Needle Modifying ??
Turbo Mini Forums

Just fitted my air/fuel meter with 4 wire lambda sensor & have been busy modifying a needle to get the fuelling right.
I'm only running 7psi at the moment but the engine seems to need bags of fuel to go properly under boost, the end of the needle is way thinner than my mates, and he's running 15psi.
I've got it so it goes pretty well, & pulls hard under boost. It pulls strongly up to around 7,000rpm, but does start to miss a little at full throttle as the lambda reads over rich. This only seems to happen in 1st, 2nd and 3rd gear as in 4th gear under full load the fuelling is spot on.
What i can't understand is why the engine seems to require so much fuel for so little boost ?
The air/fuel meter seems quite accurate, the engine always seems to go best when the gauge shows just into the rich. If i run it so the gauge shows a leaner condition it doesn't run nearly as well.
I'm going to check the fuel pressure tomorrow, as i'm wondering about this. Anybody got any other ideas ? things worth checking ?

Cheers
Phil.

WWW.TURBO-MINI.COM

have you modified your plenum restrictor?

No that's totally standard Dave .....
Part throttle lean out pipe blocked & poppet valve removed from butterfly.

Phil.

WWW.TURBO-MINI.COM

What spring are you running?

Also, get a gauge on your fuel pressure (into carb) with a long pipe. Feed it through your bonnet and hold it under one of your wiper arms. Check the fuel pressure at tickover, and see how it increases with boost...

could a different manifold make a difference, with it altering the fuel/air distribution?

Yeah i was thinking that Dave, i have a fuel pressure gauge so i will try it.
One thing i have thought of today is the fuel pipe going from the regulator to the carb, i fitted a braided fuel pipe to this a while back, when fitting it i noticed the ID was smaller than the pipe i removed. I'm wondering if this is starving it of fuel ?

Phil.

WWW.TURBO-MINI.COM