011 | 07:59 PM
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Re: fuel pressure info

You should alter your fuel pressure only after you've made mods to the intake & exhaust.
It may run on low psi (6 or 7psi), but it'll have no throttle response.
Ultimate tbi mods are simple things to do to the tbi unit, like shaving the ridges off the top, pod spacer, making the regulator adjustable, open element air cleaner, & salad bowl mod.
Some guys have put a quarter under the regulator spring to add alittle pressure.
You can bump the ignition timing up alittle too, what is stock? Zero degrees? Try it at 6 degrees. Listen for spark knock, might have to go up a fuel grade.
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Old Mar 26, 2011 | 08:11 PM
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Re: fuel pressure info

5 is do you have the ultimate tbi mods. i do. i have done the ultimate tbi, matched injectors, headers, and exhaust with no cats. right now it is running at 11 psi. and i do have a tbichips chip. just curious what other people are doing to the questions. stock is 9 to 11 psi. and i have an open air mod. and a 180 therm tuned for.
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Old Mar 27, 2011 | 04:54 PM
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Re: fuel pressure info

wow i thought more people would answer this. it would be good info for a search.
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Old Mar 27, 2011 | 05:32 PM
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Re: fuel pressure info

I am new to the site, but the things that I have done so far that had the most impact was get rid of the 2:73 open rear end. Put in a 3:42 with posi that was the most impact. Also changed to a Magnaflow system including the magnaflow cat. Also put in the L69 air cleaner. I am having a chip burnt when the car is being Dynoed. I will find out what I have then, but the three above seemed to help.
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Old Mar 27, 2011 | 05:48 PM
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Joined: Sep 2002
Posts: 9,192
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From: Cary, North Carolina
Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: fuel pressure info

New 92, you haven't done anything to need a chip yet, why spend money to have one burnt?
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