Why Do Rotaries Suck?

[GT-R32]

Yep, the first production Wankel rotary in the world, NSU Spyder was rated at 498cc for its single rotor engine.

Gary is slowly coming around. While still carrying the same attitude, his posts contain slightly different comments and information than they did at the start of the thread.

EDIT: They aren't a 3.9L piston equivalent 260RS. Not by any stretch. That's where Gary's banging on is misleading for the general public.

[~rx3~]

So what's left in this quest...........the rotors only do 3,000 rpm................no, won that one already.

Cheers

Gary

what did you win ?we already knew the rotors do 3000 rpm , when the engine is doing 9000 rpm

[ylwgtr2]

The next question do the rotors in a 13B do 3,000 rpm (call it cycles or orbits if you wish) when the crankshaft is doing 9,000 rpm? Please note that I am not asking you whether or not that's the same as 3,000 rpm of the pistons in piston engine. What I am asking you is very specific, do the rotors do 3,000 rpm or not.

Apparently the engine doesnt have a "crankshaft"

[GT-R32]

what did you win ?we already knew the rotors do 3000 rpm , when the engine is doing 9000 rpm

Precisely, the engine fires for 9,000RPM output and the sound of it is in accordance with this fact.

Apparently the engine doesnt have a "crankshaft"

He totally ignores the crank/e-shaft, how often the engines actually fires and subsequently revs. This leads to a failed conclusion as critical information is ignored and conclusions made are technically incorrect.

[bigslick]

I don’t care that Mazda say it’s a 1.3 litre. They do say it’s a 1.3 litre rotary and I understand that it means it is a totally different type of engine. I now understand how a 13B actually pumps 3.9 litres of air after completing combustion on all 3 faces on each of it’s 2 rotors, (thanks to Gary and Rice Racing) but that’s to be expected; it is after all 1.3 litre Wankel (Wankel engines capacity being determined through different criteria because it doesn’t have pistons, which is the inventors prerogative) and it spools 3.9 litre sized turbos.

I’ve heard of 13B’s lasting for hundreds of thousands of kilometres just the same as some RB26’s. And I’ve experienced 13B’s that have broken through no apparent abuse of my own (although I did drive it hard sometimes) only to find out later that they were old or rebuilt/maintained poorly. The same could be said of some RB26’s, I’ve also heard of some new rebuilds that have bitten the dust for no apparent reason. These are performance engines, this is bound to happen from time to time.

I love my RB26 and the sound it makes at 7000rpm, and I love the sound my 13B used to make at 7000rpm. Heck, I even love the sound from the in car camera in a V8 Supercar near redline, and an F1 2.4 litre V8 sends shivers down my spine. I bet I would even like the sound and feel of a 16 litre turbo diesel truck with it's shiploads of torque pulling 20 tons if I had the chance to drive one. Like a few members on SAU, I love all engines.

I like the fact that a 13B sits low and far back in an RX-7’s engine bay and gives it great weight distribution.

The fuel consumption as I remember wasn’t that great. But who cares! I didn’t. If I was concerned about that I wouldn’t own one. I loved the sound and the power from a physically small engine.

Yes the rotors only spin at 1/3 the speed of the eccentric shaft; many who know about how a rotary works already knew that, they were probably fascinated with how it works in this regard (as I was when I first found out), and they probably didn’t feel cheated by Mazda. I don’t know why you do, Gary. In fact, I’m impressed by the thought that my Rotary powered car can cruise along quite well when the rotors are only spinning (or orbiting elliptically) at only 500 rpm. Neat huh? However I’m also glad that my tacho, by reading ignition pulses and converting them into rpm of the eccentric shaft, reads to 9000rpm, thereby allowing me to use a normal aftermarket tacho, and allowing my relatively simple brain to understand the usable rev range of my engine.

Who really needs to classify the rotary as a 2 or 4 stroke? It’s neither. It’s a wankel. It might be similar

to one of them, but not the same. Do you need to classify it to build one? To drive one? To service one? No. Maybe to design one, but none of us are doing that.

Motorsport governing bodies class it according to their own research.

The answer to the original question is: Rotaries don’t suck. They have some inefficiencies, but they also produce good power for their physical size. Some people love the sound and some don’t. This is personal opinion. Some last a long time, and some don’t. Just like RB26’s. But you know what… I love them both anyway.

[~rx3~]

Lie #2, they rev to 9,000 rpm. no they don't. The rotors only do 3,000 rpm they use a step up gear ratio to spin the eccentric shaft at 3 times the rotor rpm.

Cheers

Gary

so if you calculate the rpm of an engine by the speed of the rotors and not the outout shaft, how do you calculate the rpm of a piston engine where the output shaft only spins once to complete 4 strokes/cycles of the piston?

[ylwgtr2]

I don’t care that Mazda say it’s a 1.3 litre. They do say it’s a 1.3 litre rotary and I understand that it means it is a totally different type of engine. I now understand how a 13B actually pumps 3.9 litres of air after completing combustion on all 3 faces on each of it’s 2 rotors, (thanks to Gary and Rice Racing) but that’s to be expected; it is after all 1.3 litre Wankel (Wankel engines capacity being determined through different criteria because it doesn’t have pistons, which is the inventors prerogative) and it spools 3.9 litre sized turbos.

I’ve heard of 13B’s lasting for hundreds of thousands of kilometres just the same as some RB26’s. And I’ve experienced 13B’s that have broken through no apparent abuse of my own (although I did drive it hard sometimes) only to find out later that they were old or rebuilt/maintained poorly. The same could be said of some RB26’s, I’ve also heard of some new rebuilds that have bitten the dust for no apparent reason. These are performance engines, this is bound to happen from time to time.

I love my RB26 and the sound it makes at 7000rpm, and I love the sound my 13B used to make at 7000rpm. Heck, I even love the sound from the in car camera in a V8 Supercar near redline, and an F1 2.4 litre V8 sends shivers down my spine. I bet I would even like the sound and feel of a 16 litre turbo diesel truck with it's shiploads of torque pulling 20 tons if I had the chance to drive one. Like a few members on SAU, I love all engines.

I like the fact that a 13B sits low and far back in an RX-7’s engine bay and gives it great weight distribution.

The fuel consumption as I remember wasn’t that great. But who cares! I didn’t. If I was concerned about that I wouldn’t own one. I loved the sound and the power from a physically small engine.

Yes the rotors only spin at 1/3 the speed of the eccentric shaft; many who know about how a rotary works already knew that, they were probably fascinated with how it works in this regard (as I was when I first found out), and they probably didn’t feel cheated by Mazda. I don’t know why you do, Gary. In fact, I’m impressed by the thought that my Rotary powered car can cruise along quite well when the rotors are only spinning (or orbiting elliptically) at only 500 rpm. Neat huh? However I’m also glad that my tacho, by reading ignition pulses and converting them into rpm of the eccentric shaft, reads to 9000rpm, thereby allowing me to use a normal aftermarket tacho, and allowing my relatively simple brain to understand the usable rev range of my engine.

Who really needs to classify the rotary as a 2 or 4 stroke? It’s neither. It’s a wankel. It might be similar

to one of them, but not the same. Do you need to classify it to build one? To drive one? To service one? No. Maybe to design one, but none of us are doing that.

Motorsport governing bodies class it according to their own research.

The answer to the original question is: Rotaries don’t suck. They have some inefficiencies, but they also produce good power for their physical size. Some people love the sound and some don’t. This is personal opinion. Some last a long time, and some don’t. Just like RB26’s. But you know what… I love them both anyway.

well written

[Birds]

I don’t care that Mazda say it’s a 1.3 litre. They do say it’s a 1.3 litre rotary and I understand that it means it is a totally different type of engine. I now understand how a 13B actually pumps 3.9 litres of air after completing combustion on all 3 faces on each of it’s 2 rotors, (thanks to Gary and Rice Racing) but that’s to be expected; it is after all 1.3 litre Wankel (Wankel engines capacity being determined through different criteria because it doesn’t have pistons, which is the inventors prerogative) and it spools 3.9 litre sized turbos.

I’ve heard of 13B’s lasting for hundreds of thousands of kilometres just the same as some RB26’s. And I’ve experienced 13B’s that have broken through no apparent abuse of my own (although I did drive it hard sometimes) only to find out later that they were old or rebuilt/maintained poorly. The same could be said of some RB26’s, I’ve also heard of some new rebuilds that have bitten the dust for no apparent reason. These are performance engines, this is bound to happen from time to time.

I love my RB26 and the sound it makes at 7000rpm, and I love the sound my 13B used to make at 7000rpm. Heck, I even love the sound from the in car camera in a V8 Supercar near redline, and an F1 2.4 litre V8 sends shivers down my spine. I bet I would even like the sound and feel of a 16 litre turbo diesel truck with it's shiploads of torque pulling 20 tons if I had the chance to drive one. Like a few members on SAU, I love all engines.

I like the fact that a 13B sits low and far back in an RX-7’s engine bay and gives it great weight distribution.

The fuel consumption as I remember wasn’t that great. But who cares! I didn’t. If I was concerned about that I wouldn’t own one. I loved the sound and the power from a physically small engine.

Yes the rotors only spin at 1/3 the speed of the eccentric shaft; many who know about how a rotary works already knew that, they were probably fascinated with how it works in this regard (as I was when I first found out), and they probably didn’t feel cheated by Mazda. I don’t know why you do, Gary. In fact, I’m impressed by the thought that my Rotary powered car can cruise along quite well when the rotors are only spinning (or orbiting elliptically) at only 500 rpm. Neat huh? However I’m also glad that my tacho, by reading ignition pulses and converting them into rpm of the eccentric shaft, reads to 9000rpm, thereby allowing me to use a normal aftermarket tacho, and allowing my relatively simple brain to understand the usable rev range of my engine.

Who really needs to classify the rotary as a 2 or 4 stroke? It’s neither. It’s a wankel. It might be similar

to one of them, but not the same. Do you need to classify it to build one? To drive one? To service one? No. Maybe to design one, but none of us are doing that.

Motorsport governing bodies class it according to their own research.

The answer to the original question is: Rotaries don’t suck. They have some inefficiencies, but they also produce good power for their physical size. Some people love the sound and some don’t. This is personal opinion. Some last a long time, and some don’t. Just like RB26’s. But you know what… I love them both anyway.

My sentiments all along. I have highlighted my favourite parts and I thank you very much for posting this. A very proper, take-a-step-back, unbiased look at the reality of it all.

[Sydneykid]

so if you calculate the rpm of an engine by the speed of the rotors and not the outout shaft,

Where did I say that?

When people say " my engine does 9,000 rpm" the common assumption is that all of the engine is doing 9,000 rpm. Not just one part of the engine. All I am doing is pointing out the inaccuracy of that assumption.

how do you calculate the rpm of a piston engine where the output shaft only spins once to complete 4 strokes/cycles of the piston?

The pistons still do 9,000 rpm (or cpm if you prefer) but the rotors don't.

What I was pointing out was the fallacy of the blind rotor supporters who say rotaries rev more than piston engines, when the truth is not all of the engine does. In fact the most important part of the engine, the bits that actually produce the power, only do 3,000 rpm. Yes I know the camshafts only do 4,500 rpm in a 9,000 rpm piston engine, but even they are 50% higher reving than the rotors in a rotary engine.

It has been my experience that a lot of rotary huggers don't really understand how their engine works, what capacity it truly is and what rpm the major components are actually doing. So they get all defensive when the facts are pointed out.

Cheers

Gary

[GT-R32]

The engine still fires for a full 9,000RPM worth of 1308cc air/fuel mixture and sounds as such, despite rotary-piston speed. What a clever thing to be able to do that.

[Sydneykid]

I don’t care that Mazda say it’s a 1.3 litre.

But a lot of people do care.

They do say it’s a 1.3 litre rotary and I understand that it means it is a totally different type of engine.

But a lot of people don't know that.

I now understand how a 13B actually pumps 3.9 litres of air after completing combustion on all 3 faces on each of it’s 2 rotors, (thanks to Gary and Rice Racing) but that’s to be expected; it is after all 1.3 litre Wankel (Wankel engines capacity being determined through different criteria because it doesn’t have pistons, which is the inventors prerogative) and it spools 3.9 litre sized turbos.

So you learnt something from the rantings, that's a good thing.

I like the fact that a 13B sits low and far back in an RX-7’s engine bay and gives it great weight distribution. The fuel consumption as I remember wasn’t that great. But who cares! I didn’t. If I was concerned about that I wouldn’t own one. I loved the sound and the power from a physically small engine.

Did you know a 13B weighs a lot more than a Honda F20, K20 or K24 engines and almost as much as a LS2 (that's 6 litre V8)? They aren't as light as you may think.

Yes the rotors only spin at 1/3 the speed of the eccentric shaft; many who know about how a rotary works already knew that, they were probably fascinated with how it works in this regard (as I was when I first found out), and they probably didn’t feel cheated by Mazda. I don’t know why you do, Gary.

Because a large number of rotary huggers don't know that, while their tacho is showing 9,000 rpm, the rotors are only doing 3,000 rpm. I'm just adding to their knowledge bank

In fact, I’m impressed by the thought that my Rotary powered car can cruise along quite well when the rotors are only spinning (or orbiting elliptically) at only 500 rpm. Neat huh?

Not really all that neat, because it's pumping 3.9 litres of air per rpm and a corresponding amount of fuel. So it's using ~30% more petrol than a 2 litre piston engine with the same A/F, gearbox and diff ratios.

To be continued

Cheers

Gary

[Sydneykid]

Continued from above........

However I’m also glad that my tacho, by reading ignition pulses and converting them into rpm of the eccentric shaft, reads to 9000rpm, thereby allowing me to use a normal aftermarket tacho, and allowing my relatively simple brain to understand the usable rev range of my engine.

What setting do you have your tacho on?

Who really needs to classify the rotary as a 2 or 4 stroke? It’s neither. It’s a wankel. It might be similar

to one of them, but not the same. Do you need to classify it to build one? To drive one? To service one? No. Maybe to design one, but none of us are doing that.

You need to know that information and more to tune one, to select the turbo for one, to specify the injectors sizes, the throttle butterflies, the inlet plenum, the exhaust system, the radiator, the oil cooler, in fact pretty much anthing to do with the engine requires an understanding of their workings.

Motorsport governing bodies class it according to their own research.

No they don't, they rely on Mazda's incorrect measurements and then multiply it by a random number, one that changes from time to time.

The answer to the original question is: Rotaries don’t suck. They have some inefficiencies, but they also produce good power for their physical size.

They actualy don't, there are far smaller and lighter engines that produce more horsepower and torque.

Some people love the sound and some don’t. This is personal opinion. Some last a long time, and some don’t. Just like RB26’s. But you know what… I love them both anyway.

I'm not sure that I can truly say I love them both, they both frustrate the hell out of me quite often and the fact is there are better engines around, far better engines, for every purpose.

Cheers

Gary

[GT-R32]

No they don't, they rely on Mazda's incorrect measurements and then multiply it by a random number, one that changes from time to time.

In fact, the numbers derived by CAMS and FIA come from a much greater understanding of the engine's operation and output than yourself. It's blatently arrogant to assume you somehow know more, when you have demonstrated your understanding of the technical relatives when measured by time are lacking.

All of the required information is in the chart I have provided. This demonstrates the operation of the 13B Wankel is comparable to a 4 stroke 2.6L 4-cyl. And you know what? It's not that complicated.

[PSI_GTSII]

I like rotaries....it gives me a chance to go for a Piss or get a pie at the drags whilst not offending my ears or missing anything interesting

[Sydneykid]

In fact, the numbers derived by CAMS and FIA come from a much greater understanding of the engine's operation and output than yourself. It's blatently arrogant to assume you somehow know more, when you have demonstrated your understanding of the technical relatives when measured by time are lacking.

All of the required information is in the chart I have provided. This demonstrates the operation of the 13B Wankel is comparable to a 4 stroke 2.6L 4-cyl. And you know what? It's not that complicated.

What? We take Mazda's capacity measurement for a 13B and multiply it by 1.8 to get 2.35 litres. What the hell has 2.35 got to with anything? Even creative maths using irelevancies like eccentric shaft degrees can't come up with 2.35 litres. So forget 2.6 litres as the equivalency. As for comparable to a 4 cylinder that's not true either, there is no mention of cylinder number equivalency in the regulations. Ditto stoke/cycle, no mention is made. That's zero out of 3 for your score today.

Note above I said "we", that's because I am a CAMS accredited scrutineer, CAMS accredited Steward, life member of a CAMS club and the current Eligibility Office for CAMS Category 3J in NSW. I'm more than willing to debate motorsport equivalencies with you anytime. But I fail to see what that has to do with actual capacity, rpm and cycle type of a rotary engine.

Cheers

Gary

[GT-R32]

What? We take Mazda's capacity measurement for a 13B and multiply it by 1.8 to get 2.35 litres. What the hell has 2.35 got to with anything? Even creative maths using irelevancies like eccentric shaft degrees can't come up with 2.35 litres. So forget 2.6 litres as the equivalency. As for comparable to a 4 cylinder that's not true either, there is no mention of cylinder number equivalency in the regulations. Ditto stoke/cycle, no mention is made. That's zero out of 3 for your score today.

Note above I said "we", that's because I am a CAMS accredited scrutineer, CAMS accredited Steward, life member of a CAMS club and the current Eligibility Office for CAMS Category 3J in NSW. I'm more than willing to debate motorsport equivalencies with you anytime. But I fail to see what that has to do with actual capacity, rpm and cycle type of a rotary engine.

Cheers

Gary

Oh, my apologies, as an eligibility officer, scrutineer, club member and licence holder you hold so much clout in the big decisions!!!! These decisions are made with consultation of those with an understanding of relatives, the genuine engineering facts. Maybe just a few notches up the food chain LOL!!

FIA use 1.79 and CAMS use 1.8 due to rotary engine inefficiencies (google them). Exclude those and you end up with x2 as I said above. We've discussed this before. Remitting vital information is not cause of you to proclaim me as wrong on the assumption that you are always right. It looks weak.

I used 4 stroke 4cyl as there are two chambers of combustion on the power stroke for every 360 degree revolution. Why else does a 20B give a resonance similar to that of a 4-stroke inline 6 cylinder? I'm really sorry you can't understand this. Sound, supports my arguments.

The fact is, you are too limited, be it with regard to attitude and/or mental ability, to relate this on a time scale relative. Self proclamation of you being correct is very far from actual facts and is nothing more than a reflection of the individual in question.

[Sydneykid]

Oh, my apologies, as an eligibility officer, scrutineer, club member and licence holder you hold so much clout in the big decisions!!!! These decisions are made with consultation of those with an understanding of relatives, the genuine engineering facts. Maybe just a few notches up the food chain LOL!!

In fact I do and I am a fair way up the food chain, but that's not the question at hand.

FIA use 1.79 and CAMS use 1.8 due to rotary engine inefficiencies (google them). Exclude those and you end up with x2 as I said above. We've discussed this before. Remitting vital information is not cause of you to proclaim me as wrong on the assumption that you are always right. It looks weak.

Hang on, you're the one who said times 2, when it's in fact times 1.8. So I'm hardly the one who is wrong here.

I used 4 stroke 4cyl as there are two chambers of combustion on the power stroke for every 360 degree revolution. Why else does a 20B give a resonance similar to that of a 4-stroke inline 6 cylinder? I'm really sorry you can't understand this. Sound, supports my arguments.

You lost me again, to me a 13B sounds lik a 6 cylinder 2 stroke at 3,000 rpm. A 20B sounds like a 9 cylinder 2 stoke at 2,750 rpm, as most 20B's are limited to around that maximum rotor rpm due issues to with the standard 2 piece eccentric shaft. That's fixable as there are reasonably well engineered 1 piece eccentric shafts available. Although I haven't tested one to 3,000 rpm yet, that's rotor rpm of course. Because it's the rotors that are relevant here, as it's their loading and rpm that causes the failure of the eccentric shaft.

The fact is, you are too limited, be it with regard to attitude and/or mental ability, to relate this on a time scale relative. Self proclamation of you being correct is very far from actual facts and is nothing more than a reflection of the individual in question.

I'm not the one who is limited here, I have a completely open mind when it comes to cars. But I know what I know and I'm sorry if you consider my passing on of that knowlegde to be self proclamation. I actually feel quite justified in my stance, plus I would add that some people now know some more about rotaries than they did before and that's not a bad thing.

Cheers

Gary

[Jez13]

Because a large number of rotary huggers don't know that, while their tacho is showing 9,000 rpm, the rotors are only doing 3,000 rpm. I'm just adding to their knowledge bank

Actually when it is showing 9,000rpm it is running at 9,000rpm. People times that figure by three and think its running at 27,000rpm.

[jase-r34]

plus I would add that some people now know some more about rotaries than they did before and that's not a bad thing.

Cheers

Gary

I for one know a heap more than I did before this thread started thanks to some of the great posts by a few of you guys!

[260tech]

^^^ Yup. Me too. Previously complete blank regarding finer Wankel details. Thanks to all those people who combined in a positive way to sift the wheat from the chaff.

Things I now know for sure from this discussion.

1. Wankel rotors spin a lot slower than I was led to believe.

2. There is a sound reason based on physics, for their capacity to produce hp & consume juice.

3. I did not learn this from reading Mazda brochures at the caryard.

Cheers GW

Edited September 28, 2009 by 260tech