please help, problem with wideband's

[TurboBrett]

i am wondering if anyone could help out with a problem one of the guys on my Mini club has stumbled across, i have posted his thread but i will edit parts to get rid of the 'mini short hand'

 

I've been thinking about how widebands work and how they respond when fitted on an A-Series or other 5 port engine.

 

My testing of both carb and fuel injection with a wideband on each LCB leg has shown that the AFRs can be vary by as mush as 3 or 4:1. For example, a carb at idle will give 14:1 on the inner cylinders and 17:1 on the outers.

*LCB term given to a mini's tubular manifold 'long centre branch',

So what does the wideband tell you when fitted after the LCB Y piece or after the turbo?

*Y piece is where the the 2 connected outer branches connect with the LCB

Widebands work by first of all looking for oxygen in the gas with an integral narrowband sensor. If the narrowband measures oxygen, it thinks that the mixture must be lean and measures the %tage of oxygen (O2) in the gas and calculates the AFR.

 

If the narrowband cannot see any oxygen, it decides that the mixture must be rich and measures the %tage of unburnt hydrocarbons (HCs) in the gas and calculates the AFR.

 

So if the inner and outer cylinders are both running rich, the wideband will give an average value - yes?

 

Likewise if both cylinders are running lean.

 

But what does it do when the outers are running lean and the inners are running rich? It can't give an average because it will sense oxygen and therefore indicate a value above stoich.

 

Say the outer cylinders are running at 15.7:1. It will, presumably read 15.2:1 because the percentage of oxygen in the gas will be halved by the inner cylinders.

 

No matter how rich the inners are running, the wideband will still read lean.

 

Crap or what? Have I missed something?

 

any one any ideas?, does the wideband sensor read like that?

anybody know of any problems relating to this?

 

thanks alot, i am just trying to get idea's together to help solve the efi problem with mini's:D