Car Engines...

[gazfast]

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=218 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.

 

[jitpublisher]

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.

 

[MU_Engineer]

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.

PS: does anyone know how a diesel roraty engine would handle? 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.

 

[Rock_n_Rolla]

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.


-- 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!

 

[ulysses35]

+100 from me

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

 

[ulysses35]

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)

 

[DZeroENT]

*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)

 

[rodney_ws]

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#Disadvantages

"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.

 

[jitpublisher]

I actually have a 5.9 liter "atmosphere obliterating monster" 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.

 

[joefriday]

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

 

[bliq]

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.

 

[tiotaitch]

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 !!!

 

[jsc]

The first rotary powered motorcycle:
http://www.motorcyclemuseum.org/classics/bike.asp?id=39