Mitsubishi ECU

[Peter Wales]

I do have some PCBs in England, some are being sent over next week. Anyone
who wants one send me a snail mail address.

The zener clamp looks like this:


<-to boost sensor        cut here           to boost input on ECU
-------------------------------X----------------------------
                        !                       !
                        !                       !
                        !                       !
                        Z                       !
                        Z330 ohm resistor       !        
                        Z                       !
                        !                       !
                        !-----------------------
`                       !
                        _
                       ! !
                       ! !4.3 v zener. White end to resistor
                       ! !
                        _
                        !
                        !
                        !ground
---------------------------------------------------------

The idea is that you feed the existing boost pressure sensor voltage in
through a low value resistor to preserve its integrity. Then you clamp the
voltage to about 4.5 volts with a 4.3 v zener. Both parts come from Radio
Shack. The voltage at the computer now receives the same voltage from the
boost sensor as before, until it rises to the zener voltage and then the
zener starts to draw current and restricts the voltage from rising any
further. Hence the boost can rise but the computer will not cut the fuel off.

You should be aware that the fuelling is not going to increase past the
zener voltage and the purists in this group are going to advise you that it
is a dangerous thing to do, and they are right. If you do this, use an
exhaust gas monitor and ensure the CO does not drop below 4% (Lambda number
anyone?)

This is the principle of the FCD devices sold by HKS and others and it will
work on just about any turbo car with a voltage output pressure sensor,
including the Subaru turbo. In general, do not turn up the boost pressure
more than 25% from the stock reading. Use it wisely and you wont have
problems. Go for too much boost and expect meltdown!

The Colt has two large injectors in a manifold/pressure regulator system and
they each fire alternately one at TDC and the other at BDC. Thus at low
power, each cylinder gets a squirt. At full boost they are both open
continuously. The system is curious because it uses an ultrasonic air flow
meter (mass air meter) to measure air mass until the onset of boost then it
switches to map sensing while on boost.

Peter Wales
Superchips Inc