i have a stack afr gauge with the lambda at the top of the downpipe,it reads 0.10 less than a mot gas analyser probe in the tailpipe.
would the afr changed .1 from front of ehaust to rear or is my stack gauge fudged.

 

Difficult to say without more accurate figures, especially from the gas analyzer.
A small leak anywhere in the exhaust can cause a change in AFR at the analyzer.

 

I'd be inclined to trust the mot gauge reading as more accurate, as calibrated every year, and maybe to a higher degree ?.
tabetha

 

Within 0.1 AFR is the same reading really (ie 14.6 instead of 14.7) IMHO thats well within tolerance.
If its 0.1 on the labda scale though (ie .9 instead of 1.0) then thats enough to worry about.

Exhaust blow would tend to make the tailpipe read leaner.


What were the actual values?

 

I tend to agree with the above statement, after all your in car gauge is not calibrated unless it is an innovate ls1

 

it is the lambda reading not afr.
readings are way out cos' it needs mapping i just wanted to check the stack guage was workin and accurate.