Aviator 902S

No problem--- that comment wasn't directed at you but at all those who argue that the 13B displaces 2616cc.

globi

If I had to compare engines with each other, I'd compare airflow. The more air an engine pumps the more power it produces and the 13B engine pumps about the same as a 4 cycle piston engine with 2.6l displacement.

Comparing a NA rotary engine with a NA 4 cycle piston engine regarding their displacement appears relatively simple. There's a reason why engineers placed the engine in the 2.5l to 3.0l category.
A gasturbine has no closed chambers and therefore no displacement and therefore compares to a 0.0l piston engine? Well I guess that would beat everything.

And btw: The largest 2 stroke engine has 25480l displacement.
http://www.bath.ac.uk/~ccsshb/12cyl/

rxspeed87

if anything I say it breaths like a 1.3L

the piston motors on the other hand only breath half
so if anything a 5.0 breaths like a 2.5L


:-p

t-von

iTrader: (8)

Yea only if your using one rotation. A 4 cyl 2.6L 4 stroke piston would need 2 rotations of the crank shaft to fire it's full displacment. A rotary would only need one however, when a rotary rotates it's e-shaft twice, it moves 2.6 liters of air just like the piston but without a waisted power stoke. Thats why people say they breath like a 2.6L. This is also why the small rotary can spool a large turbo fairly quickly.

rxspeed87

think the biggest par t as to why a rotary will spool quick is look at the xhuast. straight through. no valves or anything else to absorb that energy it's just a straight shot

Rx7MPGUY84

that diesel turbo 2 stroke is retardedly huge!!!!!!!!

MikeC

This is a good explanation but it's not quite correct. You assumed that "when all combustion chambers have had a combustion event" and "fired their spark plugs" is the same thing. A rotary has six chambers and if both sets of plugs have fired once then only 2 chambers have fired and none of the chambers have completed the fill otto cycle of inlet/compression/combustion/exhaust. In order for all 6 chambers to fire and for all six chambers to complete their full otto cycle 3 revs are needed and the rotary will induct 3.9litres of air.

The rotary is like a 6 cylinder piston motor that uses some trickery to share a sparkplug amongst 3 cylinders. If we measured such an engine's displacement by the air inducted in the time both it's spark plugs fired it would give a figure of one third the actual displacement, just like with the rotary.

MikeC

You're brother is right, 654cc x 6 = 3924cc.

Evil Aviator

A rotary engine only has six chambers if it is a 6-rotor engine. Otherwise, the common 2-rotor engine only has 2 chambers. While each rotor may have 3 faces, it still fires in the SAME chamber each time. This is why the 13B is a 1.3L engine. Engine displacement is based on chambers (or cylinders) and not rotors (or pistons).

Another example: Given a 5.0L 4-stroke piston engine, the rated displacement is 5.0L. Now make it into a 2-stroke. It still has a rated displacement of 5.0L, even though it now "breathes" twice as much (assuming the same volumetric efficiency). The number of combustion cycles per revolution has nothing to do with rated displacement.

Woot, we have a winner!

I'm not sure how good you are with math, but do you notice anything different between the following formulas?

Rotary Engine airflow rate cfm = (CID * RPM * VE) / 1728

4-Stroke Piston engine airflow rate cfm = (CID * RPM * VE * 0.5) / 1728

TurboSE

MikeC

A rotary with 2 rotors has 6 chambers, 3 around each. *Every* technical document you read from authors suck as Felix Wankel and Yamamoto says 6. They *never* say that a rotary has 2 chambers. Just because only 2 are ever firing means nothing, the others are still in 1 of the 3 other strokes. Same thing with a six cylinder piston engine.


I dunno how you guys work in these units :-) Your formulaes are wrong because you are assuming the wrong value for displacement of the rotary and you can't use your incorrect displacement to prove itself.

Evil Aviator

You are mis-reading those references a bit. Yes, the rotary engine has three working chambers. However, only one of those working chambers factors into the combustion event. It may help you to visualize this if you think of the combustion chamber always being relative to the housing as opposed to being relative to the rotor. If you look at the cross-section of a rotary engine, you will see that the combustion event always occurs in the same place, and therefore there is only one spark plug location on the engine, and not three. Therefore, displacement is based the maximum volume of ONE working chamber per rotor.

Since you seem to like the big names, I refer you to Kenichi Yamamoto, "Rotary Engine", Table 4.1, Formulas for calculating rotary engine output:

Total displacement V(l):

V = Z * Vh

Where:
Z = number of rotors
Vh = Volume of a single working chamber (l)

Also, Jack Yamaguchi states the same thing in this online SAE article:
http://www.sae.org/automag/global_viewpoints/01.htm

Evil Aviator

Whose formulas are wrong because they are based on wrong assumptions?
1) Mine, Kenichi Yamamoto's, Jack Yamaguchi's, SAE's, and Mazda's
2) or yours?

Hint: Your team is looking a bit outnumbered right about now.

MikeC

Yes, only one of the three chambers in involved in combustion at any one time but the other 2 are involved in their own parts of the otto cycle in *exactly* the same way as with a 3 piston engine. The only difference is that through some trickery the three chambers share the same spark plugs, inlet port and exhaust port. In a six cylinder 4 stroke piston motor only 2 pistons are ever involved in the combustion cycle just like a rotary. Counting the rotary as having only 2 chambers is a silly as counting a six cylinder motor as only having 2 pistons.

These big names are basically lying. People like that don't get to where they are without knowing the value of kissing some corporate butt. If the head honcho says the rotary is going to be rated at 1.3L then that's what they say. Everything else they say is pretty much always accurate but this one point is inconsistant with everything else they've published. Yamamoto writes the displacement as 650cc x 2, which is his way of not bending the truth as much as he needs to. I don't have his book on my but I don't recall him ever saying directly that it was 1.3L.

p4nc7

iTrader: (1)

hahaha aviator you're funny. Anyways hasn't this been discussed MANY MANY times. Mazda engineers rated it at 1.3L for a reason. People saying it is 2.6L are doing so for fairness issues (at sanctioned racing events). And other people saying it's 2.6L based on other grounds are wrong. Though arguements against that fact are resonable, it's still wrong.

MikeC

Actually those that think it is 1.3L is quite outnumbered. Most people think it is 2.6 even though that is wrong also. Taking Mazdas claims as accurate is like believing a cigarette company that cigarettes don't give you cancer. Initally mazda quoted the 10A as being 3 litres but realised they could get away with convincing everyone it was 1 litre. Many countries wanted it rated at 3 litres also but somehow mazda won out.

MikeC

Yes, it was to reduce taxes and increase their chances of winning races.

usmcjsy

iTrader: (1)

Ya its 1.3L I believe the designers of the car, before a bunch of loose cannons who hate on the rotarys HP per liter output.

mindance

wow. this is such a pointless argument.

MikeC

No offence but I see this reply repeated over and over and I've already stated why it is obviously flawed many times (including in the previous post) and people keep repeating it. Basically mazda have huge motivation for lying and you'd have to be a little nieve to believe them. It's like the cigarette company saying their product is not adictive or the govt saying that more speeding fines are reducing the road toll. Imagine if someone came on here and said cigarettes aren't going to give you cancer because the tabacco companies say so. Just because they have a huge motive for lying doesn't prove they are but using it as an arguement is pretty silly.

As for hating rotaries the only thing I hate is mis-truths. I currently own a series 6 and have owned many rotaries over the last 15 years.

Evil Aviator

I think that a lot of the misconceptions come from psychological disorders more so than plain ignorance. A rational person would at least consider the fact that they may be wrong and the engineering standards are correct. It would be like me trying to argue that a "foot" is really only 10.5 inches because that is my shoe size, or that a "cup" is 32 fluid ounces because I measured my Big Gulp cup to that capacity.

MikeC

This is a laugh coming from you. Out of all the people I've had this discussion with you've shown the greatest ignorance while at the same time throwing the greatest number of insults. This very post of yours is the perfect example, you've responded to none of the points I've raised and just told me how ignorant you think I am.

Maybe you should consider that you are wrong, you can hardly keep up with the more technical side of the conversation yet are so certain that you are right. The best argument you've had so far is that Mazda say it's 1.3L so it must be true. The very fact that you believe that and use it as an argument shows your ignorance.

I've got a mech eng degree which involved extensive mathematics and study of piston and jet engines. They hardly touched rotaries but I involved the rotary in any project I could and gained a very good understanding of the mathematical side of the engine. I also wrote this software www.mikesdriveway.com/engineapp. It is beyond ridiculous that you should call me ignorant.

13btnos

iTrader: (1)

It's interesting this whole name calling thing on this post. Man you guys just like to show off how smart you are. Cracks me up. Who cares what the displacement is I know my little engine in my car makes a shitload of power for it's size. Whether it be 1.3L or 2.6L it is still making alot of power. This argument reminds of of Motocross racers who argue about which is better a 2 stroke bike or a 4 stroke bike. It's the same argument hell they put the 2 stroke 250cc bikes with the 4 stroke 450cc bikes to make it competitive. But is the 2 stroke bike actually 500cc's I don't think so. Everyone has there arguments you have your right to voice it but please PM each other and bitch each other out. Someone lock this damn thread it's the same **** but different thread.

MikeC

I've only responsed to evil aviator who seems more intent on insulting people than contributing to the conversation, although he seems to have taken the hint now.

It's actually 3.9L.

This is nothing like that.

1) You don't have to read this thread.
2) There has been huge amounts of information on this topic not discussed, it is no-where near the point that threads on the topic should be locked. Unfortunately a lot of this is beyond those who frequent such threads so it's difficult to take the discussion further.

13btnos

iTrader: (1)

I could give a rats ***. Yes you are correct it is 3.9L. What ever. I still know that I can extract a whole lot of horsepower out of these little engines. And I guess when I tell people that it's 3.9L they will be dumbfounded. Have a nice day on your side of the pond MikeC. Man some of you guys are soo uptight.