How does one go about converting their stock FPR unit into a vacuum referenced one? I've done quite a bit of searching and have not yet been able to find anything concrete on this procedure. The best I've been able to find is thomas1976's thread https://www.thirdgen.org/forums/tbi/...rfpr-pics.html But no specifics are provided

I've also read that some TBI vehicles came with stock VRFPR's- is this truth, and what vehicles could I find one on?

Thanks!

GM sells or once sold VAFPR. I think was a marine application? Check rock auto or gmdirect....

Try turboCity for aftermarket.

Or Aeromotive has the best unit at higher cost.

I found a place online that sells them for $55 but being the cheapskate that I am I'd really like to fabricate one. I just can't figure out how the vacuum helps regulate the fuel pressure so if anybody has pictures/diagram of a VAFPR I can probably figure it out from that

Edit: And am I looking at the wrong site, or does turbocity sell nothing for our cars nowadays?

Manifold vacuum under the diaphragm allows the diaphragm to reduce the FP by pulling down on diaphragm and the needle valve attached to diaphragm sealing the pathway to the return . WOT or 100MAP(no VAC) allows the diaphragm to increase the FP opening the pathway. I would go to aeromotive site as they may have some diagrams.

Pull the regulator off the TBI unit. On the side of the housing is a slot, need to cover that up. Can solder a strip of metal over it or such.

Drill a small hole in the cover and attach a small tube. This is connected to full time vacuum.

Will need another way of preventing the spring seat from rotating, that is what the slot was for. Although reducing the length of the tab on the seat may work. As a strip of metal soldered to the shell would still leave a shallow slot.

Of course make the regulator adjustable while working on it.

Do you have a spare TBI regulator to look at? I can post some pictures if not.

RBob.

here is some info on GM VAFPR. part #'s photos and such

http://z28boy.cz28.com/main.htm

Awesome, thanks for all the info guys! Right now my FPR is off so I'll be able to know what you're talking about.
Now I just need to figure out how to get these injectors out (getting them cleaned).. is there something special I should be doing? or is it just the fact that it's 40 degrees here and everything's slightly contracted?

could very well be cold temps. Once the top is off they generally come right out. Be care putting them back in. Oil the O ring.

I'll assume that's it then and I'll try again tomorrow. I even went at them with a damn vice-grip (I used padding of course), but I didn't pull really hard for fear of breaking them.

Also, I'm looking at the FPR now- I totally see what you mean RBob. I can definitely do that.

i looked at doing that to. then i went to the external regulator route. it has a vacuum connection on it to use it also.

Your engine bay is soo clean.
I'd probably go with an external FPR, but they're so damn expensive. The only ones I could afford are the Cheap 1-140 PSI FPR's that are for sale on ebay all the time, and that looks like a potential recipe for disaster

yep they are not cheap at all. i paid around 120.00 for the reg alone. another 25.00 in fittings. and i think the block off plate i have was 20.00 also.

Yeah haha. That's a sizable chunk of money for me that I could put towards rebuilding those heads I'm going to get. Time to see just how handy I am with a soldering torch

To get the injectors out use a flat bladed screwdriver and a piece of round metal. The piece of metal needs to be about 1/4" in diameter (round screwdriver shaft works).

Lay the round piece on the top of the pod, then use the screwdriver as a lever, tip goes under the center post while using the round rod as the fulcrum.

RBob.

Worked like a charm.

Now when I solder the regulator I'm assuming I should use copper?

While all this stuff is out I might as well buy a bigger torx bit and take the throttle body off for porting

Could also use fiberglass and resin if soldering is too much of a hassle.

Actually soldering would be easier for me, as I have everything I need to do that.

I'm guessing I should replace the diaphragm and gaskets as well? It's not brittle but it does look worn compared to the new ones.

My diaphragm was 22 years old when it failed. car sat for months on end by prior owner w/o stabil. It failed cause I dead headed the spring and my TPI pump threw 45 lbs at it!
LOL

Haha well then I'll put off the diaphragm replacement. I just didn't know if the higher PSI would kill it (High will probably be around 30) or if a new one would be more effective.
When I get home I'll take the dremel tool to the FPR for a smooth and polish. My friend's going to give me a bigger Torx driver so I'll work on the throttle body this weekend.
Should I plug up the stuff in the car with a shirt or something? I walked by it last night and noticed the air smelled like gas. It hasn't gotten above 60 for the past few days though, so I don't think it's evaporating TOO much....

GODDAMNIT. Drilled too far through and ended up ripping the whole damn thing out. I couldn't see where the cap ended so I went right on through.. time for a trip to the junkyard.

Edit: Maybe all hope isn't lost. I just came across this on Ebay (pic below). (The one thomas1976 is running). It looks like the vacuum line on this one runs out the part I messed up. I'm thinking that I could run the line out the bottom, the same way, and shim the inside of the FPR with washers in order to achieve the desired spring pressure.
I got some info from the http://www.fl-thirdgen.org/tbiafpr.html and it turns out I should replace my FPR diaphragm while I'm out it.

That is easy and works, only downside, requires removal to change FP.

I use the stock spring seat on top of the shims, just in case the spring would want to go sideways.

That's something I hadn't thought of; I will make use of the stock seat then.
And I know I'll have to remove the FP, but I figure that I can deal with that little hassle to save a few bucks. Plus, it requires far less fabrication than the other setup would.

Just out of curiosity, how much would a fully modified TBI sell for? Like VRFPR, ported throttle body, shaved throttle shafts, flow-tested injectors, and modified IAC port (pending one92rs's test)? I like doing this stuff and could use a little extra income.

Here's a rough sketch of an idea for a VRFPR that retains the adjustment screw with a vacuum port- This would have been pretty damn nice if i didn't f*ck up my first one.

That is the basic concept of the VRFPR, I always wondered how well the adjusting screw would seal. Maybe something simple, like an extra rubber cap could do the trick, though there is little place to work.

Hey... just so you know FAST355 would know all about this...

I've actually been reading his stuff lately (especially the ported 193 thread). It would be pretty nice if all of his threads could be consolidated into 1 mega-thread on TBI performance.

Looks like with my 55 lb/hr injectors I'm going to have to get the 12-40 psi spring from tbiparts.com. Putting my order for that and the new regulator diaphragm in tonight.

I am currently using an external vrfpr and believe my system is not plumbed right or the regulator is bad. I have 20 psi fuel pressure but when i give it throttle the pressure drops, but isnt the pressure supposed to increase with throttle increase? I am asking becuase if its the case where its the regulator i might be looking into doing what this board is discussing.

Camarosss, I couldn't answer your question- maybe someone else can

But here are the pictures of the finished product. It looks a little rough but I'll go at it again with solder and a file to smooth it out. I first filled in the hole with solder, then used a drill press to make a hole for the barbed brass piece($4 at Lowes), put the piece in, and then soldered the middle of it to the end of the FPR to keep it in place.
I then cut a piece of a tin can , secured it to the hole with some flux and then dropped solder over the edges.
The diaphragm and spring from tbiparts.com will be coming in next week. Everything cost me $50 in total, a savings of $45-50 over the pre-made unit.

- pics to come soon -

have you put a pump in the tank that is better than stock (tpi) instead of using the stock pump?

Camarosss, make sure your hook into manifold vacuum, not ported vacuum. Make sure you have the inlet/outlet on the right side.
It should be lower psi at idle then increase alittle as you open the throttle.

So what hose should I hook mine up to? I was thinking about the one that should go to that pointless thing on the air cleaner- is that ok?

Here are the pictures promised

like stated before it needs to be hooked to manifold vacuum. when the car is running around everywhere at normal levels vacuum will be present. when you floor it then the vacuum will be gone which will raise the fuel pressure. from there atmospheric pressure and vacuum will push and pull the fuel in making performance. my suggestion is to use some sort of air fuel ratio type information gauge. with that you will be able to dial the correct pressure in and getting it running perfect.

I'll look for the manifold vacuum port tomorrow. The Whatsup display on EBL should do the job for tuning. Next step: hit the junkyard and get a TPI fuel pump and look for a set of Vortec 305 heads

here is a pump. the same one i used.

http://www.ebay.com/itm/NEW-AC-DELCO...ht_1857wt_1270

Thanks, saves me the time I'd have spent looking for a good fuel pump.