[redlin'r]

I will be adventuring into ECU tuning here soon when I purchase the cobb ap. I was thinking about getting a Walbro 255lph Fuel Pump to go along with it.

Is this acceptable and would it hurt if I got installed it with my current mods? Invidia TBE, K&N intake. Would I need anything else with a fuel pump to help out my car?

[VSGTS14]

hell no, i have one.
in fact, it'll help the stock injectors and is a safe mod.

[offset]

Originally Posted by VSGTS14

hell no, i have one.
in fact, it'll help the stock injectors and is a safe mod.

Ditto.

offset

[Nachos Libres]

Originally Posted by VSGTS14

hell no, i have one.
in fact, it'll help the stock injectors and is a safe mod.

Agreed.

[pantag]

So, what exactly this Walbro 255lph Fuel Pump does? Does it pump faster and more fuel to the injectors? How is the gas consumption after the installation? What are the advantages/disadvantages?
Lately, alot of members are using it.

[MRGLASS]

disadvantages: None
Advantages: Taken from Scott Siegel reputable tuner

We've gotten cars in with just TBE that were running 116% duty cycle. Initial tuning dropped it to 105%, adding a fuel pump down to 96%....

That's what I call "the car "wanted" a fuel pump. Some cars are under 95% with the stock pump. Those don't "need" a pump, but they certainly can't hurt.

Yes they run very rich out of the box. I meant after mods. The car running 116% duty would have been better with the pump.

Mostly important to have for tuning

[Davenow]

Conversely you have guys like me, that have datalogged an STI on the stock pump, then changed the pump and datalogged it again, and saw NO difference in duty cycle, no A/F change.. Disadvantages there? Throwing 90 bucks in the garbage for absolutely no change in anything. Advantages?? Not a damned thing.
Scott IS a reputable tuner, and in pretty much every case I stand behind what he says. But there is a reason why Gwinnet is the ONLY shop in the subaru community saying pumps make a difference.

Because they dont.

I swear that Gwinnet owns stock in Walbro or something

(ok not really, just making a point)

[redlin'r]

I did a search on this as well and found many people arguing. It seems like the new fuel pump will just ensure that proper full is being supplied with the increased performance, boost from the Accessport.

People spend was more money on body kits or other parts that don't serve a purpose but looks, so this couldn't hurt I guess.

Where are some good dealers for this product and would yo urecommend the 255 or 225, etc.? Again I will be running stock turbo and be at stage two..

Is there a risk of running rich with a new fuel pump? Will it make idle roug hat all?

[Davenow]

Originally Posted by redlin'r

Is there a risk of running rich with a new fuel pump? Will it make idle roug hat all?

No because only increased fuel pressure will actually cause more fuel to be delivered. The bigger pump only supplies more FLOW< not pressure. ANd no, more flow does not mean more pressure.

[WolfPlayer]

Originally Posted by Davenow

No because only increased fuel pressure will actually cause more fuel to be delivered. The bigger pump only supplies more FLOW< not pressure. ANd no, more flow does not mean more pressure.

Just one tweak to this statement Dave ...

"The bigger pump only supplies more FLOW, not pressure"

Yes and no By default, pressure is created through flow. The flow comes first ... and then this creates the pressure. Yes, it does supply more flow. It also CAN supply more pressure in certain circumstances.

Example: 43.5psi pressure in the rail with 18.5psi boost. The FPR (fuel pressure regulator) will now demand 62psi of fuel pressure (because subarus bump fuel pressure 1-to-1 with boost pressure). If the fuel pump can't keep up with the commanded fuel supply (ultimately determined by the Injector Pulse Width) ... then THIS is the situation where it can't sustain 62psi. The Walbro can sustain 62psi because it can flow more fuel. Thus, it can and does supply more pressure in cases where the stock pump can't keep up. When someone refers to a fuel pump as not being able to keep up, this is verified by the fuel pressure dropping or not reaching the target. Keep in mind that the correct walbro pump (GSS342) was created to supply more flow at a higher pressure. This means it can sustain higher pressures at a given flow better than many other pumps. In cases where you will see a pressure dropoff of the stock pump, you will not see this with the walbro (given normal stuff here guys - I'm not talking about 2 million cc injectors ). Put a 740cc Nismo injector with a stock pump and run it at 90% IDC. Fuel pressure will not reach target. Do the same thing with a walbro and it will reach target and hold pressure. It supplies more flow in this situation, and, therefore, more pressure.

t

[offset]

Originally Posted by Davenow

No because only increased fuel pressure will actually cause more fuel to be delivered. The bigger pump only supplies more FLOW< not pressure. ANd no, more flow does not mean more pressure.

Ya, but I know you have read other people's datalogs that show otherwise (there have been plents posted on NASIOC). Why do you insist on ignoring data when it is not your own? I would be willing to bet there are other vendors who would make the same recommendations. And to say buying a pump is throwing away $80 is garbage; unless they are absolutelty certain to never upgrading much past stock.

offset

[MRGLASS]

Originally Posted by Davenow

Conversely you have guys like me, that have datalogged an STI on the stock pump, then changed the pump and datalogged it again, and saw NO difference in duty cycle, no A/F change.. Disadvantages there? Throwing 90 bucks in the garbage for absolutely no change in anything. Advantages?? Not a damned thing.
Scott IS a reputable tuner, and in pretty much every case I stand behind what he says. But there is a reason why Gwinnet is the ONLY shop in the subaru community saying pumps make a difference.

Because they dont.

I swear that Gwinnet owns stock in Walbro or something

(ok not really, just making a point)

point well taken and noted Dave, but also inside the quote I posted earlier in this thread by Scott.....

That's what I call "the car "wanted" a fuel pump. Some cars are under 95% with the stock pump. Those don't "need" a pump, but they certainly can't hurt.

[Davenow]

Originally Posted by WolfPlayer

Just one tweak to this statement Dave ...

"The bigger pump only supplies more FLOW, not pressure"

Yes and no By default, pressure is created through flow. The flow comes first ... and then this creates the pressure. Yes, it does supply more flow. It also CAN supply more pressure in certain circumstances.

Example: 43.5psi pressure in the rail with 18.5psi boost. The FPR (fuel pressure regulator) will now demand 62psi of fuel pressure (because subarus bump fuel pressure 1-to-1 with boost pressure). If the fuel pump can't keep up with the commanded fuel supply (ultimately determined by the Injector Pulse Width) ... then THIS is the situation where it can't sustain 62psi. The Walbro can sustain 62psi because it can flow more fuel. Thus, it can and does supply more pressure in cases where the stock pump can't keep up. When someone refers to a fuel pump as not being able to keep up, this is verified by the fuel pressure dropping or not reaching the target. Keep in mind that the correct walbro pump (GSS342) was created to supply more flow at a higher pressure. This means it can sustain higher pressures at a given flow better than many other pumps. In cases where you will see a pressure dropoff of the stock pump, you will not see this with the walbro (given normal stuff here guys - I'm not talking about 2 million cc injectors ). Put a 740cc Nismo injector with a stock pump and run it at 90% IDC. Fuel pressure will not reach target. Do the same thing with a walbro and it will reach target and hold pressure. It supplies more flow in this situation, and, therefore, more pressure.

t

The one piece you are leaving out, is the only one that matters in this debate though.

The factory FPR. Increased flow MAY create additional pressure UP TO the factory pressure reg, BUT the pressure reg is going to regulate that pressure down regardless.

You still end up with the exact same pressure in the rails as with the stock pump.(this is why we install fuel pressure gauges in the return line and not the feed line)

Unless you have changed the pressure reg, you will have the same exact pressure in the rails regardless of the pump (unless you are pulling more fuel than the factory pump can flow, which wont happen on the stock injects)

[VSGTS14]

more flow = less stress on injectors
bigger injectors = more fuel which needs the 255

on stock injectors, it's just what i stated earlier and prepares for any other potential upgrades...all in all i still think it's a great mod to do.

[Davenow]

Originally Posted by VSGTS14

more flow = less stress on injectors
bigger injectors = more fuel which needs the 255

on stock injectors, it's just what i stated earlier and prepares for any other potential upgrades...all in all i still think it's a great mod to do.

Again, you are leaving the pressure regulator out of the picture.

More flow= more flow to the pressure reg= exact same flow and pressure as before out of the pressure reg.

More flow, combined with no pressure change= the injectors see absolutely nothing different.

The ONLY reason you need the bigger pump is when you have bigger injectors, which are capable of sucking enough fuel down to lower pressure. The stock injectors do not flow enough to cause a pressure drop in the rail.