Why Do Rotaries Suck?

[madbung]

Some folk think you can..

http://mikesdriveway.com/misc/rotor.doc

[DRD-00F]

yeah it's pretty simple Jez, even I gave it a go and got an output!

the only internal engine you can't do that for would be a Brayton cycle, cause it doesn't have 'combustion chambers', it's a free flowing force of air, which is rated in **.*L/Min

aka, thrust.

[260tech]

But what if, in Mazda's view that 1.3L is the truth. What if all those highly intelligent engineers that create our Japanese cars came to the conclusion that a 13B rotory is in fact a 1.3l engine. If that is the conclusion then nobody is lying or deceiving. I can understand why it is a 1.3L and connot be a 3.9L - not my fault that others can't.

Shut up Graham! No I can't help myself I'll explode if I don't write something. F#$Kit I've earned it I've read 35 pages of this debate. Dammit!

So. Please define "engine" as the highly intelligent developement (no doubt about that) engineers would.

Waits for the next 35 pages.

Seeya

[Birds]

That's not what you said. You said it was unfair.

It's very relevant. It's a buyers market, and people are comparing every aspect of every car they might choose. Are they not?

Lets head over to car sales and see how people are advertising their cars:

2007 PORSCHE 911 997 MY07 TURBO AWD PISTON

2dr 4 seats COUPE 6cyl 3.6L Semi-Automatic 9,000 kms

2009 AUDI A5 8T MY09 S-TRONIC QUATTRO PISTON

2dr 4 seats COUPE 4cyl 2.0L Sequential Manual Auto-Dual Clutch 10 kms

2007 BMW 325i E93 MY08 STEPTRONIC PISTON

2dr 4 seats CONVERTIBLE 6cyl 2.5L Semi-Automatic 32,600 kms

2009 TOYOTA PRIUS ZVW30R I-TECH PISTON

5dr 5 seats LIFTBACK 4cyl 1.8L Constantly Variable 1,399 kms

2008 MERCEDES B200 W245 MY08 TURBO PISTON

5dr 5 seats HATCHBACK 4cyl 2.0L Constantly Variable 23,000 kms

Oh well f**k my arse! They all seem to have the literage stated! That's interesting seeing how it's irrelevant. And how stupid of them to not add their quarter mile times and winton lap times... tisk tisk tisk...

Now let's check out some RX7s, cause they look cool, I might buy one of those...

2000 MAZDA RX-7 FD ROTARY

2dr 2 seats COUPE 2cyl 1.3L Manual 30,117 kms

2000 MAZDA RX-7 FD Spirit R Type B ROTARY

2dr 4 seats COUPE 2cyl 1.3L Manual 50,000 kms

2000 MAZDA RX-7 FD ROTARY

2dr 2 seats COUPE 2cyl 1.3L Manual 71,600 kms

Oh well shit, even the rotary people are stating literage! If only they knew that it was irrelevant and they will sell their car much faster if they stated how many chicks it could pull...

I spose if I wanted to compare these cars in my choice of buying one, I couldn't... well that sucks. I wish every car was advertised with a drag time or engine power, then I could compare, but alas, both of those have too many variables and are often different between each car.

Wether YOU want to face it or not, the comparison is already there, in black and white. It's not irrelevant, it's not the best way to do it either but that's how the general public do it. You're asking every person in the world to completely understand an engine before buying it as the information stated is unfair in comparison to other cars they might be purchashing. That's the reason we have stats, that's the reason we have foot notes, that's the reason we have blurbs, or reviews, or previews, so you don't have to know absolutely everything about it to make a decision. Well what if the information in that blurb/review was innaccurate? You would want everyone to suck it up and just to have KNOWN what was going on before even reading the blurb/review. That's a bit mean innit?

Also, it seems carsales.com is stupid for not adding a rotary option...

Where did I say it was unfair? Please find me a quote?

I've taken the liberty of modifying your Carsales findings with bold annotations to point out the pointlessness of it. You can compare the displacement of a piston engine to a piston engine all you like, that's fine to an extent. You can't compare the displacement of a rotary engine to the displacement of a piston engine. Not without using a formula based on crankshaft rotations. They have different takes on displacement and how displacement is used in the internal combustion process. Rotary is not just an add on like VVTi or direct injection, or a different type of fuel being used like with diesels. This is my point all along...when you call it a rotary engine, you are implying that the engine is completely different. You don't need to measure this unique engine using piston-biased science, and you can't. Why can't you people understand that the rotary is its own engine, so different to other engines that it actually has its own rules for classification? Do you have pistons inside your heads?

Carsales.com isn't stupid for not adding a rotary option...the RX7 only came with one engine. If it came with a piston engine as an option then there would be a need for a piston or rotary option, yes. Perfect example to support my case...do you think people viewing these RX7 ads on Carsales are going to be deterred by the fact they only have 1.3 litre engines? Or will they know that they have rotary engines, and that the 1.3 litre rotary is quite different to a 1.3 litre 4 stroke and therefore won't use fuel or perform like a Daihatsu? I think the latter, don't you? Displacement comparison to the consumer is ONLY relevant when the engines have the same method of internal combustion, e.g. piston engine. It's also becoming superseded as a measure of fair comparison due to the advent of different engine types in mainstream vehicles these days, e.g. diesels, hybrids. Displacement in a diesel has different meaning to that of a petrol...long stroke vs short stroke, narrow bore vs wide bore. It's particularly useless when you change the internal design of the engine completely, e.g. a rotary. Okay, let's pretend hypothetically that Mazda did call the 13B a 3.9 litre rotary...we'd still be faced with the same problem, i.e. people assuming incorrectly that this 3.9 litre engine is a friggen piston engine, and expecting the same operation as a 3.9 litre 4 stroke piston engine. How many production 3.9 litre engines do you know of that rev to 9000rpm? Or put out only 206kw? Or have less than 350nm? Case in point, and reality check, how many Mazda rotary owners have you heard bitching about Mazda lying about the displacement of their rotary engine? Can you say moot point?

Back to my turbocharged argument...I would like to know where Mazda come off deceiving the market with rotary displacement while many are left marvelling at how a 2 litre turbocharged engine can perform like a V8. AFAIK no manufacturers take the time to explain the process in their marketing literature. How is it that they are getting away with this? Or is it that turbocharged design has become so popular it's made its way into pop culture and there's no need for explanation or a conversion of displacement to the naturally aspirated equivalent for the sake of comparison?

[DRD-00F]

Outside of motorsport, for which we already have our formulas to fairly compare piston powered vehicles with rotary powered vehicles, it is absolutely nothing. Deal with it.

So if you have formulas for inside of motorsport to make it fair, not having formulas outside of motorsport would make it unfair, correct? It's like an opposites thing. Surely you know what opposites are. You know, inside and outside? Opposites?

Birds, you have way too much faith in the general public if you expect them to compare every single thing in a car with the giving stats, except the engine. Which just happens to be the most important part.

[madbung]

wtf

Main Entry: dis·place·ment

Pronunciation: \(ˌ)dis-ˈplā-smənt, di-ˈsplā-\

Function: noun

Date: 1611

1 : the act or process of displacing : the state of being displaced

2 a : the volume or weight of a fluid (as water) displaced by a floating body (as a ship) of equal weight b : the difference between the initial position of something (as a body or geometric figure) and any later position c : the volume displaced by a piston (as in a pump or an engine) in a single stroke; also : the total volume so displaced by all the pistons in an internal combustion engine (as in an automobile)

3 a : the redirection of an emotion or impulse from its original object (as an idea or person) to another b : the substitution of another form of behavior for what is usual or expected especially when the usual response is nonadaptive —called also displacement activity, displacement behavior

no matter what it's applied to displacement is still..........displacement

petrol, diesel, rotar, impellor ect it has only one meaning when applied to a pump/engine

Different bore and stroke formulas can have equal displacement but vastly different performance, I know amazing hey.

seriously fella.

Edited October 1, 2009 by madbung

[scathing]

Funny though because the rotor has three equal sides so when one combustion completes it becomes in its exact original postition only its not with the original rotor face. I think thats enough to fill the definition "returns to its original state". Just because its not the same rotor face doesnt mean it hasn't returned to its original position.

That is the single most retarded thing I've read in this thread. Original postion does not equal original state. If you took that definition, every time a piston hits TDC its returned to "its original state" because it happened to be in the same location it was when you first started observing it. That would quarter the currently accepted measurement of displacement for piston engines.

Even if I ignore that painfully obvious state vs position disconnect, if its "not the original rotor face" present in the position you're comparing from then how can you even say its "the same position"?

The definition of "original state" would be matching not only the physical positioning of the components, but also the logical positioning within the cycle.

If we talk NA (to rule out the variability of compressed intake air, and we all agree even in FI applications we define displacement by measuring the air flowed by the engine sans compressor):

In a "2.0L" 4 stroke piston engine, if we take our initial "original state" observation of a cylinder with its spark plug just about to ignite its air/fuel mixture then for that combustion surface to reach its "original state" again then 2.0L of air would have been injested and expelled by the whole engine.

In a "2.0L" two stroke, you'd have the exact same amount of air flowing through the system when everything returns to its original state. The difference is that it would have only required half as many crankshaft rotations compared to the 4 stroke above.

In a "1.3L" 13B rotary engine, if a specific rotor face is initially observed right before ignition then for that specific rotor face to return to that original state (compressed air/fuel mix inside and ready to be ignited) then 3.9L worth of air would have passed through the entire powerplant.

This is something practically everyone else has already concurred with, and moved on from.

I'd agree that it's not fair to compare the numbers between the different engine types due to their nature of combustion cycle. Just like I'd agree that its not fair to compare RPM of the combustion surfaces between the two types of engine, due to fundamental differences.

However, when you're talking about "measurement" rather than "values for comparison" then it's pretty clear-cut, and should be consistent across the board.

But what if, in Mazda's view that 1.3L is the truth.

Measuring displacement is not an opinion open to perspective. It's a science, and its conclusions are objective.

What if all those highly intelligent engineers that create our Japanese cars came to the conclusion that a 13B rotory is in fact a 1.3l engine.

You mean in the same way that all high performance Japanese-engineered cars up until a few years ago only ever made "206kW"?

Like how the Japanese engineers who went from a 206kW R33 GT-R to a car that made more torque across the entire rev-range in the R34 GT-R, yet somehow defied the basic scientific principle that power = torque x rpm, but still had its output advertised at 206kW as well?

The fact that marketing parasites advertise something, that the engineers will inevitably be forced to agree with in order to toe the company line, is no proof of accuracy.

If that is the conclusion then nobody is lying or deceiving.

If they truly believe it then they're not lying or deceiving. They're just ignorant.

[bozodos]

so the other main reason why rotaries suck is their relative inefficiency compared to modern piston engines?

[Birds]

So if you have formulas for inside of motorsport to make it fair, not having formulas outside of motorsport would make it unfair, correct? It's like an opposites thing. Surely you know what opposites are. You know, inside and outside? Opposites?

Birds, you have way too much faith in the general public if you expect them to compare every single thing in a car with the giving stats, except the engine. Which just happens to be the most important part.

You have formulas inside of motorsport to make it fair because motorsport is invariably prone to modification...thereby forcing a comparison of displacement because engine modifications have a somewhat linear effect on displacement. For the unmodified showroom car being sold to the public...displacement doesn't mean shit. All that matters are the vehicles inputs and outputs. But if someone wants to make their own formula outside of motorsport they can, or they can adopt the existing formulas from CAMS or FIA...but saying that Mazda lies just because the manufacturer didn't classify the engine the way this person wanted it to be classified...again, deal with it. We've managed to do so just fine for the past few decades.

Except the engine? I'm only naming one engine variable that I feel is somewhat irrelevant, i.e. displacement...and I only said it is irrelevant when comparing different engine types. But for the sake of you generalising my statement to mean every single engine, even of the same type...I say you have too much faith in the general public assuming they will place so much emphasis on displacement (which is just a means to an end, i.e. power and torque). Which do you think matters more to the general public...whether their engine is a 1.3 litre or a 5 litre...or whether it produces 60kw or 206kw? Are the XR6 turbo owners worried that their 4 litre engine might not be a match for the XR8 given it's missing 1.4 litres?

wtf

Main Entry: dis·place·ment

Pronunciation: \(ˌ)dis-ˈplā-smənt, di-ˈsplā-\

Function: noun

Date: 1611

1 : the act or process of displacing : the state of being displaced

2 a : the volume or weight of a fluid (as water) displaced by a floating body (as a ship) of equal weight b : the difference between the initial position of something (as a body or geometric figure) and any later position c : the volume displaced by a piston (as in a pump or an engine) in a single stroke; also : the total volume so displaced by all the pistons in an internal combustion engine (as in an automobile)

3 a : the redirection of an emotion or impulse from its original object (as an idea or person) to another b : the substitution of another form of behavior for what is usual or expected especially when the usual response is nonadaptive —called also displacement activity, displacement behavior

no matter what it's applied to displacement is still..........displacement

petrol, diesel, rotar, impellor ect it has only one meaning when applied to a pump/engine

Different bore and stroke formulas can have equal displacement but vastly different performance, I know amazing hey.

seriously fella.

The displacement figure and measurement itself might be the same across two different piston engines, say diesel and petrol, but this figure has different meaning for what it's going to be used for. 1 litre of displacement in a motorbike engine will not be used in the same way that 1 litre of displacement in a car will. The former will be a wide bore and short stroke, whilst the latter will most likely be square for more torque. Bore and stroke isn't just a measure of displacement, it outlines the very purpose/function of the displacement. Short stroke, wide bore = low torque, high power, high revolutions per minute. This is why you can look at a diesel and petrol engine of the same capacity and make a reasonably safe assumpton that the former has more torque whilst the latter has more power...just by nature and typical use of the engine. This makes the displacement variable somewhat useless when you compare engines of different type.

[Sydneykid]

Yes it is, but you can't use piston formulas on it to decipher its capacity.

A combustion engine is an air pump, we measure capacity by how much it pumps. The same as we measure oil pumps, water pumps, fuel pumps, diesel pumps etc, basially any type of pump you can name is rated by its pumping capacity. Except one, a rotary engine is not measured by how much it pumps by Mazda. If you count the eccentric shaft revolutions as being relevant than a 13B pumps 2.6 litres. If, like me, you think rotor revolutions (orbits if you prefer) is more correct then a 13B is 3.9 litres. There is no way of measurng pumping capacity that comes up with 1.3 ltres for a 13B, none, zero, zilch, diddly squat, effall.

What the vast majority of people agree is that Mazdas 1.3 litres is a lie, the discussion is about whether they lied and it's really 2.6 litres or 3.9 litres.

Cheers

Gary

[GT-R32]

A combustion engine is an air pump, we measure capacity by how much it pumps. The same as we meausre oil pumps, water pumps, fuel pumps, diesel pumps etc, basially any type of pump you can name is rated by its pumping capacity. Except one, a rotary engine is not measured by how much it pumps by Mazda. If you count the eccentric shaft revolutions as being relevant than a 13B pumps 2.6 litres. If, like me, you think rotor revolutions (orbits if you prefer) is more correct then a 13B is 3.9 litres. There is no way of measurng pumping capacity that comes up with 1.3 ltres for a 13B, none, zero, zilch, diddly squat, effall.

What the vast majority of people agree is that Mazdas 1.3 litres is a lie, the discussion is about whether they lied and it's really 2.6 litres or 3.9 litres.

Cheers

Gary

Decent post Gary, until you got to the 'Mazda lie' stuff again. Remember the engine is on licence from NSU and Dr Wankel.

1308cc comes from combustion chamber volume x2. That's pretty clear I thought.

[Jez13]

That is the single most retarded thing I've read in this thread. Original postion does not equal original state. If you took that definition, every time a piston hits TDC its returned to "its original state" because it happened to be in the same location it was when you first started observing it. That would quarter the currently accepted measurement of displacement for piston engines.

For the record please try and keep your 'retarded' comments to yourself, this is a friendly discusion on peoples view points and we keep things mature here, i respect and listen to what you have to say and i expect the same from you.

The main perspective problem here is you are breaking one single rotor into 3 seperate parts. Answer this: if a 13b rotory's full cylce was determined after one combustion from each rotor - how much exhuast would have been expelled through the exhuast port?

Even if I ignore that painfully obvious state vs position disconnect, if its "not the original rotor face" present in the position you're comparing from then how can you even say its "the same position"?

The definition of "original state" would be matching not only the physical positioning of the components, but also the logical positioning within the cycle.

It is the same position, if i took a photo of a rotor after one combustion and then took another photo after the second combustion they would be identical photos because they are in the same position.

If we talk NA (to rule out the variability of compressed intake air, and we all agree even in FI applications we define displacement by measuring the air flowed by the engine sans compressor):

In a "2.0L" 4 stroke piston engine, if we take our initial "original state" observation of a cylinder with its spark plug just about to ignite its air/fuel mixture then for that combustion surface to reach its "original state" again then 2.0L of air would have been injested and expelled by the whole engine.

In a "2.0L" two stroke, you'd have the exact same amount of air flowing through the system when everything returns to its original state. The difference is that it would have only required half as many crankshaft rotations compared to the 4 stroke above.

In a "1.3L" 13B rotary engine, if a specific rotor face is initially observed right before ignition then for that specific rotor face to return to that original state (compressed air/fuel mix inside and ready to be ignited) then 3.9L worth of air would have passed through the entire powerplant.

Correct, if you beleive that a rotories cycle is after three combustions. But incorrect if you beleive that a rotories cycle is after one combustion. Because 1 rotor is doing three things at once an one piston is only doing one thing at one time you cannot compare. If one piston combusts once in each cycle then why can't 1 rotor combust once in each of its cycles?

This is something practically everyone else has already concurred with, and moved on from.

I'd agree that it's not fair to compare the numbers between the different engine types due to their nature of combustion cycle. Just like I'd agree that its not fair to compare RPM of the combustion surfaces between the two types of engine, due to fundamental differences.

However, when you're talking about "measurement" rather than "values for comparison" then it's pretty clear-cut, and should be consistent across the board.

Measuring displacement is not an opinion open to perspective. It's a science, and its conclusions are objective.

Displacement is definative. I am not arguing that the rotory holds 3.9l of air though its rotation, I am arguing that it only uses 1.3l per combustion cycle.

You mean in the same way that all high performance Japanese-engineered cars up until a few years ago only ever made "206kW"?

Like how the Japanese engineers who went from a 206kW R33 GT-R to a car that made more torque across the entire rev-range in the R34 GT-R, yet somehow defied the basic scientific principle that power = torque x rpm, but still had its output advertised at 206kW as well?

The fact that marketing parasites advertise something, that the engineers will inevitably be forced to agree with in order to toe the company line, is no proof of accuracy.

If they truly believe it then they're not lying or deceiving. They're just ignorant.

If you were a car company and you were told that you can't have any more than 206kw and you had to be competitive with all the other high performance vehicles...what would you do? Its a different kettle of fish. If they wanted to lie about its displacement then why wouldn't they lie about its petrol consumption?

You know I was thinking about this some more and came up with a whole new perspective that can have truth to it also. If I were to see a rotories cycle being dertermined after 3 combustions of a single rotor then really it would be a 6 stroke? Remeber it turns the crank 3 times after 3 combustions of one rotor. So basically this whole arguement has come down to determining a rotories cycle. And that is where it may come down to matter of opinion and to what people find is more logical given the evidence.

[Jez13]

Decent post Gary, until you got to the 'Mazda lie' stuff again. Remember the engine is on licence from NSU and Dr Wankel.

1308cc comes from combustion chamber volume x2. That's pretty clear I thought.

And that short statement there is why I find it hard to budge my opinion. The rotor only combusts in the bottom left side of the rotor housing so that makes it the only combustion chamber in the engine x that by two and you get your 1308cc.

[GT-R32]

And that short statement there is why I find it hard to budge my opinion. The rotor only combusts in the bottom left side of the rotor housing so that makes it the only combustion chamber in the engine x that by two and you get your 1308cc.

Just as if piston engines were only rated by their combustion chamber volume, which of course they are. So you can see NSU/Mazda/Dr Wankel's convenient logic with that one.

[Birds]

There is no way of measurng pumping capacity that comes up with 1.3 ltres for a 13B, none, zero, zilch, diddly squat, effall.

Cheers

Gary

Sure there is. Turn the e-shaft 360 degrees for one whole engine revolution and then marvel at the flow of 1.3 litres worth of air.

And to the person (think it was scathing) who said displacement is definitively objective...if that were the case we wouldn't have a thread anywhere near this long.

[Smity42]

And that short statement there is why I find it hard to budge my opinion. The rotor only combusts in the bottom left side of the rotor housing so that makes it the only combustion chamber in the engine x that by two and you get your 1308cc.

Actually I like that, and it explains why we only count 1 side of the piston when looking at a 2 stroke

Edited October 2, 2009 by Smity42

[Jez13]

A combustion engine is an air pump, we measure capacity by how much it pumps. The same as we measure oil pumps, water pumps, fuel pumps, diesel pumps etc, basially any type of pump you can name is rated by its pumping capacity. Except one, a rotary engine is not measured by how much it pumps by Mazda. If you count the eccentric shaft revolutions as being relevant than a 13B pumps 2.6 litres. If, like me, you think rotor revolutions (orbits if you prefer) is more correct then a 13B is 3.9 litres. There is no way of measurng pumping capacity that comes up with 1.3 ltres for a 13B, none, zero, zilch, diddly squat, effall.

What the vast majority of people agree is that Mazdas 1.3 litres is a lie, the discussion is about whether they lied and it's really 2.6 litres or 3.9 litres.

Cheers

Gary

But for every 2.6ltrs makes two shaft revolutions, not one.

[Sydneykid]

You have formulas inside of motorsport to make it fair because motorsport is invariably prone to modification...thereby forcing a comparison of displacement because engine modifications have a somewhat linear effect on displacement. For the unmodified showroom car being sold to the public...displacement doesn't mean shit. All that matters are the vehicles inputs and outputs. But if someone wants to make their own formula outside of motorsport they can, or they can adopt the existing formulas from CAMS or FIA...but saying that Mazda lies just because the manufacturer didn't classify the engine the way this person wanted it to be classified...again, deal with it. We've managed to do so just fine for the past few decades.

No we haven't, that's why Mazdas doesn't run at LeMans anymore, a fight over true capacity.

That's why there were no rotaries in F1 in the 70's, a fight over true capacity.

Thats's why motorsport authorities world wide apply multipliers to Mazda's stated capacity.

So whether or not "this person" wanted it classified correctly or not isn't important, the fact is plenty of organisations, important ones, do.

Except the engine? I'm only naming one engine variable that I feel is somewhat irrelevant, i.e. displacement...and I only said it is irrelevant when comparing different engine types. But for the sake of you generalising my statement to mean every single engine, even of the same type...I say you have too much faith in the general public assuming they will place so much emphasis on displacement (which is just a means to an end, i.e. power and torque). Which do you think matters more to the general public...whether their engine is a 1.3 litre or a 5 litre...or whether it produces 60kw or 206kw? Are the XR6 turbo owners worried that their 4 litre engine might not be a match for the XR8 given it's missing 1.4 litres?

Their not worried because they know it's 4.0 litre engine with a turbo. The 4.0 litre capacity is on the front guard of Fords. Why do Ford bother making a badge and puting on the front guard? Because capacity is relevant to their buyers. They are not being lied to. Ford doesn't say it's a 2 litre engine, because it only fires every second revolution of the crankshaft. It's 4.0 litre and Ford promote it as such. If capacity was as irrelevant as you would have us believe then Ford would save some money delete all engine capacity badges and not promote them,

The displacement figure and measurement itself might be the same across two different piston engines, say diesel and petrol, but this figure has different meaning for what it's going to be used for. 1 litre of displacement in a motorbike engine will not be used in the same way that 1 litre of displacement in a car will. The former will be a wide bore and short stroke, whilst the latter will most likely be square for more torque. Bore and stroke isn't just a measure of displacement, it outlines the very purpose/function of the displacement. Short stroke, wide bore = low torque, high power, high revolutions per minute. This is why you can look at a diesel and petrol engine of the same capacity and make a reasonably safe assumpton that the former has more torque whilst the latter has more power...just by nature and typical use of the engine. This makes the displacement variable somewhat useless when you compare engines of different type.

That's the important point, they all state the true capacity and then qualify it with whether it's a diesel or turbocharged or supercharged or intercooleed or maybe all of the above. In all cases, but one, the starting point is the true capacity of the engine. It's where the basis starts, then the qualifiers are added. Except in one case, Mazda modify the capacity first, then add the qualifiers.

My point is Mazda should say "3.9 litre rotary engine", because that's what it is. Even if you subscibe to the 1080 versus 760 degrees of shaft rotation theory then Mazda should say "2.6 litre rotary engine". But they don't and that's why I object and why I call it a lie.

If, as you claim, capacity is "somewhat irrelevant" then why shouldn't/didn't Mazda state the true capacity? The answer is obvious, Mazda obviously consider it relevant and that makes your opinion irrelevant.

Cheers

Gary

[Jez13]

Some folk think you can..

http://mikesdriveway.com/misc/rotor.doc

yup, and that folk thinks that a combustion cycle of a rotor is 6 total combustions rather than 2. I like the formula, I just don't like the values he is using.

[madbung]

The displacement figure and measurement itself might be the same across two different piston engines, say diesel and petrol, but this figure has different meaning for what it's going to be used for. 1 litre of displacement in a motorbike engine will not be used in the same way that 1 litre of displacement in a car will. The former will be a wide bore and short stroke, whilst the latter will most likely be square for more torque. Bore and stroke isn't just a measure of displacement, it outlines the very purpose/function of the displacement. Short stroke, wide bore = low torque, high power, high revolutions per minute. This is why you can look at a diesel and petrol engine of the same capacity and make a reasonably safe assumpton that the former has more torque whilst the latter has more power...just by nature and typical use of the engine. This makes the displacement variable somewhat useless when you compare engines of different type.

.... and you label Gary pedantic.

Displacement is displacement. It can be referred to it as swept volume if you prefer but it's all the same calculation regardless of bore/stroke ratios.

Yes to re-iterate myself "Different bore and stroke formulas can have equal displacement but vastly different performance, I know amazing hey." We are discussing how to calculate an engines cubic,cc,litre capacity/displacement here are we not? or have we switched over to power/torque output formula's along with your turbocharged tangent?

Yes evaluating an engine comes down to displacement,output (power) and efficiency but that is not the question at hand is it?

A duck will always be a duck just as a goose will always be a goose.. Please stop trying to paint this duck up to look like a goose.

I realise you love a good debate, but why not let common sense and the recognised "standard" prevail this time.