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Rotary Engine Naming Conventions...

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Old 08-14-2008, 09:32 AM
  #26  
RK
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Originally Posted by Jon316G
OK... here is the link to the page that explains the naming convention:
http://turborx7.com/faqs.htm

Very informative site and good to browse through the various pages on the left side... especially under the 'Basics' section.

Also, at the bottom (left pane) you'll see a 'RX-8 Renesis Info/Specs' area:
http://turborx7.com/rx8renesis.html
I've mentioned in the past that its good for everyone to observe the Renesis Module flash animation to better understand whats going on under the hood.
This is where you can download the animation module.
Ah. You da man.

The letters "A" & "B" represent the combination of two basic production engine configuration parameters, "eccentricity" and "generating radius". The "A" is applied to the first (A), and only, combination of the two specifications actually deployed in a regular production engine of nominal 0.60 liter displacement per rotor, the 12A. The "A" was also applied to the first (A), and not only, combination of the two specifications actually deployed in a regular production engine of nominal 0.65 liter displacement per rotor, the low production 13A. Mazda later determined greater economy could be achieved by using the 12A's combination of eccentricity and generating radius in conjunction with a wider rotor, thus giving birth to the second (B) regular production rotary of nominal 0.65 liter displacement per rotor, the 13B. If Mazda were to create new two rotor engines of 0.60 and/or 0.65 liter displacement per rotor using some different combination of generating radius and eccentricity, application of the same logic previously applied by Mazda in naming its rotaries would give birth to a 12B and/or a 13C.

Engine Eccentricity Generating Radius
10A, 12A, 13B, 20B 15 mm 104 mm
13A 17.5 mm 119 mm

Eccentricity
the distance from the center of eccentric shaft rotation to the center of the rotor
Generating radius
the distance from the center of the rotor to its apex.
Very nice.

Oh and I love the animations. Rotaryillustrated.com has a ton of them too plus they have 'exploding/contracting' animations of the engine.
Old 08-14-2008, 03:08 PM
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Oh wow, so I wasn't totally off with my guess. *Cheers*
Old 08-14-2008, 04:44 PM
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So Mazda went as far as ver. B then with the 1.3l Wankel. Theoretically if the 16x goes into production then it will renamed to 16A correct?

Also I notice some 13b has REW suffix to it. What does that mean?
Old 08-14-2008, 04:45 PM
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REW was for the twin turbo 13Bs in the 3rd gen RX-7
Old 08-14-2008, 07:02 PM
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Originally Posted by CyberPitz
REW was for the twin turbo 13Bs in the 3rd gen RX-7
REW was also used on the 20B... but yeah, it means twin turbo.
Old 08-14-2008, 07:06 PM
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Originally Posted by delhi
Theoretically if the 16x goes into production then it will renamed to 16A correct?
Depends... if the eccentricity & generating radius is different than the A and B, it should become C.
Old 08-15-2008, 02:38 PM
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Originally Posted by Jon316G
Depends... if the eccentricity & generating radius is different than the A and B, it should become C.
Hmm... The way I read it they would only make it C if it stayed a 1.3l so it probably will go 16a. If they ever modify it so produce the same output but with a different eccentricity/apex distance then it would become a 16b.

I think that's why there was a 13G and 13J. They probably had even more experimental versions of them but eventually the distances used once they converted them to 3-rotor engine made them into the 20b and 26b. Had either of those ever made it into a 2-rotor production version they would have maintained their lettering.

I think if I spent some time figuring out the history of the 3-rotor it'd be clearer since the 20a was probably built off a 13b and not the 13a. The 20b was built off of the 13g/13j.

Keep in mind Mazda only labels them when they go into production so people who have built 20b's out of different 13b's might be mislabeling their 3-rotor engine...

Last edited by RK; 08-15-2008 at 02:41 PM.
Old 08-15-2008, 04:11 PM
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Strangely I find this rotary nerd-talk very mesmerizing.

What a refreshing topic from the typical threads of late.
Old 08-15-2008, 05:15 PM
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Originally Posted by RK
Hmm... The way I read it they would only make it C if it stayed a 1.3l so it probably will go 16a. If they ever modify it so produce the same output but with a different eccentricity/apex distance then it would become a 16b.
Mazda were to create new two rotor engines of 0.60 and/or 0.65 liter displacement per rotor using some different combination of generating radius and eccentricity, application of the same logic previously applied by Mazda in naming its rotaries would give birth to a 12B and/or a 13C.
In the above quote, the '12B' reference makes it a little confusing to me... I can understand the '13C'.
The way I took this was that each letter grouping is specific to the radius and eccentricity.
This is why the 13B and 20B have the 'B'... because the radius and eccentricity are the same, just the 20B has an extra rotor (hence the '20').
If the radius and eccentricity changes (different than the 'A' or 'B'), then it "should" become a C.
I'll try to research this more (after I take some Advil).

Last edited by Jon316G; 08-15-2008 at 05:33 PM.
Old 08-19-2008, 12:33 PM
  #35  
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Originally Posted by Jon316G
In the above quote, the '12B' reference makes it a little confusing to me... I can understand the '13C'.
The way I took this was that each letter grouping is specific to the radius and eccentricity.
This is why the 13B and 20B have the 'B'... because the radius and eccentricity are the same, just the 20B has an extra rotor (hence the '20').
If the radius and eccentricity changes (different than the 'A' or 'B'), then it "should" become a C.
I'll try to research this more (after I take some Advil).
I think I figured it out. The 13B and the 12B are related but the 'B' is just a coincidence because they were the 2nd 1.2L output and the 2nd 1.3L output configurations. Had there not been a 13A when Mazda determined that the configuration used in the 12B (which was very close to a 1.3L output) was the configuration they wanted for their new 1.3L engine they would have used that and call the new engine a 13A.

They've done more configurations with 13s up to at least 13L but we haven't seen any of those become available in a 2-rotor production line. And while the RENESIS was a change in a lot of things the dimensions and output remained the same so it maintained the 13B designation.

So if the 16x, when it makes it to production, will likely be a 16A since it will be the first eccentricity/apex distance production design with a 1.6L output.
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