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Modeled fuel table


CMSport
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*edit more context added*

 

Hey guys, a quick question on modeled fuel table numbers... I'm totally fresh to the world of mapping with modeled fuel equations, using VE as the display variable so you'll have to excuse me for being a little lost on this one... 

Firstly, I expected that, after putting in my engine/fuel delivery parameters, that the initial modeled base fuel table might be at least close to where it would need to be... is this an incorrect assumption to have made? 

The car started on the crank enrichment and then suddenly stalled. it clearly sounded like it ran out of fuel. I increased the VE numbers until it would start and run, then continued to increase to keep afr in a happy range. and ended up with around 65 at idle between 1000 and 2000rpm. engine is a pretty stock 993cc Daihatsu 3 cylinder... stock cams and intake etc 4-valve head, nothing fancy

This seems rather high to me, as I had expected idle VE to be in the range of 10 - 20%. I do note though that the injector PW is still in the low 1's which is roughly where I thought it should be. 

I'm so so used to looking at a table of injector pulse widths so if someone could reassure me that this doesn't sound outrageous and I need to go searching for a cause, that would be much appreciated! 

 

Cheers

Tim

 

p.s. I'm running ID1050x injectors and it is blowing my mind that I can hit 1.0 Lambda  at NORMAL idle rpm on a 993cc engine... amazing :D 

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You will typically see 45-65% "VE" at idle on most common automotive engines.  This may not accurately reflect real life VE if for instance you were measuring the real VE with air flow measuring equipment but it is within the limitations of a model/equation based on MAP. 

Have a look at our Atom or Monsoon base maps for a typical modelled fuel table (these are set up to be on the safe/rich side) so on a properly tuned table you would see maybe 10% smaller numbers than these examples.

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OK thanks, that comforts me a bit - why then do you think the base table that the ECU calculated first up was lean? it started out in the low 20% region and I ended up with more than twice that number. 

Is this normal to expect? 

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It sounds like you started with a fuel table that was set up for a traditional ms based equation.  The software will not automatically calculate or create the fuel table numbers for you, they will just stay at whatever they were in the map that you started from.

For a closer starting point you could just copy and paste the fuel table out of one of our modelled maps such as the atom/monsoon samples.  

 

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