The tuning thread

Started by 94touring, October 16, 2018, 11:37:22 AM

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jeff10049

impressive that a small chamfer like that made a noticeable difference. How much did it lean it?

94touring

A solid half a point through various parts of the powerband.  I've been having to experiment with different spring weighs to dial in my high cruise.  The difference from blue to yellow is 15-16 afr to 14.5 afr at high cruise.  Effects idle significantly too.

94touring

Had my carbs off today fixing an idle issue.  What I discovered was the piston at full lift hangs into the airflow a good 1/8 inch. which explains why the bevel job works so well. 

Back to needles as a result.  Initially after the build I was using aak needles with ok success but it was a tad lean at cruise. Well I had bought aaa needles which was WAY too rich. To get it to run I had to lean the jets so much it wouldn't run at idle. Fast forward past port matching, vizard mods, and the latest piston chamfer, and guess what, the aaa needles now work the best out of my pile of needles! 

94touring

One last air flow mod to be made.  The little guide that rides along the piston sticks down into the air flow at max piston lift.  Cutting about an 1/8" off gets it out of the flow and still provides piston guidance.

MiniDave

Better watch it, you'll wind up needing different needles again!   :D
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

I've bought so many needles it's almost embarrassing lol.