Is the fpr on tbi systems vacum referenced? The reason I am asking is, is it possible to use an external afpr, or is it a waste of time?

 

you can put an external regulator on. you just make a block off plate to guide fuel past where the stock regulator is on the tb and then put the external regulator on the return side of the tb. pretty straight forward really, and you don't need a special regulator as it is a low pressure system.

lata
tim

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91 Camaro RS-LO3,Auto.
14.301 @ 94.39mph
The car is going street strip for next season. 13's here i come!!!!!
Edlebrock TES Headers, Cat Eliminator Pipe, Borla Adjustable Cat Back,Marche Pulleys, HyperTech Chip,Transgo Shift Kit,B&M Convertor(2000stall),Steve Spohn Rear Rig( all rod ends), Poly Front Bushings,Ported TB, 350 Injectors, Edlebrock Performer TBI Intake, Performer Heads, 1.6 Roller Tipped Rockers
http://www.mycar.net/mafb/registry/detail.cfm?id=299

 

I guess your saying that it is not vaccum referenced then, so any afpr that will allow up to say 15 to 20 psi will do ok?

Steve

 

you can keep your stock regulator, and put in a vacuum referenced external regulator. that way, you can have normal fuel pressure when not hot rodding, when you get on it, it bypasses the internal regulator. this is all stuff ive read on a web page somewhere, and i dont have the link, so dont quote me, my memory is fuzzy, i just wanted to throw the idea out to you so you could research it more. pablo gave me the link, so when he gets back, you can get it from him.


if you ask me, just get the bypass plate, and put the external on. you could plug your return line and put the regulator on your feed line too. but then you could send bad stuff thru your injectors instead of having go back to the tank. hey, thats what you got a filter for though right?

 

Snf thanks for the replies. I think I've learned a thing or two tonight.

Steve

 

Will it hurt the fuel pump to have it 'deadhead' against an aftermarket, external regulator and have the return blocked off? I thought about doing this, but thought the pump wouldn't be able to handle the constant load against it. Also, what kind of pressure should the pump be able to put out. My engine likes about 16.5#, but has slowly went down to 15# and won't do anymore. The filter has been changed.

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'93 2wd truck
408 sb, vortecs, 454 TBI, Comp Cam, dual exhaust

[This message has been edited by SCRA rules! (edited January 21, 2001).]

 

There is no need to use an external regulator. I recently modified my stock regulator to be manifold vacuum referenced and it works super.

Deadheading a stock pump will cause it to hit its cutoff pressure and stop.

 

i wasnt aware of the fuel pump problem. i was mainly relaying info that pablo has posted, he has a truck fuel pump though so it pumps at a higher psi.


HOW DID YOU MODIFY IT TO BE VACUUM??
i would like to know. that sounds very interesting and a nice improvment.

 

GM TBI regulator P/N 17113186 is a direct bolt-on jobbie, and will give you about 18-20psig fuel pressure. Additionally, this regulator has vacuum compensation capability. If you hook the included vac port to manifold vacuum, then you'll get a part throttle fuel pressure decay of roughly 1psig per every 2"Hg manifold vacuum. This comes from certain marine and HT502 applications.
A little bigger step beyond.......GM TBI regulator P/N 17113079 is a direct bolt-on jobbie, and will give you about 26-32psig. It does not have vac compensation. This comes from some of the late 90's BBC applications

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1992 Camaro RS
Mods:
Custom chip, 14x3 Open element w/ K&N filter, MSD 6a, MSD GM blaster Coil ,MSD 8.5 SC wires, AFPR,Fuel Pressure gauge,A/F guage, 3-Row Al rad. , 180* t-stat,Proform 1.5 roller rockers, Hooker 1 5/8 headers, 3" Catco cat, 3" Hooker Aero Chamber cat-back, "Ultimate TBI" mods, Nitto 555R Drag Radials

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454 TB,intake,SLP Posi,3.42 gears
Al Driveshaft, Underdrive pulleys,
LT1 cam. 2400 stall Tq converter

Best Time: 15.279@89.02MPH
Underdog Racing

 

Ramsey,where can I get info on the man vac fpr mod?

 

fuel pump: my app is a truck and i have already had to switch to a high flow Airtex pump and it will stop when dead-headed after only a few seconds. This pump is rated at 40gph with a shutoff pressure of 17-20psi.

GM fpr: I would like to know what the flow rates for the higher pressure regulators mentioned are. I have had fuel starvation problems for a while and have installed a needle valve in my relief line to restrict relief volume to compensate.

vacuum reference: i assume all concerned already have control over their static fuel pressure by modifying the preload screw on the regulator... anyway, the fpr is referenced to atmospheric pressure. simply plumb the reference port to a vacuum reference on your TB or manifold. On my app I sealed the atm ref with rtv and drilled and tapped a hole to the ref side of the reg and installed a 1/16" hose barb and plumbed that to an open vac port on my TB. Seems to help with the over-rich idle a hotter cam creates while supplying the significantly greater amount of fuel necessary to feed a hotter motor.

Just my .02

 

wouldnt happen to be able to write a tech article on that would you? how about pics or diagrams, and parts list and directions in order???

that would be great, and people here would love you very very much.