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Old 09-09-2009, 11:39 AM   #1
mjg OP
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Why did rotary engines never catch on?

ISTM they make sense.
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Old 09-09-2009, 11:42 AM   #2
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There were problems with the initial ones with the seals used for the combustion chambers...
I'm sure they've fixed it by now but the stigma is still there.

I always thought rotary engines were cool as well.

I'm waiting for an application of the Sterling engine.

John
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Old 09-09-2009, 11:43 AM   #3
Sir Not Appearing
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Quote:
Originally Posted by mjg
ISTM they make sense.
Poor fuel consumption
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Old 09-09-2009, 11:45 AM   #4
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I belive thier biggest down falls are the life span of the apex seals and emissions.
Four stroke piston engines are more reliable and burn cleaner.
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Old 09-09-2009, 11:46 AM   #5
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Seals are a problem. Sir is right, fuel consumption is high for such a small motor. Rotary motors are also very sensitive to heat. Overheating can kill a rotary.
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Old 09-09-2009, 11:56 AM   #6
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Oil consumption, seals, fuel consumption. Just look at the Mazda RX-8 and talk to some of the owners. Very good idea in theory, but the technology is still not up to it.
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Old 09-09-2009, 12:32 PM   #7
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see also: 2009 Iron Butt Rally.
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Old 09-09-2009, 12:39 PM   #8
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They sound like poo, and have 2 lb.ft of torque at 13,000 RPM
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Old 09-09-2009, 04:47 PM   #9
Fishyhead
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Two words: Apex and Seal
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Old 09-09-2009, 05:43 PM   #10
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Not easily rebuildable. Maybe not a huge car issue but it is a huge (to me) offroad issue.
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Old 09-09-2009, 05:48 PM   #11
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Heat.
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Old 09-09-2009, 05:57 PM   #12
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The 79-85 RX-7 burned some oil by design (probably newer ones did too, I dunno, never had one). There was a metering device that dripped oil into the carb. Obviously not suitable for idiot consumers who don't know how to check their oil. Gearheads who were a target market of the car had no problem.

I had over 160,000 miles on my 1985 and loved it. Screamed like a banshee. Has an overrev warning buzzer that sounds like a stall warning in a small plane. I'd keep it redlined for laps at a time on trackdays, then drive it 200 miles home Sunday evening. One of my favorite sportscars of all time, no question.

FWIW, a little 1.2 rotary with straight pipes is just about the loudest thing you've ever heard. Seriously.
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Old 09-09-2009, 06:00 PM   #13
Solo Gato
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Quote:
Originally Posted by crampfan
They sound like poo, and have 2 lb.ft of torque at 13,000 RPM
I have a hercules aircooled rotary (just the engine now) whose exhaust pipe will cook chicken at 20 feet.
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Old 09-09-2009, 06:16 PM   #14
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They used to do a horrible backfire, also. And all too easy. I think a major problem is that if the timing is off ever so slight it screws up everything.
More so than with regular pistons.
dc
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Old 09-09-2009, 06:16 PM   #15
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I raced RX-7's for years. It was common to go two seasons on a single motor. High rpm use required carbon or ceramic apex seals which were very sensitive to detonation. Iron seals last forever. I had two rotors that last four seasons, and they had 100,000 street miles on them before I built the race engine.

Excessive heat warps the alloy/cast iron sandwich that makes the engine, usually ruining the epitrochoidal chambers (expensive).

They do use oil, sort of like a two stroke, to lubricate the apex seals. And are generally filthy with respect to emissions. The exhaust gas temps were usually about 1700F at race speeds because of the hydrocarbons that continued to burn in the exhaust.

If you remember Jim Downing's three rotor WSC from the 24hrs of Daytona back in the heyday, you'll remember the orange glow of the exhaust as the car circulated the track. And the heinous racket. The pit crew would put a muffler on it when it came in the pits so they could fuel it/change brakes/tires.

Man, do they love a turbo. 300+ HP was easy on a low boost 2 rotor.

IMHO, the emissions regs made them an unworkable solution.
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