Drive by wire and the wish to survice the experience.

[David-HMSE Higham]

     Hi Gents,
     
     First posting for me so I suppose a brief intro. would be appropriate. 
     I'm developing an EMS (engine management system) for my 1972 Hillman 
     Imp (1ltr) which is being called back into regular service after I 
     took a fall from my CBR600 yesterday (must be getting old or 
     something). I digress, I'm basing the system on an 40MHz 512K Flash 
     32K RAM device, so I've hopefully got a lot of time and memory to play 
     with. The intention is to develop it for MPI using MAP initially (due 
     to availability of bits) and then move to MAF in near future. I'm also 
     contemplating drive by wire which has the potential for some 
     interesting failure modes! 
     
     Does anyone have a feel for a safety strategy for such a set up? (Did 
     he mention safety?....what sort of foolish thinking is that!) As I 
     understand it, there is a TPS feedback signal and the Idle Switch. 
     Along with the BRS (big red switch) I was thinking of using the Idle 
     Switch to validate the TPS signal which used in the control loop along 
     with pedal position. Call me cautious or something, but this does not 
     seem enough to me! Cruise footbrake switch(s) not viable due to left 
     footbraking if I'm feeling daring! Are there two pots. in the TPS, if 
     not could I install a 2nd one? Any recommendations of A/D sampling 
     freq. for the TPS? 
     
     On a general point re. engine protection I've worked with Diesel FIE 
     before, (please don't black list me! I bet you would if I told it was 
     Lucas!) and these EMS's have various maps/controls to limit 
     torque/fuel, e.g. max speed, max torque curve, boost limit, coolant 
     temp protection (hot and cold). What's the score in gasoline engines 
     and how's it achieved?
     
     One last thing for now, when you talk of MAF and MAP used for timing 
     and injection calcs, do you actually mean MAF and MAp that's 
     compensated for atmospheric pressure and intake temp?
     
     Cheers,
     
     Dave