lookup resolution

[Greg Hermann]

>i am toyiong with the idea of using a STAMP BS2SX as the heart of a simple
>EFI system.  For anyone who doesn't know the STAMP, go to...
>
>http://www.parallaxinc.com/
>
>anyway, that doesn't really matter, my questions are regarding the
>resolution of the lookup table, it is being designed primarily for my own
>1.6 Litre Isuzu turbo engine, running 15 PSI boost max... therefore it will
>be using a 2 bar MAP sensor, and will rev to around 8000 rpm
>
>I was planning on using 16 RPM points and 64 load points, this would given
>around 500 RPM and .5 PSI MAP resolution...
>
>my questions;
>
>is this resolution high enough for a street driven engine ?

If you can, I would say go to twice as many rpm points (32) and use a
logarithmic scale to lay them out (equal percentage increase from each rpm
level to the next) for best streetability.
>
>what sort of interpolation would i require, if any ?

Linear interpolation at most, mebbe not necessary.
>
>would the engine still remain drivable without any interpolation... simple
>chosing the next highest point in the lookup table ?

Should prolly be OK, particularly if you go with 32 rpm points and make
them log scale.
>
>
>
>and some others, if you've got time :)
>
>Is it ok to have the program say that whenever TPS = 0% simply go into
>"idle mode" supplying a predetermined injector pulse ?

Might look at shutting off fuel on decel, and turn back on at low rpm.
>
>can anyone design a simple, adjustable curcuit for sensing when the
>"accelerator pump" enrichment should be added... just something that went
>HIGH when the TPS had been opened faster than a predetermine rate ?
>
>is it ok to just use 1 bit for temp... ie, when the engine is below normal
>operating temp add a set percentage to the injector pulse width, or does it
>have to vary as the temp rises ?

I think four, or even eight steps might be a lot better for streetability.

Regards, Greg
>
>I know, there is heaps of questions here, but any help would be greatly
>appreciated...
>
>thanks in advance
>
>Matt