KRM

Reading some of the posts about RA's and the 5th injector it appears it does nothing??

Looking at buying an STi 2 RA in the near future and was just wondering why on earth subaru would have fitted it for no reason Is the fuel pump any bigger to cope with the extra injector or is this maybe why it's not in use?

David_Wallis

for rally teams, so they could switch it on in the ecu, probably like the antilag thats also fitted.

David

KRM

It's got anti-lag that's not switched on too?

Why wouldn't you have these on by default? I'm a bit new to turbos

Turbo_Steve

Cos anti-lag shortens turbo life.
The more aggressive the anti-lag, the shorter your turbo life.

Why use a 5th injector when you don't need to?

The idea behind it is that the road-going STi simply uses road going software almost identical to the normal spec car. Makes fault finding much easier at the dealership, don'tcha know.

The rally teams take the car, stick a couple of software changes in and bingo. A fully tuned up rally car.

Katana

But we've got a cunning plan don't we Steve?

scoootie5

If ya find out anything about the 5th injector I would like to know as I also have one dormant under my bonnet.

Cheers guys
Scott ;-)

Turbo_Steve

All depends how you wanna USE that injector.

Watch this space.

scoootie5

Ok thanks,

I would think I might be a good idea for it to come on under high boost conditions, or only a WOT , maybe RPM related...

Made me think about if the RA's have a larger fuel pump or not, to cater for the 5th injector, or maybe the rally teams would change this too.

Got me thinking

Cheers
Scott

Katana

I'd replace the pump with an uprated one even without the fifth injector.

jonny gav

iTrader: (1)

katana- have you got a walbro pump fitted???

if so what are they like to change?

Katana

Its a straight forward job mate. Take the back seats out and remove it from the boot. Its the big plate on the right. Remove the pump, splice the wiring in the new pump and stick it on.

Its easy but me being paranoid with fuel, had to get someone else to completely check it in the end. I've got this phobia with fuel tanks after this video that I saw.

jonny gav

iTrader: (1)

cheers mate

would have done it today if it wasn't pi55ing down

Turbo_Steve

Remember an injector isn't just "ON" or "OFF" you need to trigger it repeatedly. And of course, like all things it has a duty cycle. As it averages the amount you inject between all four cylinders, you need to think about it's duty cycle in direct relation to the amount of airflow thru the manifold and the duty cycle of the existing injectors.

Kat is keen on running an additional computer to let you map the injector, which is a brilliant second best soloution to actually using the ECU software. However, you could do it using some very simple electronics too, though it would be VERY unscientific, and John Banks would kill me for abusing the car in such a way.

john banks

LOL no I wouldn't, but you would need to check you needed the fuel in the first place, and intelligently and smoothly taper in the 5th injector when you needed it. Not sure how good the overall fuel distribution would be from a single point of additional injection.... why not raise the fuel pressure or use four appropriately sized injectors?

Also bear in mind that you can have plenty of fuel about and it doesn't stop the engine blowing up. Is there a fuelling issue with what you want to achieve or are you more likely to hit a detonation/thermal management issue for other reasons?

Turbo_Steve

Oh, and you REALLY wouldn't like my 'simple electronic' way of getting it working. More primitive than...a..um...

john banks

Was the first build because you were running too much power (well tuned) or because it wasn't tuned properly or because a component failed?

You can make quite good use of 550s at sensible fuel pressure at 350 BHP, this may or may not mean you need a rebuild depending on how lucky you feel and how careful you are about det?

Turbo_Steve

It wasn't anything to do with det!
I had had the car about 2 months and a big end went.
Went to dealership who wanted £4000 to fix it.
Scoobysport did it in the end for half that price, and changed the (knackered) clutch too. If I knew then what I knew now, I'd have specified STi internals, but I was unemployed at the time, and nearly wrote the car off!! Am glad I didn't. Just had to cough up £1000 for a new gearbox, so a rebuild definitely isn't on the cards.

Reason from dealership "Wrong sort of oil". =shrug=
That and the gearbox have pretty much blown any tuning budget I ever had. Now I am tuning it as cheaply as possible. After all it is worth less than £2000 now.

Turbo_Steve

John, you give such good answers.

I had assumed that the 5th injector was either for ALS, or was placed where it was BECAUSE it gave adequate dispersion. Though of course I have absoloutely no knowledge of these matters.

I would personally go for larger injectors too, but once you get to 550s you need to go internal before using them to their full potential.

I've already had one rebuild. Another one to put uprated bits in would just be too expensive.


[Edited by Turbo_Steve - 3/4/2003 4:08:32 PM]