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So I was having a discussion with a parental unit regarding the FD and the RX8's engines. An interesting point I found was the concept of adding an extra rotor to the RX8, theoretically granting it's 6-speed manual version 350 HP with 240 ft/lbs of torque. The figures were achieved assuming by adding another Rotor, we add 1/2 of what the car already has on it.

After A little dabbling, I found an alleged 4 rotor FD on youtube.

I'm not familiar with most technical concepts in cars, but if anyone can shed some light on this, I'd appreciate it. It's one of those things I'd like to do before I settle down in life a decade or so from now.

You can't ''add'' rotors to a car.You can swap engines,though,like a 20B which has 3 rotors.That RX7 you've seen is probably the Scoot Sports RX7,and it has an engine which is made by putting together two 12A engines.(or 13B).

But in that sense, you could put 2 Renesis together for the same effect?

With a fagged up E-shaft, you could.

Too much work though. Want good power? Just port the f**k out of an older 13b.

With money,you can even make a 12 rotor engine.But even on a 2 rotor engine,you can put out a clean 300-350hp.

@Yoshida Seiji : What's an E-shaft now?

I'm not looking for a turbo, just an advanced Naturally aspirated system. Something like an underdog that makes the RX8 look a little better compared to the FD's pure capability in comparison.

At a glance, the availability of 20b engines seems to be limited. I'm keeping that option in mind, but supposing I were to simply build up on 2 Renesis engines, what would be the basic overview of what has to be done? I'm aware it wouldnt be practical, but I'm curious.

E-shaft means eccential shaft, which is kind of rotarys crankshaft.

If you wanna build a 4 rotor engine, you need _little_ more experiense with rotaries. So you have NA-system? Just get a new intake manifold (ITB's)

If you wanna disassemble your engine, buy a 13B disassembly DVD from drifting.com. Then you wanna get power, buy a rotary porting DVD from drifting.com also. In that video they a making a streetport, but if you wanna get some serious power (and big fuel consumption) do the bridgeport.

Here is a couple link of porting:
Rotaryheaz
Mazdarotary
RX-7 Club thread about ITB's

Oh and here is a video:
Pineapple racing

Nothing sounds more mean than a peripheral port rotary!

Or drains more fuel!

This post has been edited by TTH on Jun 23 2009, 03:25 PM

Theoretically you could add rotors, but if you want to do that you have to either cast or machine extra engine. If you know how to do that, you wouldn't have asked.

Yeah though, I recommend adding an aftermarket turbo setup. I read about an RX8 in some car magazine with a turbo, it had 450 ponies.

Cast or machine extra engine? Close. You need an E-shaft. Everything else in comparison is trivial. There are companies who make such e shafts, for both 3 and 4 rotor configurations- but theyre expensive.

Huh, maybe I should make those shafts myself. I work at a freaking forge. It's probably not hard to machine those things.

Theres still the other tid bits to do, custom intake, fuel rail, exhaust, etc- but like i said, fairly trivial in comparison to a rotating shaft. If youve the means and the care, look into it.

you can make a 4 rotor, but just as Scoot did, theyt ook 2 12A motors and "put them together" in the sense that you mean

but we are talking big money here, much more money than the power you will achieve can justify....although, this is the sickest sounds in the world...

http://www.youtube.com/watch?v=eq7w7110SkQ

http://www.youtube.com/watch?v=JaAKOrOWV7Q&feature=related

overall, you are looking to spend a lot of money, research and time into making a 4 rotor like it seems like you want

and no, you can't just add another rotor to the renesis, you need to get a 20B engine if you want to go that route

EDIT : start reading.... http://protonet.org/doc/Mazda_R26B_A4.pdf

This post has been edited by backalleyracer on Jun 24 2009, 02:14 AM

Well when you know much more about rotaries, you should explore Kiwi-RE and their 3&4 rotor kits.
3 rotor kit
4 rotor kit

It was my understanding that adding anything more than 4 rotors would put unacceptable strain on the E-shaft. I would also assume that in order for each rotor to rotate at the correct time you would need to have each one turn at a different time (similar to a piston motor how each piston rises at a different time) which may be limited on the current E-shaft design.

Of more interest is why in top fuel drag cars none run more than a 4 rotor setup. It may be theory (ie: 1 rotor = 200hp so 6 rotors = 1200hp) but the practical may suggest a loss in power when you reach a particular rotor number.

My two cents

This post has been edited by Helix on Jun 26 2009, 01:35 AM

Question regarding my original computation for the original "3 rotor idea". How would one compute the engine's output; by my method or...?

Well it's kind of simple thinking. Normal 2-rotor FD gets normally about 400hp, so one rotor makes about 200hp. Of cource it's turbo, so it's possible to get even more from 13B Turbo by changing porting and turbos. N/A 13B PP-ported gets about 320hp with original 13B-T/REW rotors, with RX-8 Renesis rotors you reach almost 400hp (maybe even over 400hp)

This one is pretty bad-ass:
20B Cosmo on dyno with T51

This post has been edited by TTH on Jun 26 2009, 03:23 AM

Engine brake or Dynamometer.

Those would be excellent to measure an already existing engine's power output, but I think he was trying to get a rough idea of expected power output without actually building the engine ( armchair discussion I guess ).

More or less, apex. I'm still 16, so building it is out of the question for me at the moment. Mathematics I can do, so long as I can have a general grasp of which factors affect what by how much in numerical values.

you can get as much power as you have money for the most part

thread - http://www.rx7club.com/showthread.php?t=808935

http://www.youtube.com/watch?gl=CA&hl=en&v=UQrPNvFx8eY

809hp

he ended up making more too.....

http://www.rx7club.com/attachment.php?atta...35&d=1230337255

874.08hp

ummmm, i think you mean eccentric shaft.

Wow, a 4 month necropost for that?

Good job, sport.

I just hate incorrect information. Who knows, someday that may have saved someone from looking like a complete tard at a rotary shop trying to talk to someone about their engine.