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Fuel System - Suggestions for more fuel?

3K views 48 replies 6 participants last post by  neilschelly 
#1 ·
So I've recently gotten tuned by Dent Sport. I've got my FSP EJ22 project putting about 120-130 awhp out. It was 122 on the dyno, but we were unable to adjust ignition timing at all due to my own wiring issues. Now that I've adjusted them, I have added another 10lb-ft of torque or so in timing (measured with G-Tech), so that's about where I am for power right now. More details, if you're interested, at http://www.jenandneil.com/28fsp.

Anyway, we noticed on the dyno that torque really really drops off after 5200RPM or so. By "really really" I mean that it goes from about 120lb-ft of torque to somewhere in the 80s. It's pretty sad. The fuel injectors are running overtime with about a 92% utilization rate and mixtures are really rich no matter how lean we tried to make it. We suspect the injectors aren't actually closing, so fuel is basically just spraying non-stop into the cylinders after 5500 or so.

So I'm trying to rectify this. I've got the stock fuel pump (??lph), stock injectors (280cc), and stock fuel pressure regulator and I want more fuel. I'm curious how others have approached this problem. I haven't yet hooked up a fuel pressure gauge anywhere to see how the fuel pump is keeping up and I can't find anywhere even an estimate of the flow capacity of the stock pump.

1. I could get a new fuel pump and assume that fuel pressure is dwindling at the top end. I don't suspect this is the case, but I'd love to hear someone else's experienced opinion here.
2. I could do a fuel pressure regulator, increase fuel pressures, and consequently lower the injector durations to get the fuel into the cylinders faster and allow more space between injector pulses.
3. I could replace the injectors. 440cc WRX would certainly flow more than the 280cc ones I've got and I could decrease the injection duration to accomodate that. It's not such a big jump that I expect to have any idle troubles with that and it's not a daily driver, so even some idle issues are just fine by me.

Anyone have any valuable experience I could learn from?

Can I assume that any top-feed Subaru injectors will fit or are there fitment issues with certain injectors?

Should I just assume that all options will require a new bigger fuel pump?

Does anyone have any good experience with electronic fuel pressure gauges that I can run inside the car or is that not worth the effort/money?

Thanks in advance!
-N
 
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#2 ·
First, put a mechanical gauge on the feed line so you get a baseline fuel pressure reading at idle. Then disconnect the vacuum line at the regulator and see what the pressure goes to (cap off open vacuum line).

Once you do this, you can slowly crimp the return line so the pressure jumps up 5psi. Repeat your tests until you get the most power/tq with decent IDC's. Once you know the best pressure, you can either crimp the stock regulator to match it or use an adjustable unit to get you to the right amount.

What did you use to bump the timing? PP6? Nice numbers for an EJ22....you got power on me for sure!
 
#3 ·
That sounds not so bad/random. Maybe I can do that after all - it sounds so much more scientific. Can I trust that a crimped return line will be stable enough as time goes on?

As for timing, I'm using an eManage Ultimate for tuning. I decided against the PP6 only because I wasn't confident that it could do as much for tuning as I wanted and I had a good line on an eManage Ultimate. As for power numbers, I'm pretty happy with them. Now that I've got timing adjusted (G-Tech tuned too, so I'm sure it's not exactly great), I think I'm doing about 130-135 lb-ft of torque to the wheels and the horsepower numbers ought to be a lot higher (135+?) if I can get this fueling issue at high speeds figured out.
-N
 
#5 ·
From everything I've read, the RS and 2.2 ones are both 280cc injectors anyway, so that shouldn't be much of an upgrade. Mine look like the ones on the right in your picture though. The RS injectors in your pic look like they have the IAC functionality in them to mix in some air for idle in the neck of the injector, yes?

Which leads of course to one of my questions though. Can I assume that any Subaru top-feed injectors will fit? Clearly not, but what can I assume will fit?
-N
 
#6 ·
The greens from the 2.2 are 267cc, the greys are 306cc - I had both flow tested.
You can actually use the entire 2.5l intake manifold on the MAP 2.2's - I did.

MAF 2.2's with the 1.8 style v-covers & side feed injectors have an entirely different intake manifold so the above WILL NOT WORK.
 
#8 ·
So you're saying that I can use the gray ones above from an RS if I can find them and that will give me an injector size boost? I'm already controlling fuel, so I'm not worried about getting a CEL. They just don't look like they'd fit to me. Am I missing something? Were those injectors used on all 2.5RSs or only certain years?

I'm not interested in using the intake manifold from and RS - already spent enough on mine to make it worth getting injectors that will fit in it.
-N
 
#9 ·
Yeah you are missing the part were I used the 2.5l intake manifold & fuel rails to make this work - everything else was the stock 2.2l bits (T-body + all other sensors), between your old manifold & a 2.5l one from the J/Y you'll have all of the parts to make this work!
 
#11 ·
Opps, I did not read the part where you said you wanted to keep your I/M.

I don't think the greys will fit but did buy a set of 470's from Marren Fuel Injection in CT that did fit my old 2.2L I/M.

The return line pinch is an old trick that works well & will allow you to increase fuel pressure for the cost of a hose-clamp!
RC engineering has the pressure Vs flow equation that will allow you to predict what your injectors will flow @ a given fuel pressure level.
 
#12 ·
So I have been trying to get to this forever. I finally got everything together and am at a loss again. I tried putting a hose clamp in the return fuel line, but I can't get it to register on the gauge as any increase. I can't find any smaller hose clamps, but I imagine it would be tough to get them around the hose to begin with too. I'm shopping McMasterCarr now and not finding anything smaller. Am I missing something?
-N
 
#13 ·
And I'm stubborn, so I went out again with another idea. I used a standard worm-drive clamp this time and put some extra rubber between it and the fuel hose to keep the edges from digging into the hose. I successfully got the fuel pressure to rise by tightening the clamp. I could not stabilize the pressure though. It seemed decently stable just under 50psi where I was aiming for.

Then the cooling fan kicked on (as per normal) and the fuel pressure jumped to over 65psi. I dialed it down again to 48-ish and then the fan stopped and pressure dropped back to stock. I adjusted slowly up again to 48-ish. The cooling fan came on again eventually and pressure stayed stable. Then the fan went off and the pressure dropped back to stock. I turned it up a bit more and got it up to 48-ish again. Cooling fan came on and pressure jumped into the 60s again. I left it alone to see what would happen and it dropped to stock again when the fan stopped.

So in the end, it seems that any given position of tightening can translate to anywhere between 43 and 65 psi of pressure. The only exception is running without any crimping on the fuel return, which stays steady at 43-ish stock.

I guess my next option is some bigger injectors. I saw someone selling some of the RS injectors with special rubber or something that would make them fit an EJ22. Does anyone know anything about that?
-N
 
#14 ·
That's weird....... I put '00 EJ25 manifold next to my '00 EJ22 manifold and they are identical. Both have grey injectors, identical again. I even swapped them out, trying to get rid of a nagging WOT/launching misfire.

I've crimped my return line to the point where some clamps under the car started to leak! virtually zero flow on the return, no fans came on, nothing..... (didn't help my misfire either). I've never seen the green injectors.......

Neil, pull the vacuum line off the FPR and cap it at the manifold. See what the pressure reads then....and note if the fans kick on.
 
#15 ·
I know my injectors are green - they were on my '99 motor and on my '00 motor that I use now. But you're right that the manifold should be identical to an RS. In fact, I initially ordered the wrong phenolic spacers for my car from GrimmSpeed because I ordered the EJ22 ones instead of the EJ25 ones - the '99+ EJ22 intake ports match the EJ25, not the earlier EJ22s.

And I did pull the vaccuum line on the FPR. When first I turned on the car with the fuel pressure gauge hooked up, it came up to about 35psi or so. When I pulled the vac line, it jumped to 43-ish. As for the fan, it just came on as is normal for the car to do after sitting idling for a long time. It wasn't as a reaction to fuel what I was doing with fuel as far as I can tell. But it coming on and off certainly had something to do with the fuel supply somewhere. I can't explain it because as far as I can tell from electrical diagrams, the car has no fuel pressure sensor and no ability to "correct" the fuel pressure except the FPR, but it proved damn good at defeating me nonetheless.

Ugh.
-N
 
#16 ·
Ugh is right....... Short of putting a voltmeter on the fuel pump and seeing if it changes when the fans come on, I can't think of any reason why the jump in idle (fans cycling on) will cause the pressure to jump like it does.......

Maybe you just need to upsize the injectors slightly. I know the ECU can pull them back for daily non-WOT needs. I'd be willing to split a set of 8 injectors with you since it's usually cheaper to buy 'em that way......
 
#17 ·
Yeah, the more I think about it, the less it makes sense. Even if there was a jump in the fuel pump voltage, that still shouldn't make the fuel pressure go jumping so high when the idle goes up. Tapping the throttle doesn't have the effect of making pressure jump so drastically. The FPR, if doing it's job, should be taking any excess pressure from the fuel pump and sending it back. Perhaps somehow, the return line was getting completely stopped up and 65-ish PSI is just what the maximum pressure the stock fuel pump will do? That might explain it.

Anyway, I can't find the info on the RS injectors that I was looking for. I was thinking of trying out the dimpling of the fuel pressure regulator as an alternate means of increasing pressure. I know it works for WRX/STi folks and I know my FPR has a dimple on it. Has anyone done that to increase pressure or is that something that only some FPRs allow?

I guess if that's not going to work, I'd go in for 8 injectors if you want, but then I'd worry about getting the right ones. Do we know which ones fit? And does yours accept the same ones as mine? I think you're running a Phase 1 EJ22, right? Sounds like that might be different, especially if I've got the green ones pictured above.
-N
 
#18 · (Edited)
The fuel pressure went crazy because the cars voltage changed when the fans kicked on - ? if the Alt does something to compensate for the fans being on - which sounds kinda silly.

? if a capacitor from a car audio system will stabilize voltage, but if you have an old one laying around i'd try it.

I also had the green injectors on both '99, & a '01 2.2l both of which wer MAP cars.
I got the greys from a SOHC 2.5l.

Since you are raising the fuel pressure you can get a cheap MSD 1:1 rise with boost 5/16" barb fitting FPR for about $52 from Summit Racing.
This can be plumbed into the return line, but will only allow a increase in Fuel pressure when installed inline with the factory FPR - which is what you want anyway.
 
#19 ·
I can't find that on Summit Racing. Got a link? Is that an adjustable FPR?

I have been looking at that too. There's a pretty one on NASIOC for sale for $100 right now, though it doesn't appear to have the right fittings on it for this application, so if a universal one here is designed to work with the stock FPR, maybe that is a good thing?
-N
 
#20 ·
The price went up to $72 on these, but the part # is MSD-2222.

This is an adjustable fuel pressure regulator for use on fuel injected cars (? the working PSI Range but a Summit tech could help with that), 1:1 rise with boost, + 5/16" barbed fittings so you don't have to spend $50 on fittings like I had to with my Aeromotive FPR.
 
#22 ·
I can't get on Summits web-site so I could not see specifics sorry....

An aeromotive will work I currently have one on my car & have set fuel pressure as high as 60PSI nice & steady with no probs.

? on the Model# of the one I have, but it has 2 springs 1 is 3-20psi, & the other is 20-60psi Red & black about $120.
 
#23 ·
Is it a given than any FPR can be used in serial with the stock one? Obviously, it's not too hard to take any FPR with two barb fittings on it and stick it inline with the return line. It makes sense to me that if the second FPR is aiming for a higher pressure, the stock one just sits there idly by not doing anything, which is fine by me. Would I be missing anything?
-N
 
#24 ·
Thinking about it more, when the fans kick on, the alternator draws more current, which increases load, so the ECU bumps the idle up to compensate....as a result, the vacuum signal changes, which effects the fuel pressure.

When adding a second FPR inline, the stock one would have to be maxed out (no vacuum) which will also reduce volume through the return line. The second one will hold the return back even more to give a net gain in pressure. The only downside would be reduced flow at the tank return.

I'm running a phase II motor now, so our stuff should work the same. (I'll just be a little faster :) )
 
#25 ·
If the idle goes up though, and the vacuum then goes down, the fuel pressure normally would go up to compensate, assuming the vac line was hooked up. Since it's not hooked up, the engine will take more fuel and the fuel pressure regulator won't compensate by raising the pressure to match the increased pressure in the intake manifold. Instead, I'm seeing it go way up.

Anyway, I'm onto other ideas... I may just get the used FPR for cheap on NASIOC if the seller returns my PM. I'm also wondering about this: http://forums.nasioc.com/forums/showthread.php?t=480255

Does anyone know if that's a WRX/STi only thing or can I bump in the dimple a bit on my FPR and get it higher?
-N
 
#26 ·
You can definately push the dimple in on yours, mine, or anyone's for that matter. The principle applies to just about every regulator out there. Some of the cheapie adjustables replace the upper part with a can that has a simple threaded bolt and locknut to adjust the preload on the spring inside.
 
#27 ·
If you're still in need of a used FPR, and can't find one, let me know. I've long since upgraded my fuel system with the Parallel fuel rail mod, and am using an SX adjustable FPR now. I'm about 90% sure I kept the OE FPR (i'll have to double check though). It's out of a 2000 2.5RS, if it's compatible with your setup.
 
#28 ·
Thanks but no thanks. If I'm buying an FPR, I'll get a better-than-stock adjustable one.

The options I see now are:
A. Tap in the dimple on the stock one until I get it where I want it. I don't know how far you can go with this and certainly don't want to go so far as to just render it useless and in need of replacing. Is 10psi a given with doing this sort of thing? Or do some FPRs not have that much flexibility?

B. Buy an adjustable one for $100. That would give me a fuel pressure gauge port without having to plumb one in/out as much and obviously be more reliable in general.

I'm leaning toward B now... I just don't want to break stuff.
-N
 
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