Rotary VS. Piston; The never ending battle!

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First off, if you don't know how rotaries work go to http://travel.howstuffworks.com/rotary-engine.htm

Pay special attention on the producing power section.

Now, I've heard a lot on this subject and done a lot of research on my own. But I want to hear some more opinions on the subject.

Rotary engines are my prefrence, and while they may seem complicated, if you learn more about them they are actually incredibly simple engines, especially when compared to piston engines; they only have 3 moving parts compared to piston engines which have hundreds. They also rev incredibly high, but unfortunatley this produces an extreme amount of heat, which is its main flaw. Another big flaw are the apex seals (the seals that seperate the combuston chambers) which are very weak at around 100k miles. But if you get a good cooling system and upgrade the apex seals to a racing setup, then you will have an incredible engine that can easily handle 350 hp without changing anything else. And once you upgrade the output shaft(crank shaft to you piston lovers) you will be able to push around 600 horse without any worries to your engine. Now turbos, tranny, chassis, and rear end are a different story at 600 horse, as with any car.

But any way, let's here some opinions on the subject shall we?

posted by  Zalight

this thread will end up getting closed really soon, im sure of it.

but i guess ill just lay off my very simple opinions without going into details.

first, they are called eccentric shafts.

that out of the way. well, i can bet over and over again, that if one tuner builds a piston engine and a rotary engine with the exact same quality, the piston engine will last longer cuz of obvious reasons. it is said that rotary engines can rev at high speeds, but only if built correctly. the RX-8 is able to do this cuz of their new SiC seals and some other nice mods. its pretty much a modified 13b.

the advantage rotaries have are, they produce very nice power levels of their small displacement. they are also alot more compact than the average conventional piston engines (obviously). they are cheaper to tune due to alot fewer parts, so cheaper to build too. also, no problems with center of gravity like in piston engines, such as inline 4's needing 2 balancer shafts, just like other engines.

the rotary disadvantages would be that, well, very few mechanics actually work with them. many of those few dont even know wat they are really doing. even though they contain very few parts, they are hella expensive. they need alot more attention than piston engines too. when they break, its bye bye engine, unless you have hurley seals or something similar. another thing is their low compression levels, which is a problem in NA vehicles, atleast more of a problem anyhow. these also need a more sophisticated fuel system.

piston engines.... everyone should already know how they work if they are browsing around here, else they need to pay a visit to howstuffworks.com and read a few manuals. disadvantages of these engines are that they contain alot of moving parts. this means that there is alot of vibration that needs cancelling (balancer shafts come into play when needed). some engines dont need this balancing, such as inline-6's, V12's, and boxer engines, but they still cause more vibration than rotaries. these also weigh alot and need a larger displacement than rotaries to produce equal power. also, since there are so many parts in these engines, it takes alot longer to fix things and find problems.

advantages of the piston engines. for starters, they obviously last longer and are alot more reliable in any sort of climate. they are far more efficient than rotaries fuel-wise. compression in these engines can be easily controlled. you can throw more crap at these engines than in rotary engines with a higher room for mistakes. these engines have also proved themselves to be able to rev at high limits, it just depends on the application and internal components, which are usually defined by the purpose of the vehicle (raw massive torque power or high revving drifting vehicle). a bit more expensive at first than rotaries but parts for piston engines are actually alot more cheap compared to rotary engines, specially if u know where to look (connections help so much). every mechanic should know how to work with these engines, so help is easily found. its even really easy for people to learn how to deal with these engines.


ok, so i got into a bit of detail, but screw it. i could have gone even further but im not even gonna bother since it will get closed after everyone starts fighting.

posted by  Inygknok

This subject crossed my mind before and I came to a little thought.

THe piston engine has had more time and money to be developed. But the rotary engine, even though the idea has been around for a long time, hasn't had the same amount of attention and money put into it. If the rotary engine and the piston engine were to "compete on a level playing field," I think the rotary might be a lot more competitive if not surpassing the piston.

I can't say I know all the specifics on both engines, but that's just something that I thought of.

Also, I think I read somewhere that rotary engines are unable to produce as much torque as piston engines. But since that wasn't mentioned, is that true?

Personally, I like the rotary engine. I like how it's sort of the underdog. Kinda inspirational in a metaphorical kind of way. :thumbs:

posted by  MaChao

rotary engines havent been given the same amount of research cuz all manufacturers, except mazda, say they are too inefficient for practical uses and such. with today's really strict standards, rotary engines need alot of development to keep up with piston engines in every single aspect. even though rotary engines are simple, they are complicated to work with.


it would be impossible to put an equal amount of research into rotary engines, since piston engines have had so many more times amounts of research put into them. its already past the "point of no return". its just like the Miller Cycle piston engines.


as for the whole torque issue, yea, it's true. many people will argue that they have less torque capacity due to their incredibly smaller displacement, but lets face it, rotary engines dont like producing that much torque. the displacement is just something huge rotary fans use as an excuse. others will just say, "fine, ill just get a 20B or a quad rotor engine (the 2.3liter one)". fine, you do that, but 3 rotors are even more expensive by A LOT. while you would be spending around $330 per ceramic apex seal, and there are 3 per rotor, and its 3 rotors. you do the math :D. dont forget the even more complicated fuel system and such. theres also the extra machine work, which hardly any mechanic knows about.

posted by  Inygknok

Rotaries do produce a lot less torque then piston engines, but they certainly aren't lacking tourque. And the idea that if somone put in as much money, research, and time into rotaries they would equal to or greater than piston engines is a very valid point of view. Just look at the differences between the 13b(RX-7 engine) and the renesis(RX-8 engine).

The renesis makes 235 horsepower naturally aspirated, the 13b makes 255 pushing 10 psi...think about the power out put of a NA 13b. Thats about 150 horsepower, see my point. Mazda made a jump of 85 horse power by changing two major things; the exhaust port was moved from the side housing to the housing face, the same location as the intake. This put a stop to wasted fuel by cutting down on the amount of unburned fuel to be expelled with the exhuast. It also added huge amounts of power by stopping something called rotor overlap. This is when leftover exhaust in the combustion chamber before the intake stroke because the motor starts drawing in fuel and air before the exhaust stroke is complete... Get that? Basically the engine starts drawing in fuel and air while the exhast port is still open. This does two things, it allows unused fuel to escape, and used gases to be reused. Not much of either, but enough to cut out about 50-60 horsepower. the renesis put a stop to this. Unfortunatley, for reasons of which I am unaware, this also means a huge loss in back pressure. Which means the renesis can't spool a turbo. Still, it doesn't make sense why mazda didn't release a superchaged version of the RX-8, more power than the RX-7 with all the wonderful new goodies of the RX-8. But that's not important, the second way the renisis makes more power is that mazda added another fuel injector that sprays an incredibly fine delivery of fuel that is easier to break down and therefore easier to combust.

Anyway all this rambling was to make a point. With just two major engine modification the renesis produces about 80 more horsepower then the 13b, think of the number of these modifcations that have already been done to piston engines. just wait till mazda finds a new way to squeeze more power out of there wonderful rotars. :drool:

posted by  Zalight

actually, the RENESIS is just a modified 13B with natural aspiration.

posted by  Inygknok

That's exactly my point. They only changed very little and got tremendus horsepower out of it.

I don't think anyone is really posting on this because, like you said, not many people know how they work. :ohcrap:

posted by  Zalight

yea..... i dont blame them though. rotary engines arent common at all, like boxer engines. though, boxers are piston engines so they really aint so complicated to understand. a lot of people say they know how rotaries work, but when it comes down to details, they really have no idea wat they are talking about.... so maybe others dont wanna make mistakes in order to get a flaming fest on them.....

posted by  Inygknok

its always been quite common knowledge among rotory owners that just a little bit of port work results in huge gains. relative to other engines. rotory engines are probably the easyest engine to mod for performance, due to the inefficiancy of the factory set up. My old colegue is a rotory fanatic that drives me bonkers!

I'm not a rotory nut or anything, but I do like them! we got a qaud rotor over here n/a that's pushing out 447kw (i forget the hp conversion, i think about 600hp). thats with no turbo, no blue bottles, nothing! :clap:

I admit i know nowt about how they really work, but looking at an engine caseing, it seems to be a type of 2 stroke motor? of sorts anyway?
and i do know, that from the series 6 i just delivered to a customer, they are great fun :thumbs:

posted by  Unlicensed

I have had the chance to drive a RX-7 turbo (engine manifold and turbo manifold cracked even) and I have to say that I have never seen that performance out of any other car. I do love my little gas efficient Honda, but man! **Drools** Too bad those cars are so finicky! That poor thing is rotting in a driveway now because someone engaged the turbo repeatedly on a rebuilt engine before it had reached 100 miles. :ohcrap:

posted by  cheezysweet

A rotary engine will inherently have less torque than a piston engine: torque is force multiplied by the distance it is applied over. Think of a weight on a see-saw: the longer the see-saw, the more torque is applied.

With a rotary engine, the force is applied to the side of the rotor, which is a shorter distance from the centre of the crankshaft than on a typical piston engine.

People often confuse torque and power. Power is basically torque, multiplied by rotational speed (rpm). Here's where a rotary engine comes into its own: there's no piston constantly accelerating, decelerating anc changing direction, so it can easily spin much faster. That means that it is more powerful than an equivalent piston engine, because although it has less torque, the crank is spinning faster.

Unfortunately, rotary engines also use a lot of fuel. For most applications, rotary engines offer more problems than they fix, when compared with a piston engine. They're only really suitable for light sports cars or motorbikes, where people are happy to use high revs.

posted by  heebee

Yeah, which is why one of my favortie cars of all time was the Datsun 510. A rotary powered, all wheel drive, ultra light wieght, rally beater that revvs till the cows come home!

posted by  Zalight

ok, a rotary could concievably reva farther than a pisotn engine. In theory. In reality, the flame front across the large face of the rotor limits it, as well as total breathing. You can increase the breathing, but what passes for low end driveability goes away in a hurry.

A stock 13B revs to about 7500 rpm. A modded one that retains useable drivebility (i.e a street port, rather than a bridgeport) doesn't rev that much higher. it takes a fairly radical porting jopb to get a 13B to rev past 9000 rpm, and it will not be very streetable at that piont, nor will it last very long. the 12A could rev higher (my long street port 12A powered RX3 made peak power at 9250 rpm) but it makes noticeably less overall power than the 13B. the 20b makes more power yet, but the added rotating mass linmits overall rpms.

The old IMSA RS engines that I helped with for the IMSA RS RX3 team I crewed with could turn 12k, but not for long periods of time (the front runners could go to 14k, but would only last one race at a time).

Contrast that to modern 1 liter sport bikes, with piston enignes that turn over 10k regularly. or the old Chevy DZ302 from the 1967-1969 Z/28 that turned 8000 rpm in stock form (yes a pushrod V8) and with minor mods, could turn 9000 rpm regularly in streetable form.

My Ford 302 in my RX7 turned the same peak rpm as the original 13B in it, but made 3 times as much hp and 4 times as much torque, for less money than a swap to a stock TII engine, and vastly less than the equally heavy 20BTT. In fact, my swap gave me better weight distribution and handling, as well as vasly more power down low without sacrificing any high rpm ability that the 13B had.

I love rotaries in little light cars, and I think a 20BTT in a '65 Mustang fastback would be cool (weighs the same as a 2nd gen RX7...). But the rotary is not a "better" way to make power, merely a "different" way to make power.

posted by  ChrisV

I forgot to mention, besides the IMSA RS RX3 I mentioned, The team also had a rotary powered Formula Libre. I've also owned an R100, RX2, 2 RX3s, a pair of first gen RX7s (one with a highly ported 13B from an RX4) and the second Gen RX7 that was a rotary powered autocrosser for teh first year I had it before the V8 swap. I've also put rotaries into other cars, including an MG Midget I had.

posted by  ChrisV

I don't know if anyone has mentioned this yet, but the Rotary is a very inefficent motor. It burns gas MADLY. I saw somewhere where one review site got the SAME mpg from it's Rx-8 as it did it's Nissan Titan. It may be small (1.3L, but really 2.6L in comparison to a piston motor due to the cycle of the engine compared to a piston motor) but it's a gas guzzler.

My girlfriend's 13b-rew just crapped out a few weeks back in her 94 Touring RX-7...it lasted to right before 100k....stock motor (yes, it was a apex seal)..cool thing is, she surprises me before we go on our trip with a shane's racing 20b we ordered and she installed it right before our trip. It's nice...big power (ported out...etc.)...best of all it's N/A and doesnt have that extra heat from forced induction.

One thing I want to know is this...has anyone ever supercharged (if it's possible) a rotary?

posted by  thunderbird1100

Yes it's possible to SC a rotary engine, ive only seen it once though and he was only running 8 psi. It was on a first gen, carburated RX-7, it was a centrifugal style SC. When i asked him how it worked he said it took a huge amout of work, mainly because everything had to be custom made. And yes we've already addressed the fuel consumption issue. It sux, but hey, it's the same as a V8 and there are plebty of people out there who will only swear by them. You know the type, 50-60 years old, constantly droning on about the Hemi.

posted by  Zalight

Yes it's possible to SC a rotary engine, ive only seen it once though and he was only running 8 psi. It was on a first gen, carburated RX-7, it was a centrifugal style SC. When i asked him how it worked he said it took a huge amout of work, mainly because everything had to be custom made. And yes we've already addressed the fuel consumption issue. It sux, but hey, it's the same as a V8 and there are plenty of people out there who will only swear by them. You know the type, 50-60 years old, constantly droning on about the Hemi. :laughing:

posted by  Zalight

whoa... it submitted twice...

posted by  Zalight

I always laugh at those idiots in the new 'hemi' dodge products...they dont even really have hemi-sphereical combustion chambers....WTF, it's not a hemi people WAKE UP (does Homer simpson crazy dance)

posted by  thunderbird1100

now that I think of it, doesn't the 13b lose a lot of heat during each rotor cycle due to the high compression? If it does wouldn't it have cooling problems? i.e. massive radiator and intercooler.

posted by  s13_Drifter

Yes it does. Did you read all the posts? The two major problems with the rotary are its apex seals and its enormous heat production. And they are both easily surmountable. You can upgrade to better apex seals for $500, instead of paying $4000 for a new engine. To get over the heat you can get an aluminum radiator, set of fans and a swirl pot. Blat. great cooling.

If any of you don't know what a swirl pot is I won't be surprised, they are more common in europe then any where else and not even that common there. You mostly see them on race cars, rallycars etc. They swirl the water around to get rid of any air in the water by centrifugal force, by fitting a Swirl Pot into the top hose of the radiator you will eliminate hot-spots caused by cavitation in the cooling system. They connect directly into water(header) tanks, with either dash fittings or conventional push on fittings. Plus they're cheap; about $80 for a good quality cooling tool.

posted by  Zalight

How did you put the much longer 20B into the RX7, and get it running with the computer and all the accessories, in car that engine was never supposed to go in, in a matter of a couple days? iv'e seen a lot of people do 20B conversions, and it's never a simple "run it into the shop and take it home the next week" affair... Just ordering up a rather hard to get 20b would have taken a while, and the instal isn't just a plug and play. The radiator has to be relocated, new mounts made, the exhaust has to be redone, the computer is used to a 2 rotor turbo engine with a completely different ignition and fuel delivery system, etc...

posted by  ChrisV

Yes, the engine IS a hemi. It does indeed have hemishperical combustion chambers, they just filled in a couple corners to get better quench. the heads are very similar to the original hemi engines that Chrysler made from '53-up. Unlike those early hemi's it has 2 spark plugs per cyl (necessary to get the 2 valve Hemi to meet emissions. While it makes more power than a wedge head, it aslso makes more NOx, due to the cooler flame front), and the aforementioned quench areas, which is why it makes more power, torque and fuel economy that the larger engine it replaced.

posted by  ChrisV

Yes, the engine IS a hemi. It does indeed have hemishperical combustion chambers, they just filled in a couple corners to get better quench. the heads are very similar to the original hemi engines that Chrysler made from '51-up. Unlike those early hemi's it has 2 spark plugs per cyl (necessary to get the 2 valve Hemi to meet emissions. While it makes more power than a wedge head, it aslso makes more NOx, due to the cooler flame front), and the aforementioned quench areas, which is why it makes more power, torque and fuel economy that the larger engine it replaced.

http://www.dodgeboy.net/news/57hemi/index.htm?http://www.dodgeboy.net/news/ 57hemi/57hemi_frame.htm

posted by  ChrisV

The newer Apex seals are great for race applications, but they don't seal well when cold. And the cost of Apex seals doens' tinclude the costs of pulling apart the engine and putting it back together. if the engine has been together for years, then you'll need to check the housings to make sure that taking them apart didn't warp them (which would mean th eengine wouldn't last more than a few weeks after being reassembled). You also have to replace all the OTHER seals in the engine (there are multiple O rings on each housing to seal the water jacket that have to be replaces when the engine is pulled apart). there are also multiple side seals and oil control seals per rotor, and corner buttons and springs on the outside corners of each apex seal.

While there may be only three major moving parts, there is a lot more to it that that. Holding all those seals in place while reinstalling a rotor is a major PITA, and I've seen numerous rebilds fail due to a side seal coming off of a rotor during installation (on the back side of the rotor from where the installer is at). And don't forget the oil pump and timing equipment.

posted by  ChrisV

One tric that we use is to stick the seals in place with a celulose glue, burns off harmlessly and gives you alot more control.

posted by  cinqyg

That's what I've used (as well as a tight string holding the apex seals in until the rotor gets about halfway into the housing).

The point was that there's a lot more to a rotary than 3 moving parts, and a lot more to think about than just swapping in new apex seals.

posted by  ChrisV

I haven't asked her about it fully. All I know is she took it to a guy that builds RX-7's with any kind of swap known to man (5.0's, 350's, etc), she said the engine got in about 6 days before our trip...6 days seems plausible for most any-engine swap. Especially with someone knowing what they are doing.

posted by  thunderbird1100

To most people I spoke to they say it's not really a 'real' hemispherical combustion chamber. You can kind of argue both sides...oh well.

posted by  thunderbird1100

I know that , as with any other engine, there is a lot of work involved when trying to upgrade engine internals, and that there are more then a few things that have to be donte in order to make a very good quality engine. I was merely saying that the first things any rotary owner would want to think about upgrading would be his cooling system and his apex seals.

And I know that replacing the seals isn't a esay matter, but its not incredibly difficult either. In fact last weekend I watched someone, who uses his RX for track racing not street use, replace his apex seals with a custom made set that cost him close to $1000. They can handle 600 horsepwoer at the flywheel for 80-100,000 miles. Which covers him since hes only running 450 RWhorse and 375 rw torque. It took him two sittings of 6-7 hours each to take apart his 13b replace the seals and put it all back together again. with a break in between where we went to get wendys tasty,tasty junior bacon cheesbugers and frosties...mmmmmmm...frosties :drool:

By the way, Has anyone heard of the cryogenically frozen parts some companies offer? I heard that the U.S. government is giving out grants for people to start doing this. Apparently the freezing process forces all the impurities out of the metal leaving behind a stronger material without changing size or shape. Well it does change it but only on a very insignifagant scale. But I havent heard much beyond that. Anybody here anything about this? Does it actually work? How much does it cost?

posted by  Zalight

Plausible, but considering that much of it still has to be fabricated, and the electronics completely custom made (the 20B swap is not a very common one yet, and if he's done enough of them to have it a plug and play like that, he'd be as famous as Pettit...), and considering shops like Pettit and PFS don't complete a 20B swap in that amount of time, I just question it.

Not to say it wasn't done. But I'd like to see pictures of it...

posted by  ChrisV

The fact is that the new Dodge Hemi uses the same basic layout as the old one, with valves offset to either side of the combustion chamber. The main difference is in the dual spark plugs and the fact that there are quench areas around the edges of the chamber.

This is how the Hemi head valve arrangement is, and it's the same for the new Hemi as the old one.

http://abbysenior.com/mechanics/images/valve.10.jpg

Who are these "most people" you spoke to, and what do they really know about Hemis, or engines in general?

posted by  ChrisV

I've watched guys rebuild their V8s between rounds at a drag race, too. It's easy if you're familiar with it and have the tools. I've rebuilt a 12A on my dining room table (not recommended if still living at with your folks or with a spouse...)

The point is to not try to say that it's a breeze to just upgrade the apex seals and everything will be peachy.

posted by  ChrisV

600cc sport bikes redline at 15,500 rpms. Small two strokes can rev till about 17 or 18K.

I think the idea of a rotary powered sportbikes would be pretty cool. If I remember correctly, Suzuki made a rotary bike, but discontinued it. I'll look into it.

posted by  abless

the Suzuki RE-5. 62 hp at 6500 rpm.

http://www.rotaryrecycle.net/re5originalrelease.asp

http://www.allenmuseum.com/images/re5red.jpg

Yamaha had a prototype in '73, and a company called Van Veen put an NSU rotary into a Moto Guzzi frame and sold them from '76-78. Norton had a number of rotary bikes in the '80s, including one that set a world speed record of 191 mph in the early '90s...

posted by  ChrisV

Thanks alot. I didn't know Yamaha, Van Veen, or Norton had made rotary bikes.

posted by  abless

ahhh! the good old jps nortons! :clap:
weren't they banned from racing cos back then they couldn't decide what the cc rating was? something like that?

that and the fact they kept winning :oops:

posted by  Unlicensed

well it depends on what you are trying to achive but i would say that its a very desperate effort. There are much cheaper ways of achiving almost the same result.

posted by  cinqyg

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The wankel is hugely inefficient. Combustion occurs at TDC, which means the rotor is slammed against the eccentric shaft, not driven in the direction of rotation. The rotor imprint is carved into the sidewalls on high mileage engines. At ignition the rotor is sliding nearly parallel to the chamber frame, which means the downforce is not in the direction of rotation. The power-party is over in less than 90 shaft degrees because once pressure equalizes on the full rotor face it produces no viable torque (the rotor is balanced - between going forward and backward). The Wankel is fired early and weakly to burn [poorly] the charge on the trailing end of the rotor [wasteful and polluting]. The carbon build-up is striking. The combustion chamber is long and narrow, consuming a lot of heat that should be producing pressure, and impeding full and rapid combustion. The 13b exhaust is an after burner, consuming fuel and sucking in the intake mixture in the 13b [that is why there is nominal backpressure in the renesis]. The Wankel will be remembered for the miracle that it ran at all, and for how little of the rotary potential it used.

The next generation of rotaries is coming. They will blow the papa wankel, and all reciprocating engines out of the market. Think torque limited by material strength. Mileage of 100 plus. Multiple fuel options. Rotaries will rule, utterly and completely. Two years or less.

P.S. Anybody have the torque formula for the wankel? Or the engine on CAD? THANKS.

posted by  megamotor

I have a very simple staistic to post
RX8 1.3 liter engine
output: 250 hp @8500 rpm
S2000
2.0 Liter engine
240 @ 8300rpm

thats why I'm 3k away from owning an RX8 of my own!!! :thumbs:

posted by  TopRPm

the rx8 is actually ESTIMATED at 238bhp at the FLYWHEEL, not the rear wheels. the rear wheel hp is much different (not that much, but its the important number) to that of the hp at the flywheel or crank.

posted by  Inygknok

Besides that I wouldn't get the RX8, mazda announced Possible plans for a MK4 RX7 that will be based off the 8 but will be a true coupe instead of a quad coupe and have a supercharger on top of the renesis, oh and it's probably going to be brought up to a 1.6 liter.

All this leads to rumors of 340 bhp, but who knows. Makers announce plans for stuff that never gets made all the time.

I saw this on a rotary forum:
http://www.ads234.com/adView.aspx?requesturl=http%3A%2F%2Fwww.rx8club.com%2 Fattachment.php%3Fattachmentid%3D1396&mac=7c0ba875&Segment=1

It looks kinda photoshopped so I don't know if its real.

posted by  Zalight

remember this, the 13B is nominally rated at 1.3 liters, but it's essentially a 2 stroke in that all four cycles happen on 1 revolution of the combustion chamber. that means it has one power stroke for every revolution of the crank. It uses it's full rated displacement to make power at any given rpm.

The S2000 engine, like all 4 stroke piston engines, has one power stroke every OTHER revolution of it's crank. Therefore it is using half it's actual displacement to make power at any given rpm.

This disparity in power strokes is why racing bodies class the 13B as a 2.6 liter engine, just like they'd class a 1 liter 2 stroke as a 2 liter engine (and you'll notice that in motorcycle road racing, 2 strokes are considered teh equivalent of 4 strokes that are double the displacment.)

this is also why the 1.3 liter rotary gets approximately the same fuel mileage as a 2.6 liter engine at the same hp levels.

posted by  ChrisV

Rotarys might revv high but that just means you have to push it harder to get max power rotarys dont like revving at 9000rpm you can wreck the engine in 5 minutes doing that in a rotary yet in any car a rotary revvs high but it only likes revving high at mabe 5500 6500 max weras a piston you get max power at 4000-5800rpm which can be easily done for a time besides i get my 1990 celica up to 8500 and i feel it loses power from when it goes past 6700 rpm so you dont need a full 9000rpm :wink2:

posted by  revv_head

Ooooooooooold Tttttttttttthread.

posted by  GreekWarrior

that and sssssstttttuuuupppppiiiiiddddddd ccccoooommmmmmmmmeeeeennnnnttttt!!!!!!! :banghead:

posted by  Low Impedance

I'm sure that made sense to you. :wink2:

The gyst I get is you have a problem with revs? Let me put one thing straight and dispel the myth that high revving engines suffer some inexplicable fatigue: they don't, they are built to rev high and guess what, a horsepower is a horsepower. To put it in perspective do you think tractor makers sit around lamenting that a V8 sedan has to rev to 5000 rpm to make peak power?

posted by  Wally

that and take what he [tried] to say and reverse it. the rotary doesnt like to rev high eh...hmmm...interesting. where did he pull that from? apprenaently he knows something that 99.9% of everyone else in the world doesnt. or he is making it up as he goes.

posted by  Low Impedance

I didn't read all the posts verbatim, but there is a lot of posts about torque, power and revs.

The rotary HAS TO spin at higher revs, otherwise it wouldn't supply the requisite torque to accelerate the wheels. It was said earlier that Power = torque x speed ... exactly, therefore if an engine doesn't produce much torque it must spin at higher speeds to achieve the same power.

And if it's spinning faster, you can therefore gear it down more, multiplying the torque back to the same as a piston engine with the same horsepower for the same WHEEL speed (excepting obvious losses in transmission etc etc)

That's my understanding of it anyway .... feel free to contradict it.

posted by  windsonian

yeh sorry i made dat up i was having a fight with my rx-7 n i hated it 4 a day it blow at 8500 rpm 1978 model not bad effort but i fixed it myself really cheep im a machanic now i love her oh n da celicas my bros gt4 n it does do that sorry 4 wastin ur time. mi rx-7 does lose a bit of power wen ova 7500rpm only like 5bhp

p.s i does ruin ur engine revving high its not a good idea exept rotorys wer da main powers high but pistons like it lower but not like 3000 or 4000 it really depends on da car i screwed 7 piston rings in a v8 holden(1987) i had once couldnt get it up my slope of a drive way i did like 170kph all da way from da country 2 city so dat probly screwed it dont remember revvs but mostly 5000 i think dat cars gone so cant check but doin it again.

Nath :banghead:

posted by  revv_head

:ohcrap:

posted by  Low Impedance

Can I quote you on that?

posted by  Wally

wtf?!?!!?!

i know ppl who dont like using punctuation marks and such, but u seriously take the beating as the new crowned champion and as the leader in not making any sense at all. wat kind of a mechanic are u???? i feel sorry for whoever takes their car to ya and they have a harder time listening to ya telling them wats wrong with their car than deciding wether to pay u or not.

posted by  Inygknok

you already did! :smoke:

posted by  Low Impedance

Fine i'll use puntuation.

I don't see why people think that rx-7's use to much petrol (gas for you americans) they 're only 1.3L 1300cc and use 2.6L and lots of family cars are more than that the 350z is 3.5L so its not that much petrol when you think about my brothers celicas 2.2L and it has no powere compared to my Rx-7 so i dont think the petrols an issue besides the fuels not going to run out in our life times or our kids so it really dos'nt matter oh and the torque can be fixed with a good quality TC or SC my 78 rx-7 is a Twin Turbo it hasnt been on the dyno by it hauls a trialer with 3 motorbikes on it (160cc,80cc,750cc) friends bikes im the only one with a car anyway RX-7s just need time put into them and they are better than 5000cc, 5700cc V8s so overall rotarys have quite an advantage to begin because a 4Cyl 1.3 has 60kw not 210kw STOCK like an rx7 (my rx7 i think is 190kw 1.2A only TURBO mod and carb tune up).

I n conclusion the Rotory engine has a simply more easer more efficient way of making power not a better one. :thumbs:

Nathan

posted by  revv_head

LOL homo

posted by  revv_head

Grow up, moron.

posted by  ChrisV

i think if the ouputshaft (crankshaft) was like hell longa it would generate lots more touque

posted by  revv_head

^^random...

posted by  Low Impedance

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