ilia

I'm new to rotaries, and trying to learn as much as possible.



Here's something I'm trying to wrap my brain around. Do you still get heimholtz resonance? How does it work? If there's none, is there no such thing as plenum resonance tuning with these engines? Can anyone shed some light? Thanks.

ilia

Sorry, it wouldn't let me edit the first post, so I'll just reply.



I'm reading further, and it looks like inertial supercharging is still possible. Is chasing off flow reversion a PITA on a rotary? It seems like it'd be easier to do it on an engine with valves.

Lynn E. Hanover

While the effect may be more profound on a piston engine (half frequency stronger reversion pulse) it is used to very good result on the RX-8 with a rather complex set of valving to vary the tuned length over the usable RPM range.



Rotary tuning is very similar to 2 cycle dirt bike tuning, with exhaust system design having just slightly less importance than intake tuning.





Lynn E. Hanover

RONIN FC

The late closing of tha atmospheric (6 port,"Renesis", "N/A") rotary enhances this intake reversion of the closing chamber to generate a stronger pulse on the opening combustion chamber of the other rotor.



The 4 port(factory turbocharged and old school rotary) motors with earlier closing dont deal with this as much



The flow reversion can be a PITA if attempting to run "IR"( isolated runner) manifolds on the 6port engine. When I started to run my Holley 600 in IR form, I could actually see fuel charge getting blown back out of the carb into the air at different RPM. Kinda showing a lack of engineering and research from Racing Beat, but thats another subject.

ilia

Hmmm, ok. I think I'm starting to grasp the dynamics of a rotary, then.





Next question: what's the deal with quench area on these motors? It seems like it'd be very high, relative to the size of the motor. What kinds of compression ratios are typically seen on these?





Also: Valve float is not an issue. Rod/rod bolt stretch is not an issue. What "stops" a wankel at higher RPMs? How prone to "x" order harmonics is the eccentric shaft? What breaks first?

RONIN FC

Im only speculating, but i imagine that quench area is high in a moving chamber. 87 octane is what ive run in my N/A and I always felt that was too high(9.4-1 C/R). Compression is 8.5, to 9.-1(turbo) , 9.4, 9.7, and 10.-1(N/A).



Eccentric shaft flex, along with contact with the rotor tips on the side plates causing damage is a typical failure with high speed operation. Giving an "X" amount of harmonics would require testing of a particular assembly. Many variables exist that can yield very different results.

ilia

How are the eccentric shafts made? Are they forged, or cast?



Also, how does spark advance/retard work on these? I was thinking about that too, and it seems odd that the shape of the combustion chamber changes as you advance or retard spark. I'm sure that would do all kinds of confusing things to the way the flame traveled across the rotor face.



Thanks for all your help so far.

ikari89

from my understanding the Eshaft flex is what causes the tips of the rotors to touch the side plates, the proposed fix is machining the rotors a slight bit thinner, along the lines of .005", there was a thread about that some where to... rotaries are also limited in RPM because of the apex seals. metal and ceramic ones have to much inertia behind them and start skipping on the housings, you can see marks on over revved engines all the time. a fix to this is carbon seals, for their lighter weight, but those last no were near as long as other types nor are they as strong per say.



i want to say the Eshaft is forged but im really not sure.... good question



and as far as spark timing. you dont see any erratic changes when timing is changed by small/large amounts. its pretty linear as in piston engines. and the size of a piston engine combustion chamber does change with changes in timing it gets longer/short. same idea with the rotary it just gets deeper at a different rate.



the other thing is that the stock intake manifolds are designed the same way as exhausts, so that they can use the pressure pulse that occurs when the intake port opens it travels up the intake manifold and causes another one back down the other runners to force more air to the other rotor, there was a name for it I just cant remember it right now. there was also thread about that awhile back with some very interesting information in it.



Im sure more people have better info then that but its all I got.

ikari89

and as far as what breaks first... seals go, mainly apexs... people rarely actually snap things, other then seals, in a rotary unless you are going for very high power/rpms. from what i have read. they are very very cool motors

j9fd3s

in a non turbo application theres a few little bits that can be problems on a stock engine.



ive seen the tension bolts snap, they apparently hit a resonance around 8000-8500 rpms, its very rare, and you can put rubber or silicon on the bolts to fix em, or now the cool thing is/are stud kits



2; also rare, the stationary gears can break, the factory has had hardened gears available forever, and all the 89+ cars got em. this problem is more akin to wear, its not the 1 run to 11,000 that kills it, its the 500th...



along with #2 the gear can walk out of the rotor, and hit the side housing, this problem has also been incrementally fixed, they keep putting more roll pins in there.



also the oiling system seems to suck over 8500, theres several other threads about that. we revved our motor to 9400, and the bearings took quite a beating, although everything else looks ok