After reading the reply shown below, I got to thinking. I have heard that in a Rotary engine, the crank shaft rotates three times per rotor revolution. That said, on your RX8 tack, is it showing the speed of the Rotor, or the output shaft? I thought it was the rotor, not the shaft as written below...

Take a look at this animation.
http://www.rotaryengineillustrated.c...tions/RE3a.php

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1.3L's Avatar
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Quote:
Originally Posted by Ninonemo
I got to do some long-distance highway driving and took a look at the RPM meter. I was shocked that at 60mph, it's at about 3000rpm. At 75mph, it's at about 3500rpm!

Isn't this too high, or are all rotaries like this? Or is just my car?
No, that is normal. And don't forget, when the tach shows 3000 RPM, the rotors are only spinning at 1000 RPM, which isn't much.

Also, as a comparison, a Honda S2000 spins at 3250 RPM at 60 MPH, so the RX-8 is right in the ball park (in terms of crankshaft and eccentric shaft speeds).

1.3L

 

The tach is showing the rpm of the output shaft (eccentric shaft). So in reality, the rotor is "revolving" 1/3 of the rpm's the tach is showing. And yes, on the highway, even while cruising you'll get a hell of a lot of buzzing if you don't have the stereo cranked. It's even worse when you're trying to get somewhere in a hurry!



edit: Just to vent on this a little, I don't really feel that 6th is overdriven quite enough. Honestly theres a bigger gearing reduction from 4th to 5th than there is from 5th to 6th. Considering you can hit the eight's highest possible speed in 5th gear... 6th is practically useless. Now the viper knows what overdrive is really about, in 6th you could hit 1000mph on a dyno with no wind resistance (while this is an exaguration... its not far from the truth.

 

OK, so is this right? The 9000 RPM red line, is really 3000 RPM rotor speed?

 

Definatly.

 

OK, another question, why is the engine SO loud when your up at say 9000 RPM when the rotors are really spinning at 3000 RPM?

Lastly, Since the Rotor is REALLY spinning much slower than say a piston engine, why is the gas mileage MUCH lower is most cases? Yes the compression is much lower thanks to the shape of the rotor and since your "pushing" a triangle in a oval...

 

Yeah but think about the # of ignition cycles per rev. For a piston engine (4 stroke), there's 1 ignition cycle for every 2 revolutions. Now look at the rotary, with 3 rotating chambers and 3 ignition cycles per revolution of the rotor.

So, at 3000 rpm (at the tach') a piston engine is igniting 1500x a min. However in a rotary with 3000 at the tach' the rotor is spinning at 1000, which is 3000 ignition cycles. So, double the ignitions mean more fuel consumption.

 

the compression isn't any lower in a rotary engine than in a piston engine (gasoline...diesel is a different story). the compression ratio of the renesis is 10.1:1, right there in the same ball park as boingers.

 

when it comes to gas mileage start thinking 2cycle and you won't be disappointed.

 

Intake noise and exhaust pulses are more frequent than a piston engine.

 

Yes, 3000 sparks from the LEADING plug, plus the other 3000 from the Trailing!

You also forgot to include the OTHER rotor!

So at 9000 rpm, we have 18,000 rotor ignition events, triggered by 36,000 seperate sparks!

That's a lotta sparx!!

S