Re: water injection

[Robert Houk - WorkGroup Server Firmware <Robert.Houk@East.Sun.COM>]

   >         you mentioned previously about your disapointment with a tap
   > modified ecu. following your post i noticed that although my car moves
   > really fast... the on board boost guage never goes above 1.4. is this an
   > indicator of a similar mod? 

   Yes, that's _precisely_ the sign of the resistor/diode hack. Ned's mod
   for the 10v allows the boost gauge to go above 1.4 so he definitely uses
   another approach.

Specifically limiting discussion to the MAC-02, the pressure transducer
is fed by +8 volts while the ECU can only read ("make sense of") up to
+5 volts of signal. Using a simple resistor divider network on the
output of the pressure transducer extends the ability of the ECU to read
linearly (for practical purposes) to about 24PSI (about 1.5Bar) of boost.

My MAC-02 ECU code assumes this (uses a .77 voltage-divider network)
and remaps the Boost/RPM/Timing maps to handle [in theory] up to 24PSI
of boost. I currently run with ECU shutdown at 19-20PSI Boost detected,
so I can't really say my 24PSI timing is optimum, or even safe...
(but the bigger problem is the _stock_ fuel system runs out of gas
delivery at -- roughly -- 16PSI/5500RPM!).

I believe most "later-model" ECUs would need a different transducer to
respond to substantially higher (e.g., 24PSI) boost levels, but my
hands-on experience is limited to the MAC-02.

You can also concoct an external (to the ECU) pressure-divider network
but I'm not sure how reliable/practical that is, and you'd have to
then recalibrate the ECU (for best results...) to whatever response- 
curve you'd get out of the network...and it'd probably be altitude-
sensitive too...

					-RDH