anyways to add a fuel pressure guage on a TBI car? id like to know what is going threw the injectors but were the FPR is located is it possible to put a guage there?

 

On a return style system, like all FI cars have, line pressure is the same anywhere in the system. but easisent place is to "tee" into the rubber line near the frame rail.

3 options:

-use an electronic gauge, mount the gauge in the dash (use one of the vents) or in a gauge pod.

-use a mechanical gauge mounted in a gauge cup and secured to the hood.

-use a mechanical gauge with an isolator to keep fuel out of the car's interior, mount the gauge in the dash (use one of the vents) or in a gauge pod.

An underhood gauge is dumb how can you tell what type of fuel pressure you have WHILE driving the car. However an underhood gauge is nice WHEN used with an external gauge to baseline fuel pressure while your head is under the hood.

 

I'm looking for one right now...

Anyone have any recommendations for the Autometer brand that will mount in the dash?

 

Autometer "Z" series will fit it is 1 1/16" dia. all depends on the look you want...

I have Z series in mine...

 

FRMULA, looks kool.

I'll be getting the sport comps to match the rest of mine. I need to know about getting the electric or mechanical with the isolator.

And if the need will ever arise to have over a 15psi guage or just get the 100psi to start with? The 100 just doesn't have as much space between the numbers for seeing what exact psi it's at for fine tuning.

Thanks

 

so i should run a guage by the tank where the lines are rubber...how would that show what kinda psi im getting the injectors....wouldnt the fuel pressure reg be stopping regulating the pressure down lower?

 

I have the isolated 15psi AutoMeter FP gage. VERY Nice but limited to 15psi, which i need to go over in the near future, unfortunately.

 

FB...How far will 15psi take an engine with larger injectors?

Have you reached that limit yet?

 

You connect the fp gauge to the rubber supply line under the hood, NOT at the tank.


I run Holley projection 4Di 900 cfm, set at 12 psi. My stock fp was around 8-10 that was a while ago so I don't really remember.

Even with the 500 horse setup I have I will never need more than 15 psi. I have even run as low as 9 psi on a 100 degree day, and still ran a 12.61 at 103 with a 114 degree track temp. There is a .5 second still lurking in there that needs to be fine tuned, but it is not fuel pressure related.

I bought the 100 psi gauge, problem is that it starts at 20 psi anything lower will not register. That gauge is made for High Pressure EFI systems which TBI is not.

 

So the 15psi guage should be enough?

 

A four barrel 900cfm ProJection has 4 of the Holley 80pph injectors, enough for over 600hp at 13psi. But, if you only have TWO of these injectors, like in a 454 Rochester GM TB unit, you only have enough fuel for 300-350hp... I am looking for 400 and cannot get it without the 90pph injectors at 15psi, which is good fora bout 425-450hp, supposedly.

I fyou have a mellow motor and don't plan on too much additional power stuf, 15psi gage and max limit should do you ok. 15psi up from 11psi stock is a 16.8% increase is supportable hp. After you reach 15psi, you'll have to get bigger injectors...


305's come with VERY small injectors... You can upgrade to truck injectors (55pph) or caprice (65pph) injectors for moderate pricing, should you need more hp.

 

i used a summit 30 psi liquid filled gauge...



it is shown there in line with my braided line, but you dont need that. as long as you have a few inches of rubber line, it can be plumbed in very easily.

-brian

 

Do you also have a Knight Rider TV installed with a camera in your engine bay... I mean that gauge is nice to have to establish baseline pressure... but how do you really know whats going on while you're driving the car?

 

haha, no, but i use it as just that...a baseline type thing. i tune it at a given FP, and go with it that way. i havent done it yet because i my car is off the road for winter, but i'll use a laptop with winaldl and tune it at a given FP to get everything right. or at least as close to right as i can.

what FP i am running at while i am driving isnt that important as far as tuning goes because i am tuning it while the car is parked. if FP was adjustable while driving i may be more inclined to add a FPG in the dash or whatever, but its not.

and i believe the question that was asked was whether or not you can put a gauge where the fuel pressure regulator ws located.

and to answer your question, i really have no idea what is going on with FP when i am in the car. oh well...

-brian

 

Later I will reinstall a 350 but it sounds as if I could reach 350 to 370ish with the Vortec heads would be as far as I would take it.

For now the 305 in the sig is going to be it.

I had the 55lb injectors in it and could not turn it down enough to not be running rich. Now I have the stock ones in there and am slowly turning the psi up.

What I've been fighting is the psi not staying where I set it all the time. Some have said replace the fuel pump, fuel filter and check for restrictions in the lines. I have found the rubber line from the pump at the tank to be bent and almost flat. I straightened it the best I could and it has seemed to help a little. I was hoping to monitor the psi from in the car while driving to see how or if it was varying.

It looks as though I will get the 15psi guage that you have with the isolator and probably go ahead and replace the fuel pump since it's 11 years old and 150K down the road. Advance has an AC Delco TPI pump for $66 and I thought about trying it.

Thanks for all the help!!!

 

if any of your fuel lines are suspect, replace them. Doesn't cost much and you'll be sure they are good. pinched lines as you stated are not ***. Might also want to monitor the pressure in our return line. It should never get above 2psi or so, preferably lower than that. Your FP should not vary much at all (supply pressure) even under loads. if it does, which the in-cab FP gage will show you, you have some sort of fuel delivery problem, which can be traced.

 

Thanks Fast!

I'll replace line(s), filter, pump and tbi gaskets and add the inside fuel pressure guage and see what's happening then.

Somethings got to be happening as this morning the car ran like sheet going to work and this afternoon once it warmed up it ran better and by the time I drove about 20 miles it was running great..lean but great (off idle and low throttle). Before turning the car off I checked pressure and it was at a little over 10psi. Once again WTF? I had it set at 12psi.

It's gettin' on my last nerve againLOL!!!!!

Later

 

sounds like a weak/dying fuel pump. guess you'll find out soon enough