i bought a walbro for my fc.. it should be here in a few days.. i have been reading about the rewire.. but whats the purpose of this .. i know you have to cut some wires cuz the connectors dont fit up . i have been looking for the how-to on someones site. i havent been able to find it again .. someone please clear this up for me ??

 

The old wires make it so your fuel pump does not see full voltage under boost. The lower the voltage the less fuel being pumped. New wires = more fuel flow and a healthy engine.

 

Is this true of the N/A cars as well? That the pump is getting less then nominal voltage?

 

yeahi have a na ..

 

why did you buy a walbro for an NA? it'll probably be supper rich.

 

Yeh, the stock N/A Fuel pump seems more then adiquate :O

 

cuz the fuel pump was rusted up and not working all that well

 

cuz the fuel pump was rusted up and not working all that well


and shouldnt the ecu regulate the amount of fuel???

 

THe pressure regulator regulates the amount of fuel.
You might be overloading it (Causing the car to run rich), but I dont know how much our stock PRs can handle.

You're probably fine

 

thats what i think to

 

i found a walboro 255 for 60 bucks is that a good price? and is there a write up for the install and does it need to be rewired as said for a t2?

 

i paid 95 shipped for mine.. i cant tell how i like it yet , the car wont be able to start till sat when the rest of the parts comming

 

Dude, $60 for a fuel pump is fantastic. Usually fuel pumps dont need any special wiring, and pop right in where the other pops out. I dont know the walbro tho, but it will probably be the same as all the others.

 

Read the how to at www.1300cc.com/howto/how2/rewire.htm. It explains why rewiring is a good idea and how to do it. Note that if your car is a S4 NA (you need to tell us these things) the rewire is different and much simpler.

No, the full rewire keeps the system that drops fuel pump voltage at low load. There is nothing wrong with that system and there's no good reason to bypass it with a stock ECU. If you do, you simply get richer mixtures when you don't need them, and that does not make an engine healthy. The rewire is to reduce the voltage drop that occurs through the factory wiring, particularly when the electrical system is heavily loaded, which reduces fuel flow at high engine load.

S4 Turbos and all S5's drop fuel pump voltage at low load. Only S4 NA's don't. All cars suffer from voltage drop from the battery to the pump simply because of the stock wiring. People have been rewiring electric fuel pumps for this reason for ages.

That pump is total overkill for an NA. I wouldn't use it. Look for a stock replacement, as it has proven sufficient for all but the most seriously modded NA engines.
No, the ECU only controls when and for how long the injectors open. It has no control over the other things that dictate how much fuel actually gets injected, like injector size and fuel pressure.

It doesn't actually. It only regulates the pressure differential between the fuel rail and the manifold. If you increase the upstream fuel pressure, the rail pressure will increase by a similar amount. The ECU has no idea that pressure has changed, so it opens the injectors for the same length time it normally would, and the result is richer mictures.

 

Are you sure that the regulator woulnt handle it? As I saw it, the regulator just keept the rail at a certain pressure level, letting anything over that level return to the tank.

 

Put a fuel gauge on your fuel lines. Observe the pressure with the car fully warmed up and at idle. With the car idling, depin/disable pin 3D on the ECU. Look at your fuel pressure.

Now you won't be confused about whether or not going from 9volts at the pump vs battery/alternator voltage at the pump will/will not make the fuel rail pressure rise/fall.

 

Ah, I've got an FD fuel pump in right now (It was lying around and my old one went bad, I dont consider this a prefomance mod...) do you think that I'm running richer then before now?

 

The FPR's job is far simpler than most think. All it responds to is manifold pressure, because the only thing it's required for is to keep a constant pressure differential between the fuel rail and the manifold. This is to ensure the injector flow rate stays constant. It's not like say the oil pressure regulator, which simply caps oil pressure at a certain level.

So fuel pressure is kept a fixed amount above manifold pressure, in our case ~37psi higher with a stock pump and FPR. If you put a fuel pressure gauge and manifold prssure gauge next to each other you'd seem the fuel pressure gauge following the manifold pressure gauge's movements almost exactly.
Yes. A bigger pump will always have more flow and pressure, not just one or the other.

 

same reason the 5psi wastegate runs 15psi when you stick a 3" exhuast and intake on. there is more flow then it can handle and divert.

 

Scott's analogy is a good one. FPR's and wastegates work in a very similar fashion. They attempt to regulate a pressure level by bleeding air or exhaust away. If either are too small, you get too much of what you want. An undersized wastegate gives too much boost and an undersized FPR gives too much fuel pressure.

 

Are there any other adverse side effects other then me just running rich?

When I get my ported intake on with its working aux ports, and finish my exhaust work, I plan to take it to a dyno to get the S-AFC tuned, so that should fix this, but untill then, any idea of a baseline of HOW much I should dial the fuel out? (That was quite the runon)

 

In the short term you'll be fine.
Don't guess, just wait until it's tuned properly.

 

how much do the walboro fuel pumps cost and are we talking about intank pumps or the inline pumps?