Just because 2 stroke engines were set aside in production vehicles, it doesn’t mean development stopped, in recent years there has been increasing attention paid to these powerful and compact engines and the Grail Engine is an interesting example. It’s a multi fuel, variable compression, highly efficient 2 stroke with built in supercharging and intercooling.
The Grail Engine claims to eliminate cross contamination of fuel and oil,
the primary cause one cause of high emissions in 2 stroke engines and why we don’t see them used anymore, otherwise, their high power output would make them ideal as a power unit. Two strokes have always had a higher power to weight ratio and the Grail also claims greater thermal efficiency than current 4 strokes.
A single exhaust valve, 3 spark plugs and a direct fuel injector are located at the top of the cylinder.
Compression takes place within the reed valve air box, pre-compression chamber, vent-to-piston ports, piston-intake-ports & crankcase. As the piston travels upward creating a vacuum beneath the piston, fresh air enters via the intake air box through the one-way reed valve, and fills the external pre-compression chamber, vent-to-piston ports and piston-intake-ports with fresh air.
Compression occurs within the cylinder as the piston travels upward. At Top Dead Center (TDC), direct ignition then single or multiple ignitions occur. This forces the piston down into the cylinder compressing air in the engine crankcase, external pre-compression chamber, vent-to-piston ports and piston intake-ports. Just prior to Bottom Dead Center (BDC), the exhaust valve opens via a standard cam/push rod mechanism or electro-mechanical valve control. Exhaust gases exit via the exhaust valve opening at the top of the cylinder. Compressed fresh air enters the cylinder via piston valve, which forces out the final exhaust. As the piston travels past BDC the exhaust valve and piston valve close and cycle repeats.
The specs state that a 1 liter Grail could have 100 mpg, 180 foot pounds of torque and 200 horsepower, though they don’t specify what sort of vehicle size and weight these mileage figures are claimed for.
As always, another new engine with lots of potential, but until it’s tested and actual output is measured and confirmed, we don’t know how close these numbers are to being true, but wouldn’t it be nice to see powerful and compact 2 strokes returning to production vehicles?