Jump to content
SAU Community

Recommended Posts

Well just read all 16 pages, what a read. Definetely one of the most interesting threads lately. Gary dead set you should be on the Australian Debating Team or something lol. Keep it coming mate, very interesting stuff indeed. I for one never knew about this whole rotor debate and find it very interesting indeed.

I understand where both parties are coming from however Gary does make some sense of this all. After a bit of searching on the net, most of what he has said is backed up on similar topics about it all. The way i look at it, pretend piston engines didn't exist, therefore you can't compare anything to a piston engine. Compare it for what it is, an engine is a mechanical air pump where fuel is added and the spark is there to ignite it all to create a reaction and transform that engery into movement. When you think of it like that, his calculations and theory are spot on are they not?

It's ENGINE RPM!!! Not rotor RPM, you measure horsepower, torque and RPM at the flywheel, not at the piston or rotor!!!

So what? The important rpm (or cpm if you prefer) is the combustion medium, that's the rotors and they only do 3,000 rpm. After all they are what produce the horsepower and the torque. The eccentric shaft is just the same as a gearbox output shaft, it changes the ratio between the combustion medium and the wheels.

Dictionary check

"An internal combustion engine cycle completed in two strokes of the piston."

"denoting an internal combustion engine whose power cycle is completed in one up-and-down movement of the piston."

"designating or having to do with an internal-combustion engine in which a complete fuel cycle in a cylinder requires only two piston strokes"

"A two-stroke engine provides power on every other stroke of the piston. It is the most common and affordable type of engine."

I can keep going, but I don't have the time...

You don't need to, just read what you posted, note the term cycle. Now go back an read what I posted.

And you fail to see the difference in potential energy... Try breaking it down into a single rotor engine vs a single piston 4-stroke engine to make it nice and simple for you, when the single piston engine finishes its combustion cycle it has no more potential energy stored, when a single rotor completes a combustion cycle it has two more combustion cycles in progress, hence still having potential energy!!!

But a single rotor engine has 3 combustion faces, so the best you can do is compare it to a 3 combustion face piston engine. a 2 stroke one at that. Even then it's not a good comparison, but go ahead if you feel you must.

I totally agree with you they should not be classed as a 1.3L 4-stoke engine because they are not... But they are not a 3.9L 2-stroke with 3000rpm on tap!!!

But they (a 13B that is) are a 3.9L 2-stroke rotary engine with 3,000rpm on tap;

1. they pump 3.9 litres in one complete cycle of the rotors, even Rice agrees with that fact.

2. they inlet at the same time as they exhaust on opposite sides of the rotor, just like any other 2 stroke/cycle engine. Are you saying they don't?

3. the rotors only do 3,000 rpm. We all know they do, so how could you dissagre with that fact?

What I didn't say and you seem to think that I did, was that "they are the same as a 3.9L 2-stroke piston engine with 3,000rpm on tap". That's not what I said, anywhere, anytime, in any post.

Cheers

Gary

Why do you all keep saying the rotors "do 3000rpm" ? Wouldn't it be correct to say the rotors do 1/3 the RPM of the eccentric shaft.

I know of rotors that regularly see 11000rpm or more on the track (when measured correctly from the eccentric shaft :(

Why do you all keep saying the rotors "do 3000rpm" ? Wouldn't it be correct to say the rotors do 1/3 the RPM of the eccentric shaft.

I know of rotors that regularly see 11000rpm or more on the track (when measured correctly from the eccentric shaft :(

He is using it as an example, we know "your mates RX3" does 11000rpm measured incorrectly at the eccentric shaft.

Gary,

We are going nowhere so I'll just leave it at that!

But I'll ask you a question along a different line...

Why when you are refering to a combustion cycle in terms of RPM and combustion strokes of just one face of the rotor but suddenly when your talking about capacity you switch to talking about all 3 sides of the rotor...

A full combustion cycle would therefore be when all 3 sides of the rotor had completed their stokes, hense a even lower "RPM" (1000rpm) to fully claim that it's a 3.9L

Gary, why should rpm be measured at the rotor rather than the ececntric shaft? rpm in a piston motor its taken from the crank isnt it?

not trying to start arguments here, i just dont get where your coming from...

Edited by VB-
Gary, why should rpm be measured at the rotor rather than the ececntric shaft? rpm in a piston motor its taken from the crank isnt it?

From a technical perspective it was mentioned earlier in the thread that your tacho reads ignition pulses, so you're arguably "taking the RPM" value from the combustion chamber.

After reading through the thread, I think that Gary's taking the stance that you should be measuring the amount of air passed through one cycle of every combustion chamber. An engine is always described as an air pump when you talk about base principles, and so the action that directly involves air moving through the engine should be the guiding factor of how you should measure its behaviour.

In a piston engine that's a 1:1 ratio between the moving part of the combustion chamber and the crank but as far as Gary's concerned its a coincidence that they're the same. An engineer could have decided to stick a gear ratio in there "rotary style", but didn't. However, the fact that it is 1:1 has mislead people into quoting the speed of the wrong thing as a measure of engine behaviour, which happens to be correct by chance rather than comprehension.

My interpretation of Gary's perspective on the engine speed (and I'm not necessarily supporting it, just explaining from what I see as his perspective) is similar to the old "boost equals power" misconception. That is an erroneous conclusion based on incomplete or mislead understanding of basic principles.

Wind up the boost in most instances people have experience with and you see power gains, so certain people think the two are always directly related. However, in reality its air flow, not air pressure, that determines the power you can gain from tuning the induction system.

Feel free to correct me if I'm wrong Gary. :) I'm enjoying the thread, as hard as the slog has been at times, and feel like I'm learning quite a bit.

Edited by scathing
Wind up the boost in most instances people have experience with and you see power gains, so certain people think the two are always directly related. However, in reality its air flow, not air pressure, that determines the power you can gain from tuning the induction system.

actually it's air volume

But they (a 13B that is) are a 3.9L 2-stroke rotary engine with 3,000rpm on tap;

1. they pump 3.9 litres in one complete cycle of the rotors, even Rice agrees with that fact.

2. they inlet at the same time as they exhaust on opposite sides of the rotor, just like any other 2 stroke/cycle engine. Are you saying they don't?

3. the rotors only do 3,000 rpm. We all know they do, so how could you dissagre with that fact?

In my view if it counts for anything:

Engine RPM is the output revolutions of the of a complete engine. I don't believe you can base it on ignition (a rotor will actually use it's ignition twice during a single side of the rotor combustion cycle)

Capacity is the ability of a engine to hold a maximum volume of air at any given time. This definition works well for both a rotor and a piston engine and makes a 13B a 2.6L capacity!!!

It's not a 4-stoke, it's not a 2-stroke it's a rotarty...

Edited by Cerbera

Rotaries are neither a 2 stroke or a 4 stroke, I'm sorry, but they do not have any pistons, so they are neither. There is no way around that. They are however MOST SIMILAR to a 2 stroke piston engine in how they operate.

A 4 stroke engine completes it's combustion cycle in 4 strokes of the piston - the classic suck squeeze bang blow.

A 2 stroke engine completes it's combustion cycle in 2 strokes of the piston - more or less suck-squeeze bang-blow (grossly innacurate simplification :D)

I don't even want to try and classify a rotary, but they are in fact neither. They are similar to a 2 stroke in the way they operate, using ports not valves, and that a single rotor is performing multiple parts of the combustion process at once.

On the other hand, they do perform a classic 4 stroke cycle in the form of suck squeese bang blow, on each face of the rotor.

2 stroke / 4 stroke, irrelevant, they are neither.

RPM, thats a tricky one. I tend to agree that the output shaft is the most appropriate way to measure RPM, but if someone were to put a 3:1 gear inside a piston engine to triple the output shaft velocity, where would you then measure it?

When you look at RPM in regards to the forces acting on the parts of the motor, well then it is really the 3000rpm the rotors themselves are doing compared to the ~6000 or whatever the pistons are doing. But then, a piston needs to actually stop and change direction, while a rotor just keeps spinning the same way, resulting in far less force anyway. But this is one of the ingenious things in the rotory design.

Capacity again, a tricky one. I personally would call it a 3.9L, but with the caveat that it compares more or less to a 4 stroke piston engine of 2/3 that. But I can see the points of the other arguments.

Basically it is very hard to compare piston to rotary motors as they are so different.

I am not a rotary fan boy, I love all types of engines, 2 stroke, 4 stroke, rotary, radial, jet. If it burns fossil fuel and moves stuff around, I like it.

Edited by Smity42
Rotaries are neither a 2 stroke or a 4 stroke, I'm sorry, but they do not have any pistons, so they are neither. There is no way around that. They are however MOST SIMILAR to a 2 stroke piston engine in how they operate.

A 4 stroke engine completes it's combustion cycle in 4 strokes of the piston - the classic suck squeeze bang blow.

A 2 stroke engine completes it's combustion cycle in 2 strokes of the piston - more or less suck-squeeze bang-blow (grossly innacurate simplification :D)

I don't even want to try and classify a rotary, but they are in fact neither. They are similar to a 2 stroke in the way they operate, using ports not valves, and that a single rotor is performing multiple parts of the combustion process at once.

On the other hand, they do perform a classic 4 stroke cycle in the form of suck squeese bang blow, on each face of the rotor.

2 stroke / 4 stroke, irrelevant, they are neither.

RPM, thats a tricky one. I tend to agree that the output shaft is the most appropriate way to measure RPM, but if someone were to put a 3:1 gear inside a piston engine to triple the output shaft velocity, where would you then measure it?

When you look at RPM in regards to the forces acting on the parts of the motor, well then it is really the 3000rpm the rotors themselves are doing compared to the ~6000 or whatever the pistons are doing. But then, a piston needs to actually stop and change direction, while a rotor just keeps spinning the same way, resulting in far less force anyway. But this is one of the ingenious things in the rotory design.

Capacity again, a tricky one. I personally would call it a 3.9L, but with the caveat that it compares more or less to a 4 stroke piston engine of 2/3 that. But I can see the points of the other arguments.

Basically it is very hard to compare piston to rotary motors as they are so different.

I am not a rotary fan boy, I love all types of engines, 2 stroke, 4 stroke, rotary, radial, jet. If it burns fossil fuel and moves stuff around, I like it.

simon likes this!

except for the 3.9L, it has a capacity of 2.6L... yes it uses 3.9L in complete combustion of all the rotors but it only every has the capacity (volume) of 2.6L

Capacity is the ability of an engine to hold a maximum volume of air at any given time. This definition works well for both a rotor and a piston engine and makes a 13B a 2.6L capacity!!!

Well there's another person...

At least we've moved on from 1.3L, that's a good start. But it's still not correct.

Your reasoning here would make an RB26 less then 2.6 litres. You have taken a moving item and stopped it, taken a freeze frame of the moment that it would hold (assumedly) the most amount of air at one time. Thanks to the differentiating strokes of the pistons in the RB26 engine (and any other piston engine) this would mean that there is NO SINGLE POINT that there would be 2.6L of air inside the engine. The 2.6L calculation is taken from one full 'cycle' of all the pistions, as is the 3.9L in the rotary.

But I could be wrong.

the big problem i see with a lot of peoples argument (those saying it's only 2.6L) is this: they are classing it as a 2.6L becuase it has only fired 2 sides of the rotor for the same duration as a piston engine would for a full cycle (2 rotations in the case of a 4 stroke). however the big flaw in this is the comparison. the simple fact is that a 2 stroke and a 4 stroke engines have their capacity based of the same theory despite the fact that a 2 stroke firing every cylinder on every stroke and the 4 stroke only having fired on half the cylinders during the same stroke. so it is only fair to then extend the same principle to rotaries who will only have complated 2/3 of a cycle in that time.

if you want to class a 13b as 1.3L on the argument that there has only been 1 combustion per rotor per rotation of the crank/eccentric shaft then you also have to class a 4 stroke as only half it's given displacement and the only engine you can class as it's full given displacement is a 2 stoke. you either class engines by displacement of chambers combusting on 1 rotation of the crank/eccentric shaft or you class it as total displacement of all combustion chambers regaurdless of the amount of rotations of the crank/eccentric shaft makes for one full cycle of the engine. 1 rule for all, not just bending the rules to make 1 seem better.

even with people (the mazda fans) saying that if calculated the same way as a 4 stroke the displacement would be 2.6L, they themselves are admitting that mazda has basically lied by calculation the displacement in a way that benefits them.

i will agree with them though on the fact that a rotary is 'similar' to a 2 stroke, but not the same.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • I know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
×
×
  • Create New...