So oneday I felt like giving the car a push and it ran real good on 15 psi, next day I though I'd give it a push on the highway hit 15 psi AND my A/F ratio gauge said lean, very lean... I felt no power from the car, when on around 13 psi it ran richer, 1 bar on rich on the A/F gauge. what could be causing this problem. It's only when it hits 15 psi this happens

The FPR is working just fine at 2.5 bar I've ran tests on this. It sat on around 65-70 psi.

Stock injectors and fuel pump


Mods:
TiAL 38mm
LINK Afm (I have upped the fuel in the zones where theres no fuel and no changes, so the computer isn't the issue.)
Venturi delete
New vac lines
New head gasket
New intake gaskets
MBC on 15 psi
Guru racing chips which have been ran on 18 psi (by OZ 951)
New fuel filter which has done around 5000 miles


Anyone know what would be failing at this point? injectors? fuel pump?

- Paulyy

 

You need a higher FPR, and bigger injectors...

Right now the injectors are your limmiter, followed by the FPR..

55Lb injectors and a 3 bar FPR are a good start if you are elevating the boost, the reason you see no change when adding fuel to your map is the injectors are already at 100% duty, you simply can't get more fuel into the motor using your setup.
3 BAR will get you a LITTLE more, but not much... 55Lb injectors are almost 50% larger than stock!
Also look to replace your fuel filter, and possibly down the road look for a fuel pump, but in all reality the 55lb injectors and posibly 3 bar FPR (or adjustable) should get you where you want to be..

FWIW here is a quick calculator... if you plug in 250HP, 4injectors, .7 BSFC, and 1.0 duty cycle, you will see the flow rate on the injectors REAL close to the stock 951 injectors... (32Lbs IIRC).. lower the duty cycle to a more reasonable level (.8 or below) and you will see the injector size jump up closer to 50Lb...

http://www.injector.com/injectorselection.php

 

but its been on 15 psi for a while and no problems,
i though this was fine on stock fuel system with 95% stock engine (k26/6 stock head ect)

fuel filter is like new, only replaces it 5000 miles ago if that,

you think the injectors the injectors could be running 100% duty? even though it wasnt doing that 2 weeks ago?

 

Guru chips were designed to be run with a 3bar FPR.

 

No, not without a significant change in something (such as weather - did it drop 50° lately?).

I don't understand your test for the FPR - can you tell us again your testing method and results?

 

nop, just **** cold weather in melbourne, Australia.

well what i did was i got a ball pump, spair vac hose, T piece & a pressure testing gauge goes up to 15 psi. i connected the ball pump and the gauge to the t piece and the other end of the t piece went to the FPR, i put 15 psi of pressure on it and the FPR gauge hit 57.5 psi. i put abit more pressure it to max the FPR out and hit 78 psi.

i know the FPR is 1:1 with pressure also,

 

Ok, well if it was fine at 15 psi and now its lean then there is a fueling issue... Or - you are measuring AFR with a WBO2 correct? NB are extremely suspect at anything besides stoich.

 

I am using a NB A/F gauge at the moment, a WB02 was used for tuning. when i hit 15 psi on the NB02 the gauge literly just hits the last red led light and you feel the car not going anywhere. its like the boost was pushing the cylinders along.

 

Have you pulled the plugs yet? You could be misfiring, which will appear as a lean-condition...

 

not yet, if i was misfiring, wouldn't it make a popping noise?
if i where to pull the plugs, how whould i check if its misfiring?

 

Not necessarily be popping...
All the plugs should look the same/similar, not damaged, and not carbon fouled... Also the gap should be within spec as well. I think JohnKoaWood posted a picture of plugs earlier - I'll see if I can find it.

 

il go check the spark plugs right now and see how they are

 

spark plug leads. are they the same as the 924s leads? because i need new ones, one of mine are broken

 

The 951 plug-wires should be the same as the 8-valve NA (944, 924S).

 

i just bought some new ones, 8.8mm TopGun leads. new spark plugs, il get the leads in by tuesday so i wont be able to test the car untill tuesday, unless my dads 924 leads will work on my car?? for the time being