5 THINGS YOU NEED TO KNOW…
At partial throttle settings, which is where a lot of trail riding is done, carbs run relatively rich, but our TPI bikes are 30-40% more efficient. On a wide-open throttle, it’s 3-5% better than a carb’d machine.
Oil consumption is way down too, reduced by 50% to ratios of 70:1 to 100:1, and with a 700cc oil tank that means eight tanks of fuel are covered, useful in competition events in remote areas.
Although you’d struggle to see the changes to the configuration of the transfer ports and thermodynamic arrangements from the 2007-spec engines, we had to work hard at getting the stream and direction of the incoming charge right with the injector positioning.
Like a four-stroke engine there are five sensors detecting engine speed, throttle position, crankcase pressure, coolant temperature and intake air temperature sensor. We had to position those sensors smartly and work in collaboration with Synerject, a French Engine Management company. It took almost ten years to painstakingly learn what each combination of data meant in the combustion chamber so that we could develop the perfect control strategy.
Although we call them two-stroke engines, there are some sophisticated thermodynamics happening through each cycle of the piston with varying exhaust pipe pressure waves meaning you need completely different charge compositions. If that’s not detected you can have a 6-8 stroke engine as some charge goes into the exhaust unburnt or it ignites before the optimum point and the engine needs 50 cycles to come back from flame-out to a steady flame cycle.
No fuel flows through this 39mm Dell’orto – just air You only have to fill up the oil once every eight tanks of fuel
Expansion pipe returns unburned fuel to the cylinder
Injectors spray premixed fuel directly into the transfer ports
Slight tweaks to the cylinder transfer ports were needed