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View Full Version : Yawn, another fuelling question....


bigdur
20-09-2011, 21:09
Sorry guys, it's another carb question, I've got my 2nd stage drilled out to 1.4mm with a 0.9 AC, was still running a bit lean up the pod in 4th.

What else can I do? I have a vague memory of one of you helpful chaps saying I could 'shim' the spring but I'm not 100% on exactly how. Don't slap me but would a 130 main help?

Here is my current carb setup.
1.2mm main jet
0.9mm air corrector
1mm 1st stage
1.4mm 2nd stage
0.45 idle jet
0.4mm acc pump jet
2mm needle valve
Markey Mark (BD)
20-09-2011, 21:13
I'd poss start looking at condition of fuel system mate, pump, filter and the regulator, check if its all ok and suppling enough fuel. Your carb spec doesn't look too bad for a fair bit of boost.
bigdur
20-09-2011, 21:15
It's the old Boris/Jesus shell and IIRC Jesus was running big boost. :crap:
bigdur
20-09-2011, 21:16
We had to back it off to 20psi at the pod to stop it leaning Mark.
Markey Mark (BD)
20-09-2011, 21:19
I'm just wondering if pump is getting little lazy
bigdur
20-09-2011, 21:21
Where is the FPR mounted Mark?
Mart
20-09-2011, 21:22
Measure fuel pressure at carb inlet @ wot, then decide if it's a supply issue (sounds more like it) or jetting.
Markey Mark (BD)
20-09-2011, 21:23
Its down on the bottom of the drivers side chassis leg mate, just under the brake servo
bigdur
20-09-2011, 21:27
Ok cool, I've nothing to measure it with though. I might try and find a malpassi and change that first. Anyone point me at a nice cheap gauge? Is there one on the market which can be left fitted for regular checks? I do worry about running lean once I get to a track.
bigdur
20-09-2011, 21:27
Its down on the bottom of the drivers side chassis leg mate, just under the brake servo

:agree:
Mart
20-09-2011, 21:28
You can use a boost gauge if needs be. Just be careful & make sure the gauge doesn't leak!
bigdur
20-09-2011, 21:29
Do you just put a T piece in temporarily near the carb then?
Mart
20-09-2011, 21:37
Yep, on the pipe running between the fpr & carb inlet.

Ideally you want to be seeing ~4psi more than boost pressure at all times.
bigdur
20-09-2011, 21:42
Christ, my old boost gauge won't go that high lol, do you know of one which can be mounted in car? In otherwords something fit for purpose full time?
Mart
20-09-2011, 21:46
If it's full time fitment, play safe & get a dedicated fuel pressure gauge.

If it's for temporary testing, and assuming you're running ~20psi boost, a normal 2bar/30psi scale boost gauge will do the trick.