Turning stock FPR into an AFPR

[eclipsh]

I decided to pull apart a spare FPR I had from my 2.4 Galant block and see if I could make it adjustable and remove the restriction that causes problems with large fuel pumps in our cars. The Galant FPR appears to be identical to the 2.0 turbo one save that the return line comes straight off rather than having bends in it.

At any rate, after taking one unit all the way apart I found the restriction. It is this little bastard which is press fit into the top of the return line.

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It measures ~0.196 inches in diameter and has a tiny little hole for all the returning fuel to go through. It is also incredibly hard metal and damn near impossible to drill so enlarging the hole doesn't seem like a viable option. Unfortunately there was no way I could get the first unit back together so I got another one out of the junkyard and worked on taking that little restrictor out without tearing everything down. It turns out it can be done, at least on the Galant regulators. I managed to get it by drilling the return line out with a 0.204 bit and a little finesse. By removing the vacuum chamber on the top of the FPR it is possible to tap the restrictor out far enough to drill the entire return line enough to get the thing to just drop out the bottom. In doing so the diaphragm on the top side just barely clears the ring surrounding the top in this photo.

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If it is done right the ristrictor just falls out the bottom like so:

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So now there is no restriction on return flow. I've already come up with a way to add adjustable spring preload to the factory cap but can't figure out how to clamp it back down to the top of the regulator.

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That is where I need some help. Whatever it is needs to be able to hold up to all the pressure coming in from the turbo under 20+ lbs of boost. The rubber ring in the picture below is part of the stock sealing system for the cap. I figure that combined with a thin layer of RTV should seal it fine but how the heck do I hold the pieces together after that?

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Let me know what your thoughts are unless they are "just buy an AFPR." I know that is an option but if we can figure the clamping out the whole thing can be done for less than $5 or so and an hour or two of tinkering around. Of course I'll need to test the setup and see if the 1:1 ratio holds and how well it seals but it sure seems worth checking out.

This could also make the B&M unit actually work for our cars. If it can be had for less than the $75 it lists for here on Tuners it might actually be a deal.

Oh, I also don't know if this is covering new ground or if it has been done before and failed. Anyone with info please chime in.

EDIT: So the B&M is $40 if you are a member of Yo Parts (and pay their $30, 3 month membership fee) but it doesn't say if the unit has a vacuum reference or not. I'd still rather clamp my unit back together if I can figure out how.

 

[Brutal_r3drum]

it doesn't seam like fuel will be getting to it so you could try some jb weld i use it for a lot of stuff. this looks great i wanna see how this turns out.just my .02 cents

 

[eclipsh]

I laid down to bed and came up with a possible answer: fender washers. If I get two the right size, drill matching holes just past the lip of the hat for bolts I can either cut a notch out of the lower washer to slip it into place or cut it in half and have enough little bolts that it won't just taco out instead of evenly distributing the pressure. I'll hit the hardware store tomorrow and see what I can come up with. Due to the design of the FPR I can't just slip the right size washer up into place. Too much stuff in the way. Maybe three washers and overlapping and opposing two notched ones underneath will be the way to go (keeping the notched part and putting it back in to keep pressure on the lip even) or using to washers each split in half and rotated 90* out from each other underneath and one on top. I'll toy with it and see what I can come up with.

 

[PieEyedPiper]

Maybe this clamp will hold it together?
http://www.dsmtuners.com/forums/art...cooler/97971-1g-bov-crushing-alternative.html

 

[eclipsh]

Thanks, that is a really good idea. They've got a few different sizes too. McMaster-Carr

 

[LiquidX]

You couldn't just weld it? Compress the 2 ends together, get a ring of metal going around the rubber seal and weld on the two sides of the ring and it'll hold up.

 

[eclipsh]

I don't want to risk too much heat damaging the valve.

 

[the_mork]

I have been looking at ways to make the stock FPR work too. I am extremely please to find what you've done here and I'm excited that you've gotten this far. I'll think about your clamping problem but it seems like someone could weld it. The Peepers mod calls for welding the wastegate actuator back together and that seems like a more fragile piece than the FPR but perhaps we could use a clamp then use a plumbing solder to keep the heat down but make a solid bond. Otherwise the JB weld is probably the way to go.

 

[eclipsh]

Well it has been a busy couple weeks but I got a chance to work on the FPR again today. A while back I bought six allen-head machine screws and lock nuts as well as three large washers. Today I split one of those washers on one side and bent it apart like a lock washer until the gap was big enough that I could thread it up onto the FPR from the bottom where the fuel return line comes off. Once I knew that would work I pulled it back off. After that I marked six spots around the washer and drilled through all three washers far enough out that the bolts wouldn't hit the FPR flange. Then I took one of the washers and ground the center out far enough that it would sit around the FPR flange as a spacer. The washer is just slightly thinner than the FPR flange so when everything is bolted together it allows the bolts to be tightened but not overly so. Of course I also bent the split washer back to being flat once it was on the regulator. I also had to machine out some space around the vacuum line and the fuel inlet so the FPR could slide back onto the rail. The little tab sticking out on the rail (you'll see what I mean) will need to be machined down but that won't be a problem.

The only other fitment issue is that the set screw on top will hit the head. I'll have to spin the unit around and add a 90* fitting to the bottom. The internals of the FPR are large and stout enough that I can just cut the stock return line off then drill and tap the base for a 90* pipe fitting. Anyhow, here are the pictures.

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Oh and of course anyone who tries this does it at their own risk. If your car explodes in a flaming inferno it isn't my fault.

 

[turboglenn]

have you put this into use yet? Just wondering if it's going to leak at this point. I am pretty sure it could be welded with a TIG and a carefull operator... Some tig units have a pulsing feature which is desinged for materials that are thin or where heat input needs to be kept to a minimum... It bascally fires up enough to melt one dip of filler then cools to a lower amperage before the next pulse of higher power. This is mainly used on this stainless where warpage and distortion can come from the slightest amount of heat input. I have welded wastegate diaphrams back together using this technique before with good results... Mind you i still had to dip the part in water and blow it dry with an air hose after every 2-3 spot welds but it did work without ruining the diaphram inside.

 

[Hubbard 0]

I can understand the thought process behind using stock parts and saving money, but I feel like this is stretching that idea a little far. An AFPR is not expensive, it is absolutely proven and has serious R&D behind it. They also are usually fit for AN fittings to match up to after market rails, have larger openings for more flow, and have ports for a pressure gauge. They also look infinitely better.

I just can't get behind the concept of this idea, though your work put into this is quite impressive.

 

[TofastForU_99]

I agree with you ^^^^^^


but hey it does not hurt for someone to experiment with this and see if they can get it to work it should be a good deal for the not so rich typical DSMERS.

but yah keep it up and cant wait to see if it works

 

[97eclipseNT]

i'd be curious to see what the pressure at idle is just without the restrictor. looks good so far though i'm def interested in seeing if this works out.

 

[TRSblader]

This will definitely help those on a tight budget if it works. Let them run a little better until they can afford an afpr. Like the rest, eager to see how this works out

 

[eclipsh]

have you put this into use yet? Just wondering if it's going to leak at this point. I am pretty sure it could be welded with a TIG and a carefull operator...

Haven't put it into use. I need to get a pressure gauge together first and have some more free time to test. The only chamber I messed with is the vacuum side, not the fuel side. So worst case scenario is I have a small boost leak and pressure may not rise 1:1. I'll run a fuel pressure gauge out onto under the cowl and tape it to the windshield while I'm driving so I can see if it is or isn't working properly. As soon as I get a chance I'll get it on the car and see what the base pressure is.

Hubbard, a lot of this is just seeing if it can be done. As far as cost, an AFPR is $100+ and doesn't include the AN fittings or lines which can easily run another $50. If this works I'll have spent about $15, won't need any expensive fittings and I've have had some fun making it.

Mike - the restriction in the return line rises up slightly above the rest of the section it is pressed into. This means spring tension would be reduced a bit and that combined with the larger return makes me think pressure would be a bit lower, though I wouldn't venture to guess how much. Try it and let us know

 

[97eclipseNT]

That is what i would assume as well. i'm just curious to see how much it lowers it. I have an aeromotive on my 2g right now (my 1g has been in pieces for a few years now) but if i get some extra time when i'm not at school i'll switch it out and let you know.

 

[eclipsh]

Well I tried putting this on the car the other day and my pressure went WAY up. I had too much tension on the spring. So today I took it apart and ground down/crushed the aluminum rivets I used to hold my screw cap in place. They were forcing the penny inside down about 1/8" from the top of the cap and putting a lot of tension on the spring. I also had to replace the penny a the divot I added to keep the screw centered actually allowed the screw to push part way through, and slightly bend, the penny. I decided there is no need for the divot since the penny fits pretty well anyhow so I just threw a new, unmolested one in.

I haven't put the regulator back in the car but I ran some air from my compressor into the fuel inflow and it was opening up between 30-40psi (based on my compressor gauge) with no extra tension placed on the regulator spring via the set screw. I'll get it on the car within a week and see where I'm at compared to the stock regulator.

 

[eclipsh]

Short and sweet: it appears to be working.

My pressure gauge doesn't seem accurate (says my base pressure with the stock FPR is 33) but it is a good point of reference. With both the stock FPR and the modified FPR (after adjustment) I get a base of 32-34 (no vacuum) and idle of 28 (vacuum line attached.) I should be good to go.

Of course, now I've thought up an even easier way of doing this that doesn't involve cutting the cap off. I'll post up my ideas later. Gotta run to work now.

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[eclipsh]

Wow, really need to clean the engine. Anyhow, I drove back and forth to work (15 miles each way) without any trouble. The car ran great and I didn't have any leaks. Like most AFPR's I lose pressure as soon as the pump is turned off so the seal isn't that great. Not surprising since the new seat cannot be polished flat to create a good seal.

The idea I had for a simpler FPR mod is this: the base where I cut return line off and tapped it for pipe thread could be the source of baseline pressure modification. It should be possible to cut the return line off, drill the center out to remove the factory restriction in the return line, then tap the whole return area for a bolt (probably metric since most of us will have those taps), then drill out the center of the bolt to allow for fuel to return through it. Then this bolt could be threaded in/out to adjust pressure on the spring from the opposite direction, from underneath instead of above.

The benefits of this would be avoiding cutting up the cap of the FPR and building the mess I had to use as well as saving a lot of time and effort. The problem would be sealing the threads of the adjustment bolt such that 50-60psi of fuel won't be a concern. I think that is doable since my pipe thread base with Teflon tape is holding fine but I don't know if a straight cut thread will seal as well. The other benefit is that it would make polishing the mating surface of the seal possible (the end of the bolt in this case) so that pressure could be held after the car is shut off. It would also allow for fine tuning of the return aperture. I noticed that right now my fuel pressure flutters just a little bit, +-1psi or so. It isn't hugely concerning but I'd like to resolve that if possible.

At any rate, I thought I'd post up my results. I hope this can inspire some more innovation. Maybe someone can chime in with a few other ideas.

 

[eclipsh]

I found a little time to try out the other version of my FPR mod. Unfortunately I made a mistake and tore the internal diaphragm. That is the risk with this particular way of doing it. I think if I had another FPR I could do it right and make it work though. Here is what I came up with:

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I just cut the outlet line off flush and drilled out the base to the correct size for a m8x1.25 tap. When I got deep enough I used a punch to tap the restrictor out into the body of the FPR and then drilled the rest of the way in to remove the restrictor. Once that was out I drilled the rest of the body out so I could tap the whole body of the FPR with the 8x1.25 tap.

I actually tore the diaphragm when I was tapping the threads. I just went too far and put too much tension on the diaphragm and it gave out. If I hadn't screwed that up I'd be ready to go.

The other half of this setup is taking a m8x1.25 bolt, and drilling out the center so fuel can flow through it. After it is hollowed out you can cut the head off so the return line can slide over it and be clamped down. By threading this bolt in/out of the body of the FPR it should be easy to adjust the base fuel pressure and then set it with a lock nut. Some thread sealer should be enough to stop any leaks. The 8mm bolt is large enough to support a much larger hole than the factory return and provides a large seat inside the FPR that the diaphragm can seal against. It also allows the tip of the bolt to be polished for a better seal.

I considered just drilling a larger hole in the factory restriction and tapping the FPR for a pipe fitting to slide the return line onto but drilling the restriction in place means there is no way to deburr the mating surface inside the FPR. I haven't tried doing this though so it may not be a problem. Someone else can give that a shot and let us know how it works out. Doing that won't allow for adjusting the base pressure but will allow greater flow. I just don't know if it'll be enough or if the base pressure will remain the same.

For now I'm all out of FPR's. My nearest supply is an hour away and wants $5-10 each. I may take a trip and get a few when I have some free time. For now the FPR I have is working fine.

If you have the tools you can do this mod for the cost of a bolt, some sealer and a little time. Figure $2 or less plus the cost of an extra FPR if you don't want to mess with your stock one. Seems like a good deal to me.

 

[kchaazz]

Well, after happening upon your thread, I decided to try this myself, and bought three Galant regs at my local jy. I have a different plan, though.
First, with my tools at work, I was able to remove the restrictor without cutting the top off the reg. I then tapped the bottom for 1/8 npt and installed a 90 degree fitting exactly the way you have done.
Now, Im guessing that the restrictor is used to "calibrate" these things, and Im hoping that when I put this reg on the car without the restrictor that the base pressure will now be significantly lower that stock, so that I can watch a fuel pressure guage while I use a c- clamp or the like to incrementally crush the top of the reg down to create more preload on the spring inside until my guage reads 37.5 psi with the vac line off (factory 1g dsm fuel pressure).
Ill let you know if it works this way, and just in case I have to cut off the top, Ive bought some tri clamps, and have the means of just drilling a hole in the top for the the set screw and tig welding a nut for the screw to the cut off top. Still going to use a penny inside for the preload though

 

[eclipsh]

Well, after happening upon your thread, I decided to try this myself, and bought three Galant regs at my local jy. I have a different plan, though.
First, with my tools at work, I was able to remove the restrictor without cutting the top off the reg. I then tapped the bottom for 1/8 npt and installed a 90 degree fitting exactly the way you have done.
Now, Im guessing that the restrictor is used to "calibrate" these things, and Im hoping that when I put this reg on the car without the restrictor that the base pressure will now be significantly lower that stock, so that I can watch a fuel pressure guage while I use a c- clamp or the like to incrementally crush the top of the reg down to create more preload on the spring inside until my guage reads 37.5 psi with the vac line off (factory 1g dsm fuel pressure).
Ill let you know if it works this way, and just in case I have to cut off the top, Ive bought some tri clamps, and have the means of just drilling a hole in the top for the the set screw and tig welding a nut for the screw to the cut off top. Still going to use a penny inside for the preload though

I hadn't considered crushing the cap. Nice idea. How did you pull the restrictor out? I know you had to drill down in but what did you do after that?

Honestly, I think just pulling the restirctor creates too big of a return orifice and a poor seat for the seal. That is a couple of the reasons why I came up with the other option listed above.

With a drill press and some good bits it might also be possible to drill out the center orifice of the restrictor slightly larger. I didn't have a press when I started this but thanks to a good friend with a spare I've got one in the garage now and may try this out.

 

[kchaazz]

Well, to get the restrictor out, I just drilled carefully downward a little further, stopping to be sure I wasnt getting into the seat, and the restrictor just dropped out. I did drill into the restrictor a bit, though. This is with a milling/drill press with a machinist's vice mounted securely to the table, makes it easy. Ive got 2 more regs, one Ive only cut the return line off, the other is unmolested. the second Im going to try and drill only far enough so I can tap for 1/8 npt and Im going to try and enlarge the orifice in the restrictor instead of romoving it in order to possibly preserve the seat at your suggestion.
Ill be testing one soon, and Ill definetly post results.

One question, have you checked your fuel pressure for consistency? Test the pressure when the car is cold and when its fully warmed up, test again. See, the problem with some regs- namely the cheapos, is that the fuel pressure tends to fluctuate with engine bay temps. I have had an Obx reg that suffered this and it was a tuning nightmare, so I ditched it in favor of the Full Throttle afpr. The factory piece shouldnt have this issue, but we would want to be sure we havent caused something to become amiss, right?
Anyway, I will be testing consistency when I get around to putting the test unit onto one of my cars, along with confirming a linear 1:1 rising ratio, and Ill get back to you, if you dont beat me to it, that is.

 

[pneumo]

I crushed a stock NT FPR to raise the pressure on my car a few years ago. It was good enough to raise pressure by about 5psi. I didn't want to risk crushing it any farther that that.

 

[eclipsh]

One question, have you checked your fuel pressure for consistency? Test the pressure when the car is cold and when its fully warmed up, test again. See, the problem with some regs- namely the cheapos, is that the fuel pressure tends to fluctuate with engine bay temps. I have had an Obx reg that suffered this and it was a tuning nightmare, so I ditched it in favor of the Full Throttle afpr. The factory piece shouldnt have this issue, but we would want to be sure we havent caused something to become amiss, right?
Anyway, I will be testing consistency when I get around to putting the test unit onto one of my cars, along with confirming a linear 1:1 rising ratio, and Ill get back to you, if you dont beat me to it, that is.

I have not checked consistency on the regulator. Like I stated above, I do have some fluttering in pressure which I don't really like. One of these days when I have some free time I'll hit the junk yard and give it another go. Please be sure to keep track of the return aperture size you use. For reference, the stock size of one of mine is ~0.082 in. Drilling out to .204 seems to be too much. I'm just guessing but a ~.10-.15 might be a good start.