Competitive Advantages

In the past the rotary engine had somewhat poorer fuel economy and its weight and production cost advantage was not enough for the automotive companies to re-tool their engine and chassis plants to produce it. In addition, the emissions from the recreational and small industrial engines were not being addressed because their pollution was not an issue. The following developments now make the rotary combustion engine a highly competitive alternative:

• Pollution is now becoming so significant an issue that two stroke engines are likely to disappear or become very expensive while small four stroke piston engines must reduce their exhaust emissions as well.
• The low levels of CO and HC emissions and low production of NOx from the rotary combustion engine makes it possible to avoid a catalytic converter in applications where it will be required with the four stroke piston engine.

Comparison with a Two Stroke Piston Engine
The rotary combustion engine's equivalent of a two stroke piston engine:

• is almost free from vibration: The rotary combustion engine has only rotary motion (like the turbine engine) and therefore has no radial imbalance to generate vibrations.
• has better fuel economy: The best commercial two stroke engines achieve a specific fuel consumption of .6 Lb/HP Hr. Tests to date have shown the rotary combustion engine using .48 Lb/HP Hr.
• is quieter: Two stroke engines cannot tolerate much back pressure in the exhaust system. Hence muffling these engines is difficult without a monstrously large muffler. The rotary combustion engine uses the four stroke cycle, which is very tolerant of exhaust back pressure.
• is more reliable: Two stroke engines use roller bearings as does the rotary combustion engine. However, in the two stroke engine very large reversing stresses are induced as a result of the reciprocating motion. Roller bearings do not tolerate reversing motion and stress well. The rotary combustion engine, with its purely rotary motion, does not have motion and stress reversal.

Comparison with a Four Stroke Piston Engine
The Rotary Combustion Engine’s equivalent of a four stroke piston engine:

• produces much more power for a given weight and size: Very few four stroke piston engines produce more than one half horsepower per pound versus one horsepower per pound of engine weight for the rotary combustion engine.
• is cheaper to produce: Four stroke piston engines cost 25 to 30% more than similar two¬ stroke engines. Outboard Marine Corporation produced their rotary engine for 15% more than their cost of producing two stroke engines. OMC stated that had they produced their rotary engine in similar volumes to their two stroke engines, the cost would have been similar.
• is nearly free from vibration: The rotary combustion engine has pure rotary motion and therefore has no source of radial vibration.
• has similar or better fuel consumption: In order to preserve the exhaust valve life, small four stroke piston engines use a rich fuel air mixture running typically at close to .6 Lb/HP Hr. The rotary combustion engine's freedom from valves allows it to run very well at lean mixtures, which, in addition to lower fuel consumption, also greatly lowers emissions.
• is more reliable: With only two moving parts in a one rotar engine, compared to over 200 moving parts in a four- stroke piston engine, and only rotary motion, the rotary combustion engine is inherently more reliable. Rotary combustion engines produced in the late 1960’s by Ingersoll Rand have accumulated over 40,000 working hours to date without an overhaul. This has never been achieved by a piston engine.