Fuel Efficiency: Car #1 vs Car #2 | Ask an Expert

[xxChrisxx]

Define what you mean when you say lean. Unless we are discussing from a common reference point using the same definitons everything is pointless.

 

[The Chase]

If an engine is running 'lean' there is a more abundant amount of oxygen present under combustion than is necessary for a stoichiometric burn, being as compression ignition engines (generally) have a higher presence of oxygen than is needed for a stoichiometric burn (see my results earlier) then it is running lean. I think that's a fair definition. If the engine s A/F ratio increases from 25:1 to 35:1 as load increases then that is simply more lean. I'm unsure how to break down terminology further.

You initially stated "I'll not discuss anything diesel with someone who thinks they can run "lean"", so i presume you believe that's impossible, in which case, why? Secondly, the journal you posted also used the term 'lean' in regards to compression ignition engines several times - I quoted some pieces for you, so surely that confirms that is the correct terminology?

 

[xxChrisxx]

If an engine is running 'lean' there is a more abundant amount of oxygen present under combustion than is necessary for a stoichiometric burn

I'd agree with that though I'd make it more clear by saying.
Lean is an equivilance ratio less than 1.

I'd also further define it as over the full stroke.

 

[The Chase]

I would agree with those corrections for sure.

 

[brewnog]

I can plot NO or NOx (or both) against a BMEP value that isn't constant and provide the A/F ratio of each point?.

That would be great, thanks. Total NOx would be fine. If you could also outline the key operating conditions for each curve that would help (inlet manifold temperature, jacket water temp, engine speed, start of injection etc).

Thanks.