Throttle enrichment - why, how much?

[David Chambers]

Thor Johnson wrote:
> 
> I've been playing with 2 Fuel[MAP][RPM] curves for a a little while now & can't
> get them to run much better than Fuel[MAP] + MoreFuel[DeltaThrottle].  I
> thought you could account for DeltaThrottle automagically in the 2D maps (if
> bigMAP & smallRPM, need lotsogas), but I have yet to see a realizable
> improvement, so--
>   Am I barking up the wrong tree?

> 
> Do I still need to factor in a DeltaThrottle & how much should I need (I needed
> positively *huge* amounts with the 1d table).
> 
> Also.... at Low RPM (0-5K), my 68hc11 code can keep up with 1 sensor rdg/cam
> rotation, but at top end (I only got to 8K now... need tuning!), I can only
> read the sensors every 10-30 cam revolutions.  How much difference would this
> make?
> 
> TIA,
> Thor Johnson
> thormj at iname.com


These are only my experiences but here goes.
The RPm part of the map is to allow for the changing Volumetric
efficency of the motor through the rev range. ie coming on cam and off
cam to simplify it a lot. My experience is with mild street type cams
the MAP input on its own is enough to make the car quite drivable. You
do still need an accelerator pump type of system though. What i use is
percentage enrichment that depends on delta throttle in a fixed time and
then decays at set rate. You need to make the percentage and the decay
rate setable.
This function is needed to allow for the engines requirement of a static
richer mixture during transient acceleration and also to allow for the
lag between the air flow and the fuel flow due to their differing
densities in the manifold. Ie with something like throttle body
injection with injectors a long way from the valve you will need more
percent and slower decay. With race type inlet runners one per cylinder
and injectors close to the valve you almost don't need any boost.

With regard to the sensors it depends which ones you are trying to read.
I read load every revolution, calc RPM every rev and everything else
about 10 times a second.

Hope this is of some help and awaiting comments from others on the list.

David Chambers