Discussion and questions related to the course Understand AFR
Hello ! i have a question! Why are you saying in methanol 0.68, where pdf fuel's put methanol 6,4/1, in lambda is 0.43 ? i don't understand!
6.4/14.7 = 0.435 Lambda for METHANOL!
Pd: Video AFR vs Fuel Type
Thanks for answer and you Attention!! :)
I think you may be confusing two different, but related things.
The 'lambda' number represents the amount of unused oxygen in the exhaust gas and the value of 1.0 represents the stoichiometric, or chemical, balance where all the fuel and oxygen (air) is used up. This value is the same for all fuel types.
AFR, the Air-Fuel Ratio is how much air is required for the fuel, by mass, for stoichiometric combustion - it should actually be expressed as , for example, 6.4:1, as it is a ratio, but convention omits the latter part.. Because different fuels - petrol/gasoline, diesel, ethanol, methanol, etc - have different chemistry, and weight, they need different amounts of air for the same weight of that fuel. That is why the AFR is different for different fuels.
Air/fuel guages that read out in AFR are a further confusion source - they actually measure the lambda and convert it to the petrol/gasoline ratio that corresponds to the AFR for that fuel - if you use a methanol fuel with those guages, they will read the lambda's petrol equivalent AFR, NOT the actual AFR for that fuel.
Oh, doh (senior moment :-( ) - I may have misunderstood your question. You can run methanol much richer than you may expect and still gain power. where some fuels may give best torque/power burn around lambda 0.8-0.9, methanol can be run much lower - even with an AFR down to 3:1 and raw fuel from the exhaust, which looks damn cool!