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Old 07-21-2006, 01:10 PM   #1
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Default Do I need a new fuel pump?

I got my turbo installed a few days ago with a crossover pipe (saving the intercooler until I get the bugs worked out). I'm running a T25 @ 6psi right now, with Bipes and BEGi AFPR.

My A/F guage is giving a fairly constant 14.6 when not in boost, which seems normal to me. When I am in boost, however, not full throttle, it stays around 14.0. No weird noises or poor performance. When at full throttle, it goes way lean, like 16.5. Again, no weird noises, and still pulls strong.

My AFPR has the adjustment screw almost all the way in. I don't have a fuel pressure guage to tee into the fuel line right now, I thought I could get away with just the wideband.

If I do need a new pump, eBay lists a walbro 190 as OEM replacement, so I need to go bigger than that? The 255's are $100 if so.

Sorry for the long post, I hope I gave all the appropriate details.

Thanks,
SamS
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Old 07-21-2006, 02:29 PM   #2
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Quote:
Originally Posted by SamS
My A/F guage is giving a fairly constant 14.6 when not in boost, which seems normal to me. When I am in boost, however, not full throttle, it stays around 14.0. No weird noises or poor performance. When at full throttle, it goes way lean, like 16.5.
EDIT: What wideband are you using? The LC with the gauge? Or are you using a blinky a/f gauge?

Just FYI, the 14.7 is desireable for cruising. It's the most effecient air/fuel ratio.

When you are in boost however, the AFR should drop down, not go up. If you are really running that high of an afr, you need to park it. Just a ballpark number for you, that 16.5 needs to be more like 11 to 12 BALLPARK

The leaner you run the engine, the more power/heat it's going to put out. It will make good power at a safe AFR. A little leaner "pushing the envelope" will make more power, lean it more = more power, then your pistons melt.

Soooooo. Figure out what AFR you want to run based on your specific mods, then use the wideband and shoot for that number. You might need that pump to achieve it. Also, make sure you're using a calibrated wideband, that 16.5 at WOT =

Check it:

https://www.miataturbo.net/forums/sh...ghlight=tuning

Last edited by UofACATS; 07-21-2006 at 02:36 PM. Reason: see EDIT
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Old 07-21-2006, 05:31 PM   #3
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I'm using a PLX Devices M-250 which has a guage with blinky lights around the perimeter with a number display in the center, to the nearest tenth. I thought i never wanted to stray much above 14.7, so I assume that I must be maxing out my fuel pump when it leans out at WOT.

This is the only thing I can figure to be the problem, does this make sense?

Also, would the Walbro 190 be sufficient, or should I go with the 255?
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Old 07-21-2006, 08:45 PM   #4
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I would go for the 255, thats what i have and i like it alot.
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Old 07-21-2006, 09:19 PM   #5
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Get one of the rubber tubes that go over the fuel pump. It helps quiet them down. I know my 255 was noisey as hell until I put the "sock" on it.
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Old 07-21-2006, 10:56 PM   #6
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Alright, I'll order myself a Walbro 255.

Thanks guys!

SamS
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Old 07-22-2006, 02:26 AM   #7
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What's the difference between the Walbro P540 and the Walbro GCA3312?
http://www.fuel-pumps.net/fuel-pumps...cyl--1-8l.html

They have the same pic, but the GCA3312 says pump/filter assembly. Is this going to be a standard drop-in replacement?
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Old 07-22-2006, 03:39 AM   #8
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i would tee off the fuel pressure and stick a simple guage on it. why spend the $100 on the fuel pump if you haven't properly diagnosed the problem? $10-20 in parts is better than $100, especially if the pump isn't possibly isn't the issue.

your AFPR could possibly need rebuilding.
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Old 07-22-2006, 12:40 PM   #9
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The AFPR is brand new, but I suppose you're right, it's possible.

Thanks
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Old 07-23-2006, 12:37 AM   #10
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Are you using a real wideband sensor. Those afs are way lean even on a stock fuel system something has ot be wrong with the gauge or the sender. The 190 high presure should be plenty for your project as it flows enough fuel to support 200 whp up to 95 psi the 255 will over power your stock fpr and not give you to much of a noticable increase over the 190 hp. FYI the stock pump is 160lph and maxes out at 85 psi with th eend of its real operating range for 200 hp is about 60-65 psi i dont see anyway you would running that lean in boost and still be making power.
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Old 07-23-2006, 02:26 AM   #11
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Yes, it's a genuine $369 wideband O2. I tee'd in a fuel pressure gauge today, only to find 0psi at idle. I'll try to find/borrow a new gauge tomorrow.

So the GCA3312 at that link is a 190 high pressure?
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Old 07-23-2006, 02:47 AM   #12
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i cant tell from the pic here is a site with walboro specific info though might make osme intersesting reading with 0 psi at idle i would think FP is dead heck i don't see how you idle. http://www.autoperformanceengineering.com/
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Old 07-23-2006, 12:14 PM   #13
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Thanks for the link, I'll have to check it out after work.

With the 0psi, I'm pretty sure it's just that the fuel pressure gauge doesn't work, as I don't believe the engine would run with zero fuel pressure.
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Old 07-23-2006, 12:25 PM   #14
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http://shopping.lightningmotorsports..._Kit-p-89.html

Might want to check pricing here.
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Old 07-23-2006, 05:41 PM   #15
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Thanks guys, I just ordered a Walbro 190 HP as well as a new fuel pressure gauge.

I hope this solves the problem, thanks again!

SamS
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