Custom/Hybrid Why not a rotary engine?

[eeerieski]

I'm not talking about that monster rotary x2.6 on youtube, this could be what saves stand-ups this time around.

AIXRO XR50 Specifications
4-stroke single rotor rotary engine
44 hp at 8750 rpm
37.5 lbs
28 ft-lbs at 7500 rpm
294 ccm
10800 max rpm
magnet ignition with variable ignition timing

Change that to a 2-rotor engine at 88 hp, weight would be roughly 5/3 of a single rotor engine ~ 62 lbs + no heavy GIANT expansion chamber exhaust, can probably use common jet ski carbs, common 2-stroke fuel, common starter, comparable fuel efficiency (or lack thereof), can be turbo'd and there are karting guys getting 50hp out of a N/A single rotor engine.... minor problems would be engineering a 2-rotor monster to work with our common parts and mounting it to the hull (enough clearance?). similar water ingestion issues but there is no crankcase to drain, and COST, I imagine these wankles are expensive.
http://www.woelfle-engineering.com/

 

[Matt_E]

They're not terribly practical. Otherwise, you'd see a lot more of them.

 

[Waternut]

Rotary engines are really cool and I've always liked the concept but there are certainly some serious issues that go along with them. First off, they like to blow the apex seals. They can't do high compression...in fact they can barely handle normal compression ratios. They have absolutely horrible fuel economy. I'm not positive on this part but I'm pretty sure they produce almost all of their power in high revs so they have very little torque. Very little torque without a transmission would most likely not even get a jetski on plane.

Even most ported 701 can produce more than 88hp...

 

[SuperJETT]

Ditto the above. I looked into them pretty hard several years ago when some guy was doing the Mazdoo conversions. For a standup, size is a limiting factor plus you need an offset drive to mate up with the driveline which adds more weight/friction/complexity. Just not worth the hassles.

 

[eeerieski]

They have absolutely horrible fuel economy. I'm not positive on this part but I'm pretty sure they produce almost all of their power in high revs so they have very little torque. Very little torque without a transmission would most likely not even get a jetski on plane.

Sounds like a 2-stroke to me

I was stumbling around on the internet, a bunch of karting guys use these and performe maintenance on them as frequently as they would on a 4-stroke. life is probably about the same as a 2-stroke but you can't easily do a bore and hone job... These are also modified to be used in airplanes after a bit of de-tuning so they must be reliable to some degree. Also sounds like the karting guys have problems with cooling and sound, we have a solution to that and it's called water. we can water-jacket the exhaust header and use a waterbox to take care of the sound. Also something that needs mentioning, these are positive displacement engines so emissions are much lower then a conventional 2-stroke.

I wish I could find some dimensions on the engine, a complex drive system may not be required because these engines seem small enough.

I just realized there is no crankcase therefore an electric fuel pump would be required.

 

[ATS_Aaron]

Norwood Autocraft had a 2 rotor (RX-7 motor) in a X2 about 11 years ago. I didn't know anything about jet skis back then so I didn't look at it. ATS_Scott got a glance at it once. I think Tom Stephens was the guy that built it. He no longer works there so I am not sure how to find him or information in it.

Aaron

 

[eeerieski]

More research led me to the same engine (single rotor) producing 96hp at 42 lbs although it does cost $37,000. To get there it is fuel injected and supercharged running on 95 octane. we could use a liquid cooled inter-cooler. Log-in to see the pic below

 

[Matt_E]

You'd have an engine with the performance level of a standard big bore engine, costing $37k.

 

[eeerieski]

yes, but you would be different...

 

[Matt_E]

Win. :biggrin:

 

[OCD Solutions]

Wasn't there somebody putting Rotary engines in skis a few years ago? I thought I saw a couch with a modular powerpack with somewhere around 550cc's per unit. It had 2 units mounted to a modular gearbox.

 

[jetpilot08]

yes, but you would be different...

I had no idea being broke and homeless was being different :nana:

 

[eeerieski]

there's 3 moving parts in the N/A version, I'm sure production costs can be scaled down.

 

[SUPERJET-113]

Hope im not thread dumping, but I like this 2 stroke. Its called the Opposed Piston Opposed Cylinder, or OPOC for short.

Bill Gates just dumped 25 million in it as a investment. He likes it:

http://twostrokemotocross.com/2010/08/bill-gates-invests-in-two-stroke-engines/

 

[OCD Solutions]

http://www.rotaryengines.ca/main/marine.htm

Sales in the marine industry are governed by power and performance which accounts for the current predominance of the two-stroke engine. The new WANKEL rotary combustion engines, which are all four-stroke, give both high power and excellent performance while reducing harmful emissions to levels set under California standards.

A number of boats are already using the GR-OC650M series of marine engines. With power ratings up to 240HP, (add 35% to 40% HP to engines with a Camden Supercharger installed), these boats are operating throughout the United States, with very happy owners.

The boat industry has a definite requirement for clean-running rotary-powered engines in many marine applications. The GR-OC650M series of engines will fulfill a large niche market in this area.

Besides boats and PWC’s, hovercraft have been tested using the GR-CC402M-Fi engines, with highly satisfactory results.

Engine Power Weight L x W x H L x W x H (mm)
GR-CC401M-Ca
40 HP
29.83 Kw
79 lbs. 30.3 Kg
18.76" x 18.0" x 16.77"
481 x 462 x 430

GR-CC401M-Fi
40 HP
29.3 Kw
79 lbs. 30.3 Kg
18.76" x 18.0" x 16.77"
481 x 462 x 430

GR-CC402M-Ca
80 HP
59.66 Kw
115 lbs. 52.1 Kg
23.4" x 18.0" x 16.77"
600 x 462 x 430

GR-CC402M-Fi
80 HP
59.66 Kw
115 lbs. 52.1 Kg
23.4" x 18.0" x 16.77"
600 x 462 x 430

GR-OC651M-Fi
90 HP
67.11 Kw
190 lbs. 86.1 Kg
18.5” x 16.5” x 20.0”
470 x 419 x 508

GR-OC652M-Fi
180 HP
134.23 Kw
260 lbs 117.8 Kg
24.5" x 16.5" x 20.0"
622 x 419 x 508

GR-OC653M-Fi
240 HP
178.97 Kw
390 lbs 176.7 Kg
30.5" x 16.5" x 20.0"
775 x 419 x 508




Marine Engines:

GR-CC = Charge Cooled rotor
GR-OC = Oil Cooled rotor
400 & 650 series refers to displacement & no. rotors
M = Marine
Ca = Carbureted Fi = Fuel injected

Superchargers available for 650 series engines will increase power output by 35% to 40%.

 

[Boris]

I love the rotary motors and have owned quite a few but don't call them 4 strokes. That's an insult.

Back when Rexx was working out the deal to stick Mazda 13Bs into couches I wanted a kid so bad but nothing ever came out and all the Beta testers gave up on the setup. Shame.
Would love to have a 400BHP+ rotary in my GPR for years of ultra reliable power and fun.

 

[OCD Solutions]

How do they handle water ingestion?

 

[Boris]

Never tried running one on water but seeing how there's no long rods to bend, they might survive the odd drink.
The seals might blow out (no, they don't blow on a regular basis) or maybe the stationary gears will take a hit. Either way, you think our 2 strokes are easy to rebuild ? Check out how a rotary is constructed and you'll laugh.

 

[Waternut]

90 HP
67.11 Kw
190 lbs. 86.1 Kg
18.5” x 16.5” x 20.0”
470 x 419 x 508

GR-OC652M-Fi
180 HP
134.23 Kw
260 lbs 117.8 Kg
24.5" x 16.5" x 20.0"
622 x 419 x 508

Good find. So basically, in order to get the power we currently get out of a basic stock bore, limited setup, the engine would have to weigh about almost 3 times what our engines currently way. Let not forget the way 2 strokes make power and the way rotary engines make power either because they aren't the same.

It's good to hear brainstorming to make our sport better but I don't think this is a valid option.

 

[eeerieski]

Then how is aixro getting 1.17 hp/lb when GRP is getting .5 hp/lb? Can someone quote me some numbers on say a 701 or 951 in terms of hp/lb?