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¯\_(ツ)_/¯
¯\_(ツ)_/¯ UltraDork
9/12/18 1:31 p.m.

I like rotaries, but they have their... issues.  The early EFI ones have ancient sensors and management, the Renesis engines have newer super complicated stuff, the really early carbureted stuff is old and carbureted, standalone EFI isn't always the best.  What is the most reliable rotary engine one can build/buy, within reason?  Defining reliability as "start and runs pretty well without a bunch of berkeleying around."  Just to make it fun let's assume we want, say, 200hp minimum.

My personal guess is an N/A 13b with a mild port, no emissions stuff, and a carburetor.  Or a really well dialed in standalone.  Or maybe some sort of simplified Renesis instead.  What say you?

java230
java230 UltraDork
9/12/18 1:41 p.m.

I want 3 rotors and a turbo added. 

I know very little of rotaries, but they are cool, and I kinda want one.

GameboyRMH
GameboyRMH MegaDork
9/12/18 1:45 p.m.

The Renesis has the best basic design, although it comes with troublesome emissions and ignition systems. So "simplified Renesis" seems like the right path.

I'd say Renesis with some porting work, emissions stuff delete, aftermarket ignition, external oil feed system w/ 2-stroke oil tank, well-tuned standalone, maybe ceramic rotor seals if the budget allows.

GameboyRMH
GameboyRMH MegaDork
9/12/18 1:51 p.m.

Troll option:

Ian F
Ian F MegaDork
9/12/18 1:52 p.m.

In reply to GameboyRMH :

Rotary. Not Radial. wink

The0retical
The0retical UltraDork
9/12/18 2:01 p.m.

It's not but there is the Gnome Rotary Radial engine. So. Much. Rotating. Mass.

Anyway I'd think a simplified S2 13b-MSP would be the correct answer.

A S4 or S5 NA, fuel injected, mild street port, with a standalone would also likely work well. (Ultimately the route I opted for for the RX-3)

Really though, as long as you keep them full of oil, change the coolant from time to time, and don't get greedy with the boost they likely only have a slightly shorter life than the mean of vehicles on the road.

 

 

¯\_(ツ)_/¯
¯\_(ツ)_/¯ UltraDork
9/12/18 2:17 p.m.
The0retical said:

Really though, as long as you keep them full of oil, change the coolant from time to time, and don't get greedy with the boost they likely only have a slightly shorter life than the mean of vehicles on the road.

And actually a longer life than piston engines in racing applications provided they're not making crazy power, which is why I'm interested in them- our RX7 sucked straight sandy dust at WOT for two days straight and still ran at the end.  And why I'm way less worried about things like seal life than I am about things like "will it start and run without a million sensors needing to be perfectly happy all the time"

wvumtnbkr
wvumtnbkr UltraDork
9/12/18 3:01 p.m.

my current issues aside....

 

S5 13B with a street port, stock ECU and a new wiring harness.

Robbie
Robbie PowerDork
9/12/18 3:13 p.m.

I think the most reliable rotary is the one that is currently at WOT and high rpm.

fidelity101
fidelity101 UltraDork
9/12/18 4:52 p.m.

I built an engine for dave on here w the hillclimb rx7. I could build you a copy basically. 200hp simple and stealing petes idea is to use a 4 barrel manifold with the easy efi square bore and you get short runners with good flow. I like to do certain miscellaneous mods when i build the engine like heavy duty springs, improved oiling, viton o rings for high temp abuse resistance. My franken wankels easily have parts as early as 1983-2011 in the engine. Generally mazda is the best place to go to when you want updates they have the best r&d on the topic so generally they are always improving their parts through the generations of engines.

 

Renesis swap could be done and i believe they have hacked s1 ecus so you can essentially transplant the powerplant or again just carb that engine they got a manifold adapter

 

Also a big ass radiator helps

 

A reliable rotary is a non boosted one.

RevRico
RevRico UberDork
9/12/18 4:59 p.m.

Where do 4 rotors fall on scale? Are they even available for "civilian" use?

I don't know anything about them, just that they sound spectacular and I put them in everything I can in Forza. 

The0retical
The0retical UltraDork
9/12/18 5:07 p.m.
Tom Suddard
Tom Suddard Digital Experience Director
9/12/18 5:41 p.m.
¯\_(ツ)_/¯ said:

What is the most reliable rotary engine one can build/buy, within reason?  Defining reliability as "start and runs pretty well without a bunch of berkeleying around." 

HAHAHAHAHHAHAHHHHHHHHHHAHAHAHA

Toyman01
Toyman01 MegaDork
9/12/18 5:52 p.m.

I put 200K on a 12a before it puked. That's pretty reliable isn't it?

Wally
Wally MegaDork
9/12/18 5:52 p.m.

iceracer
iceracer UltimaDork
9/12/18 5:56 p.m.

In reply to Wally :

I have a couple of those, still connected but not used.

fidelity101
fidelity101 UltraDork
9/12/18 6:30 p.m.
RevRico said:

Where do 4 rotors fall on scale? Are they even available for "civilian" use?

I don't know anything about them, just that they sound spectacular and I put them in everything I can in Forza. 

Its just so costly, thats the problem. And availability of specific parts can be tough.

Knurled.
Knurled. MegaDork
9/12/18 6:44 p.m.

12A.  Except ypu can't build them anymore.   If you kept fluids in them and the air clean, they were good for 200k miles minimum.

 

Same for the GSL-SE engine.

 

Biggest problem with both was chrome flaking.  Mazda made that better with the S4 engines but they moved the coolant lands to the side housings, where they could break off if you got the engine hot and/or overtorqued the tension bolts.  (25ft-lb and NO MORE)

 

 A reliable 200hp engine would be a street ported 13B built around as many 12A parts as would work in a 13B, with FC rotors for the RPM- and chrome-friendly 2mm apex seals and 12 pin rotor gears.

 

This is by no coincidence the basis of the engine in my '84, except I bridge ported it.  I got six years and ridiculous miles out of it before it started to suck coolant a little.  (Non Mazda coolant seals).  Just a little bit over 200hp...

thatsnowinnebago
thatsnowinnebago SuperDork
9/12/18 6:47 p.m.
The0retical said:

In reply to RevRico : 

They're available if you really want one.

That's only 12,642.38 Freedom Dollars. Huge savings from Aussie Bucks...

Hoondavan
Hoondavan Reader
9/12/18 8:37 p.m.

It seems like the Renesis had more than their fair share of issues/problems.  Regardless of the reality,  I'd say the early RX8s effectively poisoned the well.  

 

Knurled.
Knurled. MegaDork
9/12/18 8:55 p.m.

The problem with the RX-8 was that people bought it to toodle around in and rotaries do not like toodling around. Need to run heavy throttle all the time and control your accelerating by shifting early.  A loaded rotary is a happy rotary.

 

I'd shift my bridge port at 2000rpm and/or skip gears, to keep pace with traffic.  But remember, all rotaries have no torque, and bridge ports especially are worthless below 6000rpm.  Need to swap in a piston engine so that you have to reset the lash every 1000mi and maybe replace the lifters every 3000mi because solid rollers suck from a reliability standpoint.  (And if you are not running a solid roller cam, you are taking a huge performance downgrade compared to a rotary)

 

 

gencollon
gencollon New Reader
9/12/18 10:57 p.m.

In reply to RevRico :

The Rotors youtube channel told me that a 3 rotor swap is basically a $20,000 motor swap. https://www.youtube.com/watch?v=Nn9oPyhY3z4.

Maybe we can find out what Matt Huffman knows about building a reliable rotary? https://www.youtube.com/user/mchuffman/about?disable_polymer=1 IIRC, he has a Pineapple Racing motor.

He seems to have a good amount of seat time, and success.

Oh. And I can't forget about the rotary specialists: https://www.youtube.com/watch?v=HbYkV024bJo We could ask them what they'd do to make a reliable rotary

Dave
Dave Reader
9/12/18 11:09 p.m.

The consensus seemed to be the early 80s 12A motors when I was into them a over decade ago. They are getting pretty old now though. Not 200hp though.

WonkoTheSane
WonkoTheSane Dork
9/13/18 12:33 a.m.

My s4 had 217k on it when I tore it down, and it was largely within spec still.  I put a further 30k on it with a port job and megasquirt before I sold it.  The only problems I had were still induced (crappy crimp job, cheap hose clamp that broke, etc.)

 

So I'll echo the s4, s5, mild port, rebuilt with quality (largely OEM) parts, fresh wiring harness, and a standalone.  Then make sure you redline it often.

 

That being said, I'm up to almost 80k on my rx8, and it's been reliable as gravity.

GIRTHQUAKE
GIRTHQUAKE Reader
9/13/18 2:42 p.m.

Can't forget ya'll- a reliable, properly working rotary is one that's allowed to warm up to temperature. Even a 5-minute warmup is a big deal to them.

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