Booted up a .Mac laptop in windows to reprogram the #innovatemotorsport wideband O2 sensor to display in lambda rather than AFR air fuel ratio – now it reads correctly whether I run the #vwt3 doka on lpg or benzine. Basically lambda 1.0 is stoichiometric – ie perfect fuel burn – irrespective of what fuel you are burning –

“Stoichiometry (/ˌstɔɪkiˈɒmɪtri/) is the relationship between the weights of reactants and products before, during, and following chemical reactions.”

So basically at ‘stoich’ there is enough oxidant to oxidise all the fuel completely. – with benzine/petrol this is an AFR air fuel ratio of 14.7:1 ie, for every 1kg of fuel burned you need 14.7kg of oxygen….

For other fuels this is different – eg for LPG (autogas) that the Doka also runs the Stoich AFR is 15.5:1 so needs more air for each Kg of fuel.

Expressing the data from the lambda sensor in lambda rather than AFR allows the gauge to read correctly whether the double cab is burning benzine or LPG.

Commonly in internal combustion engines the fuel mixture is a little rich to allow part of the fuel to cool and lubricate in combustion and reduce temperatures.

With benzine/petrol the target lambda is often 0.89. From the small amount of LPG tuning info i’ve been able to find it appears that the consensus is to run LPG leaner than Benzine – closer to Lambda 1.0 and not less that 0.9 or 0.92/ The reasoning being that LPG, as a gas, is a dry fuel and thus there is not a cooling effect from fuel vaporisation than there is with petrol. It also seems that there is a discussion that as LPG excess fuel continues combusting after the exhaust valves open creating valve burn?

all the same I now have a working lamba sensor – the main use has been tracking the Lambda / tuning when running benzine. Particularly as the 1.9 DG style carb on the 2.1l MV motor is very lean and needs both jets increasing….

https://en.wikipedia.org/wiki/Stoichiometry