Scotty's Dirt Bike Spares

Gas Gas use Magneti Marelli EFI system developed by American Brian Gillen.

The system uses 5 sensors

-Throttle position sensor - tells the ECU (electronic control unit) the position of the   throttle butterfly.

-Crank angle sensor - reads crank speed and signals top dead centre (TDC)

-Air temp sensor - measures the temperature of the air going into the throttle body.

-Water Temp Sensor - lets the ECU know how hot the engine is.

-Barometric Pressure Sensor - this sensor tell the ECU how thick the air is. This meters for altitude adjustment.

 Interestingly the bike will still start and run with only 2 (Crank angle and Throttle position) of the five sensors connected.

The Magneti Marelli EFI system is an open loop system unlike the closed loop type system that most road cars use. A closed system would typically have an air flow metre or intake manifold pressure (MAP) sensor along with an oxygen sensor in the exhaust manifold.  The closed system is better for the longer service intervals that car owners want due to there ability to adjust them self's for variables like dirty air filters and ageing catalytic converters. They can also provide better fuel economy at constant revs, experienced during highway use.

The open loop systems are more suitable for dirtbikes due to there relative simplicity and with modern ECU mapping you don't need all the information collected from the extra sensors. The ECU already knows the intake flow at all revs because it can be measured and programmed in. It then inputs the variables like altitude and throttle position etc to work out the best fuel squirt.

The intake pressure would varied due to things like engine ware, valve clearance changes and air filter condition, but they would be relative minor, except for a clogged air filter which should be cleaned.

Because of the variables mentioned above except airfilter (which should be cleaned all the time as per any dirtbike) over time maybe 3 to 5 k the fuel trim which is the base line mixture will need to be adjusted. This is a simple procedure.

We attach an oxygen sensor to the exhaust pipe header at the blanking plug fitted near the top of the header pipe, to read the exhaust gas mixtures. We then plug a palm pilot computer into the bike and with the software we have (IAW15P) we can change the base line fuel trim. Despite popular believe we don't change the ignition mapping. We only charge $ 110.00 for the job.

There are many benefits of fuel injection over carburettors.

-Simplicity very few moving parts compared to a FCR carbie.

-Self adjusting mixtures at all altitudes.

-Throttle response and smooth power delivery.

-Fuel injection atomises fuel better than a carbie so it burns better.

-Better fuel economy.

-No breather tubes allowing dust into the engine, this is a big problem on ti            valve bikes.

Many people express concern about de watering a fuel injected bike after they accidentally take it for a swim. Its never good fun drowning a bike but if the waters clean, simply dewater it like you would any bike. The only extra thing that might need attention would be the relay that operates the fuel pump. See Gas Gas setup for a trail side fix if needed.

It would be hard to buy a new car with a carbie these days I carnt think of one, in fact most road bike, sports ATV, watercraft etc are all fuel injected. Suzuki has just released the EFI 450 MX bike seems there all following the leader, what next Slipper Clutches?