First things first, congratulations. rotary engines are fun, but they are also more maintenance than a piston engine. i will go through that in this post along with some other things. i hope that this post can inform and educate you without adding a lot of excess. this is just kind of the bare bones of what you need to know. PM me if you want to add anything. contributions have already been made by a couple of other members and i am willing to add or take away as the info comes in.
Oil Consumption: the rotary engine is designed to burn oil as a part of the lubrication process. the rotors cannot seal the combustion chamber like the piston engine can, so the engine meters a little bit of oil into each combustion cycle in order to lubricate the parts inside of the chamber. because of this, there is some debate on what oil to use, but i will go into that a little later. since the engine burns oil, you either need to top off the oil occasionally or just do more frequent oil changes like i do. i change the oil at 1000 mile increments rather than the 3000 mile recommended increments. this means that i never have to top off the oil in normal driving conditions, but i have to add about a half a quart between changes under harder conditions. just keep an eye on the oil level for the first few months until you can get into a pattern of changes and top-offs.
Fuel Consumption: if you have been through your first tank of gas already, then you know that the rotary engine isn''t fuel efficient. it hasn''t been built for efficiency nor has it had the kind of research and development that the piston engine has had. these two factors combined, means that the rotary is expensive to operate per mile. the engine is, however, extremely efficient in power per liter. the rotary engine can easily produce 100 hp per liter naturally aspirated, where a modern piston engine has to have serious tuning and valve timing to produce that without forced induction. turbo rotaries tend to consume more fuel, but produce more power (which brings me to my next point).
Forced Induction: with a rotary engine, there is really only one type of forced induction to consider; turbo. the rotary engine is pretty small, so if you supercharged the engine, you would be almost doubling the size of the engine. the engine also lacks the torque to efficiently power the compressor. turbo, on the other hand, does not tax the engine the same way that a supercharger would. it basically operates on wasted energy of the motor, in that it uses exhaust pressure to turn a compressor which forces air into the intake. rotary engines can handle larger turbochargers than piston engines of comparable displacement, so that is a good thing to consider when choosing a compressor size.
Oil: i have talked about oil already, but this is a little more specific. as i said above, the rotary engine is designed to burn oil. this means that the engine is a little more restricted on what types and weights you can use. i will say that you need to stay between 10w-30 and 10w-40 for moderate weather conditions and step a little higher or a little lower for more extreme conditions. now, here comes the constant struggle and debate. synthetic or conventional. i will say that i know a few synthetics that are fine to use with a rotary, but i will stay neutral on this subject. some say that synthetics may not burn correctly in the combustion chamber and may clog up the ports to the point where the peripheral ports will just no longer work. some say that synthetics are fine as long as you stay with certain synthetics. those are the opinions of some and the proven facts of others. i, personally, use conventional (castrol gtx) and i have good luck with it. there is no lack in performance and the ports all open from what i can hear. you can pull the oil metering pump and premix gas and oil in the tank if you prefer, but you always have to remember to mix when you pump gas. i will put formulas up for this in a later post.
Gas: this is also kind of an area of debate. do you use premium, do you use regular? all that i can say is that you need a gas that will keep your ports clean. this is why i recommend premium for forced induction (thank you dave and R2s99zoom). regular octane is fine for naturally aspirated, but don't cheap out here either. there is a difference between the neighborhood gas station and a corporate station (shell, exxon, etc.) since the corporate station refines their own petroleum. all that i can really say is don''t be a cheapskate when it comes to gas. this is what could make or break your motor in the long run. some people are doing E85 conversions, which are pretty simple to do on a rotary since there are no valves to burn up and the motor benefits from higher octane. i will go into methods for that in a later post also.
Idling: this is a very important issue with rotary engines. the engine has aluminum and steel components which tend to shrink and expand at different rates when heated. if you don''t let the engine idle for a few minutes before driving, you will be forcing the aluminum parts to expand much faster than the steel parts which will cause the seals between these parts to be stressed to the point of breaking. this is one of the things that will make the difference between going 100k miles between rebuilds or going 300k plus without a rebuild. you might notice in your rx7 that the engine idles really high for a few seconds when it first starts up. this is designed to warm the pre-cat before operation, but really isn"t the best thing for your engine. if you don''t want the engine to idle high, tap the gas pedal right after ignition to stop it or just start the car in gear with the clutch pushed in.
More to come, stay tuned.