I'm trying to figure out why 3 rotors sound so differently. Why does a stock 20B NA with open pipes sound so completely different from the 3 rotor in the ALMS LMP2 car? Compression ratio? Ignition Setup? PPort? Exhaust header?

How do you make a 3 rotor scream?

 

well as you add one more exhaust pulse per engine revolution its definately going to make a different sound thats also why the 4 rotor makes the unique sound it does. The factor of how an engine sounds is also going to mainly rely on your porting. Heres mine stock port open dump at the track:

http://myweb.cableone.net/mjbless/20...20bquarter.wmv

(New wheels and tires are on the way, I can only cut a 2.2 60' with what i've got now)

 

I like the sound of your 20B

What im trying to figure out is why a 20B would sound like yours or why it would sound like this one, http://www.rotary20b.com/videos/20b-2.WMV Why do some get high pitched and screamy while others stay low and flat? Its pretty much the same motor, why so much noise variance?

 

Porting

 

Also on that video, that car is muffled so it's doesnt apply too much to the true sound of the motor. Why are you concerned about exhaust tone?

 

That's what everybody says, but I don't get it. You are on stock ports in your video but your car gets high pitched, in the video I supplied the car is on stock ports as well.

Header maybe? Muffler? Are you running stock rotors?

Edit: I'm concerned with it just because its something im curious about. Its really weird to me how a motor can have so much variation in its pitch when its still being revved to the same limit. I will also say that the exhaust note on a car is a big piece of how much I enjoy driving it, im a little strange that way.

 

I'm basicaly running open header, my block is all stock.

 

Not the end-all answer, but never underestimate an exhaust, either. Exhausts have a HUGE affect on how it sounds. I remember hearing the $1800 NSX JGTC exhaust, and O M G I almost fell to the ground lol. It made a STOCK NSX (I think it only had headers) sound EXACTLY like a JGTC racer. Sexiest, most amazing sound I've *ever* heard. So don't forget the small things

bcool, when you say open header, do you mean you have headers, and the end in a downpipe that just vents right there? No MP or exhaust/catback? Or do you just mean open exhaust ie no cats?

 

Yep, it's all about exhaust tuning!


-Ted

 

The main difference is Bcools 20b still has the stock directional sleeves with no porting and open header. That first gen has better flowing turbo sleeves and the exhaust goes out the muffler. Different exhaust configurations as Reted stated will change the pitch.

 

Ok I also have a link to a specific 20b exhaust note, but I don't know how to link it from 3 rotor.com. I've been in love with this particular tone for years.

 

Right click on the link, click on "copy link location" then come here, and paste

 

Do you know sleeves they run on the racing 20B? I would think that motor would have some agressive porting but it screams.

Exhaust pipe diameter and header pipe diameter should also affect the sound as well? smaller pipe higher pitch?

Pics are from the BK Motorsports LMP2 car. Is there anything in the pics that indicates why it has a high note?

Bigger pics here http://www.russmarshall.com/v/cars/mazda-courage/

 

In a race 20B the P-port intake engine will have more overlap between exhaust and intake cycles and a VERY direct route for exhaust noise to exit the intake tract.

This and careful manifold tuning also creates a relationship of intake/exhaust dynamic waves that will audibly vary through the rpm range. It will really scream when all these things are working together.

It is common in all engines for the intake/exhaust noise to change dramatically with overlap or duration.

Race engines typically don't run exhaust port sleeves- the ports are too big.

 

Still can't do it, but heres the link to the page.


Go to "HB Cosmo Specific" then "HB Cosmo Audio Clips" It's the 3rd one. Almost sounds like it's in a tunnel or something. I get a hard on everytime I here it.

http://www.3rotor.com/index2.htm

 

http://www.3rotor.com/cosmo_wave/1st2nd.wav

Right clicked on the link, selected "copy link location," pasted here, vioala

~Ramy

 

^ Yep that's it. Ramy you have a Pm.

 

A n/a engine vs. a turbo one will sound quite different due to the turbo making the exhaust much more quiet. Rpms also matter, that First gen sounded like he was shifting at 6800, and was turbo? If you listen to mine, I shift at 8,600 and has 3 mufflers, no turbo.

http://videos.streetfire.net/Player....5-64809850FAD0

 

Some additional info: A few years ago at VIR, the Mazda Sportscar Club of Washing, DC sponsored an event. There were two professional teams there, Kudzu and Spencer Racing. Kudzu had a 3- and a 4-rotor. Spencer had a 2- and a couple of 3-rotors. (These were all in prototype/sports-racer chassis.) AFAIK, all were peripheral ported.

The 2-rotor had a low-pitched sound (think: baritone). The 3-rotors all had a higher-pitched sound (think: alto). The 4-rotor was higher still (think: soprano in pain on steroids).

My working theory is that the pitch went higher as the number of rotors (sound generators) went higher, because the number of waves per second increased.

 

So the motor isn't running sleeves in the pictures I attached?

GtoRx7: That FB is N/A AFAIK

Attila the Fun: I have heard the same thing about piston engines, hence why V12s get high pitched.

All the info you guys are posting is great.

 

When I say open exhaust i really mean open header for the most part, i have a 3" exhaust cutout directly after the header.

Yes, just take a look at this guy's 4 rotor, you can tell that these motors just keep going up in pitch.

http://videos.streetfire.net/search/...CBD70EE2F7.htm

 

Your block is untouched? You're still running the stock rotors?

 

Yes and yes.

 

240rwhp NA with the stock CR? Wonder what it could do streetported with 9.7:1 CR rotors...

 

So the motor isn't running sleeves in the pictures I attached?

The race car? No, you can see the exhaust ports in the 1st picture.

240rwhp NA with the stock CR? Wonder what it could do streetported with 9.7:1 CR rotors...

RE Amemiya GT car w/ NA 20B, streetport w/ a throttle body per each set of primary/secondary port was making 360ps or ~350RWHP.

Another thing that makes a racecar scream is the straight cut gears of a race transmission. On turbo cars it is not uncommon for the gear whine to be louder than the exhaust!