If you slow the "brap" down, what you're actually hearing is six pulses, followed by silence for the same amount of time. All three faces of each rotor fire once, then misfire once, then fire once, then misfire once, and so on.

 

yeah the brap is when its firing, depending on port and exhaust it might brap every 4th chamber event (you have to look at each chamber individually)

if you would like to learn more, the book 'rotary engine' is out on the web

 

IIRC, Mazda's rotaries have a 3:1 ratio of rotor to e-shaft speed.

 

Whoops, the White One goes hmmmmmm, not brap. Is there something wrong with it?

http://www.youtube.com/watch?v=3bcwNT6XoX4

 

That was a very strange video ray...I'm not entirely sure what to say.

 

what made you guys say its "brap" "brap" "brap" thats Aus interpretation. Us in the US must make our own.

In comparison to a dog, a dog bark is interpreted by every country differently. here's a good example.

# English - woof, woof; ruff, ruff; arf, arf (large dogs and also the sound of sea lions); yap, yap (small dogs); bow-wow
# Afrikaans - blaf, blaf woef, woef keff, keff (small dogs)
# Albanian - ham, ham
# Arabic - hau, hau; how how (هو هو)
# Armenian - haf, haf
# Basque - au-au, txau-txau (small dogs), zaunk-zaunk (large dogs) and jau-jau (old dogs)
# Balinese - kong, kong
# Bulgarian - bau-bau (бау-бау); jaff, jaff (джаф-джаф)
# Catalan - bau, bau
# Chinese, Cantonese - wow, wow (汪汪)
# Chinese, Mandarin - ****, ****

 

+1 on the weird video, but non the less cool.

mine just goes purrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr rrrr

 

Mine goes: *cricket* *cricket*

God rest my little motor.....

 

At idle outdoors near traffic, you have to listen close to even hear if mine's running...

 

Its really called 3:3 ignition misfire by Mazda.

This from Kenichi Yamamoto's book.

Barry

 

My 50mm P-port can idle as low as 500rpms but i keep it around 1500.

 

ZOMG!!! A bridgeported Skyline!!!

http://www.youtube.com/watch?v=Cxg3Llt4cU8

Same principle.

 

^^ **** yeah lol

 

Ok I read through that part of the online book, but the preceding paragraphs explain the situation a little better. Basically, when the intake manifold is at high vacuum it will suck exhaust into the intake chamber via the overlap. It will want to do this because the intake is at high vacuum, whereas the exhaust chamber / exhaust system will be a bit above atmospheric pressure. When the air in the intake that has been polluted makes it's way to the spark plug, nothing will fire because it is too diluted with inert chemicals (CO2, H2O). Of course it will also contain the full dose of vaporized fuel and some fresh air. When this chamber comes around the exhaust port again, the same thing will occur, but this time when the over-lapped intake chamber sucks crap out of the exhaust chamber, it will contribute to a mixture that will experience combustion. So on a chamber to chamber basis, each chamber will skip an ignition due to dilution, that succeed in an ignition the next time. I understand why each rotor skips 3, then succeeds in 3, but why is it that both rotor (in a 2rotor) will have success at the same time, and failure at the same time.

My next question is:
Could an ECU theoretically cut fuel on the 3 intake events that are destined to fail anyway (and then give a little more fuel to the ones that will succeed to make up for the fuel that would be lost in carry over). I know this only would help at idle, but you could probably greatly improve fuel economy at idle. This isn't something that most people on these forums would care about, but I'm sure Mazda tried something like this. Is this how the stock ECU works?

Max

 

Series 4 injection timing:



Series 6 injection timing (FD):



Series 2 Rx-8 injection timing ('09 spec):

 

I actually understand it

 

Hmmm, not sure what you've been smoking lately, but I want some!


Nothing wrong with the car, but if you listen closely to the exhaust note after she warms up, you'll hear about 10 stumbles per second (average for a stock 12a). They are more pronounced with an open exhaust, but they are still there from the factory. This is because, as PercentSevenC pointed out, ALL mazda rotaries have overlap. Even the renesis, which is the reason mazda decided to put valves in the thing (that's what I heard, I haven't ever studied the renesis design).

 

Also explains why bridges and other "wide" ports have a bigger problem with this; the port is not just exposed earlier, but MORE of the port is exposed earlier in the overlap.

The width of the port doesn't just perform the function of "lift" in a conventional engine, it also changes the RATE of opening... e.g., the "slope" of the cam-face, which governs how rapidly the port opens.

With a valved engine, there's a mechanical limit to how fast the port can open, because there is a mechanical limit as to how much slope-per-degree the cam and follower can tolerate without jamming. The rotary can be ported to open much more rapidly in comparison.

Also, the drawing leaves out the indentations in the faces of the rotors; makes it look like there's only a tiny path from port to port when overlapped, when in fact it's a sizeable volume that joins the two ports during overlap.

 

Nope, the Renesis doesn't have any overlap, nor any valves besides the auxiliary port actuators. That's the beauty of side exhaust ports.

 

Ah, then I stand corrected. Just goes to show that I should do my own research instead of trusting another.

 

I looked at the OP and thought what a stupid question. I have actually learned a bit about porting by reading all the posts. Thanks OP... for asking a question which is common knowledge ;D

 

you probably could. if you keep reading the book, mazda's solution is to inject the air pump air into the exhaust ports.

 

my PP has a scary amount of overlap, i put a degree wheel on it and spun it a couple times, its pretty obvious why its going to be angry...

 

That would not be a problem to me. Mine braps too stocky, I like it.