i just bought a walbro high flow fuel pump and have the mods i have below can i run this without a flash and what will it do for my car good or bad?

 

why not just wait till the day of the tune and do it. It's a 20 min. affair.

 

i wanna do that but if it will help me without it why not do it for now? thats what im trying to figure out...

 

It should be okay if you don't go WOT because the fuel pump just makes sure that you have the fuel before you need it

 

You don't use the fuel pump until you get tuned for it. It won't help you at all right now...in fact, it will make you more rich than you already are.

 

i dont think that is correct.... the fuel pump is only going to pump what fuel is needed. just because it is a 255 doesnt mean it is always pumping that much. it just has the ability to pump that much when needed. the walboro is more or less a precautionary device for when you are modded and running higher boosts to make sure you have enough fuel to not cause any damaging effects.

 

Bigric, it happens. It's a known thing. Log your AFRs pre- and post-Walbro, and it's richer across the board. I did it on my Evo in case you're wondering...

 

Warrtalon,

How much was the decrease in AFRs across the board? More in some RPM ranges than others? Was this closed loop and open loop?

The reason I ask is that because on DSMs that would definitely be the case...you would need to run an aftermarket adjustable FPR so that enough fuel could be bypassed through the rail at idle. The stock DSM fpr wouldn't allow enough fuel back to the tank with a pump the size of the 255, most notably as idle, where fuel demand by the injectors was the lowest. The LTFT, or fuel trim at idle, would become very negative, so much so, that it maxed out at -12.5, and couldn't adjust anymore, causing the car to run too rich at idle. At WOT, though, it wasn't much of a problem, because now fuel demand was high and the injectors were consuming a lot of fuel, and therefore, less needed to be returned to the tank.

However, on the Evo, the fuel pump is on it's own circuit directly to the battery, that is switched between a low and high voltage circuit, depending on fuel demand. Sort of like a rewired fuel pump, straight from the factory.

I figured that this was done to help FPR overrun when installing a bigger than stock pump, but since you said that you saw a decrease in AFRs (richer) across the board, that tells me that even with the switched circuit, the stock Evo FPR cannot pass enough fuel back to the tank to maintain a stoich mixture. Or, are you saying, that it was richer across the board only in open loop? I would imagine that you are talking about closed loop operation, in lower RPM ranges, like idle. The AFRs should have been unchanged at higher RPM, WOT open loop fueling, unless you base fuel pressure was raised due to the pump install. Was this checked?

I guess I just want the hard data that you recorded. I was under the impression that the Evo's stock circuit and fpr could handle the bigger pump. I'm wondering that maybe in your case the FP increased a bit, which was causing your richer readings.

Thanks in advance,
Eric

 

k thanks guys! ill just wait...

 

do not argue with wartalon (just a warning). If you do , a 1-2 pg thread will turn into a 4-6 page thread just for everyone's info. hehe.

 

when i put my pump in i noticed a slight power loss.

 

Wtih the 255 you won't have any problems with start-up, idiling, or any closed loop operation. It's only under WOT that you'll run alot richer. And you'll also hit fuel cut before the stock rev limiter kicks in.

I lost 4mph in my trap speeds consistently after installing the pump with no tune.
I wouldn't install it untill your ready for your tune, like others have said.

It only takes about 20-30 minutes to install. Unless you try to rush it and re-install the metal ring on upside down. Then it will turn into a 3 hour nightmare.

 

99GST, only in open loop at WOT is it an issue. We don't have to mess with the FPR and don't have to do the old fuel pump rewire mod either. Mitsu addressed that issue in the Evo.

 

Hmmm...intersting.

That leads me to believe, and backed up by data that I have seen by members that have logged it on the DSMLink forums, that the stock pump can't handle the fuel demand of the increased airflow of modified or even slightly modified Evos.

Since open-loop WOT fueling is controlled by fuel pressure and injector pulse-width, the bigger pump shouldn't cause the Evo to run richer at all at WOT, if it is not causing the Evo to run richer at idle.

I guess that just backs up the fact that the stock pump should be replaced sooner than later. I'm guessing what you saw in your experiences is that the stock pump couldn't handle your increased airflow, which caused it to run a bit leaner than the ECU wanted it to, and when you installed the 255, it could handle the increased airflow no problem, and matched the fuel according to the stock fuel maps, which returned the car to running pig-rich, like the factory designed.

Well, at the very least, it's good to hear that the Evo's fuel-pump circuit and FPR can handle the 255 with no modifications.


Thanks,
Eric

 

Just found this thread searching for the EVO's base fuel pressure. Couple weeks old, but I might as well drop in my 2 pennies on my way through.

Despite the stock dual circuit setup for the pump, the stock pump on stock wiring can not keep up with the turbo. The most airflow it could support on the stock wiring (full voltage line, not the dropped voltage) at 11:1 AFR on pump gas was 34-35 lbs/min. This number was arrived at mathematically, and was then measured and confirmed on the WBO2 in DSMlink. At 40+ lbs/min AFR would go straight to mid 12s. I've seen the mid 12s on many other EVOs that are maxing out the turbo, regardless of AFC settings, flash settings, etc. It's all the stock pump can do on stock wiring when the turbo is maxed out. A rewire with 8 ga wire dropped AFR right to my 11:1 target, even at 40 lbs/min. The WBO2 trace overlayed perfectly on DSMlink's target AFR trace. In this arrangement the stock pump will support ~44 lbs/min, and indeed I have seen 42-43 regularly with no deviation between target AFR and measured AFR.

On to the regulator thing. My theory when going to the 255 was that DSMs came with small pumps, the 190 barely over runs the reg, and the 255 blows it away. Since the EVO comes with roughly a 190, the 255 may be similar to the 190 upgrade on the DSMs. And indeed this seemed to be the case. Trims were only going 5-9% negative at idle and cruise, not too bad. But the 255 is over running the stock reg, there is absolutely no question about that. The question lies in what one is willing to tolerate. Some poeple let the ECU make the necessary adjustments and don't care to think about it further, while others want the fuel pressure to be what the ECU expects it to be.

Upon switching to an aeromotive regulator, it also became apparent that the return line to the tank can not handle the output of the rewired 255. Hose off base can be set to 43, but with the hose on (12"hg, or 6 psi vac) it won't go below 40 psi (Should be 37). And this should be no surprise, since the return line is the same size as it was on the 2Gs, and they also could not go below the same 40 psi value on a rewired 255. On the 2g a 3/8ths return line allowed fuel pressure to drop to ~20-25 psi, much lower than we would ever need. I will be doing the same mod on the EVO next week after I refresh my memory on what the connection at the tank is. I should also note that I am aware of the problem with the aeromotive's signal ports leaking, and that has been resolved in it's previous installation. Despite the return line restriction, the addition of the regulator has made a huge improvement in trims. -2% at idle, 0% at cruise.

Unfortunately with the rewire of the pump bypassing the dual pump circuit I have no data on the 255 with the voltage dropped, so this regulator stuff doesn't apply to guys with stock wiring most likely. I'd personally rather give up perfect fuel trims to get maximum flow from the pump, so I can't sleep at night without a rewire. I'm sure someone could rig up a rewire that is only in effect on the high voltage circuit, but unfortunately running DSMlink disables this feature for me, or I'd do it.

Hopefully someone finds something in this post helpful in future searches.