A/F ratios
Turbo Mini Forums

Hi,

I have plans for installing tbi system (custom one) on my mini, but for now I just need to tune my needle...what A/F ratios should I aim for in what rpms...let say from 1000 to 3500,3500-4500, and 4500-7000...? The car has 8.2:1 CR, avonbar phase 3 cam big intercooler and it should run from 0.7(9psi) to 1.2 bar boost (16psi)

best regards,
Tonci

Rich all the way, you will see that Mini does not idle well with lean mixtures like today?s cars do so you will have as much as 13,5:1 - 14:1 at idle. From there one it is getting gradually richer, richest at max torque revs and just about the same from thereon. Depending on A/F meter my engine stays rich all the way. The lambda sensor voltage is around 0.85-0.88 V.

Jukka

My A/f is 12:1 when being driven hard, is this about right??

Team Racing

12:1 is about right on a turbo... its a touch rich but that will help keep the engine a bit cooler as A-Series arn't the best at cooling!!

Too rich thou and you loose power...


Alex

AlexF

Tonci,

When i was involved with the EFI A-Series - i got very strange results from the Lambda (positioned in my turbo elbow) when i was getting charge stealing...
I guess (now) it was seeing a combination of unburnet fuel, from two cylinders and a lean mixture from the two others.
This was obvious, as you could set it steady to read 14:1 at tickover, but if you went near the exhaust, the fumes would make your eyes water!!!
Confirmation came when it was hooked up to a pukka SUN diagnostics machine. The HC's nearly went off the scale, but all the time, the A/F was reading between 13.5:1 and 14.5:1

Be VERY careful !!!!!!
Turbo engines running lean on any cylinders melt very quickly...

Edited by turbodave16v on 18th Oct, 2003.

Be VERY careful !!!!!!
Turbo engines running lean on any cylinders melt very quickly...

Yes I know...I'll try since I allready have ECU and since it is a chalenge...isn't it?

regards,
Tonci

tonci, what ecu do you have?

Team Racing

tonci, what ecu do you have?

I have DIY Megasquirt AVR ECU...this is the link: .. It is going to be tbi system with wet manifold (not mpi like you and Dave are planing to build). I am planing to use std metro turbo manifold with custom tb instead of carb.

Tonci

Sorry bad link here is a good one:

regards,
Tonci