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Old 07-03-2008, 07:19 PM   #1
JSarv
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Default Fuel Pressure with Walbro 255lph HP pump on stock regulator

I don't have a gauge, and haven't had time to really check the static pressure of the pump with the OE Regulator. Does anyone know off hand if the pressure is raised using a 255 hp pump, stock injectors and stock FPR.

I ask this because on my H22 civic the FPR WOULD NOT keep up with the pump and I was seeing 60-62PSI static. Curious if the WRX would have similar results, because if so that would explain my learned fuel correction and means I need to mess with injector scaling.


Thanks

Btw, I read the faq and it stated that there is no difference in pressures, but DID not specify HP or standard 255 pump.
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Old 07-03-2008, 07:35 PM   #2
wrxdrvr
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No difference/change from stock as far as I know and fuel pressure should be around 43PSi If I remember right...
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Old 07-03-2008, 07:39 PM   #3
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No difference/change from stock as far as I know and fuel pressure should be around 43PSi If I remember right...

Even with the HP Pump?
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Old 07-03-2008, 08:05 PM   #4
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Yes, the fuel pressure regulater can/does keep it there, The HP/HF pump only helps at full throttle, your fuel pressure/flow should keep up...
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Old 07-03-2008, 10:19 PM   #5
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The reason the suby's don't have this issue (my civic did too) is that the fuel pump has a controller that turns down the pump so, when you're idling I believe the pump is running at 30% duty cycle. The ECU can then step the duty cycle up as need be.
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Old 07-04-2008, 10:20 AM   #6
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Now... that makes sense. I knew it did not bypass, but could not figure out if it stepped voltage down. (Guess I should have known I've logged FPDC)

Anyway the reason I ask, is I have h ad some pretty extreme variance in my learned A/F correction tables, and I'm seeing -7% at less than 5 g/s.

It was 0 or -.5% consistently prior to the pump, am I imagining things?
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Old 07-04-2008, 10:27 AM   #7
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Well, -7 means it's pulling fuel. It does suggest something changed with your fuel pressure. Are you sure the vacuum line's connected to the FPR? I did my injectors the other day and missed connecting that line.
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Old 07-04-2008, 10:41 AM   #8
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Everything is spot on. This isn't something new, just ignored it at first.

Yea, when I reset it runs pig filthy f'ing rich for about 30 seconds and starts pulling fuel.

I logged my Inj. flow on Romraider, and according to it my stocks are flowing around 437cc's... where they are scaled to 420 (stock)... This is making me think that fuel pressure is up a bit, which would cause the stock injectors to because "technically" larger injectors.. Correct?

I'm mainly trying to figure out if this is a MAF scaling problem (stock airbox) so I highly doubt it. Or if this is a Fuel pressure problem, which could be.

Because all of this changed after the installation, however, I figured it was the onset of summer and ignored it. Well it was 61*F last night and it actually dipped to around -8% in my A. Learning table (Idle)
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Old 07-04-2008, 11:17 AM   #9
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If you change one thing and have problems well, that's probably the problem. I'd guess fuel pressure. My 565's are scaled to 550, so I think the flow versus size is normal.
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Old 07-04-2008, 11:20 AM   #10
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Well when I'm not sick... I'm going to get unlazzy and get a gauge setup to see what is going on. I have this strange feeling I'm seeing a rediculous amount of fuel pressure, but I could be crazy too. I'm going to guess around 46psi....


Maybe I'm just sick and crazy?
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Old 07-04-2008, 12:06 PM   #11
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I'll find out before too long. I have a Walbro sitting in a box here waiting for install. The problem with the Honda's was that the return orifice in the FPR was too small to flow enough fuel back to the tank so, the fuel was backing up at the FPR and the idle fuel pressure would run well over stock. Switching to an AEM FPR in the honda with a larger orifice solved that problem though, the AEM was a POS that leaked down from the day I bought it, even after a rebuild.

I wouldn't be surprised if your pressure is alot high to change the mixture that much. What's the FPDC look like?
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Old 07-04-2008, 01:05 PM   #12
JSarv
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Quote:
Originally Posted by MasterKwan View Post
I'll find out before too long. I have a Walbro sitting in a box here waiting for install. The problem with the Honda's was that the return orifice in the FPR was too small to flow enough fuel back to the tank so, the fuel was backing up at the FPR and the idle fuel pressure would run well over stock. Switching to an AEM FPR in the honda with a larger orifice solved that problem though, the AEM was a POS that leaked down from the day I bought it, even after a rebuild.

I wouldn't be surprised if your pressure is alot high to change the mixture that much. What's the FPDC look like?

Sounds good, FPDC is 33.33% at idle, never seen it move, even under wot... haha. Every now and then the pump makes a funky noise, but everything seems to be fantastic other than an insane change in fuel corrections and a huge inconsistency in fuel corrections.


Yea we had it on an JDM H in a 94 civic, fuel pressure was WAY WAY high, car wouldn't idle, bla bla... took an AEM FPR and drilled out the orifice (since the only one we had was the small one) car ran like complete ****. Bought a Walbro 190 and its ran perfect since. Traction less, but perfect.
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