Morning all, Just a quick question. I've been looking thru numerous threads trying to find the max power standard sti V6 440 injectors can handle before maxing out. So far I've read different information, some have found around the 320 bhp mark and other around the 350bhp mark with various supporting mods?

So my question is will standard 440s with the right supporting mods handle the 350bhp mark ok, or will it be pushing them a bit and I need to upgrade to 550s?


Cheers
G

 

At standard fuel pressure (3Bar) i got 310bhp @ 100% IDC

If you raise the pressure to 3.5 Bar atmospheric, you can up the flow to approx 480 cc/min, and squeeze a bit more from them

 

Or 4 bar they're more like 505cc

I've seen 320 at std pressure and 342 at 3.5bar on the same car (but different mods) with a little headroom, but not enough for comfort.

Andrew...

 

Forgot to mention I'll be using an Aeromotive fpr and a walbro pump, so the pressure will be running higher than the standard fuel pressure.
I was hoping for around the 350bhp mark, but am unsure if this would be pushing standard 440 injectors to their limit and significantly reduce life expectancy.

 

320BHP, standard pressure and 97% IDC at 7,000rpm approx.

 

Rough idea of outputs..

 

speirsy, even at 4bar differential fuel pressure you will be well over 90% IDC with 440s to make 350bhp, one or more injectors may well be fully open causing flunctuations in AFR.

Nice spreadsheet Alan, is that using BSFC of 5.5 cc per minute/bhp ?

 

Scott,
The spreadsheet says that 380's max at around 276BHP. This is about the power output of your scoobyecu's as I recall. Are the stock scoobyecu's limited by the injector size on the early classics or something else? Also is it possible to raise fuel pressure with a correctly mapped scoobyecu?
thanks
will

 

All, thanks for all the helpful comments and info. Alan cheers for the graph too, well handy. Possibility I may have to move to the 550 sized injectors to make my 350bhp target.

 

I've seen just over 300 with some late pre-facelift WRX and STi, but these had full decat, headers and increase fuel pressure IIRC on 380's.

The main limiting factor on the Pre-facelift is the small slanty intercooler.
Once you get rid of that the injectors would be the next stalling point. From here on in something like an apexi pfc is a much better tuning tool.

 

That sheet provides guidelines, not definitive results, so don't look too deep into them and expect to see power results based purely on IDC and fuel pressure. I posted because it was coincidental that results typed on previous posts were pretty close, so thought it may be beneficial.

There are many variables that can affect power output as you know, but there's other things like type of fuel and what AFR you're running which can affect "estimates" based on IDC.

borat52
Not all import Impreza's came with 276bhp, but also, bear in mind the claim of 276bhp is based on higher octane fuel than we have available in this country, hence why a lot of people run the highest octane we have, plus octane booster, to save engine damage or re-mapping the ecu. You also have to take into account what static fuel pressure the car runs as this also affects what power output the injectors can provide.

Andrew.

Yes based on 5.5cc. It's proved to be pretty close against my results to date, though i haven't got a dyno result since last year.

 

How does turbo boost pressure affect the total inj duty? i mean what sort of boost could be possible with 550cc injectors running at 4 bar pressure? because im told that my 550s are maxing out at 1.45 bar on a 20G can this be right?

 

Depends on interpretation of "maxxing out".

Some reckon anything above 85% IDC is as good as fully open, so you could say generally they are "more or less" "maxxed out".
Certainly at 85% and above, you don't have much leeway if you want to tune further and leaves little room for error, so either more fuel pressure or bigger injectors are the way to go, though i wouldn't run more than 4bar static personally, i'd go for bigger injectors.

At 85% IDC on 550's at 4 bar using the formula above that gives a figure of 393bhp, which is ballpark to what a 20G gives.
90% is 415bhp.

As for what boost to run, this will be determined by engine build, plus what AFR can be run at peak bhp/revs. You could run more boost in the mid range (engine dependant) but the limitation at the top end of the rev range will be dictated by being able to supply enough fuel to meet the airflow requirements.(along with the engine being able to take it) and also the efficiency of the turbo.

 

And to add..

If you're running 1.45 bar and see 100% IDC at peak power/revs, then if you ran only 1 bar of boost, you will not see 100% at the same point because the engine is consuming less air and hence using less fuel.

 

What a long winded reply to say that more boost will require more fuel...

 

cheers Alan

 

Just seen your post on 22B. You also need to take into account what AFR you're running when looking into IDC's.
Like for like, a richer mixture will show higher IDC's.

 

As said on my text Grant, i seen my 380's maxed out with a similar setup, on my old RA which was about 320-330hp. Ok, i was fairly playing with OB and fuel pressure, but Andy will be able to do some digging around in your ECU.




I reckon they'll be ok on the TD05, but yer, if you decide to go further later on, i'd defo suggest getting ones with a bit more guts.

 

Took me frikkin AGES to find it, but if this car is anything to go by, you'll be fine....
https://www.scoobynet.com/drivetrain...injectors.html

 

iirc my afr is 11.3 on full boost

 

OK phase 1 380's I had first, these were fuelling fine for 1.4 bar of boost but getting well over 90% IDC range at full boost. I swapped them for yellow topped 440's and they cut the IDC right down to below 80, they are totally cruising at 1.4 bar and roughly 300bhp, mapped by Zen on a Power FC. When Lateral tested them out they flowed an easy 500cc at standard fuel pressure IIRC.

 

Interesting,so my 550s running at 4 bar pressure should be running in excess of 650cc allowing me to run at least 1.5-1.6 bar of boost on a 20G unless as Alan says the car is mapped too richly

Sorry i took this a bit off topic

 

Some intresting points and information raised thru the thread. Bloody hell Dave thats an seriously impressive power torque figure from Rich Wilds car
running standard with injectors and ecu

G

 

scooby-tc

Is the 20g an efficient turbo at 1.6 bar at peak revs? No point in running high boost if the turbo is going off its' efficiency scale i.e. if it's not efficient then it's creating more heated air (whereas air temp is lower in the turbo's peak efficiency zone) which doesn't help to produce power.
Sometimes it's better to run at a lower, more efficient boost range and run more timing.