stock fuel system capacity?

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cranswick
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Joined: Mon Feb 27, 2012 2:10 am

stock fuel system capacity?

Post by cranswick » Mon Aug 11, 2014 1:59 pm

so recently, as you know, I increased boost to 14psi...I usually don't go much past 6500rpm (even when I race) cause I'm not making as much power up there, but the AFR leans out at the top end, I've added considerable amounts of fuel up there using the boost fuel maps (both mivec and non-mivec, even though I'm in mivec when it occurs), but it didn't seem to make much difference...am I missing something, or have I reached the capacity of the fuel system? what data should I be logging to verify...also how many "fuel numbers" approximately decrease AFR by 1?

note: my fuel system is completely stock, except for the 440cc injectors, obviously...is it likely that the stock pump can't keep up with demand? should I look into aftermarket pressure regulating, or larger injectors?

edit: this might actually be more appropriate for general tuning discussion, sorry.

hackish
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Re: stock fuel system capacity?

Post by hackish » Mon Aug 11, 2014 10:19 pm

Hi,

The symptoms you describe are consistent with a fuel pump that is running out of flow or fuel injectors that are already running at their maximum. You can log your injector pulsewidth to see if the pulsewidth is increasing but the AFR is not dropping. If this is the case then the fuel pressure is one place to look. If the injector pulsewidth reaches a maximum and does not increase beyond that then it is possible that the injectors are too small. The WRX blue tops are about 420cc so they can support close to 300whp.

I have installed a walboro 255lph pump in the past. It required me to drill a hole in the stock plastic pump mounting assembly and to adapt the rubber seal slightly. For the price it would be a good idea. I have also seen people install thicker wire to the fuel pump with a small gain in fuel pressure at the limit. I don't advocate using this as a reliable solution.

-Michael

cranswick
Posts: 124
Joined: Mon Feb 27, 2012 2:10 am

Re: stock fuel system capacity?

Post by cranswick » Tue Aug 12, 2014 12:24 pm

A friend of mine has a spare walbro 255 he will part with...but it's for a 2g Talon TSi...looks the same as any other for Mitsubishi...i'll give that a try, and log pulsewidth...

cranswick
Posts: 124
Joined: Mon Feb 27, 2012 2:10 am

Re: stock fuel system capacity?

Post by cranswick » Thu Sep 11, 2014 12:38 pm

how is fuel pressure regulated?

hackish
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Re: stock fuel system capacity?

Post by hackish » Mon Sep 15, 2014 7:46 am

I don't remember how fuel pressure is regulated on that. I believe it was fixed at a regulator in the tank.

-Michael

cranswick
Posts: 124
Joined: Mon Feb 27, 2012 2:10 am

Re: stock fuel system capacity?

Post by cranswick » Mon Sep 15, 2014 8:56 am

ok, cause i picked up a walbro 255...but i was wondering, if the new pump is able to keep up with demand, but the injectors are not, increasing pressure slightly could work until i find an affordable set of injectors...keeping my eyes open for a set of STi pinks.

cranswick
Posts: 124
Joined: Mon Feb 27, 2012 2:10 am

Re: stock fuel system capacity?

Post by cranswick » Fri Mar 25, 2016 1:48 pm

I never actually finished, this thread...what do you know?

As it turns out, installing the walbro 255 (which the 2g eclipse/dsm pump fits with some modification), resolved the issue. I have recently acquired a set of 560cc injectors.

hackish
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Joined: Wed Jan 05, 2011 1:49 pm

Re: stock fuel system capacity?

Post by hackish » Mon Apr 11, 2016 9:59 pm

Cool! I'm always happy to hear back as to what the solution was.

-Michael

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