Mixture and Needles
Turbo Mini Forums

Hi Everyone,

I have just converted my road car, using parts I've had lying around.
Very happy with the results so far.

Engine spec-

Standard 1275 with a crosspin diff.
BV head with large ports.
Ive chambered it out myself to lower the cr.
286 cam.
Standard T3 turbo, metro turbo carb and manifold.
Standard flywheel to keep things smooth.

Currently have it adjusted to 5psi and its running really well.

Using a Innovate LM-1 reader and wide band lambda, its running around 12AFR up to 4k.
But at 5 to 6k its heading upto 15-16AFR which is to lean at those revs.

Normally I use a fibreglass bonnet with a hole in.
Remove the dashpot plunger and have a homemade measuring stick through the bonnet to guage where to adjust the needle. Thats on a n/a engine of course.

How to I do this on a turbo carb?
Is it just a case of trial and error?

Also what AFR should I be looking for?
I know 14.7 is theoretically the best, but ive seen tuned engines running 12 or 13.

12-12.5on the AFR is what I would be aiming for.
There is a thread on here how to make a sealed dashpot with stick in it somewhere. If I find it I'll drop the link in here.

If something is worth doing, it's worth doing half of.

14.7 is far too lean on boost. As said aim for 12.5 on boost. Off boost cruising areas 14.7 is OK.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=159683

&

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=231607

Edited by John on 14th Jul, 2011.

If something is worth doing, it's worth doing half of.

I bet that's interesting with a 286.

In the 13's at last!.. Just

If something is worth doing, it's worth doing half of.

You obviusly thought it 3 times!

If something is worth doing, it's worth doing half of.

What needle are you starting with? a standard turbo BDD should be OK with that amount of boost.

Have you got your part throttle lean of connected up or blocked?

Thanks for all the response.
Part throttle lean off connected.

The 286 cam is not to wild, its quite a nice drive. I believe its due to the full weight flywheel.

I have the same cam on my supercharged car, but with flywheel and backplate at under 5kg combined, its fierce.

Will definatly look at machineing/sanding the needle down. Was worried about the lean out, and you guys have confirmed that for me.

Anyone else use the LM-1 air/fuel ratio meter?
I think there great.

Thanks again for all the help!