Wankel Engine

I’ve recently found out about a Wankel Engine, much more sensible engine design then the usual engines we are used to. This is something most people are unaware of.

Most of us are used to common 4-stroke cylinder engines found in most today’s cars. One such engine consists of a cylinder body, piston that moves up and down, and a connecting rod that connects the piston with the crankshaft, turning linear movement into a rotational. Of course there are much more elements to it then these but these are basics. In four strokes of the engine air and fuel are inducted, compressed, ignited and exhausted out. Here is the schematic view.

Four stroke engine work diagram

These are the most widely spread engines today although they have many disadvantages. A lot of moving parts which makes them complicated to build and maintain. It also adds to the weight of the engine. Due to transformation of linear to rotational movement noticeable vibrations occur and the limit is imposed on maximum RPM (so called redline). Efficiency of such engines is normally only around 30%, which means that 70% of power is lost during one combustion cycle to other sources like heat. That means that your 100hp car in reality has a 300hp capable engine. Add transmission and drive train losses which are usually about 20% and you see how much power (and fuel) is wasted.

Naturally if someone could solve this efficiency problem connected with engine design they would become the richest man in the world.

The Wankel Engine

A German inventor called Felix Wankel first proposed a design of an ultra simple and efficient engine which was called after him the Wankel Engine. Wankel engine uses rotor instead of a pistons which allow it to deliver power without vibration in much higher RPMs. The design is so simple and brilliant. Here is how it works.

Wankel engine work cycle

In the basic single-rotor Wankel engine, the oval-like housing surrounds a three-sided rotor. The central drive shaft, also called an eccentric shaft or E-shaft, passes through the center of the rotor and is supported by bearings. The rotor both rotates around an offset lobe (crank) on the E-shaft and makes orbital revolutions around the central shaft. Seals at the corners of the rotor seal against the periphery of the housing, dividing it into three moving combustion chambers. Fixed gears mounted on each side of the housing engage with ring gears attached to the rotor to ensure the proper orientation as the rotor moves.

Wankel engines deliver much more power output then a cylinder engine of same displacement. They are also much lighter and since they consist of only three or four moving parts they are much easier to build and maintain. In case of engine problems in combustion, the Wankel Engine would only slowly seize to work while in a piston based design engine a possible destruction of inner parts of the engine is likely.

Wankel engines just start to have a wide recognition with car manufacturers. Only Mazda actively uses Wankel engines and their model RX-8 is best known for it. From a 1.3 liter engine a power output of 238HP is achieved without use of turbo or compressor. That is 183hp per liter which is impressive. Best atmospheric cylinder engines in the world like those in BMW and Honda achieve only around 100Hp/liter of displacement.

So the advantages are obvious, what about disadvantages? Well Wankel engine uses more fuel per displacement (although it produces more power) . Also design of seals is complicated and still much can be done in that perspective. There are several other problems but they are mostly connected with relatively low amount of research money spent on these engines today. There is also a lack of awareness of the existence of such an engine design.

Engine design has so much room for new inventions that this is a brilliant opportunity for those of you with innovative ideas to contribute. More efficient engines designs would help radically bringing down the cost of transportation, ultimately saving our planet in the process.