What Capacity

[jprimera]

What capacity are the p11 primera injectors? can a run safe with 5 psi of boost?

[Anthony]

I believe they are about 260cc, which will probably be OK for low boost applications. For higher boost levels though, you will need at least 370cc units.

[b-b00gie]

The stock injectors should be good for about 6psi, once you get in the area of 8+ you should upgrade.

[jprimera]

[P10DET]

They are 259cc (yeah, I know, what's 1cc?, but just for the record....)

My understanding is that at around 200 bhp you are getting dangerously close to the limit of these injectors. I think you would be wise to switch to the 370cc injectors.

[b-b00gie]

True, at 200hp you should switch them, but you surely arent getting 200hp off of 5 or 6psi are you??


From what I've seen 6psi would only put you to about 180whp.

[P10DET]

Originally posted by b-b00gie
True, at 200hp you should switch them, but you surely arent getting 200hp off of 5 or 6psi are you??


From what I've seen 6psi would only put you to about 180whp.

I was talking about crank hp, so yes, they should be changed IMHO.

You might be able to get away with it, but I wouldn't risk my engine on it.

[Anthony]

If you reach the limits of the stock injectors then they simply won't flow any more fuel and subsequently the engine will run lean won't it? Surely this would stick out like a sore thumb on a dyno, especially as it would probably pink slightly under load. Or will the problems of inadequate injectors be somewhat more terminal than that, like misfiring or cutting out under power?

On a side note, am I right in thinking that in order to use 370cc injectors you MUST get a remapped ECU, else things will start to go very funny indeed?

[jprimera]

it can be regulated with the apex´i s-afc or you have to reprogram the ecu? (370 cc injectors)

[P10DET]

Originally posted by Anthony
If you reach the limits of the stock injectors then they simply won't flow any more fuel and subsequently the engine will run lean won't it? Surely this would stick out like a sore thumb on a dyno...

Especially when it goes BOOM!

Running lean on a turbo engine is a receipe for disaster. You don't want to run out of injector.

[P10DET]

Originally posted by jprimera
it can be regulated with the apex´i s-afc or you have to reprogram the ecu? (370 cc injectors)

I couldn't tell you. I have never looked into it, but I think it's possible. I don't really know for sure though. I think Luke could tell you how to compensate.

[G-Forces]

Originally posted by Anthony
If you reach the limits of the stock injectors then they simply won't flow any more fuel and subsequently the engine will run lean won't it?

IIRC what happens when you reach the limits of an injector, which is around 80% duty cycle, they become static. Meaning that they will stay open constently. So what happens is you're dumping an unregulated amount of fuel into your combustion chamber and on the backs of the valves when they are closed. Which then just pours down into the chamber when it opens. This will contribute to poor burn charicteristics because of the droplets of fuel. If the amount of fuel doesn't happen to be enough for the amount of air then it will go lean and slag your motor. So you'll probably run pig rich for a while then blow up your motor in the higher rpm where even a static injector will not supply enough fuel.

I'm not an expert on this but it's what I've read and I'm taking if from my admitedly flakey memory. So if I missed anything i'm sure someone will clean it up for me.

[jprimera]

I have read that a fuel presure raiser can help any info?

[Anthony]

OK - at least I know what really happens when you reach the limits of the injectors... thanks

[G-Forces]

Originally posted by jprimera
I have read that a fuel presure raiser can help any info?

The problem with the pressure riser is that you'll need some way to adjust the pulse width of the injectors. All you're going to do is shoot more fuel into the chamber, the injectors will still go static and you might escape a lean condition at higer rpm but the car will run like crap under some conditions.