Mazda Rotary Engine?

[hibbert6]

I heard the other day that the Mazda rotary engines can achieve 13,000 RPM, (with rev limiter removed) due to their not having reciprocating pistons. Seems like a perfect boat motor. Has anyone ever heard of someone trying it?

 

[Bondo]

Re: Mazda Rotary Engine?

Ayuh,... Considering that outdrives are happiest at 5000rpms or less,...

Why would you want a motor spinnin' 13000rpms,..??

 

[Philster]

Re: Mazda Rotary Engine?

The rotary engines are notorious for flashy peak HP numbers, weannie power curves and... someone forget to tell them that torque matters.

It might spin to 13,000 RPMs, but with a gear reduction that wouldn't fit inside any drive. You drop in a 300 HP rotary, you'll need huge gear reduction and a tiny prop, and she'll run a 22' boat up to 40 MPH.

They get by in wee little cars, with short gears (high numerically) and lack low end punch (so much I can't stand the little buggers).

My numbers might be off, but the point stands.

 

[sqbtr]

Re: Mazda Rotary Engine?

Electromotive in Manassas, Va. built a prototype with their ignitition installed on it. I'll find out if they went any further with it

 

[Aloysius]

Re: Mazda Rotary Engine?

The limiting factor is the apex seals on the rotor. Rotaries have a tendency to be "dirty", and do not meet EPA emission guidelines without alot of tweaking and bandaids.

 

[guyaverage]

Re: Mazda Rotary Engine?

Taking a stock rotary up to 13,000 is possible (though highly inadvisable) but it wont survive long before the side gears go for a walk or the apex seals self destruct. Been there done that, I have torn them down to see the results. Its ugly.

Adding a turbo will add significant low rpm torque, I dare say my previous turbo Rx7 was one of the torquiest cars I have ever owned. Without a turbo though, as previously mentioned a non turbo 2-rotor is a low-rpm weenie. I have owned a few of them too. You wont like it in a boat. They like to rev, and pretty much need to, but they do it quite well. But low rpm torque is not part of the package.

If you were or are to embark on this project (I love rotaries, and I wouldnt dream of it), start off with a 3-rotor 20B engine, and go from there. They werent used in any North American Mazdas, but they are easy to import, and a lot of import tuner shops even keep them in stock for the Rx7 boys. I hope your pockets are very deep.

 

[Brentathon]

Re: Mazda Rotary Engine?

Huge gear reductions also mean more losses.
Wankels also have large surface areas for their combustion chambers, and much heat loss resulting.....resulting in efficiency drops.
Remember.......the best shape for a combustion chamber is one with the least surface area......hence, the sphere.
That's why Dodge touts their Hemi's (hemi-spherical combustion chambers).

 

[Aviator5]

Re: Mazda Rotary Engine?

Marinization of Mazda rotary engine was done commercially a while ago. They ended up with some resonance problems, that kept driveshaft breaking. Also it was done on DIY level to e certain degree of success. The only advantage of having rotary engine on the boat - low vibration, but it cancels by much higher fuel consumption.

Apeerently they are available commercially now: Atkins Rotary Marine
http://www.atkinsrotarymarine.com/

 

[hibbert6]

Re: Mazda Rotary Engine?

Well, that's a whole bunch of good reasons the rotary wouldn't make a good marine engine. Pesky torque requirements

Thanks for all of the very intelligent input .

Dave

 

[Philster]

Re: Mazda Rotary Engine?

Huge gear reductions also mean more losses.
Wankels also have large surface areas for their combustion chambers, and much heat loss resulting.....resulting in efficiency drops.
Remember.......the best shape for a combustion chamber is one with the least surface area......hence, the sphere.
That's why Dodge touts their Hemi's (hemi-spherical combustion chambers).

NitpicK:

Dodge engines are now Hemi? in name only, as Dodge owns the name "Hemi". It's mostly marketing and not engineering. Some engines flirt with a hemispherical combustion chamber shape, but I believe none are true Hemis in shape, just in name.

That thing got a Hemi? Well... not really...

http://www.automobilemag.com/features/news/0407_hemi_engine/index.html

 

[HT32BSX115]

Re: Mazda Rotary Engine?

Yeah that place is "down the street" from me. They also did produce an (experimental) aircraft engine. It doesn't appear that they do now though.

http://www.rotaryeng.net/

Aside from the wrong RPM and high fuel consumption, It would probably work well in a jetboat........ not so good in a sterndrive or inboard unless you use gear reduction to the right prop speed..... which further reduces efficiency.

 

[Todd157k]

Re: Mazda Rotary Engine?

agreed, the rotary engine gets pathetic mileage.

Philster.. Interesting article, but please don't let it out.. people at the launch ramp constantly look at me in awe when I rip my boat out of the water without nary a cough (they don't see the little "4x4" badge in the back.. they just think it's my mighty HEMI.) lol.

 

[Philster]

Re: Mazda Rotary Engine?

It's our ''little'' secret. The Hemi thing. Not your shrinking manhood!

.

 

[Lou C]

Re: Mazda Rotary Engine?

See what you think...
first pic is the original "Elephant"

next 2 are the new one...
if it is a true Hemi may be somewhat debatable...but the engines make good power with a single cam, pushrods and good old hydraulic lifters...Love it....

old
http://www.youtube.com/watch?v=MXIGLrGZiU8

race version
http://www.youtube.com/watch?v=x6_1_5VOxWQ

 

[Philster]

Re: Mazda Rotary Engine?

If that is the vaunted 5.7 modern "Hemi"

So close.... but not hemispherical

In case you missed it: Chrysler/Dodge engineers acknowledge it ain't a hemispherical combustion chamber in the so-called Hemis.


Edit: The current-production "Hemi" V8 with its pinched chamber, does not have true hemispherical combustion chambers despite the name; rather, it bears a closer resemblance to the mid-1950s Polyspherical chamber

From Allpar.com:

Bob Sheaves noted:

The Hemi design combustion chamber is one of the poorest designs for emissions - why do you think it took so long to get it into production? It almost did not make emissions test requirements even with the modifications. ... Today's Hemi is that (a "Hemi") in name only. [Editor's note: Bob is referring to the head design. It is not a true hemispherical head, but looks vaguely like a hemispherical head with parts filled in.]

 

[sethjon]

Re: Mazda Rotary Engine?

I heard the other day that the Mazda rotary engines can achieve 13,000 RPM, (with rev limiter removed) due to their not having reciprocating pistons. Seems like a perfect boat motor. Has anyone ever heard of someone trying it?

Not anyone of sound mind.

 

[sethjon]

Re: Mazda Rotary Engine?

Ayuh,... Considering that outdrives are happiest at 5000rpms or less,...

Why would you want a motor spinnin' 13000rpms,..??

Well put Bond-o

 

[Limited-Time]

Re: Mazda Rotary Engine?

Does any one else hear Elephants??

 

[mkast]

Re: Mazda Rotary Engine?

427 SOHC
Entirely new heads featured hemispherical combustion chambers with large valve encourage high volumetric efficiency over a broad rpm range

 

[zbnutcase]

Re: Mazda Rotary Engine?

427 SOHC
Entirely new heads featured hemispherical combustion chambers with large valve encourage high volumetric efficiency over a broad rpm range

Blue Oval rules!