600+ hp can and has been done with a 3 or 4 rotor, some NA as well, so it can be done without a power adder. And a 3 or 4 rotor is not as long as you would think.

It's not a you-vs-us situation, I'm not trying to beat you with anything, just bringing up some points

Honestly, that is a good question, one that I am not qualified to answer

Mazda only has 1 plant in hiroshima that builds rotary engines. This one plant puts out all the new engines for the RX-8, all the racing engines, and all the parts for previous engines. So I'm pretty sure it's running fairly close to capacity

The rotary engine also still has a stigma about it that I think inhibits mass-market apeal, so that could be a reason. Your guess is as good as mine

I wasn't arguing that that did not happen, I was saying it's an example that humankind had no control over, i.e. nothing we can/could have done to change it. Whereas this question covered a topic where it WAS a choice, one that if made differently may have had an interesting outcome.

We could discuss turbine engines in cars, but again it's a different type of "what-if?". Mazda has proven that a rotary can be, on some level, used successfully in passenger cars and to a better degree race cars. It's also something that was PLANNED for the corvette, as well as the original engine intended to go into the corvair (or chevette, I forget).

That was part of the reason for the rotary vette concept, and again there was a GM passenger car that was planned to go into production. When the emmissions standards changed and then the gas crisis hit, instead of working on the rotary GM decided to go with what they had in hand and replaced the motor in the cars with a piston motor they already had. Again, I think this sums up the main point of this topic:

If mazda can make a 700+ hp race car in the late 80s to early 90s that could run on 87 octane, imagine what GM could have done with it's bigger stable of engineers and bigger bankbook.

I hope you don't feel like this is a discussion trying to say the rotary is better or anything like that, it's just interesting to see what mazda has done with it and to wonder what someone like GM could have done. I mean if GM can build a pushrod engine that makes 500hp and gets almost 30mpg, they've probably got some talent working for them somewhere

 

OldSStroker, somewhere along the line I think you misintepreted my point behind my original post. It was not saying I think the rotary is the better engine, it was just a post about theoriticals. We could go on all day about various "what-ifs", but seeing I only brought one "what-if" into this post, it is all I am really interested in discussing here. I was hoping maybe there was rotary technology that may have been tested to help tone down some of the engine's weak points, that has not been introduced to a production rotary.

My guess would be that Mazda doesn't put rotaries in everything for the simple reason that the piston engine is tried and true beyond a shadow of a doubt. It is much easier to monitor a small volume niche car with a unusual engine than a whole assembly line full of them, not to mention the training that all Mazda techs would have to go through to work on them.

 

I have to agree with you and wonder what any of the big three would have done with the rotary - if they had decided to persue more R&D on the rotary.

As to the cost of building a rotary, it's a catch 22. The parts currently are expensive so you end up spending more money for not as much power, when compared to reciprocating engines. To bring the cost down you need to increase production.

In reference to why it's not used in more than just one model, how many corner chain repair shops do you know of that would know how to perform a full tune up on a rotary as compred to a v6 or v8? It comes down to what people are familiar with. Most people who see a rotary tend to get the glazed over look in their eyes and say 'uh-huh, ok' and continue to walk away.

 

That's true, I'd forgotten about that. So I guess while a rotary SHOULD be cheaper and easier to build, it's low-production numbers probably don't make it easy to hold to that.

And that's very true with repair shops! Go ask most mechanics and they won't work on a rotary, just because most of them don't know what the heck is going on with one. Even trying to find parts at autozone or Napa is an experience for rotary guys, since even though most of the parts are carried there, the guys behind the counter tend to glaze over when you ask for something

 

Perhaps I've missed something in my education, so please bare with me.
If I recall my wankle engine basics correctly. The "piston" rotates one time for every three rotation of the output shaft(crank). And the rpm is taken at the crank. So that would be 1/3 of a power stroke(pulse) per rotation.
On a four stroke engine you get 1/2 pulse per rotation. So at 6000rpm a four stroke is giving you 50 pulses per sec. while a rotory is giving you only 33.3333- per sec.
If you have a twin rotor your getting 66.666- pulses per sec. While your buddy with his 4 banger is get 200 pulses per sec.

This is from an old article.

 

The Otto-cycle reciprocating V8 will live on forever, regardless of any future technology. I only need one reason: It sounds the best.

I saw a new-ish Porsche 911 Turbo today. 3.6L flat six. Started drooling. Then he accelerated away, and it sounded like poo compared to pretty much anything I heard at M10 (except that red GTP, which, while surprisingly fast, sounded like a huge bumblebee).

I drove an RX-8 last week. It didn't have a pleasing sound either. It just sounded buzzy.

I have yet to hear any powertrain, of any kind, that was as pleasing to the ear as any big American V8. Small block, big block, headers, manifolds, pushrod, ohc, straight pipes, y-pipe, x-pipe, Corsa, Borla, Flowmaster, whatever. If it's an American V8, it sounds good.

Ferrari V12's sound nice, but I stand by my original statement.

 

A one rotor engine recieves 3 power pulses every rotation. There are three "chambers" to a rotor, and everyone one of them is fired upon as it passes its compression stage. A two rotor 13b Mazda rotary engine has the same amount of power pulses every rotation as a v6 piston engine would. My guess as to their bad gas mileage would be the simple fact that they have all of those power pulses per revolution, and they typically need to rev very high to make power. A rotaries injectors are typically sized very large.

 

I don't think Ferrari's engine note would ever tire on me. V8s do sound better than most anything out there though.

 

The emissions part was very true of the earlier rotaries. If you ever see an engine out of a 3rd gen RX7, it's a nightmare of vacuum lines and hoses. The biggest problem was the overlap between the intake and exhaust ports. This problem has been fixed in the Renesis motor by moving the exhaust port to a side housing instead of the rotorhousing.

The part about manufacturing costs is probably still true since it's so low-volume.

Yup, a 2 rotor will "breath" more like a larger displacement 6cylinder. That's why there's so many arguments about a rotaries "true" displacement.

One of the reasons they have large injectors is due to one of the in-effeciences of the rotarys design. Rotaries have a very large combustion area when compared to a piston engine, so there has to be more fuel to cover that area. Stock the 2nd gen turbo models have 4x550cc injectors and the 3rd gens came with 2x550cc and 2x850cc.

So this in-effeciency is what causes higher fuel consumption when compared to similar sized engines as well.

One other problem that I haven't seen mentioned is the fact that they have to burn oil in order to run. To lubricate the mating surfaces, a small ammount of oil is injected into the housing. This oil is then burned off, causing more emissions problems. Not nearly as bad as it used to be, but again an inheret flaw in the design.

One nice part of de-smogging a rotary or using one for racing is you can do away with this oil injection system and run 2 stroke pre-mix oil in the gas instead.

I wonder how many, if any, of these problems would be solved/less of an issue if there were more companies doing R&D


And as to their sound, 2-rotor engines have a very bad tendancy to sound very buzzy, due to the fact the engines exhaust cycle ends in the exhaust. If the piping wasn't designed specifically for a rotary, it sounds horrid.

3 rotors sound much better, and they have an almost F1 engine-like sound when they're revved. Click here to see Video

 

Thoughts:

OEMs whether US Japanese, German, Korean, have continued to throw billions (with a B) of whatever currency into development and tooling of recips over the last 40 years (since rotary appeared), If there was even a remote chance that by spending similar money on rotary technology they would end up with an engine which was better, or even equally suited to the job of powering cars and trucks, meeting all the requirements and was CHEAPER to produce and warranty, they would have gone rotary already.

Despite some head-in-the-sand thinking, the OEMs understand economics, technology and manufacturing. I might question staying with recips if at least one major player had gone *****-out for rotary technology, but, except for the niche market Mazda has, all have decided not to go there. My conclusion is that keeping the recip, making clean screen redesigns, building new plants, using the latest manufacturing technology, etc. has made it even more difficult for the rotary to compete in the OEM marketplace, even if money had been spent.

If you took a renesis rotary back 30 years to 1975, it would probably really look like the savior personified to what OEMs were struggling with then. Of course if you took a current LS7, M3, S2000 Hemi. or LSanything back to '75 they would all look like deities. Given the choice, I'll bet those engineers and bean counters in '75 would choose today's recips over today's rotary when everything was taken into consideration. Especially money.

Even the best forward looking thinkers and mavericks in the OEM system didn't think rotary was the way to go. Evidently Mazda doesn't either, or they'd be there scooping everyone and taking a bigger slice of the pie. I don't think it's because nobody (OEM) is willing to bet the farm on something like the rotary, because there are some who would if it were better/cheaper. I just don't believe it is. That's coming from and engineering and manufacturing point of view. I've been doing both for a long while.

One more what-if, and maybe on topic. If the US gov'mint hadn't imposed pollution/emission laws and CAFE rules on manufacturers, and IF gasoline was still $.33/gal (adjusted upward for inflation), there's a pretty good chance we might have an interesting mix of rotary and recip engines on the road. That wasn't the case, so perhaps that's one of the big reasons we don't. It doesn't mean the rotary couldn't have been developed to meet the requirements, it just means that it wouldn't meet them as cost effectively for both the manufacturer and us, the consumer. In the end, we pay all the car bills.

Not trying to bust anyone's chops or their balloon here. Too bad you guys don't like what-ifs. Rocket science comes to mind...it's a LOT older than the recip IC engine.

 

You make some very good points there. I think, however, one of the big deal-breakers and turning points was the fact that once the gas crunch and new emissions standards hit, piston engines had 60+ years of development from multiple companies where as the rotary basically was experimental still with NSU being the only ones really working on it. Had the rotary engine had the same ammount of R&D behind it at that point in time, I think your scenario of a mix of rotary and piston based engines would be true as well, even with the events that happened.

Initial investment I think is what killed it. Again, a bird in the hand applies when manufacturers look at something. Just like GM and DOHC or SOHC V8 engines. Although it may be true that they could do some great things with them, GM for the most part sticks with what it has because it's a known variable with a minimum of investment. And that's not a bad thing, just the way it is. If they already have something that works, they're not going to invest in something else, no matter how much potential it has.

 

I just knew I had to be missing something really obvious.
So that still gives us one pulse per rotation of the crank not three. Which is 100 pulses per sec. at 6000rpm, or 200/sec. for a two rotor. Compared to 300/sec. for a V6.

 

I don't have time to read through all of this right now, but somebody back there got a detail wrong, and nobody has caught it yet.

A two-rotor makes SIX pulses per revolution of the crank. Three from each rotor. That's the same as a V12, not a V6.

 

When your are counting pulses per rotation, shouldn't you count the other pistons on the crank for 1 full rotation?

 

New, I beg to differ.

The LS series (GenIII and beyond) engines required completely new tooling as well as design and development. GM could have gone SOHC or DOHC as Ford chose to do with their Mod, but after lots of R & D, they decided that a new OHV V8 engine was a BETTER way to go for both cars (minority) and trucks (majority) that it would be used in. Better meaning lots of things including performance, cost, durablility, etc. Whether or not the LS engines do a better job than the Ford Mod is another discussion. I don't think torque/power output is a problem, nor is rpm.

I loved it when the pushrod CTSV racers had their rpm limit dropped from 7900 to 7000 after the cleaned up at Sebring in '04. Of course they had a major advantage over the DOHC rev machines from the competition; they made 5.7 L the good way by using the block form the not-then-released LS7 with a 4.8L crank and the LS7 heads. Nice beta test for the LS7.

GM's DOHC engines, the 12 year old Northstar and the Vortec 4200, 2500, 2800 family do pretty much what they are meant to do. The 4-5-6 family makes just about the same hp/cube and torque/cube as the LS2. They have 90% of max torque from converter stall to WOT upshift which makes them very driveable. The Blown 'Star makes 469 hp from 268 cubes which is about 15% better in grunt/L than the 500 hp Blown Ford GT. The problem is that DOHC 4V V8's not only have more parts than OHV pushrod 2V, but they are heavier and have a higher center of gravity. Every pound slows acceleration, but also decreases lifetime fuel economy. I find it ironic that the current Cadillac Northstar runs on 87 to save the 'wealthy' Cad buyer $.20/gallon or so. Same power as when it used 91.

Some of the reason for DOHC is marketing. If German high-end cars (BMW, Merc, Audi) have DOHC 4 and 5-valve engines, you need the same to entice their buyers to buy your non-German, non-Japanese "Bimmer". Or so goes the logic. Of course the pushrod CTSV grabbed a few who actually wanted to go fast.

DC could easily have gone DOHC with their new V8s. They have tons of Mercedes experience and $ behind them, but they, too chose to use 2V pushrods in the Hemi. Here's a marketing case where "Hemi" blows OHC out of the water, and is cheaper to build & maintain over it's lifetime than an equivalent DOHC. DC did a great job there. Well, maybe more C than D.

How about this: by using larger displacement, with DOD thrown in, you can get the fat, flat torque curves as well as good mpg and have a lighter, cheaper-to-build engine that's just as technologically advanced as a DOHC which spins higher. Nice for trucks, and not all that shabby for a car. I really like 70 mph cruising below 2000 rpm, and the boot in the rump from 6 L. When they are looking at my tail lights, does the DOHC really matter?

Sometimes simpler can be better, sometimes not. It depends on how well you do it.