Rotary smotary....

You guys know what the coolest thing about rotary engined cars is????

Once you get the rotary POS out of one, there's plenty of room for an american V8!

-Mindgame

 

I couldn't have said it better myself.

 

I didn't see the motor. I think it was more of an experimental rotary project than a real honest to god drag car. I can imagine it would be hard, but why do you consider it almost an impossibility? Forgive my ignorance in rotaries, but perhaps you could elaborate. I just googled this site, it is for some rotary company or another, and they have data for a 6 rotor engines towards the bottom of the page.

http://www.monito.com/wankel/rpi.html

My thoughts would be that a 6 rotor engine would be too big to fit in a convential automobile, but as I stated earlier, I am far more ignorant of rotary engines than I would like to be.

*Edit- Woops. Didn't realize someone already used an example of a 6 rotor in this thread.

 

LOL nothing personal there JimLab - I've gone through way too many rotaries to count - over 10 years of nothing but rotaries No there has never been an 5 rotor engine built. As to the 6 rotor engine somewhere I have the size and weight specs on it, was contemplating on putting one in my old tow truck - 79 Suburban. From what I remember it would fit in there, partialy pushed into the trans tunnel though.

 

The only way to increase displacement with a rotary engine based on 13B rotors and housings is to add more of them. The more you add, the longer (and heavier) the engine gets. You also need a support bearing and plate in between every 2 rotors which adds to the length.

Basically a 5-rotor engine would be about 4-5 feet long without accessories and incredibly heavy without aluminum end plates, which are incredibly expensive. This isn't something that's going to fit in any regular passenger car, so unless it was a tube-frame based drag car or rail dragster, it's not feasible. Even then, you're talking about an engine for which everything, including engine management and ignition would have to be custom made.

You can see the size of a Cosmo 20B 3-rotor engine in relation to my RX-7 in the picture below. Just for reference, it weighed ~525 lbs. on its pallet with the stock turbos, intake, and accessories. The stock 13B-REW 2-rotor weighs about 430 lbs. in the same trim.

http://home.gci.net/~jimlab/images/Misc/20B.jpg

 

One thing that hasn't been talked about at all is SIZE. Every rotory I'm familiar with from the original Wankle to the present Mazda has aproximately the same size rotor. There are some very small model airplane engines. So going smaller doesn't seem to be a problem. But when ever someone talks about increasing power they talk about stacking rotors. Why not increase the rotor size? Why aren't there any big two rotor engines or huge industrial rotory engines? Recips. come in every thing from tiny thimble size engines all the way up to cyclinders you cam stand in.

If going smaller is not a problem why not stack two 3 row engines in the same case? Or even three 3 row engines in a triangle? You'd have 9 rotors in a package the size and shape of a V8.

One other thing I've noticed in discussion like this, is that many people refer to this technology (rotory engines and over head cams.) as NEW. Most of this suff has been around for a very long time. And I don't think GM et.al. looked at this just once 30 years ago. I'm sure there keeping a close eye on Mazda. And should some tech. beak-though happen that makes this engine viable, I'm sure they will jump on the band wagon.

This is particularly true of OHC engines. People keep saying that GM needs to step into the 20th c. and build OHC engines. They seem to forget that GM did build (or had built) DOHC engines for the Corvette. This engine in 350ci. size, was very large and didn't fit under the low hood line very well. In streetable form, where low end torgue is desired, it didn't produce overwelming benefits for it size. The only appearent benefit for this arrangement is the ease of adding VVT. Almost all modern OHC engine are fairly small and need all these modern tech. to produce enough HP to move the car. I believe GM prefers to simply overwelm the competion with larger high HP engines in a very small packages.

 

They put LT1's and LS1's in the Mazda RX-7 all the time. I know two people in the Chicago area that have them.

 

Actually, they have changed size, but not by much. I believe the original engines were 1.0 liters, the 79-85 12A engines were 1.2 liters, and the 86-up engines were 1.3 liters.

But what you say is fairly true. In fact, they've been doing research on miniscule rotaries as a power source for laptops. They run on some form of natural gas (I think), and supposedly are super-effecient.

I think the biggest problem of just making the rotor bigger is it accentuates one of the problems of a rotary, and that is ineffecient combustion chamber shape. As you widen the rotor, you'd have a harder time maintaining the compression ratio and any kind of effeciency.

 

Mazda experimented with a prototype 15A and even a 21A, but the combustion chamber shape of the rotary is already grossly inefficient and making it larger doesn't help matters at all.

How are you going to get fuel and air into and exhaust out of all these engines? Making a rotary engine longer works as well as increasing the number of pistons because the intake and exhaust manifolds simply get longer. The minute you start trying to make a very complex housing, you'll vastly increase the cost of the package and complicate the plumbing significantly.

True, but the majority of rotary fans are young and/or ignorant and not well-versed on the history of piston engines -- or even their own engines, for that matter. They think that DOHC engines were only recently invented by Honda and assume that more cams must be better in all applications simply because "newer = better".

Don't hold your breath.

Most people don't understand that multiple small valves have a greater benefit in small displacement engines where two large valves are not feasible. Not that multiple valves won't help in almost any application, at least in low rpm filling of the combustion chamber, but they also don't understand the penalty in package size, weight, and cost that go along with overhead cams.

I like to use this picture to illustrate the concept...
http://home.earthlink.net/~jimlab/pi...comparison.jpg

As you mentioned, the LT5 was a tank both in size and weight, even with an aluminum block.

 

Although the rotary isn't "new", it's a lot newer than piston-based engines. Both in terms of time and especially in terms of development.

The first rotary engine prototype (DKM) was completed in 1957 in conjuction with NSU. That's a far-cry later than the first piston engine. And the first rotary powered car didn't apear until 1965, then again in Mazda's cosmo in 1967.

But I agree, most of the younger tuner crowd has no idea how long the DOHC design has been around. And it's not just new=better to them, if it supposedly has "more technology" in it then it's got to be better.

And I think a lot of rotary fans are actually older, if you don't appreciate the engine for what it is, it's frustrating BEYOND BELIEF. Most of the 16year old kids who actually own a rotary don't for very long, it's the kids who DON'T own one who are always spouting off crap like "they can rev to infinity yo!!1!".

 

Perhaps, but it's been around long enough for the people tinkering with it to have figured out how to make it work properly. After all, it's a very simple design with only 3 moving parts...

You'll have to excuse me. Over 8+ years of rotary car ownership, I got tired of hearing all of the excuses made for the rotary engine over and over again.

The kids who do own one tend to spout that kind of crap as well.

I think if you pay a visit to the RX-7 Club forum you'll find that the average age of owners of even 3rd gen. RX-7s is relatively young. Any teenager with understanding parents can own one now that the price has fallen to less than a new Honda Civic.

 

It's not an issue of it working properly as much as it is an issue of it working effeciently.

Why the crap did you have a rotary for 8+ years if you had so much trouble with it? I know if I had a car for that long that was crap I wouldn't be so forgiving.

 

Working properly is a valid point when you can't achieve the power levels of a relatively inexpensive V8 without putting a lot of stress on the engine and running a very good chance of having it fail.

I didn't say I'd had rotary engines for 8+ years. I've had a rotary car for 8+ years.

The second and last (barely) running rotary engine was pulled out of the car in May of '98 with ~13,000 miles on the odometer, which is where it still sits. Since that time, the car has spent the majority of its life on jackstands while I drove sports cars that didn't require such babying (MKIV Supra twin turbo, Corvette Z06) and fiddled with it occasionally, modifying or replacing pretty much everything but the body along the way.

http://home.gci.net/~jimlab/images/Misc/P2130006.JPG
http://home.gci.net/~jimlab/images/E...d/PA030002.JPG
http://home.gci.net/~jimlab/images/Cobra/PC080019.jpg

I still have it because no one who wants it could even remotely afford it and no one who could afford it wants it.

 

Well said! Can I use that, Jim? I'll give you credit when I do.

 

No problem, but I'm not the first to say it.