tuj

This is largely just my own curiosity, but given lots of cubic ft of cash, how high could you rev a rotary? In general? How about a modified 12a or 13b? At what point can the housing no longer contain big enough ports to justify extra revs?



I believe the R26b could rev to around 11k in testing. What are some of the top PP motors redlining at? What are the biggest obstacles to going even high (like 15 or even 19k)? Certainly not valve springs.



Thoughts?

heretic

You can buy sportbikes that rev higher than the highest revving rotaries, endurance or sprint. I think there's a Honda on the market that doesn't see fuel cut until 17k.



The R26B had a redline much, much lower than 11k. It was an endurance engine.



The main problem isn't getting the ports to work so much as keeping the engine intact for a useful length of time.

mazdaspeed7

The highest Ive heard of is 12500-13000 in qualifying, and about 1000 rpm lower for the actual race. Even still, thats a short, hard life for an engine.



Heretic, the Yamaha R1 is the bike you were thinking of. Redline was published as 17k rpm, but in reality pretty much everyone that dyno'd them were hitting fuel cut before 16500.

heretic

It wouldn't be the first time a drag racer lied to me. The bikes in question were 600s and they claimed that factory redline was 15k but they were shifting at 17k where the fuel cut was.



The tachs could be off, too. Either way, factory 15k is higher than the highest (intentional) revs that I'd ever heard of for a Mazda-based rotary, which is 14.5k, and heavily disputed. (See IPRA engine thread at www.ausrotary.com )

mazdaspeed7

The IPRA bridges are what I was referring to with my redline numbers as well.

MazdaRx323

I heard from someone that for the sake of seeing how many rpms a rotor could pull got a 13b to 21k before it created a black hole and emploded into another dimension kinda unbelieveable tho really.

tuj

What is the typical failure point for an ultra-high rev unit? Apex seals? Eshaft flexing? I'm just trying to understand what the engineering barriers are to F1-like revs? Certainly not reciprocating motion in the same way a piston engine experiences.



Would it be necessary to change eccentricity from the 13b-type geometry? Ie. the equivalent of making the engine more oversquare?



BTW, supposedly the R26b made 900bhp at 10.5k. Never saw that during the race tho.

heretic

Where did that information come from? Every paper I ever read that mentioned engine speed said that max-rev was 8000, with 9000 available for an emergency.



I would figure that the biggest problem is fitting enough gears in the transmission. With a half-decent transmission, shifting at 9000 drops you to 7000. Shift the same transmission at 13,5 and the drop would be to 10,5, which may not be close enough for best acceleration. If you don't do it, someone else will, and you'll be behind the curve again.



Dropping the outer diameter would help with seal friction, but the ports would not be able to be as large for a given timing, so it may be an overall loss. The main bearings would be even further apart than they are now, so shaft whip would be a worse problem.

j9fd3s

ive read it made 900hp, or i think would have made 900hp if revved higher too, i think its on wikipedia. since wikipedia is on the internet that makes it true, right?

heretic

Nothing on Wikipedia is evar wrong!!!



The new tried of requesting citations for everything is annoying, but in situations like this it is nice, since you could just google up the paper in question and say "Oh! Well I never saw that before."