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Discussion Starter · #1 ·
does anyone know if it would be worth going rotary 13b over the ka in my 240? just kicking the idea around. I believe it would balance the weight from front to back some what, and more rev as well. I realize this isnt a mazda forum but any info is welcome.
 

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What exactly are you wanting the swap to provide you? I see the only thing you bring up is weight. I would think that a SR20DE would be an easier swap and it would also cut down on some weight over the front end. However, it wouldn't take off as much weight as the 13b would. According to the "The LS1 is heavy" thread the KA24DE weighs in at 330 lbs. The 13b, according to Wikipedia, comes in at 247 lbs. This means a roughly 83 lb drop in weight on the front end. According to Motortrend the 240 weighs in at around 2,760 with a weight distribution of 54% - 46% (F-B). According to your numbers and if you were do the swap your weight would roughly be 2677 lbs and the distribution would be roughly 52.6% - 47.4% (F-B).
 

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Discussion Starter · #3 ·
this swap would be inexpensive on account of my own welding and fabrication. the 13b would also sit farther back since it is a shorter engine. If there is enough room under the hood, (big time wishing and probably not possible) I think it would be great to connect two 13b s end to end welding the shafts making an equivalent four rotor. I would be willing to give it a try room permitting.
 

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First off, no swap is inexpensive! I understand that the engine would sit farther back since it's a short engine, it would probably throw my weight distribution off very little though. You are wanting to link two 13bs with a jack shaft or actually connect them together? Honestly you would probably be better off looking for a 26b.
 

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Discussion Starter · #6 ·
26b is hard to come by and expensive. what I have in mind is a long term budget build.something that has not been done, or at least seldom talked about. you know, one of those tedious learn as you go projects. even just a single 13b is a step up from the ka in my opinion, and not run of the mill for a 240sx.
 

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26b is hard to come by and expensive. what I have in mind is a long term budget build.something that has not been done, or at least seldom talked about. you know, one of those tedious learn as you go projects. even just a single 13b is a step up from the ka in my opinion, and not run of the mill for a 240sx.
26b is hard to come by and expensive, hell the 20b is hard to come by and expensive. Point is it would be way easier and probably cheaper in the long run. If you are dead set on a rotary I would say a turbo 13b would be the way to go.

However, I use to have a buddy that was always messing around with RX7s I remember seeing a 13b all apart on his work bench. I'm sure somebody has though about this before but I don't feel like searching. You might be able to bolt 2 13bs together. Here's a picture of a dismantled 13b to help me explain, I know the picture is large but it's better that you can see the parts in detail.



If you look closely the block is actually five separate pieces that bolt together. The first piece is machined for the water pump, accessories, an intake and an exhaust port. The second and fourth pieces house the rotors. The third piece (center) is a coupler for the second and fourth pieces with two intake ports and an exhaust port. The Fifth and final piece has an intake port and an exhaust port and is machined for the bell housing.


Now that I've explained what the pieces are for and have posted up a picture of what the 13b looks like I'm pretty sure you are thinking the same thing I'm thinking. What's to stop you buying two 13bs, discarding the #1 piece on one engine and the #5 piece on the other engine and using another #3 piece to link the two. The only custom pieces that would then be needed would be a new crank shaft (or whatever the rotary counterpart is called), a new intake manifold and a new exhaust manifold. No need for a custom camshaft since there is none on rotaries. Plus it would be at least 10% shorter than two complete 13bs end to end.

There's something to think about!
 

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Its not that hard of a swap. Its just time consuming. Ive seen 3 or 4 in person and the most dificult part is the wiring. The mounts are fairly easy to make and the trans sets the shifter back around 1.5 to 2 inches so u have to cut a little bit.
 
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dude this would be sick as fuck.. i've never seen a rotary engine dismantled.. would be a great build thread if you get this going
 
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