Shashank Moghe

Let us scientifically discuss an idea: The idea is to have petrol to be direct injected in a very small quantity, using the stratified charge methodology, making the air-fuel mix appropriately rich near the spark plug tip. The spark plug ignites the charge thereby increasing the pressure (and hence the temperature) beyond the auto-ignition point of Diesel. In the mean time (which is a very very short time), as the pressure (and temperature) is rising, we have diesel Direct injected through a different nozzle into the chamber. After the pressure and temperature hits the desired auto-ignition temperature, it combusts.

Of course, this idea must have some pros and cons, here are some I envision:

Pros:
1) No high compression ratios needed for Diesel combustion- which serve only in increasing engine size and weight.
2) A smaller + lighter engine, capable of providing the efficiency of a diesel.
3) Possible fuel savings - since the engine has smaller Frictional losses (due to a smaller stroke length)
4) Greater peak temperatures and pressures (greater torque) due to the already high starting point for the diesel combustion thermodynamic cycle (thanks to the petrol pre-injection).

Cons:
1) Emissions of a diesel engine.
2) Combustion timing to maximize the torque - the diesel injection has to be timed perfectly so that it starts combusting after TDC. To make this happen, the petrol pre-injection+spark must be timed well before TDC to let the combustion peak pressure (hence temperature) just occur before TDC.
3) Better material requirement for engine components to withstand such high thermal+structural loads.
4) Complex instrumentation.

I am discounting the instrumentation part, since this is just an idea under consideration. All people, just chip in.

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