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Old 10-14-2008, 09:46 AM   #1
ProDarwin
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Default Fuel Starvation... what's the easiest solution?

So, the RS has horrible fuel starvation problems @ autocrosses, especially the lower speed, tighter courses. This past weekend I had to run ~8 gallons of gas to keep the starvation under control. I've heard that a bugeye WRX fuel pump may solve/help this problem... Its believable as my friend's 03 WRX does not run into fuel starvation problems during AutoX like my RS does, even when running ~1/16th of a tank.

Any thoughts on this? Is there an easier option?

And no, I don't want a surge tank.
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Old 10-14-2008, 09:55 AM   #2
Skidd
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I can't understand what a different pump will acomplish. It's not the pump that's the problem, it's the baffles in the tank and the location of the pickup. I happen to have a 04 STi pump in my RS. As I understand it, the 03 WRX has a slight difference in the tank baffles. That's why they dont' get the fuel problems we RS guys get. Mind you, I don't know what the 2002 RS has for a tank design. I used to have to run over 3/4 of a tank to keep fuel cut away on hard right handers at the AutoX. I usually just showed up with a full tank just in case. Now, I can run under 1/4 tank easy.

Inspired by what Storm did in these threads
http://www.rs25.com/forums/showthread.php?p=1356352
http://www.rs25.com/forums/showthread.php?t=49108
I made my own
http://www.ludicrous-speed.com/wiki/...fuel_slosh_mod

I speak from experience.. it works.

Last edited by Skidd; 10-14-2008 at 10:01 AM.
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Old 10-14-2008, 11:16 AM   #3
Qman
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I also ran a wrx pump in my '96 2.5 conversion. Never had an issue with starvation.
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Old 10-14-2008, 11:27 AM   #4
ProDarwin
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Quote:
Originally Posted by Skidd View Post
I can't understand what a different pump will acomplish.
I've never seen the pump, but I kind of assumed that in order for it to solve the problem it would have a different pickup.

I like the mod you did, I'll look into doing something like that. Thanks.
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Old 10-14-2008, 11:52 AM   #5
Skidd
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Quote:
Originally Posted by ProDarwin View Post
I've never seen the pump, but I kind of assumed that in order for it to solve the problem it would have a different pickup.

I like the mod you did, I'll look into doing something like that. Thanks.
Speaking only with knowledge of my 00RS pump and tank setup, I can tell you this much.
The STi pump I got did indeed have a slightly different pickup. Well.. actually, it was the mesh sock that was different. Different enough that it was not compatible with the pump brackets and tank design of my car. Easy fix though, I simply swapped the sock from my original pump to the STi pump.

So.. in the end, the pump changed, but the pickup remains exactly the same as stock.

Note.. one of the key things when designing the "Storm Slosh Box" is to try putting holes only one one side of the tank. Without testing holes on both sides on the same car, we can't confirm that it really makes a critical difference. But, I can tell you that it has no adverse affects on my car. I think Storm is planning to re-do his some time with holes on one side. Once he does this we should have more stats on how much it does or does not help.
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Old 10-14-2008, 05:37 PM   #6
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I am planning on it and am hoping to put it in the car by this weekend.

When I saw the price of the STi fuel pump assembly.....I just couldn't stomach the cost for something I could make for a fraction and still be just as effective.

Jay Storm
Sti= Storm tuned it.....
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Old 10-15-2008, 01:41 AM   #7
formula91
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Sorry to thread steal, but what years are affected fuel starvation?
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Old 10-15-2008, 08:17 AM   #8
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I get this in my 05.

Only a problem with hard RH corners + <1/3 tank - as the pump/pickup is on the RHS.

Easiest Solutions:
- Run more fuel (1/2 tank+)
- Anti-surge pump/pickup (Tyre RA?)
- DIY something anti-sruge
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Old 10-15-2008, 12:02 PM   #9
formula91
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Ah, I see.
I did little more reading and it only seems to affect those with suspension upgrades.

I'm not planning on going STS soon. I'm going to mod all things allowed in G stock, so I shouldn't run into this problem.
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Old 10-15-2008, 12:10 PM   #10
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Quote:
Originally Posted by formula91 View Post
Ah, I see.
I did little more reading and it only seems to affect those with suspension upgrades.

I'm not planning on going STS soon. I'm going to mod all things allowed in G stock, so I shouldn't run into this problem.
interesting but i'd be willing to bet you'll still have the problem based on a GS RS driver i used to know just run it with a half to 2/3rd tank and all should be good and GS legal.
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Old 10-16-2008, 11:43 AM   #11
EastsideLegacy
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To start i have a 1995 Subaru Legacy 2.2L with a 2.5L DOHC swapped in.

short ram intake, GFB lightened crank pulley, Catback exhaust, lightweight flywheel.
( no CEL )

Ha sorry guys for stealing the thread, but I have the same problem, but its not when i corner hard it kinda comes once or twice a week when i drive normal.

It basically cuts out (though i have my foot on throttle) comes back for like 2 seconds, cuts out again and then doesn't happen for a 3 or 4 days, maybe even 5 or 6 in some instances.

I changed the pump, filter and plugs and wires look good and there NO codes thrown.

I also feel some definite power loss while im revving up like something isn't working right but its still working.... you know? kinda weird .
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Old 10-16-2008, 01:56 PM   #12
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Also the fuel pressure is good.
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Old 10-16-2008, 03:46 PM   #13
Storm
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Knock sensor or O2 sensor....... My best guesses.

Jay
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Old 12-08-2008, 02:41 PM   #14
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Another option to consider (still more expensive than the homemade tank) is to find a wrecked STi and get the whole assembly out of it. The local guys will run their 04+ STi's at 1/4 all the time with 275 slicks and get no fuel cut. There's even a local hotshoe who's competed with the fuel light on and had no issues.

Other issue behind this is you have to be somewhat mechanically minded to replace your whole fuel tank, but if you're capable of doing a fuel pump swap I would guess you'd be able to do the fuel tank swap.
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Old 12-08-2008, 04:59 PM   #15
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I disagree ^^^. To take the tank out, you have to drop the entire rear driveline by enough to clear the corner of the new tank. It's not a fun job.....way more intimidating than swapping the pump assembly. I'll pull my back seat instead of dropping that rear subframe assembly thank-you.

The baffle box in the RS is pretty small. Smaller than a mold for a home made bread machine anyway.....I don't believe the STi pickup assembly will fit inside the RS "breadbox". Using a 32oz R/C plane tank and some ingenuity flat out works......for a fraction of the cost.

Jay Storm
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Old 12-08-2008, 05:23 PM   #16
Skidd
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I concur with Storm.. The "Storm Slosh Box" has been proven to work for me. I'm down from needing over 3/4 of a tank, to well under 1/4 of a tank and still no fuel cut experienced.
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Old 12-08-2008, 05:38 PM   #17
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Quote:
Originally Posted by Storm View Post
I disagree ^^^. To take the tank out, you have to drop the entire rear driveline by enough to clear the corner of the new tank. It's not a fun job.....way more intimidating than swapping the pump assembly. I'll pull my back seat instead of dropping that rear subframe assembly thank-you.

The baffle box in the RS is pretty small. Smaller than a mold for a home made bread machine anyway.....I don't believe the STi pickup assembly will fit inside the RS "breadbox". Using a 32oz R/C plane tank and some ingenuity flat out works......for a fraction of the cost.

Jay Storm
Hmm, I hadn't thought about the driveline. Guess it's a bigger job than I thought. See, you just need to run SM like me so you don't ever have that pesky back seat in the way to get to the assembly

I had read rumors that people had trouble fitting the STi assembly in, but never found a solid report on it. I read through all the writeups you did on the home made tank, so I'll probably do that. Thanks for the info
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Old 12-08-2008, 08:38 PM   #18
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No Problem. I had saved some pics of the STi assembly for ideas......but after looking at the shape of it, and the acrobatics of getting the pump assembly in the tank by itself, it didn't make much sense (to me). The price was the real inspiration in coming up with a fuel safe container that would accomplish the same idea of holding the fuel right at the inlet and make use of the return line.....all without modifying the tank itself.

Scary thoughts of running SM go through my pea brain every now and then.......if I happen to win this raffle next month, I'll be in SM with an 03 WRX swap. Of course it'd become an EJ257 clone with cams, bigger turbo and romraided management in short order, but I'd still have fun getting there!!!!

Jay
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