I was watching a Japanese car documentary that had several cars racing against each other in a track. All of these cars are NA, and they all revved to around or above 10k RPM. The winner of that race is an RE-Amemiya RX-7 FD equipped with an NA 20B engine.

That got me thinking, I am unable to quote a reliable source but I recall reading somewhere that the Renesis is certified by Mazda engineers to be able to rev up to around 13K RPM reliably. The Renesis currently redlines at 9K, could the extra 4k RPM provide the car with more power? If it does, why is no one actually looking into that option?

If the Renesis is revving at 13k RPM, how much more horsepower would it provide compared to the current redline of 9k RPM?

 

There is no reliable wankel motor revving beyond 11k even in racing. It would take another 50 ft/lbs at 10k to make in excess of 300 horses. Although the renesis is quite an impressive breather it just isn't going to easily behave like a peripheral port race motor. In other words, it would take more than increasing the rpms to increase the power.

 

Well, you kinda answered your own question. If it provides any more power just-because, it surely isn't worth the cash. There are more threads like this one https://www.rx8club.com/showthread.p...2&page=1&pp=15 floating around. Look for RotaryGod's posts, particularly. He's well informed about how it would work out.

 

You'd need to accomodate the extra airflow somehow, I'd think. The Renesis (as-is) would still peak right where it peaks now. It's a question of whether or not the extra area under the curve is a worthwhile trade-off. The alternator and other engine powered equipment might not withstand those revs for long. If you somehow enlarged the ports to flow the extra air up there, you'd suffer considerably down low and through the mid-range. There's just not much room for bigger or better flowing ports (at least on the exhaust side).

 

Higher rpm = higher compression ratio = different timing ???

Don't think our fuel supports

 

Last time I checked the 10K plus RPM is only on the e-shaft. The rotors are only running at 3300 RPM when the e-shaft is a 10K.

That means the rotary engine is still running far slower that most piston engines when the tac is reading 10K.


It would be interesting if any of the self appointed theorists even took that into account when they came to their lofty conclusions.

I suppose that would be the limit for those who only race thier car on the dyno.

 

You might want to edit that to say 3000 instead of 30000 :b

 

Thanks for the heads up.

 

Why do people always want more? More, more, more! Stop it ! Stop it! Stop it! Design sensibly and utilize the engine where it is designed to work. That is not above 10,000 rpm. More is NOT always better.

I don't believe for a second that some engineer "certified" the Renesis to 13,000 rpm. Ignore the fact that the heavy flywheel will nearly literally explode from the g-forces. Ignore the fact that the eccentric shaft would flex to the point of possible permanent warpage. Ignore the fact that the rotors would physically contact the side housing from the eccentric shaft warpage. Ignore the fact that the water pump has been cavitating and not supplying enough coolant to the engine this high. Don't forget the fact that the engine cooling system aren't designed for this capacity and neither it the oiling system. Your bearings would say sayonara. I can just keep going on and on. Yep an engineer would definitely certify that as safe!

On a more practical note, the engine has already passed it's power peak at it's current rpm. Revving it higher isn't going to change that. It will just keep losing power. There is no point going higher. Even if you shrtened the runners to compensate then you run into the issue of the engine ports not having the capacity to flow the needed amount. Intake tuning will only go so far on it's own. Then you also run into another issue in that the port timing is not optimizes for this high of an rpm. Port timing plays a very important role in determining what rpm range the engine is happy at.

You'd have to do so much to make a Renesis work well from 10,000-13,000 rpm that even if you did do it, the engine would have pathetic low and midrange power. Believe me all top end isn't terribly practical. It's not even terribly practical at a drag strip. Go llok at Mega horespower Supra's sometime and compare them to Supras with lower power. Comparable times with different trap speeds. Get rid of the more rpm idea. It isn't practical and wouldn't work that well. You wouldn't like it. It would never be reliable either. Even the 4 rotor race engines with far more breathing ability with peripheral ports didn't even rev as high as the Renesis does. They shifted at 9000 rpm. They did pretty good. There's more to it than "more".

 

I'm not sure if I'm included in the self proclaimed theorists but I'm sticking with and standing behind my previous stsatements. Safe rpms on racing rotaries are under 11k and a lot never see in excess of 9k, and yes, that's shaft speed.

 

Well nice to have you on board RG. Typing faster than me I see.
Paul.

 

FWIW i believe the RMagic ecu does raise the rev limiter to 10k or slightly above...

 

They are doing that because "more" sells product. It's all about money. It isn't a useful increase for the above reasons. You are already past peak power at this point. It is going back down. This isn't the ecu's fault. It is the manifold and port combination.