Helpful Videos

There are many videos online that illustrate how the rotary works, but I particularly like this one. It illustrates how the major components fit together, and their functions.

This next video gives you a sense of how the rotor positions and rotations relate between the eccentric shaft and the rotor itself. Again, nothing new, but most of the animation videos go so quickly it's hard to get the same sense that this one provides.

Rotaries require in-chamber lubrication of the apex seals, even during the combustion cycle. Whereas in a piston engine the oil scraper ring would be removing oil from the cylinder walls before combustion occurs, in a rotary oil is deliberately injected into the housing prior to combustion. Even if you disable the OMP and convert to “premix” you will still run “dirty”.

In a car it's OK, and even healthy, to redline the engine periodically (at least once per drive) to help burn off deposits. In an aircraft this would be fine, too, but we don't have clutches and static RPM limits restrict our ability to really stress the engine.

There is a technique known as “steam cleaning” that is supposed to help burn off these deposits. The basic concept is simple. While the engine is running, slowly pour a gallon of water into the intake. As the water flashes into steam inside the rotor housings, it will clean off any deposits that may have built up, and allow them to pass out the exhaust.

In an Rx7Club forum post, a contributor has posted several photos, a description, and a video of the process. It's fairly simple. While the engine is running, remove the vacuum tubes from the intake manifold. Use a rag to hold the throttle open to around 3000 rpm, then connect the manifold ports to a tube running into a gallon jug of distilled water. Manifold vacuum will draw the water into the intake. The engine will run rough during this process, but it won't stall, and the end result will be a much cleaner engine.

Warning: This process will heat up your exhaust. In a car it could destroy your catalytic converter, if done too quickly. In aircraft use, watch your EGT to avoid damaging your turbo. Also, note that water will make it into your oil pan. Always change the oil after performing this procedure!