Sandman FC

Ive always wondered why 2 rotor engines sound something like 4 cylinders, 3 rotor engines sound like I-6's and 4 rotors sound like F-1 cars only better.
But yet I went to a race at VIR and there were these 20B rx-8s which sounded just like the 787B. But they were perephial port also. So heres the question does a perephial port 2 rotor engine sound like a 787b? or some thing else

marcus219

i thinks in P port motors in general that sound like what your describing...although i could be very wrong.

auricom

i would imagine its a combination of higher revs (more explosions per second) and the sound bouncing around and out of the p port. the p port engine will have a MUCH larger overlap than an ordinary port, so i'm sure that creates all sorts of unique harmonics bouncing around the engine. i would imagine that any rotary with a p port would have extensive engine balancing and such to allow them to rev to at least 10,000 rpm. i don't think you get much power in a p port below 4,000 rpm, and anyone with the money to p port a 3 rotor and drop it in a new RX-8 would likely spend aditional money on getting their revs up. i would guess the p-port engines were naturally aspirated, so a lack of turbo will considerably alter the exhaust and intake note. if they WERE turbo, then frickin' sweet

auricom

did the 787b's R26B engine have the same rotor dimensions as the 13B/20B...i think its 80mm rotor thickness with a max volume of 0.635 liters per rotor face. i know the 787b rotors had the same max volume per face (since its an R26B), but i wonder if they were...ehem..."de-stroked" at all, with a rotor deeper than 80mm (higher "bore"). anyone know?

Sandman FC

nah the rx8's were NA but the team said they were putting down 420 hp

Sandman FC

im not to sure about that I thought I read somewhere that they were close to the same. R26B rotors dont look like your average rotor in any street 13B or 20B though.

rotarygod

iTrader: (1)

The R26B rotors did have the same dimensions as the 13B rotors in the street cars. However they were custom made with 10.0:1 compression so they aren't just your average everyday off the shelf rotors.

ProChemBroTCM

Damn, I want some 10:1 rotors. That would be fine even in my plain ol' 2 rotor. You are right though, those racing rotary engines make such an intoxicating exhaust note; how could you not love that sound?

Attila the Fun

iTrader: (1)

It's a matter of frequency: higher frequencies have higher pitches. In any given time interval, a 3-rotor puts out more pulses than a 2-rotor, and a 4-rotor puts out even more.

Sanspistons

Hmm, don't know about all that, guys. But I went to the 24 hrs of Daytona and the RX 8's on the high banks had the most gorgeous scream you've ever heard in your life. So I say 3 rotors=Formula One howl!!! Never tired of hearing it even at 4:00 in the morning (if only the stupid PA guy would have shut up!!).

By the way; one of the RX 8 guys told me 500+ hp... Again, don't know but only the leading prototypes could catch and pass them in the infield straits. The 911's had better top end, though...

Sanspistons: totally ruined for 2 hr races; I want to go back!!!

PercentSevenC

Well, a 2-rotor fires twice per revolution, same as a 4-cylinder. A 3-rotor fires three times per revolution, like a 6-cylinder. A 4-rotor fires four times per revolution, as do 8-cylinders. So it makes sense that they would sound somewhat similar.

Jeff20B

iTrader: (13)

I noticed an interesting effect when I upgraded my old REPU to a direct fire ignition system similar to what's found in an FC. The exhaust note sounded like it had more pulses per RPM than before, like comparing a stock 1st gen to a 2nd gen.

I've noticed similar effects when adding direct fire to other old school rotaries. That late leading spark (sometimes called wasted spark) changes the exhaust note in subtle ways. It occours 180° after the initial leading spark and must be burning left over fuel at the trailing edge of the rotor to produce an audible change in the exhaust note. I even tried it on my 20B and it sounded a little bit different from everyone elses 20B.

rxtasy3

iTrader: (2)

2 rotor engine will NEVER sound like 4 cylinders. something's wrong with ur hearing.

Jeff20B

iTrader: (13)

Uh, I'm affraid they do... sort of. That is to say a stock 1st gen ignition system sorta does. Once you upgrade to direct fire with the dual leading sparks, it sounds uniquely rotary.