control algorithm for MAF setup

[Jeremy Edmondson]

Dave Williams wrote:
> 
> -> Remember with the MAF sensor it will measure airflow in both
> -> directions and in the FORD strategy there is a lot of compensation
> -> for backflow and pulsation at low engine speeds.
> 
>  So will most MAFs.  So far I like the idea of sampling the MAF at a
> particular crank position.  That would tend to even things out quite a
> bit.

I suspect you are better to integrate it over an entire engine cycle, need high 
sample rates though.  Remember you are interested in the total quantity of air 
induced rather than some value at some point in the cycle.  Also because the intake 
system is tunned it will exhibit distinct resonant frequencies and hence 
considerable phase changes will occur throught the rpm range.  Obviously triggering 
at a specific crank angle will not always trigger with the same airflow event.  
 
>  If backflow becomes too much of a hassle, I'm likely to just go down to
> the motorcycle shop and get a bunch of two stroke reed blocks.

WHY????  This is the exact reason why efi is used, compensation for non-linear 
effects such as reversion.  It is easy, compensate for it in the fuel map, this is 
why the maps exist otherwise it would be really easy and a simple formula could be 
used.  The backflow/reversion ocurrs at exactly the same rpm/load point so just 
tune the map accordingly.  Carbs cannot easily do this.  Efi works great on race 
motors as far more wild cams can be used without the tractibility problems 
associated with poor fuel metering.

Alfa tried reed valves in the intake ports so that wild cams could be used but the 
parasitic losses associated with the obstruction in the air stream far out weighed 
the benefits.  Its a good idea, I had though of a similar scheme as it allows very 
radical cams to be used without losing low end torque.