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Which Is Best?

Total: 46 votes (4 blank votes)

  • Piston Engine
  • 70 %
  • Wankel Rotary Engine
  • 31 %
September 9, 2009 2:17:47 AM

Well here is the thing... pistons have been around for a lot longer so the technology is much more advanced... but theoreticly wankels are much more efficient at their jobs... they just have a few design draw backs that are hard to overcome =)
so give "us" xD your opinion

PS: does anyone know how a diesel roraty engine would handle? o_O since they run hotter that would kinda help with diesel combustion right? lol

More about : car engines

September 9, 2009 2:38:26 AM

Wankel engine - used in the spitfire, won the war.
September 9, 2009 2:44:30 AM

^ good a reason as any :D .

Anyway Rotary certainly has advantages, but too many are simply comfortable with what they are use to, which is why pistons are more common. It's the same reason we use unleaded instead of diesel (or even electric cars), why there were zealous Intel Fan Boys when the P4 got spanked by the Athlon 64, or rabid AMD fans in the face of the i5 and i7.
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September 9, 2009 3:12:00 AM

N19h7M4r3 said:
Well here is the thing... pistons have been around for a lot longer so the technology is much more advanced... but theoreticly wankels are much more efficient at their jobs... they just have a few design draw backs that are hard to overcome =)
so give "us" xD your opinion

PS: does anyone know how a diesel roraty engine would handle? o_O since they run hotter that would kinda help with diesel combustion right? lol



You are right I would suggest. People are used to piston engines, and how they operate, their power curve, how they run.
The rotary engine is different, different power curve, simply runs and feels different than a piston engine. That is one thing an electric or hybrid has had to accomplish, they must "feel" like a gas/piston engine, albeit a very, very quiet piston engine.
People just were not comfortable with the the rotary, even though they could be made in theory to be vastly superior to a piston engine. Longer life, way fewer moving parts, light weight, better fuel milage, cheaper to maintain. They had some design problems to overcome, but holy cow, so did the piston engine. Their were plenty of those made that turned out to be complete duds over the years as well!

Remember the Volkwagon commercial where the 2 guys are talking, one has a hybrid and the other has a new volkswagon?
When they ask what their cars sound like, the hybrid guy kind of yawns out a bit of air "haaahhhhhhhhhhhh", and the volkswagon guy goes "VROOOOOOMMMMMMMMMMMM!!!!!!" You could also add to that that the rotary engine goes "hmmmmmmmmmmmmmm". Kind of boring you know........Mazda had a commercial back in the early 70's, if anyone remembers where they actually sang this little jingle, "piston engine goes boing, boing, boing, boing, boing, boing, boing, but the Mazda goes mmmmmmmmmmmmmmmmmmmm.........."
September 9, 2009 3:17:16 PM

For now piston engines, a ton of R&D has already been done on it. But if there are some significant developments over at the rotary side, people might just change their tune. If somehow rotaries would have some distinct property that would make them an advantage in a hybrid car setup, then it would have a very big future ahead of it.
September 10, 2009 1:21:24 PM

will_chellam said:
Wankel engine - used in the spitfire, won the war.



Ermm.... Sorry dude but the Supermarine Spitfire was powered by a Rolls Royce Merlin engine.... V12 / 23 litres not a Wankel
September 10, 2009 4:25:28 PM

Wankel Rotary engine has only one BIG issue - 2 much heat. that is the reason why mazda rx8 has 2 smaller engines instead of single big one. at this time, the heat issue doesn't seem like being taken care of in the near future, simply because the piston engines do the job quite good. after all, i personally believe that till the time comes for rotary engines 2 become more attractive and needed than pistons, fuel reserves will be long gone, and electricity/hydrogen era will be the next best thing.
September 10, 2009 7:08:29 PM

jimishtar said:
Wankel Rotary engine has only one BIG issue - 2 much heat. that is the reason why mazda rx8 has 2 smaller engines instead of single big one.


are you telling me that a bugatti veyron has 16 small piston engines because 1 12L piston engine would just generate to much heat?

plus heat isn't a bad thing on its own... its like having organisms withstand 200ºc degrees of heat... is hot for us, but they seem to have no problems with it... if you develop an engine to work hot, it will just work hot...
plus as i said before this might be helpfull for diesel combustion as its even a better fuel then petrol or gasoline since it has more energy per litre
just to rememeber hidrogen on its own kinda "burns like any other" gaseous fuel... so it can work in a piston\wankel engine... (but i know you meant hidrogen fuel cell lol)
plus we have used vegetal oil can be used in diesel engine so if we increase our need for chinese fast food we might also be getting more fuel production...
September 10, 2009 10:56:22 PM

What of Chrysler's attempt at the turbine concept.
September 10, 2009 11:11:36 PM

jsimeon said:
What of Chrysler's attempt at the turbine concept.


dont know much about turbine engines, but they are rotary engines... to bad i cant take the wankel out of the poll name
September 11, 2009 3:18:35 AM

someone may get a kick out of this.

1964 turbine car specs

* 130 horsepower at 3,600 rpm (output shaft speed); 425 lb-ft of torque at zero rpm!
* Weight: 410 lb - 25 inches long, 25.5 inches wide, 27.5 inches tall (without accessories, which make the overall length 35 inches).
* Fuel requirements: what've you got? diesel, unleaded gas, kerosene, JP-4, others. No adjustments needed to switch from one to the other.
* Compressor: centrifugal, single-stage compressor with 4:1 pressure ratio, 80% efficiency, 2.2 lb/sec air flow
* First stage turbine: axial, single-stage, 87% efficiency, inlet temperature 1,700 degrees F.
* Second-stage turbine: axial, single-stage, 84% efficiency, max speed 45,700 rpm
* Regenerator: dual rotating disks, 90% effectiveness, 22 rpm max speed
* Burner: single can, reverse flow, 95% efficiency
* Maximum gas generator speed: 44,600 rpm
* Maximum output speed, after reduction gears: 4,680 rpm
* Exhaust temperature at full power: 500 degrees Farenheit.

http://www.allpar.com/mopar/turbine.html
September 11, 2009 10:54:03 AM

N19h7M4r3 said:

plus heat isn't a bad thing on its own... its like having organisms withstand 200ºc degrees of heat... is hot for us, but they seem to have no problems with it... if you develop an engine to work hot, it will just work hot...
plus as i said before this might be helpfull for diesel combustion as its even a better fuel then petrol or gasoline since it has more energy per litre
just to rememeber hidrogen on its own kinda "burns like any other" gaseous fuel... so it can work in a piston\wankel engine... (but i know you meant hidrogen fuel cell lol)
plus we have used vegetal oil can be used in diesel engine so if we increase our need for chinese fast food we might also be getting more fuel production...


if u make 1x12L piston engine, once u start the car, the piston will blow away as far as the Moon, passing along the International Space Station. there is a mechanical limit to how big a piston&cylinder can be. + the bugatti has w16 engine just to show that i can be made W16, u can go 400 km/h with just v8. plus, heat issue with wankel is that it concentrates heat on particular parts of the block, leaving other part relatively cold. this heat concentration requires the block to be made from special materials, such as ceramics or some metal mix, which makes production expencive, which brings us back to piston engines being better.



to the other guys - wankel engine is different type of rotary engine (there are many rotary-type engines, this thread is about wankel).
September 11, 2009 12:59:10 PM

Yeah, we are kind of getting off base here talking about turbines. Although I guess they are a type of rotary engine, the priciple behind what makes a Wankel and and a turbine engine run are 2 very different technologies. A Wankle is still a 4 stroke, reciprocating engine. The reciprocation is just minimized to the extreme.
September 11, 2009 1:06:37 PM

its more of a 3 stroke, actually.
September 11, 2009 1:28:47 PM

jimishtar said:
its more of a 3 stroke, actually.

Yes, now that you mention it and I think back to what the Wankel looks like, what it does for "strokes" is more like 3, they kind of overlap.
September 12, 2009 7:47:32 AM

will_chellam said:
Wankel engine - used in the spitfire, won the war.



Sorry Will, suggest you might want to check that, last i saw/heard, the Spitfire was powered by the Rolls Royce Merlin V12 piston engine.

a former boss had one in his boat, helped him source some parts out of South Africa.

don't mean to rain on your parade, don't even know you, please take as friendly comment only.
September 12, 2009 8:14:42 AM

The piston engine is more fuel efficient
September 12, 2009 8:43:15 AM

jimishtar said:
if u make 1x12L piston engine, once u start the car, the piston will blow away as far as the Moon, passing along the International Space Station. there is a mechanical limit to how big a piston&cylinder can be. + the bugatti has w16 engine just to show that i can be made W16, u can go 400 km/h with just v8. plus, heat issue with wankel is that it concentrates heat on particular parts of the block, leaving other part relatively cold. this heat concentration requires the block to be made from special materials, such as ceramics or some metal mix, which makes production expencive, which brings us back to piston engines being better.



to the other guys - wankel engine is different type of rotary engine (there are many rotary-type engines, this thread is about wankel).



Large pistons are not really viable on cars / trucks - but large ships have enormous diesel engines, some with pistons big enouhg to hald a man. The problem with large pistons in small numbers (1 x 12 ltr eg) would be a very rough idel / turn over.

Small pistons in larger quantities are best... Jaguar proved this with their 6 ltr V12... still rated as one of the smoothest engines ever made. F1 cars used to be 3.5 ltr V10's which was one of the best balanced high revving engines ever use in motor sports.

September 12, 2009 9:37:48 AM

bigger pistons have better torque, higher RPM, something that big objects, like trucks and ships, really need. but check out how huge is the cylinder that hold a ship's piston.
September 12, 2009 10:31:33 AM

Just a quick search on google :-

http://people.bath.ac.uk/ccsshb/12cyl/

larger the capacity of the engine the lower the RPM as a rule.... too much inertia / weight behind the moving parts for it to be truely effective.

Thought some airfcraft engines do have large capacities and high RPM. Aforementioned Rollys Roye Merlin reach 27 litres... 3000 RPM and just over 2000 HP
September 12, 2009 3:21:15 PM

Holy cow there are a few bad assumptions up there a ways^
The large engines in ships rotate very, very slowly. The parts are simply to big, if you spun a engine that big at 4000rpm it would explode like a bomb. Diesel and large truck engines run much slower than their smaller gas counterparts. How smooth an engine runs is NOTHING to do with how big it is. Those huge ship engines make a lot of noise, but they are amoung the "smoothest" running engines in the world. But indeed 1 thing they do supply is just an amazing amount of torque.

The spitfire, and many older planes, used Radial engines. Pistion engines with the cylinders configured in a circle around the crankshaft. They are air cooled, and each cylinder needs direct exposure to the incoming air, or it would literally melt in a short time.
September 12, 2009 4:36:55 PM

jitpublisher said:
Holy cow there are a few bad assumptions up there a ways^
The large engines in ships rotate very, very slowly. The parts are simply to big, if you spun a engine that big at 4000rpm it would explode like a bomb. Diesel and large truck engines run much slower than their smaller gas counterparts. How smooth an engine runs is NOTHING to do with how big it is. Those huge ship engines make a lot of noise, but they are amoung the "smoothest" running engines in the world. But indeed 1 thing they do supply is just an amazing amount of torque.

The spitfire, and many older planes, used Radial engines. Pistion engines with the cylinders configured in a circle around the crankshaft. They are air cooled, and each cylinder needs direct exposure to the incoming air, or it would literally melt in a short time.



+100 from me
September 12, 2009 11:20:38 PM

ulysses35 said:
Large pistons are not really viable on cars / trucks - but large ships have enormous diesel engines, some with pistons big enouhg to hald a man. The problem with large pistons in small numbers (1 x 12 ltr eg) would be a very rough idel / turn over.

Small pistons in larger quantities are best... Jaguar proved this with their 6 ltr V12... still rated as one of the smoothest engines ever made. F1 cars used to be 3.5 ltr V10's which was one of the best balanced high revving engines ever use in motor sports.




and let us not forget the fabulous BRM V-16 F1 engine, 1500cc and 16 cylinders, plus overhead cams and four valves per cylinder, mechanical fuel injecion, no EFI, awesome.

Plus it was reputed to be reliably producing 400+ horsepower - in the 1950s.

In the 1980s Ferrari and Honda bult 1.5 litre V6 turbos good for 900 horsepower, and again this was when EFI was in its infancy.

All of tis is not to say the Rotary is not a bad design, but it is a limited application design...rotaries as a rule produce limited amounts of torque, but relatively high horsepower, at high rpm, making them a great racing engine, you are not limited to try and make the car driveable at 60-80 km/h, the designer can go for the big numbers, remember a Mazda (Wankel) rotary remains the only Japanese engine to win the Le Mans 24 Hours, Mazda also had big successes with roatry engines in Touring Racing.

however, if you try to fit a rotary engine to a large passenger car, then the lack of low-down torque is instantly a problem, you get a carwith prodigious thirst and a distinct lack of acceleration, although given its head on the highway it suddenly becomes a slightly better proposition, howevre very few people get to just drive 500-600 kilometres at a stretch every day in a passenger car, hence thepopularity of the pistone engine for every day use.

Personally, I am a huge fan of diesel passenger cars, we own a Peugeot 307 HDi, but in my job a I drive a large varietyof vehicles, and there are some monsters out there, the Mercedes-Benz S 320 is an eye opener, although it is even better whenfitted to the C-Class, lighter bodyfor same huge power/torque figures.

sorry, this is a little off-topic, but thought it might add to the general flow.
September 12, 2009 11:39:22 PM

jitpublisher said:
Holy cow there are a few bad assumptions up there a ways^
The large engines in ships rotate very, very slowly. The parts are simply to big, if you spun a engine that big at 4000rpm it would explode like a bomb. Diesel and large truck engines run much slower than their smaller gas counterparts. How smooth an engine runs is NOTHING to do with how big it is. Those huge ship engines make a lot of noise, but they are amoung the "smoothest" running engines in the world. But indeed 1 thing they do supply is just an amazing amount of torque.

The spitfire, and many older planes, used Radial engines. Pistion engines with the cylinders configured in a circle around the crankshaft. They are air cooled, and each cylinder needs direct exposure to the incoming air, or it would literally melt in a short time.



There seems to be a certain misconception about the Supremarine Spitfire on this thread.

Can I suggest we check this website: www.militaryfactory.com/aircraft/detail.asp?aircraft_id... it has the specifications listed, including the powerplant, the Merlin V12 piston engine.

Sorry if I am harping on this one, but it is a little frustrating to see incorrect information.

Yes, the radial engine was popular, but primarily with American manufacturers, most European, ie German and British, used piston engines, such as the Junkers Jumo and Rolls Royce Merlin,which was also built inthe USA under licence by Packard as the Packard Merlin, and fitted to the P-51.

Possibly the best known radial-engined aircraft were the Thunderbolt fighter-bomber and the B17 Flying Fortress and B29 Superfortress bombers, although there were plenty of others.
September 13, 2009 12:57:22 PM

I stand corrected. That for binging the facts to light. Not sure why added the Spitfire had a radial engine, as now that you state the facts, and I think about it, it simply was not so. My intention was that some were thinking that the radial engine was a rotary, while in a way it is, it still was not a Wankel.
September 29, 2009 8:33:44 PM

N19h7M4r3 said:
Well here is the thing... pistons have been around for a lot longer so the technology is much more advanced... but theoreticly wankels are much more efficient at their jobs... they just have a few design draw backs that are hard to overcome =)
so give "us" xD your opinion


The problems with rotary engines are that they have little torque, they have poor fuel economy in current implementations, they consume a ton more oil than piston engines (which makes for worse emissions), and the rotor tips wear out a whole lot more quickly than piston rings. The things rotaries are good for is making a lot of horsepower in a small, lightweight package.

Quote:
PS: does anyone know how a diesel roraty engine would handle? o_O since they run hotter that would kinda help with diesel combustion right? lol


I bet it would work, but I also bet that the rotor would wear out quickly since the compression ratio of a diesel is about twice that of a gasoline engine and the power stroke is much more powerful.
October 3, 2009 6:22:38 AM

For a Tuner point of view, Rotary engine mods and other after market engine parts suited for these type of engines are more expensive and hard to find and usually not available in small auto shops though it depends, but most i asked, they'll just say we have your item but you just have to wait to get it coz were gonna order it and wait till the shipment to get here usually 20-40 days. :o 


-- If you're in Japan and you own an RX-7, tuning it to the max and buying those
accessories, engine mods, aftermarket parts and carbon fiber body kits is like you're in a
K-Mart buying Groceries. Cheap too!
October 3, 2009 3:06:05 PM

jimishtar said:
+100 from me



Must mention again Spitfire used a Rolly Royce Merlin V12... not a radial or a wankel as some have pointed out....

October 3, 2009 3:14:31 PM

jitpublisher said:
Holy cow there are a few bad assumptions up there a ways^
The large engines in ships rotate very, very slowly. The parts are simply to big, if you spun a engine that big at 4000rpm it would explode like a bomb. Diesel and large truck engines run much slower than their smaller gas counterparts. How smooth an engine runs is NOTHING to do with how big it is. Those huge ship engines make a lot of noise, but they are amoung the "smoothest" running engines in the world. But indeed 1 thing they do supply is just an amazing amount of torque.

The spitfire, and many older planes, used Radial engines. Pistion engines with the cylinders configured in a circle around the crankshaft. They are air cooled, and each cylinder needs direct exposure to the incoming air, or it would literally melt in a short time.



smaller lightweight components run smoother and faster - run a ships diesel marine engine higher than a couple hundred RPM and the engine would shake itself apart.

so in theory 24 cylinder engine at 24 litre capacity would run a lot smoother and higer RPM than an engine with 6 cylinders at 24 litre capacity. there are some obvious exceptions though :- Petrol uses a spark ignition system and can usually run a lower compression ration, diesel relies on a much higher compression ratio - if you ever hear a london taxi cab the "knocking" is a result of high compression and the use of an anti knock agent (like lead in on petrol supplies)



December 22, 2009 5:48:34 AM

*Sigh* This is an impossible discussion, however, the "wankel" original concept is highly inefficient and unpredictable. (Materials and Technology available at the time)

Not until Mazda got a hold of the idea did it outperform the piston engine. The piston engine is fundamentally flawed do to the fact it has to transfer a linear mechanical movement into a rotary movement losing energy, yes, energy in the process. The Renesis, yes renesis, not wankel rotary engine has very little energy loss in trasferring its off-axis rotary mechanical movement to a rotational mechanical movement.

The heat issues are only limited to the alloys available. What Mr. Wankel dreamed of was far far beyond his time or even ours right now. The main failure in off-axis rotary engines is the apex seals, the three points of contact of the so-called "piston". These apex seals not only are succumbed to extreme friction but also have to resist thermal dynamics, as the engine block grows in size as it gets hotter the apex seals must grow proportionately or leaks could occur causing detonation.

Plus, "rotary" engines weigh much less than your 5.7L V8 atmosphere obliterating monster. They are not as appealing as the mighty roar of a caveman, but they outperform, period.

P.S. 1.3L "rotary" engine can produce 276 HP turbocharger aided, a piston engine of the same displacement is not much more than 101 HP DOHC w/ vvt-i (toyota). (It surprised the hell outta me too)
December 22, 2009 12:49:35 PM

If the rotary were truly better, more cars would use it. An RX7/RX8? That's it?!? Well, I guess there's your answer.

And I love how someone refers to a 5.7L V8 as an "atmosphere obliterating monster" ... I'm pretty sure rotary engines pollute more than traditional ones.

http://en.wikipedia.org/wiki/Wankel_engine#Disadvantage...

"Indeed, comparison tests have shown that the Mazda's rotary RX-8 uses more fuel than heavier V-8s with over four times the displacement."

When a small car like that can barely muster 20 mpg and virtually no torque I think I'll pass. I owned an Acura RSX Type S and although it was low in torque, it easily got over 30 mpg over its life (mostly highway miles) and was the most reliable car I've owned. Maybe some new tech will change this, but for now? I'll pass.
December 22, 2009 2:26:23 PM

I actually have a 5.9 liter "atmosphere obliterating monster" :D  But even at 5.9 this is only 360 cubic inches, it is still what I consider a "small block" V-8.
In my day, our favorite saying was "there's no replacement for displacement".... 632 cubic screaming inches of 850 crate horsepower aluminum big block Rodek is what I am talking about! Arghh-arrrr-arrr-arrr-aargggh! I think about those days with an alcohol/nitro fuel induced tear in my eye.....maybe one of these days when I retire, I'll have the time to build one of those ground pounding Deuce's again.

You are right though rodney, if the rotary engines were so great, there would be a lot more of them. Apparently the design that looked good on paper had problems that simply do not work well in practice.
December 22, 2009 9:12:44 PM

jimishtar said:
mazda rx8 has 2 smaller engines instead of single big one.

December 22, 2009 9:33:58 PM

Wow, there's a fair amount of poor information in this thread. For starters, Renesis is Mazda's name for their wankel rotary motor, not the other way around. Second, heat was a problem in rotaries but not just heat in and of itself but rather its effect on apex seals, which is to mean, they fail and when they fail, no more compression. This affected many RX-7s and earlier RX-3s and RX-2s. The newer RX-8s have iron out many of the heat issues but they've failed to get much traction in today's market because there's still the problem that are very thirsty motors. the RX8 was unlucky to be around at the height of the gas crisis. They only get 16/22. not bad for a sports car you say, but this is a relatively tiny, light car with just 232hp. Alternatives in the same class of car get much better fuel economy and better performance to boot. If they could straighten out the problem with fuel economy and address the issue of low horsepower (somewhat countered by low weight, size, and center of gravity), then I'd vote for rotary power.

Until then, you can get 300hp and 20/25mpg from too many other cars.
December 23, 2009 2:28:59 AM

1. I second joefriday comment! 2. Have owned tweaked '93 rx7 and numerous '60 - '70's Detroit v-8's and have to say HANDS DOWN: rx7 (properly tuned!!) best ACCELERATING and most ENJOYABLE car I've ever driven!! That said; I would love to get behind the wheel of a Tesla !!!
!