Scott hit on a lot of good points on a rotary installation. I’d like to embellish some of the points he made and address two omissions that will drive the fabricator up the wall.
First the exhaust. You cannot use standard mild 16GA steel exhaust tubing. I used a thick wall mild steel cause that is all I could bend on our exhaust machine. 14GA, if I remember correctly. It still blew holes through at the exhaust port. I finally solved the problem by forming and welding on a high grade steel plate of some unknown type.
The biggest problem with a street machine is noise as Scott alluded to. Personally I had a hard time accepting the piercing chain saw sound in an every day car. I spent hours on the phone with Racing Beat exploring the theory and application issues of rotary exhaust systems. And I spent years fine tuning the system.
Here is what I came up with and it worked very well except for one problem, which I’ll explain later. First, there were no Mazada exhaust mufflers or resonators that could be used on the Alpine cause they are just to darn big. Don’t fit, no way. Now I should add, this was in 1980. Times change so maybe there is something today. Anyway, based on what I learned from Racing beat and reading lots of tuner articles, this is what I learned. The Rotary likes a free flow exhaust system. Its power gains are based on exhaust flow characteristics at the port area and very short distance of the header. After that, keep system open and free flowing. The rotary engine produces a high frequency component in the exhaust flow. It traverses as a laminar current in the exhaust flow. So the first mission is to reduce the high freq amplitude by disrupting the high freq component. That is done by using a pipe with a fluted baffles in the interior, similar to what GM was doing in some of their large cars in the 70’s. Another example would be the side pipes used on Vettes. I accomplished this by using a cheap “cherry bomb” glass pack muffler. It worked great but the exhaust was still loud. The next thing I did was use “turbo” free flow mufflers. One midstream and one as a resonator at the tail pipe end. I tried dozens of mufflers til I found a combination that worked well to quiet the exhaust. I was able to get the sound level down to about what a MAzada was. Now to that problem. In the 70’s and 80’s there were NO aftermarket mufflers designed to work with a rotary engine exhaust. The high frequency component of the exhaust would cause the mufflers to resonate giving off a tin can sound.
I wrapped the midstream muffler with a 1/2″ layer of fiberglass and then wrapped that with a piece of aluminum flashing. It looked just like a normal muffler. This also reduce a lot of noise. Now the real problem, the internal baffles would vibrate and fatigue crack at the weld attachment points. Pieces of the baffle would then float around inside the muffler and rattle like a can of marbles. I never got more than six months out of a muffler before the baffles would disentigrate
Now the two omissions.
1. Cooling. The rotary engine uses water AND oil to cool the engine. I forgot the percent of cooling the oil does but something like 40% is what I remember. Any way, the fabricator must allow for cooling for the oil too.
2. Clutch. It doesn’t make sense to me but in Mazada’s infinite wisdom the throw out lever comes out the top of the bell housing, It makes for serious fabrication problems.
Tom Hall in CA did a rotary Alpine several years ago. I am not aware of him making it quiet Alpine.