MoTeC Screwdriver ECU - Manual (Page 5)

Page 5 of 5
TURBO OR SUPERCHARGED ENGINES
The vacuum line (now a pressure line when on boost) should be placed so that it will read what the
engine sees under all conditions. If a Plenum system is used a tapping into it is O.K. If multiple
runners with butterflies in each runner is used the tapping must be on the engine side of the
butterflies. The set up is carried out exactly the same way as for a naturally aspirated engine, but
giving only enough throttle to avoid the boost mix light from coming on. This allows the
establishment of a fuel curve for the engine under naturally aspirated conditions. Once this has
been achieved the examination of the fuel numbers will show where the highest number occurs.
This will be peak torque speed. Then run the engine at this speed and gradually increase the load
and throttle opening, the boost mix light will come on and the mixture enrichment should be
wound on while watching the CO levels. We must emphasise that the load should be increased
slowly to allow the boost mixture compensation to be given relative to the increased in load. If the
load/boost is increased too quickly relative to the increase of fuel, detonation or piston burning will
occur as a result of a lean mixture. We suggest that 6% CO be a minimum level. This is a little on the
rich side but safe. Under some circumstances where turbo temperatures are a problem at high
engine speeds due to other problems, a richer boost mix setting can help cooling although after 8%
C0, some power loss will result. It is only necessary to do one full boost run to establish the upper limit
of engine operation. At this point it is related to the previously set naturally aspirated curve
however, it is advisable to check the level of enrichment 1000 RPM either side of the max. torque
setting. If necessary the naturally aspirated settings can be compromised a little to give adjustment
to the full boost fuel curve.
THINGS TO BE AWARE OF DURING INSTALLATION
1. It is advisable not to take battery 12V * from master switch (if fitted to vehicle) supply problems
can occur if switch is worn or has high resistance contacts.
2. Never supply 12V + direct to injectors for checking or testing as permanent damage usually
occurs. All injectors run at considerably reduced, but various voltages depending on type. The
MoTeC E.C.U. allows for this.
3. The brown fuel pump supply wire is designed to operate only one Bosch type high pressure fuel
pump (current capacity is a peak 10 amps continuous). If additional pumps are required the brown
wire can be used to signal external relays for multiple pump operation. This system is protected by a
15 amp fuse in the E.C.U. We strongly advise that that brown supply line be used wherever possible,
as it is controlled by the microprocessor to isolate pumps in the event of accident where the engine
has stopped, but pumps are not manually stopped. After 3 seconds this is done automatically, thus
reducing any potential for fire if, the driver is incapacitated.
4. If connection for purple ignition supply is made at coil positive terminal make sure that the system
is not fitted with ballast resistor and that full 12 volts is available.
5. The temperature sensor must be placed in the air stream that the engine sees, eg. in turbo it must
be placed after the intercooler if fitted or after the compressor if no intercooler fitted.
6. Vacuum lines must be after the butterfly(s) and from each runner if individual runner multiple
butterfly system is fitted. Length of this line is not critical.
7. The E.C.U. must not be fitted in the engine compartment of exposed to direct sunlight through
glass, and should always be mounted on soft anti, vibration mounts.
8. In the case of V8 engines fitted with twin points and twin coils it is necessary to connect the white
wire to the points or earth side of one coil only and the E.C.U. to be switched for 4 cylinder
operation.
9. If a rotary engine is being used the white wire is to be connected to one coil only (points side)
and the E.C.U. to the switched to 4 cylinder operation.
10. Fuel regulator vacuum lines to be connected below butterflies apart from high boost turbo or
supercharger applications.