ShapeGSX

Hmm, they must have changed it since I ibought mine. Not surprising.

Smogrunner

iTrader: (5)

Thanks very much guys. I reinstalled my stock unit and am going to get the "kit" this week from RRE or some other vendor that can take care of me quickly.

Smogrunner

iTrader: (5)

For what it is worth, I installed the Walbro a couple of days ago and it is working fine. I reused the tea bag strainer and it worked fine.

I can only hear it when my back seat is out. No need at all for additional soundproofing.

SinCityEvo

iTrader: (3)

I also read the April issue of Turbo mag. Seems like the stock Evo pump is good enough for 350 whp or so. I am confused, tuners are now recommending upgrading the pump, but I have not heard of one member losing his engine over it and some of us are running 400+ HP. Seems like our pumps are a good quality, Denzo, and should be fine for simple bolt-on mods.

Members are complaining of their cars running crappy and losing power once they swapped the Walbro in. Too much fuel and running too rich. I would think they must be tuned immediately.

SILVER SURFER

At over 20 PSI (65-70PSI fuel pressure) it seems that the stock fuel pump flow starts to drop off sharply and become some what eratic. So while there may be enough flow for 350WHP the eratic fuel delivery at these values can affect reliability. Especially at these higher boost levels, consistant fuel delivery obviously becomes more critical. Keep in mind that on a stock car your only running around 16 PSI above 5K.
I have found that the stock fuel pressure regulator works just fine with the Walboro pump at idle and low/mid RPM, but above 5K the Walboro is able to maintain higher flow compared to the stock pump so you will run richer in the high RPM's. If your installing this pump you will definiately want to be able to readjust your fuel curves in the upper RPM's.

GokuSSj4

iTrader: (7)

so if you have a flash already and install the Walbro , they shouldnt be any issues ???
I was told i can add the walbro after the flash with no problems ,
I plan to give RRE a call tomorrow to get my fuel pump ...

ez76

iTrader: (5)

My theory is that some reflashes are significantly richer than others in the high RPM's and it's these reflashes (combined with higher boost levels) that have fuel demand that overtaxes the stock fuel pump in certain circumstances. The injectors might not be at 100% duty cycle but the stock fuel pump has little to no headroom. To see why, check out this very rough approximation of fuel demand vs. fuel supply:

Stock Evo injectors flow about 560cc/min x 4 so running static you're looking at 2.1L/min or about 121L/hour. More practically, a rich reflash might run injectors at 90% duty cycle at high RPM's or closer to 110L/hour.

Now, the stock fuel pump driven at 12.5V was measured by RRE to flow 119L/hour at 58psi which is the pressure in the fuel system at only 15psi of boost. That's pretty darn close to the fuel demand of 90%DC injectors, and at 20psi of boost that flow goes down even more. Even with another 1.5V driving the fuel pump you are running without much flow to spare. It's easy to see why rich reflashes with tweaked boost are just bad news for the stock pump at high RPM.

So to answer your question, if your reflash is not dumping fuel in high RPM's and/or you are not running significantly increased boost in high RPM's, you would probably not suddenly see an over-rich condition when upgrading the fuel pump because you're not pushing the fuel system to begin with.

ShapeGSX

That isn't really the reason why it works that way. At idle, the walbro doesn't cause fuel pressure creep because the Evo uses a variable voltage fuel pump circuit to slow the pump down when fuel demand isn't high. But as soon as you step on the gas, the ECU switches a relay to give the full 14V battery voltage to the fuel pump, and that can cause fuel pressure creep.

An aftermarket fuel pressure regulator would keep fuel pressure in check in those circumstances.

SILVER SURFER

Maybe, maybe not, I am aware of the two speed fuel pump control, but without monitoring fuel pressures we don't really know if the stock pump was running out of steam or if the 255 is slightly over running the stock regulator.
Most two speed fuel pumps switch to high speed under boost/high load even at moderate RPMs(3-4K). My midrange RPM A/f ratios under boost did not change, only high RPM (over 5k). If the regulator was being overrun you would think it would happen more in the lower RPM's. The difference was not huge, if you were running 11.5 A/F above 5K, with the 255 it would run 11.
Either way, with some minor fuel adjustments the 255 pump works just fine with the stock regulator.
I just don't see a need to replace the regulator at this point, if I am right it won't make a difference. With a new regulator you will most likely have to retune your fuel curves anyway. Possible a more extensive retune if the new regulator does not have the same characteristics and/or is not adjusted to the exact point of the stock regulator.

RallyRedEVO

iTrader: (5)

This is a clip from a service manual I got off ebay. It's such a simple process that I'm not sure what help this will be, but I figured it couldn't hurt.

Sorry the image is a little blurry, but the file size restriction forced me to go LOW on the quality.

bahamut

Don't ever want injectors maxing out at 100% duty cycle. It's at the point of being stuck or wear out.

80% is the max norm. RC engineering, if requested, can make a 90% duty cycle injectors if I remember correctly.

snoop

iTrader: (4)

I would rather run rich than not have enough gas. For 100$ it gives me peace of mind.

MR

Hiya,

Let say you are presetting your boost at 1.5bar/22.05psi with other bolt-on like str8 thru exhaust, 3" dp & cone-air intake.

What would you recommend the setting on the aftermarket fuel pressure regulator with the upgrated 255 fuel pump?

Thanks......

MR

Hi Shiv,

Just wanna share my experience with you guys...

Got a piggyback hooked up with a wideband O2 to my MR with 22~23psi boost setting with my HKS EVC two days ago... Went around butt-tuning. I was the driver while my fren is the "tuner"....I still have the stock pump as well as the stock fuel reg.

The low to mid rpm range A/F ratio was ok...BUT wat surprises me was that while i was reving past 4k, my A/F remains 13.1 no matter how much we tried to adjust the value.....Conclusion in layman term, not enuff fuelling at the high-end range....

Injectors size should be sufficient for my setup so i came to a conclusion that it might be my stock fuel reg failing to hold enuf pressure at the high-rev range.

So went ahead to get myself a adjustable sard fuel reg & set to 2.8 bar minimum...

Went ahead to test again...Situation improved abit, able to get only minimum increased in the A/F way past 4k rev like around 12.7 ~12.8....

Decided to put in the 255 fuel pump, & wala!!! My flat spot in the high end seems gone & the A/F is able to be adjusted to 12.3 to 12.4....

I will be trying to toy my FPR setting again....I wanna hit 12.1 A/F...Shall keep you guys updated & hopefully i can get onto a dyno to benchmark my result sooonest..


All i can say, Shiv you are absolutely rite about the fuel pump upgrade.

Safety & relaibility are better than a blown engine....

Thanks Shiv for the precious info.....

MrMejia

iTrader: (2)

okay I am running on 33000 miles on my evo and I just data logged it yesterday. I data logged rpm's , timing, A/F ratio, TPS. at around 2300 I step on it at WOT and surprisingly im running 13.2-13.8 all the way to 5k with my timing peaking at 17 degrees then starts to go way down all of a sudden when I hit 6500 I'm getting 14.4 A/F !!!! I think its time to replace my fuel filter. what do you guys think? I'm running on a STOCK 2003 EVO with NO MODS. I have an safc-2 but I need to fix my fuel delivery problem first. Would you guys or would you "shiv" recommend a walbro pump for my very lean evo???