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Old 10-09-2001, 03:26 AM   #1
the Dabbler
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Join Date: Feb 2001
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MY00 2.5RS Sedan
Abnormally Aspirated

Default Anyone running Walbro 255 + Vortech 4:1 RRFPR successfully?

I still have some tests to run, but my setup (Walbro 255 fuel pump + Vortech 4:1 RRFPR) seems to run lean under load.

At 3psi boost (perhaps 1/2 throttle), fuel pressure is only 50psi, which seems a bit low, if stock is 41-44 and the RRFPR is supposed to increase fuel pressure 4:1 with boost (so, maybe 53-56 psi). The A/F meter seems to be indicating way lean at this point, and the J&S Safeguard is starting to kick in. I haven't gone beyond 3 psi yet, for obvious reasons.

It could be that the boost signal to my RRFPR is screwed up. Alternatively, as some have suggested, the fuel pump could already be maxing out.

So my question is, does anyone else have this setup (Walbro 255 pump + Vortech 4:1 RRFPR), with no other mods? If so, does it run properly (i.e., rich while open loop), and what are your fuel pressures?

If other people are able to run with this setup, I'll conclude that either my pump, RRFPR, or vac line is faulty. If not, I'll see about getting a higher capacity pump. I'm hoping it's not the latter, since that install was a pain.
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Old 10-09-2001, 06:53 AM   #2
blaster88
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I am.

Do you have a zener diode or check valve for the boost signal cut?
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Old 10-09-2001, 09:43 AM   #3
kastle
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Default

I'm running the Vortech RRFPR and the walbro 255 along with a Split Second Voltage Clamp on my MY00 with no problems. I think you might want to go 5:1 on the RRFPR though
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Old 10-09-2001, 10:11 AM   #4
HRE | giulio
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Default

dabbler, try this:

start from a complete stop and WOT through all the gears.
Then do the same but from 2krpm in 3rd.

You'll notice that starting from a cruise gives a lean/nearly lean condition, and eventually J&S will retard.
But starting from a still gives rich condition.
I dont know if it's the ECU playing economy tricks or something.. i do know it SUCKS though.

I'm running a Vortech 6:1 FMU with the walbro, seems to be OK. I had the 4:1 but it just wasnt enough fuel.
I'm at 6psi now with the cold weather (no wastegate on the SC) and fuel is not a problem. The car is pulling like a lil' beast.
I also have an SAFC but its on very low correction. I could prob zero it out and let the ECU learn... but i'm a pus...

A recal for the FMU is only $30. I got mine from a mitsubishi dealer. It took like 5 mins to install! you wont even have to spill a drop of fuel, it's an awesome setup

Good luck,
giulio
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Old 10-09-2001, 03:21 PM   #5
the Dabbler
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Default

I have a 5.6V zener in there. It could be that the current from the MAP sensor output is so small, the zener is clamping too low, and causing the injector duty cycle to be less than what it should be. That region of the v-i curve isn't very well controlled for zeners. I'll hook up a multimeter to see what I can see. I may have to spring for that Split Second Voltage Clamp, which presumably compensates for that. I guess I would've preferred using a check valve, but the MAP sensor mounting didn't seem to lend itself to that easily (at least, not as easy as soldering in a diode).

So, for the people running the Walbro 255 pump and the Vortech RRFPR (kastle, giulio), are your fuel pressures what you would expect? Like I said, mine seems to top out at 50psi, which appears to be too low, even at 3 psi.

giulio, re the test you describe: I can see how the ECU might react differently transitioning between closed/open loop, starting from idle as opposed to a steady state cruise. Now that you mention it, if this how the ECU reacts, that may be difficult to compensate for.
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Old 10-09-2001, 05:14 PM   #6
HRE | giulio
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Quote:
Originally posted by the Dabbler
So, for the people running the Walbro 255 pump and the Vortech RRFPR (kastle, giulio), are your fuel pressures what you would expect?
I dont have a fuel pressure guage. Maybe i'll borrow my bro's odb scan machine and go for a few runs and see what it is. I'll try to remember to do that saturday morning! (that thing is so cool!!)

Quote:
Originally posted by the Dabbler
giulio, re the test you describe: I can see how the ECU might react differently transitioning between closed/open loop, starting from idle as opposed to a steady state cruise. Now that you mention it, if this how the ECU reacts, that may be difficult to compensate for. [/b]
If you downshift that seems to wake up the S/F ratio.
I cant think of any other way to compesate for it. I was tuning the SAFC for the leaner condition.. then if i go for a rip from idle the AF would be rich right off the scale!.
no matter what you do the ECU will relearn the fuel mapping eventually. Its a good arguement to buy a car with stock forced induction
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Old 10-10-2001, 12:22 AM   #7
yebokmj
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Default Above Setup

I have the above setup on my MY98 turbo and I am having no problems at all. Infact car always want's to run rich. I have it leaned out a lot with my S-AFR, this is at 6psi and stock injectors with lots of room for raising the boost.
Joshua
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Old 10-10-2001, 12:11 PM   #8
the Dabbler
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MY00 2.5RS Sedan
Abnormally Aspirated

Default Re: Above Setup

Quote:
Originally posted by yebokmj
I have the above setup on my MY98 turbo and I am having no problems at all. Infact car always want's to run rich. I have it leaned out a lot with my S-AFR, this is at 6psi and stock injectors with lots of room for raising the boost.
Joshua
Are you running 4:1 or 6:1? From some calculations (assuming my math is correct, of course), 4:1 looks like it will run a bit lean, or at least, not slightly rich, which is where I want to be. 6:1 seems like it would be okay.
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