silent running

As the title says really - what's the better option; swapping my 440's for 550's or fitting a decent adjustable fuel pressure regulator and moving the baseline setting to 3.5 or 4 bar? This is on a Power FC with Walbro pump already fitted.

SSCJAY

I have been told by various sources to use bigger injectors and lower the duty cycle, as opposed to smaller injectors running 90+% duty cycle with higher pressures, also running higher fuel pressures can lead to premature failure of injectors.

Jolly Green Monster

iTrader: (4)

what turbo you intending running?

will be able to tell then whether there is a hope in getting enough fuel or not..

I don't like running 4bar on standard hosing.. 3.5bar is fine.

Simon

silent running

VF35 (currently around 90% at 1.4 bar boost) to TD05H-16G. I guess it's more that I've got a good set of 440's in at the moment on the standard regulator that have been tested as flowing 500cc at 3 bar, 550cc at 3.5 bar and 590cc @ 4 bar.

I don't want to spend a lot of money so if I go for a set of pink 550's they'll be a new set from the States for £150 delivered. I don't know what sort of quality they are though - different manufacturers make injectors that look the same on the face of things. Better the devil you know in other words - I know my 440's work well at present and I know that upping the fuel pressure will work well also. AFAIK the difference in outright flow is roughly 450cfm for the VF35 vs. 520cfm for the TD05H-16G so a good 10-15% more airflow, presumably needing 20% more fuel flow to be on the safe side.

550's would give me this; so would a 0.5 or 1.0 bar increase in fuel pressure. And the tiny standard regulator is about the only thing left on the car that I haven't already busted and replaced, so it's kind of insurance as well to replace it now while I've got greater fuelling in mind.

Jolly Green Monster

iTrader: (4)

I'd go with a decent fuel pressure reg on that setup (fuelab, SX, aero etc).

standard injectors and standard reg with a walbro pump is about 1.3 to 1.35bar on a TD05 16g.. each car and setup varies very slightly. The fuel pressure reg will give you the extra head room.

The pinks you mention I believe you are talking about top feed injectors which won't fit, you would need side feeds.

Simon

silent running

Cheers Simon. The ones I'm looking at are here eBay Motors: Subaru 550cc INJECTORS EJ25, EJ20 STi,WRX Old style (item 120110253672 end time May-17-07 10:52:43 PDT) I know, it's an ebay link, but strictly for academic purposes! The seller has been in touch and said they are brand new, pink bodies with blue baskets, definitely to fit mid 90's Imprezas and made by Venom who seem to be a proper company over there in the States.

When you say about a decent regulator, does that include the SARD? Obviously I'll be careful about getting a genuine one, but it would be a lot cheaper than the full-on Aeromotive style and just uses standard 8mm hose rather than AN dash fittings.

SSCJAY

If you don't mind buying in from America the Aeromotive option is not that expensive, I've got an Aeromotive 13105 (Cost £100 with shipping), all you would would need is the adaptor for the end of the fuel rail (about £10) a small length of Braided hose and 2 -6 hose ends approx £30.

silent running

No, no problems buying from the States, that's where my TD05's coming from.

Jolly Green Monster

iTrader: (4)

I have had several problems using venom injectors.. unless they have improved ten fold in the last 6months I would avoid.

Simon

P1Drifter

iTrader: (7)

just to let you know i got some of those (arrived today actually) and there not direct fit, the connectors dont match up, im hoping with a little trimming and the odd bodge the might tho. Havent tried the actual injector yet and wont be for a little while, il let you know how i get on.

silent running

Sounds like they're not as plug n play as I'd hoped. Cheers for the feedback! As they were the only ones I was looking at because of the good price, that means I can focus on the adjustable FPR route rather than the injector swap.

Wonder if it'll be worth reversing the fuel flow while I'm hooking up the regulator anyway?

Jolly Green Monster

iTrader: (4)

yes it is worth reversing the flow direction.. fuel filter to number 3 etc...

Simon

Ian

iTrader: (10)

can you tell more about this, what are the gains etc?

silent running

OK doesn't look too tricky. Will it make any difference to the operation of the regulator if the vacuum line has to be long (the standard one is very short indeed) or if I take the vacuum signal from somewhere else on the manifold? I'm probably going to mount the FPR on the bulkhead unless it'll be noisy there.

Jolly Green Monster

iTrader: (4)

no gains just cylinder number 3 gets fuel first.. number 3 possibly runs hotter due to turbo heat and in the normal fuel flow gets fuel last..

just trying to ensure things remain hunky dory.

Simon

Jolly Green Monster

iTrader: (4)

yeah that will be fine (the vacuum line).

There will be noise from the reg.. although rubber mounting it may help reduce it.

Simon

silent running

OK all the help much appreciated. That's the next few weekends all sewn up then LOL