Hi all. I've been lurking on here for some time and appreciate the very knowledgable community of rotary experts. I don't have a specific project in mind with this question, but it's something I've been curious about for a long time.

What would be involved/required in raising the redline of a rotary engine waaaaaay up - like to 12,000 or 14,000 RPM? What if I wanted to make peak power at like 10,000-11,000 RPM instead of down at 6,000-7,000?

Is such a thing even possible, or will the rotor speeds just get too high? With a piston engine, you can just go more and more oversquare to keep the linear speed of the pistons down to a liveable speed, but with the rotors you can't do anything similar.

How high could the redline and power peak be pushed up the rev range for an engine that's expected to stay together for 20-40,000 miles? I'm talking about a street-driven application here, not race. I'm assuming that the issues include:

1) Making the seals work/live when moving so fast across the surface of the housing.

2) Porting to breathe at those RPMs will probably make the engine worthless below say 4,000-5,000 RPM.

3) Acessories, of course would have to be way underdriven to survive.

4) E-shaft and rotors need a wicked-good balancing. Where can you find someone to do this balancing?


Presumably there are other issues that I'm missing, but I'd love to see what people have to say about the practicalities of building such an engine. I'm curious about this because I'm also into motorcycles and I am consistently amazed by those inline 4's that can idle at 1,200 RPM, toot around town smoothly at 2,000-4,000, but then scream their nuts off from 10,000-14,000. It's an awesome rush and I'd love to see how close a rotary could come to providing that experience.

Thanks in advance for any info or insight,
Phil.

 

Nobody?

Since posting this, I've seen a mention of dynamic balancing to raise the redline of an S5 engine to 9,000 RPM. Does this apply to the eccentric, the rotors, or the whole assembly?

What other stuff can one do to push the redline higher in these motors?

Looking forward to learning,
Phil.

 

sorry if i sound too n00bish, i am still new to the rotary world.

the thing i think would be the limiting factor would be the tunability, it would be quite hard to tune an engine to spool that high without detonation at one point or another in the rev range. and i have heard that even slight detonation can bring these motors to their knees.

you also have to remember rotating mass in the transmission and clutch. unless everything is perfectly balanced, bearings cannot handle those kind of RPM's.

it just doesn't sound practical to me.

 

apex seals
clearence the sides of the rotors
higher oil pressure

 

I know you can get lighter rotors and strengthened stationary gears from atkins rotary and several other venders. That's what I plan to do next time I rebuild a rotary.

I've actually been thinking about calling them to ask their advice on such a project and see what kind of a limit has been reached. Now, I would not plan to drive a car like this on the street....much but it could be a hell of a car at the track, that's for sure.

 

To be able to rev that high, you would also need to add a 3rd bearing, in the center plate, to support the e-shaft.