rotary engine

[evader32]

does anybody know of any rc rotary engine any info would be appreciated

[mook]

OS engines Wankel

http://www.osengines.com/engines/osmg1400.html

regards

mook

[Budman_222]

I just thought I'd throw this in here and let you look at it. Liquid cooled rotary 1/8 scale car. I've seen art that didn't look this good.

[Jetskiboy77]

lol that is better than any art I have ever seen. Is that a custom car thats made to 1/8 measurments or a real 1/8 kit that was changed to fit all those beautiful goodies?

[BCSavage]

MORE INFO! MORE INFO! MORE INFO! lol

[Chris LaPanse]

I NEED INFO!!!
that car belongs in a museum. It is ART.

[Budman_222]

I don't know much about it. Someone on here posted a link to it a while back. I thought it was just beautiful so I saved the pictures. There's 3. I don't remember where the link was posted. It's been several months. I'll search a little bit and see if I can find it.

[mgs9]

I dont know if its too practical for the fcc, it probly has a lot more power than most but it only has 17,000 rpm. Neet though.

[djmtsu]

One good thing about a rotary engine is the fact that it can be easily turbo/supercharged. On a vehicle of that scale, a working turbo could be made, hell if it has a radiator, it could use an intercooler.

PS- That is beautiful, and I want one to go along with my RX-7's, full scale.

[Losi Stealth]

What exactly are the benifits to a rotary engine? It has been my understanding that they are highly innefficient, but have fewer moving parts. This would cut down on maintanance, but I have always assumed that a standard piston driven engine created greater horsepower, and was more fuel efficient. Why, aside from the novelty value, would a rotary r/c engine have a practical application?

[Chris LaPanse]

A rotary can get almost as much horsepower as a traditional poston engine because they can REV. The rx-8 redlines at 9000 rpm. What other car even comes close? (racing cars excluded) However, it would not be as much of an advantage on the small scale, because the engines we have are already tuned to rev like crazy. They are slightly less fuel efficient, but can create similar amounts of power (when tuned right)

[josh222]

that looks sweet, doesn't the S2000 rev to about 9000RPMs?

[Jetskiboy77]

The S2000 is almost 10,000 RPMs I think, but I may be wrong. Also the BMW M3 engine revs pretty high I think its 8 something. Its not 9000 RPMs but its close enough.

[Dan H]

Yeah, the old S2K's did. The new ones have 2.2L engines that redline at 8300 or so.

I have a 1:1 rotary. Peripheral ported engines typically have a near 11K redline. But the OS wankel is already peripheral port so its pretty much at its limit.

I don't see any advantage with the current state of RC rotaries. We have so much money developed into piston 2 strokes. The only advantage is probably a very smooth engine and unique sound. I'd build a custom rotary RC if I had the money.

[Chris LaPanse]

Yes, I meant the new s2k's. The rotaries also give very good power to displacement ratio, but with nitro 2-strokes, we already have that too.

[Mike Keeney]

Originally Posted by Losi Stealth

What exactly are the benifits to a rotary engine? It has been my understanding that they are highly innefficient, but have fewer moving parts. This would cut down on maintanance, but I have always assumed that a standard piston driven engine created greater horsepower, and was more fuel efficient. Why, aside from the novelty value, would a rotary r/c engine have a practical application?

I dunno if I would call a rotary inefficient. I remember back in the days when Mazda was putting them in street cars. Lots of people tricked them out for drag racing and I can tell you firsthand, they kicked some serious butt. They would also rev until they blew up.

I'm told that this type of engine doesn't have a theoretical rev limit. The only limits were due to fuel and the strength of the steel. So if they were so great why don't you see any of them today? Well, they had a terrible problem of backfiring every time you lifted the throttle. Sounded like a shotgun going off. The public was a little turned off with a car that blew its muffler to bits once a month.

Cheers,
Mike

[Dan H]

Not exactly. My RX7 backfired every now and then but only because it was modified (no cats) and my aftermarket ECU wasn't dyno tuned correctly. Otherwise, of all stock RX7's kept in good condition, they hardly, if ever, backfire at all. The reason you don't see more rotaries today is because they are thermally inefficient. Poor fuel economy and hard to meet emissions.

They have a rev limit too and there is no part of the engine that is steel. Stock seals (on the older engines) aren't too reliable after 9500RPM's or so. In severe cases, there have been instances where the rotor face met with the surface of the rotor housing. Not pretty. Besides, if its not making power past the redline, theres no point to rev it that high.

You're right though. They do kick serious butt in drag racing.

[josh222]

cool

[Freak e-maxx1]

that thing is F'n awesome

[Interstate]

I think RCCA made a truck that used a rotary engine a couple years ago, I think out of a Kyosho USA-1, and a lot of customization.

Rotary RC engines only rev to about 17000 RPM. Like their full scale models, they have very poor torque curves; producing peak torque just a hair below their "redliine". And that peak isn't very high, way less than their piston counterparts. Rotary engines have been plagued with inneficiency as well: this is because of their eccentric combustion chamber: it's not round. Because it's not round, the air fuel mix isn't completely burned by the time the rotor is about to begin the exhaust cycle. (for that power cycle of the rotor) I think Mazda did what it could do by adding a second spark plug and unique rotor surface.

The Honda S2000's engine still holds the official record for best hp/liter. Once again because Mazdas rotary engine doesn't have the torque necessary to make the high horsepower numbers. I think the Honda engine redlines at 8000 (8500 for power shifting) and has about 120 lb ft of torque. The RX-8 I think redlines at 8000, just so the everyday idiot doesn't take the engine up to 9000 rpm's. But I think it only makes about 100 lb ft.

THEORETICALLY rotary engines do not have rev limits, because there is no reciprocating parts to break at high rpms. BUT, since gasoline has it's own limits, there is only so much power that gasoline can make to keep the flywheel, rotor etc going. I've seen a video (I wish I knew where it was) of some guy in his drive way flooring an RX-7 in neutral. he took it to about 6000 revs and held it for about 30 seconds. Then he puts his foot to the floor and the tachometer more or less creeps up to 9000; not as fast as it was from 1000 to 6000.

It's really not worth mentioning hp/liter because there's really no point. My .18 sirio makes between 500-600 hp/liter. Does that mean it's very powerful? Relatively speaking, no. Horsepower doesn't really mean anything unless you have torque.

[speckamp]

Sorry about the off-topic-ish post, but there's some misinformation I feel I should clear up.

Originally Posted by Interstate

Rotary RC engines only rev to about 17000 RPM. Like their full scale models, they have very poor torque curves; producing peak torque just a hair below their "redliine". And that peak isn't very high, way less than their piston counterparts. Rotary engines have been plagued with inneficiency as well: this is because of their eccentric combustion chamber: it's not round. Because it's not round, the air fuel mix isn't completely burned by the time the rotor is about to begin the exhaust cycle. (for that power cycle of the rotor) I think Mazda did what it could do by adding a second spark plug and unique rotor surface.

Not to split hairs, but depending on the tuning of the engine, rotarys are blessed with a flat torque curve -- they make peak torque and stay there, I don't know how one could claim that's a "very poor" torque curve.

1985 GSL-SE Stock Baseline Dyno Run

Mazda has been developing the rotary engine design for years since it licensed it from NSU in the 50's/60's, piston engine designers have been doing much with multi-plug/cyl, variable valve timing, combustion chamber design over the years as well.

Originally Posted by Interstate

The Honda S2000's engine still holds the official record for best hp/liter. Once again because Mazdas rotary engine doesn't have the torque necessary to make the high horsepower numbers. I think the Honda engine redlines at 8000 (8500 for power shifting) and has about 120 lb ft of torque. The RX-8 I think redlines at 8000, just so the everyday idiot doesn't take the engine up to 9000 rpm's. But I think it only makes about 100 lb ft.

I don't know where you get your "official records" from, but by my math, and the numbers provided by the manufacturer...
S2000 - 2005 - 2.2l i-vtec inline 4 cyl, 240bhp = 109bhp/liter
RX-8 - 2005 - 1.3l inline 2-rotor wankel RENESIS rotary, 238bhp = 183hp/liter
(for reference, my car)
RX-7 - 1985 - 1.3liter inline 2-rotor wankel 13B rotary, 135bhp = 103.8hp/liter

The redline in the 2005 RX-8 is 9,000RPM, with a fuel cutoff around 10,000RPM.

As for torque numbers,

2005 S2000 - 162lb/ft
2005 RX-8 - 159lb/ft

Not much of a difference there.

Sources:

http://automobiles.honda.com/models/... tegory=S2000

http://www.mazdausa.com/MusaWeb/disp...ehicleCode=RX8

Originally Posted by Interstate

THEORETICALLY rotary engines do not have rev limits, because there is no reciprocating parts to break at high rpms. BUT, since gasoline has it's own limits, there is only so much power that gasoline can make to keep the flywheel, rotor etc going. I've seen a video (I wish I knew where it was) of some guy in his drive way flooring an RX-7 in neutral. he took it to about 6000 revs and held it for about 30 seconds. Then he puts his foot to the floor and the tachometer more or less creeps up to 9000; not as fast as it was from 1000 to 6000.

Untrue. Rotary engines are not a 100% orbital engine. There is a slight reciprocation as the apexs follow the rotor housing epitrichoidal shape (think oval with a pinched center), like any motor there are limits to the stresses the materials undergo.

Also, as the rotors spin at 1/3 output shaft velocity, there's more time to extract power from the gasoline than one might think.

I won't address the revving issue since I don't know which video you're talking about other than to say that in my humble opinion my RX-7 revs faster than any other car I've owned / driven.

Originally Posted by Interstate

It's really not worth mentioning hp/liter because there's really no point. My .18 sirio makes between 500-600 hp/liter. Does that mean it's very powerful? Relatively speaking, no. Horsepower doesn't really mean anything unless you have torque.

Funny. Horsepower is calculated as:

hp = (torque * rpm) / 5252

which would lead me to believe that torque and horsepower are very much related.

Hp/liter is simply a marketing term to show the "efficency" of an engine, I agree that it's more or less a useless number as far as performance, unless package size of a powerplant is taken into account.

[Interstate]

Originally Posted by speckamp

Not to split hairs, but depending on the tuning of the engine, rotarys are blessed with a flat torque curve -- they make peak torque and stay there, I don't know how one could claim that's a "very poor" torque curve.

It's very poor because isn't really any increase in torque at any point. So when exiting a turn, you don't have great torque to "explode" out of the turn. That dyno chart says it all: when you're needing more power than usual, there isn't any point in the rev range that has it.

Originally Posted by speckamp

Untrue. Rotary engines are not a 100% orbital engine. There is a slight reciprocation as the apexs follow the rotor housing epitrichoidal shape (think oval with a pinched center), like any motor there are limits to the stresses the materials undergo.

Please note I said theoretically there is no rev limit. It's in theory that that it has no rev limit, but of course materials come in the way.

Originally Posted by speckamp

I won't address the revving issue since I don't know which video you're talking about other than to say that in my humble opinion my RX-7 revs faster than any other car I've owned / driven.

Is that in neutral, or under load?

Originally Posted by specamp

Funny. Horsepower is calculated as:

hp = (torque * rpm) / 5252

which would lead me to believe that torque and horsepower are very much related.

Once again, you didn't read what I wrote. I never said they weren't related, or how horsepower is calculated. I said hp/liter is pointless. Note my Sirio example.

[dude12345]

more info is on the rx7 forum.

http://www.rx7club.com/showthread.ph...highlight=787b

[ducati777]

Originally Posted by Interstate

It's very poor because isn't really any increase in torque at any point. So when exiting a turn, you don't have great torque to "explode" out of the turn. That dyno chart says it all: when you're needing more power than usual, there isn't any point in the rev range that has it.

??? Uhhhh so you believe a desirable torque curve is one that peaks at high rpm, such as most 4 cyl motors. I'm a little confused because most people believe a flat torque curve is better. A 100hp motor with a flat torque curve will beat a 100hp motor with a peaky curve. I can show you a lot of math on it, but the flat torque curve will have more hp more of the time at a lower rpm. Given two motors of the same output, the flatter torque curve will be faster....

Originally Posted by Interstate

Is that in neutral, or under load?

Neutral? Why would you make any estimates off revving a motor in neutral? Every motor out there could spool up very quickly, the usual slowdown is the weight of the flywheel.

Originally Posted by Interstate

Once again, you didn't read what I wrote. I never said they weren't related, or how horsepower is calculated. I said hp/liter is pointless. Note my Sirio example.

Its a good example. Hp/liter is really just a fun way to compare motors. But in answer to your question, yes I think your Sirio is a very powerful motor. Well a very high performance motor.

[Interstate]

Originally Posted by ducati777

??? Uhhhh so you believe a desirable torque curve is one that peaks at high rpm, such as most 4 cyl motors. I'm a little confused because most people believe a flat torque curve is better. A 100hp motor with a flat torque curve will beat a 100hp motor with a peaky curve. I can show you a lot of math on it, but the flat torque curve will have more hp more of the time at a lower rpm. Given two motors of the same output, the flatter torque curve will be faster....

I suppose the desired torque curve would really depend on the application and driver preference. Wanna agree to disagree?

Originally Posted by ducati777

Neutral? Why would you make any estimates off revving a motor in neutral? Every motor out there could spool up very quickly, the usual slowdown is the weight of the flywheel.

There are some stupid people on the internet, and since that was his first post, I don't really know his intellegence level... He may be free reving the engine, and he may be drag racing, but I don't know. I've actually reved a couple lower end engines that took a relativly long time to rev.