Sydneykid

What capacity does an Automotive Engineer attribute to a 2 litre 2 stroke piston engine? Last time I checked my reference books they said 2 litres. What capacity does an Automotive Engineer attribute to a 2 litre 4 stroke piston engine? Last time I checked my reference books they said 2 litres. So my Automotive Engineering references all ignore the number of revolutions of the cranskshaft when determining the relative capacities of 2 and 4 stroke piston engines. In simple terms they are both 2 litre engines. I see no reason to not follow exactly the same logic when measuring the capacity of a rotary. So I ignore the number of revolutions of the eccentric shaft when determining the capacity of a rotary. To do otherwise would be illogical, inconsistent and just plain wrong. Cheers Gary

Yep that would be a full combustion cycle, 4 strokes if you like. Hey, maybe that's why we call it a 4 stroke. When measuring the capacity of the engine we don't care that that's 2 revolutions of the crankshaft Then a full combustion cycle for 2 stroke would be up, down. Well whadya know, maybe that's why we call it a 2 stroke. When measuring the capacity of the engine we don't care that that's 1 revolution of the crankshaft You know where I'm going now ..............wait for it............ One complete combustion cycle for a rotary would be, one complete revolution/rotation/orbit of the rotors. When measuring the capacity of the engine we don't care that that's 3 revolutions of the eccentric shaft. Well, any logical person wouldn't care, as they say you can lead a horse to water but you can't make it drink. Cheers Gary

Nope I see it as 2-stroke piston engine = amount of air for 1 complete cycle of the pumping media (the piston/s) 4-stroke piston engine = amount of air for 1 complete cycle of the pumping media (the piston/s) Wankel engine = amount of air for 1 complete cycle of the pumping media (the rotor/s) Ooooo look they are all the same, that's why I think my view is more correct. Nope, just Mazdas using marketing spin to sell a product under false pretences. Of course no other company has ever done that sort of thing. Cheers Gary

Actually no, he's miles behind me, I have known exaclty how a rotary works since I rebuilt my first 12A in 1972. Then, as now, I know exactly what is going on and I fail to see any relevance in time when it comes to capacity. It's very much like saying a 4,000 rpm engine has half the capacity of an 8,000 rpm engine because it takes twice as long. Time is completely irrelevant in capacity measurement for that very reason. Cheers Gary

OK, so on that basis a 4 stroke 2 litre is really a 1 litre as the cranskshaft has returned to its original position. Tell me how the same rotor face can return to it's original state without the other 2 sides also returning to their original states? Cheers Gary

I thought you had it there for a minute, but then, dissapointment.... How does one side of the rotor do a complete combustion cycle without the other 2 sides also doing complete combustion cycles? Cheers Gary

If we measure the cycles by full turns of the cranskshaft then a 2 litre 4 stroke is really a 1 litre. Cheers Gary

No evidence required, you have already supplied enough in your post for me to prove that I'm correct. At this point I suggest you go back and actually read what you posted. Since you reused Rice's diagrams, I'm surprised that you didn't realise why he stopped the debate, his diagram confirmed my opinion. It's actually quite simple, you measure capacity by eccentric shaft revolutions. I measure capacity by revolutions (oribits if you prefer) of the pumping medium, ie; the rotors. In one revolution (orbit if you prefer) of the 2 rotors a 13B pumps 3.9 litres. So I define a cycle of a rotary engine as one complete revolution (orbit if you prefer) of the rotor. You on the other hand define a cycle of a rotary engine as one complete revolution of the eccentric shaft. So who is right? Well I base my argument on the fact that a 4 stroke 2 litre engine is always called a 2 litre even though it only pumps 1 litre for one complete cycle (revolution if you prefer) of its crankshaft. In simple terms we don't dived a 4 strokes piston engine's capacity by 2, so why should we dived a rotary engine's capacity by 3? Cheers Gary

You can and in fact Mazda does. But is it correct to state that "a rotary engine does 9,000 rpm"? You will say, "well of course it is correct because the eccentric shaft does 9,000 rpm". Whereas I will say "no it isn't correct because the rotors are only doing 3,000 rpm". When we say "an engine does 9,000 rpm" the natural assumption is that all of the engine is doing 9,000 rpm". Now in a 2 stroke piston engine that is 100% correct, all of the engine is in fact doing 9,000 rpm. But in a rotary engine only the eccentric shaft is doing 9,000 rpm, nothing else. The rotors are only doing 3,000 rpm. Keeping the above in mind, that means 100% of a 2 stroke piston engine is doing 9,000 rpm, but only 33% of a rotary engine is doing 9,000 rpm. In other words the vast majority of a rotary engine (ie; 67%) is only doing 3,000 rpm. So when someone says "a rotary engine does 9,000 rpm" I say rubbish because the whole engine is not doing 9,000 rpm. In fact I say double rubbish, because most of the engijne is only doing 3,000 rpm. But wait, let me add even more weight to my argument. We are talking about an internal combustion engine here, so surely it is logical to count the rpm of the part that actualy carries out the combustion process. In a rotary engine that's the rotors and, like it or not, the fact is they are only doing 3,000 rpm. This is usually the point at which the rotary huggers, start throwing in cycles not revolutions, orbits instead of rotations, no strokes in a rotary engine, elliptical motion, not up and down etc etc. But to me that's just being pedantic and deliberately narrowing the meaning of common use words, in some vane attempt to escape the truth. But the truth is right here, it's not out there. Cheers Gary

I’m sorry if I come across as flaming you, it’s not intentional I can assure you Perhaps you need to go back to the start of this thread and follow the flavour. From the start I put forward an opinion and supported it with facts. A few guys tried to convince me that I was wrong, but they failed. Some guys completely misunderstood what I was saying and took it as a biased rotary attack. So they popped over to the rotary forum and got one of the big guns over to have a go. He resorted to the personal insults when he couldn’t support his stance as well as I could mine and then eventually he agreed with me and left. A few of the more regular contributors to this forum have kept the dialogue open, but one by one and point by point they can see where I am coming from. They don‘t necessarily agree with me, but what started out as dismissive, “this guys doesn’t know what he is talking about” has turned into “maybe he does know something about how a rotary works and he might just be right”. I’m not here to win anything and I’m sure as hell not right all the time. So I will apologise in advance if what I post seems dismissive or insulting. But until you read the whole thread and gain some understanding of what I’m on about you really might misunderstand the strength of my convictions and my willingness and ability to support them. Cheers Gary

Almost got it, I don't hate rotary engines, after all I am about to spend 4 days trying to win a national championship with one. But you're right in that I can't stand Mazda's lies and the efect that those lies have had. Cheers Gary

Hang on, so the outside of the rotor does 3,000 rpm but the inside does 9,000 rpm, That's a good trick, but I some how doubt it. The fact is the whole rotor is doing 3,000 rpm, and the rotor is the combustion medium, it's what makes the power, somewhat like a piston in a piston engine in that regard. So comparing it to a water pump is pretty stupid, they don't produce any power. Nice try on muddying the water with the camshaft rpm, but that's a 4 stroke. How about we compare it with a 2 stroke piston engine with no valves (like a rotary) and no camshafts (also like a rotary). Bingo, everything is doing 9,000 rpm (or cpm if you prefer) but in a rotary, oops the main parts, the bits that make the power, the rotors, are only doing 3,000 rpm (or opm if you prefer). Why do I feel like I have answered this all before? Maybe because I have. The simple truth is what the eccentric shaft lobes do is to convert the 2 styles of kinetic energy of a rotor, the rotate and the orbit, into one style of kynetic energy, the round and round rotation of the eccentric shaft itself. There is no magic here, it's much like the the throw of a crankshaft converts the up and the down of a piston into the round and round rotation of the crankshaft itself. Cheers Gary

I seem to recall Stephan Papadakis from AEM Racing doing a 7+ for a FWD at ~180 mph and a RWD 6+ at ~200 mph. Cheers Gary

Yes I am, but I believe I have good reason. The rotary huggers want to divide the true rotary engine capacity by 3 because of a step up ratio. So, in retaliation, I double the capacity because it's a 2 stroke. In truth I don't dived or multiply an engine's capacity by anything, what it pumps is what capacity it is. If you want a truthfull answer then it's obvious, there is no category advantage for 3.9 litre 6 cylinder piston engines like there is for 13B rotaries, so no one bothers building them. Ditto 5.85 litre piston engines like there is for 20B rotaries, so no one bothers. Cheers Gary

Oh come on, a 13B rotary combusts/fires 6 times in one complete cycle of it's rotors, irrefutable fact. Whereas a piston 4 stroke 6 cylinder would only combust/fire 3 times in one complete cycle of it's pistons. So it produces double the power of a 4 stroke because it has double the number of combustion process in one cysle, ineficiencies notwithstanding. Cheers Gary

Is that the sounds, I was going to leave it until I could listen to them on a decent sound system. Which I will do when I can, but I think you may have missed the most important comparison point, is the 6 cylinder 3.9 litre 2 stroke piston engine only doing 3,000 rpm? Because if it's doing more rpm then there is no wonder it doesn't sound like a 3.9 litre rotary only doing 3,000 rpm. You know that's not what I said, but if it makes you feel good, then go for it. I understand, I have my reasons for the actual capacity and Phil had his. So yes, we used totally different methodology of arriving at pretty much the same capacity. I'm not sure how that supports your argument when 2 quite different methods arrive at pretty much the same conclusion, that Mazdas claimed capacity is out by a long, long, long way. Well I've seen a few guys have a go at sticking rotaries in FWD cars, not much of success, for the obvious reasons that they are too heavy and hard to fit. But car manufacturers with actual main stream models? I actually can't think of one made in the last 5 years. Or even one made this century, let alone one in the last 20 years, or 30 years. From memory the NSU R80 started in 1968 and lasted (sort of) until 1977. So I would have trouble naming one designed even in the last 40 years. So what Mazda FWD car needs an oil cooler? The MX5 is a RWD isn't it. I certainly do remit vital information, but you omit it when it doesn't align with your argument. Cheers Gary

I will, if you will give me your opinion on why a 13B at 6.8 litres (that's 3.9 litres x 2 'cause it's a 2 stroke) can't get into the 5's like any decent supercharged 7 litre. Or if you will give me your opinion why a 20B at 11.7 litres (that's 5.85 litres x 2 'cause it's a 2 stroke) can't get into the 4's like any decent Top Fuel engine which is after all only 8.2 litres. The answer is it's irrelevant, because the engine alone doesn't do 6 seconds or 200 mph, it requires the whole car. And in case you missed it, this thread isn't about chassis, or tyres, or aerodynamics etc, it’s just about engines. Oh and don’t confuse me with an RB fan boy, they frustrate the hell out of me and I know full well that there are much better engines around, a whole lot of much better engines in fact. Cheers Gary

Ah, no more to continued after this one.......... It sure as hell is low when compared to the average n/a piston engine these days, for example an F20C is 11.7 to 1, a K20A is 11.5 to 1. Realistically 9 to 1 is even low for a decent turbocharged engine these days Of course we shouldn't ignore their 3.9 litre capacity, 2 stroke cycle and low compression ratio. Someone asked why there were no rotaries in FWD cars, I simply offered the facts of the barrel shape, heavy weight of cast iron components, low power output for a 3.9 litre engine, non cross flow lay out (inlet and exhaust on the same side) and inefficient fuel consumption as answers to that question. Let's face it the rotary huggers like to brag about how small and light their engine is, when the fact is they aren't really that small or that light whne you include their 3.9 litre engine's requirement for radiator, oil cooler, exhaust and gearbox sizing. It would be truly nieve to look at just part of the package when all of it has to fitted into an an engine bay. Plenty have tried, have you read Phil Irving's engineering paper on rotary engines? But Mazda's marketing muscle has suppressed it, rather viscously in some cases. But I like a good joust, especially when I know my point of view is correct and I have plenty of evidence to support the view. Thanks for the offer but truly there is nothing you have posted that I haven't heard before, and been able to counter argue, as I have done above. Cheers Gary

Nope, it’s due to the Mazda lies about capacity. The turbo sizing is simply one indicator of the true extent of those lies. Let’s get real here, if the rotary design is truly “better”,then why hasn’t every other car manufacturer changed over? In fact not even one other car manufacturer has changed over, despite many having tried. “Far easier to fit more spark plugs in the combustion chamber”? Surely you mean “due to it’s poor flame propagation it’s essential to fit more spark plugs in the combustion chamber”. Every one recognises that the number 1 problem with a rotary engine is that long, skinny combustion chamber shape, it’s a major contributor to the poor power output for capacity and high fuel consumption. Which is lousy for a 3.9 litre 2 stroke turbo charged engine. So now we are multiplying the torque output by the step up ratio. And around we go. They have very low torque output for a 3. 9 litre 2 stroke engine, even allowing for 3,000 rpm of the rotors. More importantly, a completely unmodified 13B uses very similar amounts of fuel to a unmodified 3.9 litre piston engine. It most certainly doesn’t use similar amounts of fuel to an unmodified 1.3 litre piston engine. Yes, it's continued again............... Cheers Gary

I have underlined the important fact, which is exactly the same as what I posted. The rest is fluff designed to confuse the reader. So now it is a step up ratio. “Angular speed”, of course, that’s far more meaningful than rpm or cpm. Do you really want to get into apex seal speed versus piston ring speed discussion? Because it’s not very supportive of your case, in fact it contradicts it completely. But I’m up for it if you are. It depends on how narrow your definition is of a “cycle”. Plus how many chambers/cylinders you include in that cycle. The fact is in one cycle of the rotors a 13B pumps 3.9 litres if you look at all 3 sides of the 2 rotors. Obviously that doesn’t suite your argument so you ignore it. But the truth is you can’t ignore the obvious, if one chamber on the rotor has completed its cycle then so have the other 2. What you are doing is the same as taking a 6 cylinder 2 stroke piston engine and only counting the capacity of 2 of the cylinders and ignoring the other 4. We don’t do it for piston engine why should we do it for rotaries? That’s because they are a 3.9 litre 2 stroke. A convenient time to say, to be continued......... Cheers Gary

Oh my, another one, having beaten the others with truth and logic along comes another with selective understanding. This post is a prime example from someone who has a result that they want and then goes looking for evidence to support that result, whilst at the same time ignoring the vast majority of evidence that repudiates it. Well let's see how incorrect I am. That's because some people needed it explained in many different ways so they could gain an understanding of the truth. You ignore that a rotary inlets while it exhaust just like a 2 stroke. You only look at one side of the rotor in isolation because it would destroy your argument if you actually looked at what is happening in the engine during its full cycle ie; one complete cycle/orbit/rotation/revolution of the 2 rotors in the case of a 13B. There is little doubt that it's a 2 stroke type of cycle, as posted, and it's a lot closer to a 2 stroke than a 4 stroke. Inletting while it's exhausting, fires every time the combustion chamber passes the spark plug etc etc. Nope, check your facts, in the time that Mazda has been selling rotaries the sales of 2 stroke lawn mowers exceed 4 stroke lawn mowers by a factor of 10. More importantly, Mazdas marketing based lies started in the 70's when there were almost zero 4 stroke lawn mowers, every home had a Victa. That's complex mechanics for the average reader to understand, hence why its usually simplified down to a step up ratio of 3. It matters not, the fact remains the rotors are doing 3,000 rpm (revolutions per minute) or 3,000 opm (orbits per minute) or 3,000 cpm (cycles per minute). Choose whatever terminolgy you like, they all mean your view is incorrect. But they are doing 9,000 cpm, (cycles per minute) or is that 9,000 spm (strokes per minute) when the crankshaft is doing 9,000 rpm. The readers of this thread will at this point relate to the aforementioned rotary huggers' usual tricks of muddying up the water with pedantic narrow minded definitions. We all know it's a desperate attempt to prevent comparison, but it fails the common use English test. Keep that in mind as we move on. To be continued...... Cheers Gary

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

Hi Steve, how ya doin'? To fill in some detail for the other readers, WA hasn't had IP racing for all that long, Street Cars was their semi equivalent category, with much freer regulations. The most recent meeting was the first time they ran IP separately, a great effort by all concerned. As a result they don't have the history of IP (nee Club Cars) and hence not a field of older cars already racing. For example in NSW we have over 100 logged pre 1986 IP cars, similarly in Vic. Plus Barbagallo as a circuit doesn't have the light weight car bias that we find at say Oran Park, Winton or Mallala. The Nationals in 2010 shoud be a great event, we just need a Star Gate or equivalent to transport us across the galaxy to WA. Or for those of my generation, beam me up Scotty. Cheers Gary

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

Continued from above........ What setting do you have your tacho on? 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. 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. They actualy don't, there are far smaller and lighter engines that produce more horsepower and torque. 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