detectiveorange

When I'm stuck in traffic I tend to let my mind wander off and start thinking about the theories behind cars and the mechanics of cars. well, one thing that popped into my head today was, why do they only make rotary engines with 2 rotors? It's an incredibly short engine, I figured you could at least fit 2 more rotors in there and still have a proportional looking hood

Yes, they made the 3 rotor rotary engine (I'm not sure what it is and all the specs, I just know Rob Dahm on youtube has one in his RX-7) but what ever happened to it? why did they stop making it?

lastly, why haven't they made anything above 3? the ft-lbs of torque has to increase dramatically the more rotors you add, right? assuming that it's tuned properly. or does the power just peak after 3 rotors?

Just curious there needs to be a forum on here (or a thread at least) for topics like this! :D

RIWWP

iTrader: (2)

Search on 20b and 26b. Newbies have been dreaming about, and orgasm'ing over, 3+ rotor production cars for a long time. Eventually reality sets in, but there is always another newbie around to wet the bed.

The 20b has been powering race cars up through last year on the Grand Am series, quite a few 4 rotors out there, LOTS of 3 rotor swaps in RX-7s, several in RX-8s. There is even a 6 rotor car in Australia, and a 12-rotor engine developed for a boat.


The core of the reason why they aren't manufactured is because they are insanely inefficient in fuel and emissions. Going from 2 rotors to 3 isn't a 50% increase in power or a 33% reduction in fuel mileage. It's more than that for each. One of the 3-rotors on the forums here can only make a best of 8mpg, and 4mpg is more common (as an example).

Carbon8

iTrader: (4)

3&4 are for kids

RIWWP

iTrader: (2)

Here are 2 of the 3-rotor race cars:

Speedsource RX-8, numerous wins, 2 championships:


Furai concept that unfortunately burned to the ground back in 2005:


A 4-rotor RX-8:


4-rotor 787B that won the 24hrs of Le Mans:


A 6-rotor RX-4:


The 12-rotor engine:

SayNoToPistons

iTrader: (8)

Why only two *********?

detectiveorange

oh wow, i saw that 6-rotor car video a while back before I actually got into rotaries. I always wondered why the furai sounded so odd. because it's a rotary, derp lol. that 12-rotor engine is absolutely stunning. that's another thought that entered my head today in traffic. "i wonder if its possible to make a V shaped rotary engine" i guess it is lol. as long as you strap 3 torpedoes (at least that's what they appear to be :P lol) to the top of it. thanks for all the awesome info guys!

monchie

Would be nice to see another (more improved) rotary in the near future...

detectiveorange

I agree. The rotary engines are cool, they're different, they're fun. but they're not reliable AT ALLL, which is feel is something people in this day and age are looking for, something reliable.

Every company is making some form of Honda Civic with some sort of ecoboost "save the environment" option on it to save money. the only cars to really rise above this trend lately are the BRZ/FRS and the Genesis. maybe even the mazda 3 and the mx-5

It'd be so awesome to see mazda put the rotary back into production. I find it funny that the rotary engine is less reliable than the piston engine, even though it has fewer moving parts lol


opinions?

detectiveorange

Although, the piston engine has been in the process of development for well, pretty much forever lol. The rotary engine hasn't even been given a chance (in comparison to the piston engine), maybe the rotary engine does have hope, it just needs time and lots of trial and error in development? :O

alnielsen

iTrader: (4)

Your basing your opinion on the current rotary engine, the Renesis. The engines in the RX7 could be quite long lived, if they were properly maintained and not over boosted.

detectiveorange

oh really? I always thought the would be less reliable because of the apex seals sweeping over the exhaust ports. what do you consider "quite long lived" too? I haven't done much research into any other rotary besides the renesis xP there's so many names that are flung around haha

mind giving a list of all the names(to research), or is it a REALLY long list?

detectiveorange

also, has anyone seen this? pretty cool.

alnielsen

iTrader: (4)

150,000+ Miles without premixing. A wiki on the rotary engine will give you the names.

alnielsen

iTrader: (4)

Yup, that came out about a year and a half ago. There is a thread about it somewhere on here.

RIWWP

iTrader: (2)

The non-boosted peripheral port rotaries were generally more reliable because of heat, not because of any seal configuration. ANY engine that makes 110hp is going to be more reliable than the same engine making 232hp. More power = more stress. The boosted rotaries had a similar drop in reliability that we see, again, more power = more stress. There is literally no way to get around that basic fact, and this is true of any engine, regardless of engine design. It has to be designed for the higher power levels to begin with to not see a substantial reduction in lifespan.


I express my opinions on that travesty here: https://www.rx8club.com/rx-8-media-n...hrough-239514/

alnielsen

iTrader: (4)

The 110 hp figure is close to what the early 12A engines made (100-105 hp). The first 13B (RX7 S3) made 135 hp. And I believe the last NA RX7 made 165 hp.

detectiveorange

I was thinking the same thing when I was watching the video. "there's no way mazda hasn't thought of this already" and he said that he built his own model of the engine and it reduced exhaust temperature by 600 degrees???? I wanna see this engine.... -_- this guy who appears to not have any sufficient means of making an engine worth putting on the production line (i.e. that shitty rotor that looked like he just dumped liquid metal and shaped it lol) made an engine that's more efficient than mazda??? I REALLY wanna see this engine lol. At the same time though, I wanna know the results that mazda came up with while trying to make a rotor with this shape. probably like RIWWP said, the rotor was probably just so imbalanced that it became inefficient. still though, i'm curious.

bse50

RIWWP is a noob.
The 787b is not a 3 rotor engine.

Damn!

RIWWP

iTrader: (2)

Whoops :shameface:

Fixed

bse50

You're getting old dude! :p

RIWWP

iTrader: (2)

Yeah, it happens every day.

Fortunately: RACING PAST 40, PART II: Slower Reaction Times, and Other Famous Lies