mixture problem
Turbo Mini Forums

Hi!
Today I started profiling my needle. I made a lot of progress, but it's not perfect.
The engine is a metro-turbo unit with New Mini supercharger blow thrue an intercooler and a turbo-hiff44. I installed a recirculation valve (blow off valve) that blows of when there is a vaccuum in the inlet manifold. I use a lambda-sensor to watch the mixture.
The following is the problem. I have a lean spot when going from cruising to part trottle, especially in high gears. I think is has something to do with the blow-off valve. When enough vaccuum dissapears, the valve closes and suddenly there is a lot of air. What section of the needle do I have to grind down?
Regards,
Remko

Hi,
Try a thicker oil in the dashpot....
Maybe a stronger spring?
Cheers,
Gavin :)

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I use SU oil at the moment. Don't know if its thick or thin..
What oil should I try?

fit another spring in there, (double up)

try a thick 20/50 oil like a valvoline vr1 ,that cured that prob for me .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

If the blow off valve is used to recirculate boost to upstream of the blower, it may need a softer spring in the valve to allow a better transition from off boost to on boost.
Just a thought before you overdo the needle.
Regards
Dave

Edited by danboy on 15th Dec, 2007.

Have you got the part throttle lean off pipe connected on the carb?

In the 13's at last!.. Just

Edit: answered wrong place

Edited by Jason G on 16th Dec, 2007.

Did you find this?

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

If it leans momenterily then picks up the oil is the best bet and SU oil is a bit thin so 20/50 will help. if it leans with light accelleration and stays lean try stations 7/8. When I did it I found I was zeroing in on the cruise (stations 2-6) full throttle (station12) polish and I didn't spend enough time on 7-10

In my view double springs are only really needed for high boost levels and whilst blocking the leanoff pipe does change the mixture in the end you can make it work either way by polishing the needle to suit.

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Thanks for all replies, I've tried all your suggestions, but nothing works.

I read somewhere that the problem can also be in the balance pipe. Can anybody tell me more about that? How does the balance pipe work. Can I adjust it, or do I just have to plug the 2 tubes?

It might have to do something with the blow off valve. It's impossible to drive a constant speed, it goes lean. When i'm off trottle (blow off valve opens completely)it goes well, i'm decelerating at that point. When i'm on trottle (blow off valve closes) it goes well to, i'm accelerating at that point.

Any suggestions?

Regards,
Remko

remko , it may be worth checking your fuel pressure regulator ,see if the diaphragm inside has a split in it ,also ,check to see if the fuel pressure at idle is around 3 to 4 psi .
regards robert

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM