Just aquired a Power FC and before I get it fitted/mapped I'm gonna replace my fooked Lambda, plus fit PFR7B plugs, all but new Walbro fuel pump... and a decat, naturally. Do I need to fit a fuel pressure regulator too? Or is the OEM one perfectly up to the job? (PFC will be running at 1.1bar, I think?)

If I do need one, what's the best one, prices, where, etc...?

Thanks, John.

 

The safe and sensible answer to this is yes. Walbro's have been known to over power the standard reg and let too much fuel back to the tank and worse case scenario is a melted piston. This happened on mine.

For peace of mine I'd get an uprated reg, SX, Aeromotive or Fuel Labs etc. Just stay away from the FSE ones they're pants.

Aeromotive Fuel Pressure Regulator Impreza 99-00 Flat4online.co.uk Subaru Impreza Mitsubishi Evolution EVO Walbro Fuel Pumps Injectors Intercoolers

This is a good price the whole kit.

 

Cheers daz - that's a sobering thought!

Would one of these ebay specials be okay - or is there a reason why they're that price?!...

Adjustable Fuel pressure regulator skyline Subaru 200sx on eBay, also Engine Tuning Parts, Performance Tuning Parts, Car Tuning Styling, Cars, Parts Vehicles (end time 29-Mar-08 21:42:50 GMT)

Cheers, John.

 

well im running 1.4 bar (peak) on a uk turbo and hit 340bhp, and had no probs not running a FPR, so don't thik its that much of an issue

 

I take it you have a Walbro pump, though? Or is it the OEM one?


What's the OEM Subaru regulator's steady-state PSI level and, in any case, would it be able to cope with the demands of the Apexi PFC running boost at 1.1bar, in harness with the Walbro 255l/m fuel pump? This is the crux of my question...

 

yeah i'm runnning a walbrough.

it wont hurt to have one, but its not a deffinate you need one.

it will need mapping, but 1.1 bar isn't a massive figure to acheive boost wise anyway, so you wont be putting any mega strain on the fuel pump

 

Cheers. I thought (hoped!) that'd be the case

 

looking into fitting an fpr on mine very soon.

 

but you cant mate, your running 450bhp, so you must have one??????

 

still have standard fpr at present.

 

lol

 

and maxed out the injectors, hence why it is being discussed.

 

Which is great until it fails then you'd wish you'd spent £200 on a reg instead of £3k on a rebuild

Incedently mine was UK turbo running with funnily enough 340bhp at the time it failed.


Bottom line is some standard regs fail with a walbro some don't. For £200 you'll have complete peace of mind.

£200 on a reg for or £3k on a rebuild the choice is yours

 

That's as transparent as it can be! Makes utter sense to invest in one, then...

 

Here's what happened to my piston when my walbro caused my standard reg to fail.







Personally mate I wouldn't buy the cheap one from e bay.

 

is it definate that the pump cause the fpr to fail? how can you tell

 

not sure how the pump could cause it to fail

 

could in theory overpressure the fpr, but would have had to be an issue further to that to make the pump push to hard, they arn't as simple as on or off afterall are they?

 

As Daz has already said Id defo fit a Fuelab or SX regulator for piece of mind.

 

I could be wrong on this but I thought the pumps were fairly simple things i'e they deliver a constant rate of fuel. Its the reg that contols the rate of return back to the tank.

If you think about it the reg is control the fuel pressure of everything before it. ie, injectors, filter , pump.

The Walbro overpowers the OE reg the reg let's too much fuel back to the tank. The injectors then can't get enough fuel resulting in atleast one lean cylinder.

I remember the exact moment mine failed. I was nailing it 4th gear then 5 th at about 130mph 1.5bar and a sudden slight loss of power.

It was then rebuilt with parallel rails 740cc and an SX reg, 500bhp now with no fuel problems on the same fuel pump.

The 440's were tested before they were sold on and they were spot on.

The only thing it could of been was the reg and it was 1 of the cylinders on the same side of the reg that had the damage.

It wasn't a mapping issue as it had done near 20K miles in this state of tune before it went pop.

Cheers

Daz

 

as far as im aware the pump isn't a simple on off thing, flows to different rates.

the fuel reg's supply all cylinders not just half, so in that case it can't have been the reg causing the failure.

a slight missfire could have done it, at that sort of pressure any number of things can cause a piston to go tity bollox.

 

right done a bit of digging around.

the fuel pump is ye old simple thing and does just flow or not.

the FPR controls the rate of the fuel flow, the reason for the upgrade is cos the normal one is a fixed thing, so if you need to up the flow beyond a certain point then you will need one.

the only way to find out if you need one or not is when its mapped, so just saying it needs one isn't true.

for the level of tune, 1.1 bar you wont need one, the flow rates wont need to be high enough to make it a requirment

 

Id put the line at say 330 - 340bhp, anything over that Id prefer to have one on the car.

 

thats pretty much the 440 standard injector max out point, but there are better ways to increase power rather than just upping the pressure in the system

 

the next step is to change injectors for higher flow units.

It depends on what your requirements are.

Scoobypedia | Trusted knowledge for everything Subaru | Knowledge / Estimated Horse Power from Injectors

 

true, but building in high pressure, for the sake of it, is asking for trouble.

high pressure systems, fuel, water, or even structural buildings (my line of work lol) tend to fail, or be a much higher risk.

personaly i don't think its the best option, unless there is no choice.

and in this case, don't think its required

 

you dont need to up the fuel pressure by much to increase the volume through the injectors, see table above.

 

Ive ran 440s at 350bhp at 3.5 bar fuel pressure.

The reason I said to change the reg wasent for power gains or to allow the injectors to flow more, it was incase the standard regulator struggles to do its normal job of maintaing pressure. A fuelab or SX is more reliable IMO.

 

i am running 340 on 440's and have fueling left.

but were nto talking 1.4 bar, were talking 1.1 bar, which if im honest, not even sure if he need's to change the fuel pump anyway

 

His car is a 1993 so I reckon the pump might be a little tired, If its being mapped id change the pump no matter what, even if the pump was only a couple years old.