Quite a few people are misinformed on the forum about this engine.
#2 - It is "gutless"? C'mon... the Toyota engine that these cars come with is hardly anything to write home about. If you use a turbo on the engine (several models came with this) with some mods to support higher boost, you're looking at 350+ wheel horsepower without even stressing the engine. I'm pretty sure that that much power in a very light car like the Lotus would be almost undrivable traction-wise. If you were willing to take a little more risk on the engine 400, 500 wheel hp would not be tough to get.
#3 - Issue number one would be how to get the transmission worked out. After that, you'd have cooling issues. The engine is certainly not too big or too heavy. Iron rotors? Yes, but they only weigh about 10 lbs each - hardly a big deal.
As I previously posted, RX-7 and RX-8 engines in formula cars work great!
I asked engine builders for opinion why the RX-7 had a bad reputation (won't make it to 100,000 miles without an engine rebuild), but the engine in the formula car went longer between rebuilds in racing application that any piston engine of similar power. Opinions I got was lighter weight (1100 lbs.) of the formula car compared to the RX-7 street car, good cooling in formula car, and dry sump. Last longer than other similar piston engines in race applications because simple, doesn't hurt to overrev a bit, and basically good overall implementation and installation for the application.
RX-8 engine in the Pro Formula Mazda isn't as reliable and doesn't last as long as the RX-7 engine in the Standard Formula Mazda. Opinions why?
- More complexity - the 3 selenoids (vacuum and electrical) fail to activate at least one or twice per race, and completely fail too often. I got to where I could diagose which one failed by sound and seat of the pants - power drops dramatically.
- Open loop lambda is a bad idea. Poor compensation for variations in fuel, etc. Implemented to prevent cheating in spec racing, but hurt reliability.
- More power, more stress, more heat.
One down-side to the rotary is that very sensitive to overheating. Even one time overheating will mean the engine will be down on power until the next rebuild.
Another concern is that the RX-7 engine cores are getting harder to find.
Another issue is change in Cg. Some claim the Honda engine in the S1 is great, but hard core road racers disagree and state that oversteer is hard to eliminate after that engine swap. I haven't driven one of these after engine swap, just know that the balance of my Sport 190 is great - I wouldn't want to mess it up.