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Rotary MX-5 Nordschleife Build Thread

Old 02-07-19, 09:42 AM
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So, doing a very quick back of the envelope approximation; every halving of the primary will be the next reflection. So 116" is the average bridgeport length for the long system and let's assume that's the first reflection, then 58" will be the second, 29" the third, and 14.5" the fourth; or 116" can be the second reflection, it doesn't matter. In the real world the exhaust will be cooling (cold gases have lower speed of sound) so add a bit to the shorter lengths which explains why the 14.5" short primary calculated from that is on the "high RPM" side of the suggested bridgeport exhaust rather than in the middle... but all of those options should be in the right ballpark for something that should work. Taking a ruler to a web image of the DAW header I'm guestimating around 34" from the port to collector which is in the right range considering it's for a street port.

Of course I could be wrong! The "right" way would be to build a system where you can try a bunch of different primary lengths on the dyno, but again, it should work.
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Old 02-07-19, 09:45 AM
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Crapengineering in UK sells custom made tubular subframes In case you want something lighter and better suited for the 13B.
They are made for the KL V6, but should fit yours better than the stock one. But i guess you are to far along to change that now.
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Old 02-13-19, 05:28 AM
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Kenku, this kind of research is great! All facts considered, I will see what I can do with the space that we have available. Thank you for your continuous support!

Originally Posted by Zepticon View Post
Crapengineering in UK sells custom made tubular subframes In case you want something lighter and better suited for the 13B.
They are made for the KL V6, but should fit yours better than the stock one. But i guess you are to far along to change that now.
This is true, the modified subframe is pretty heavy. I think back in the day when I started there was also noone fabricating tubular subframes in europe. Thanks for the hint, I have been in contact with Ali from Crapengineering already. This surely is something I want to fit for the weight benefits later down the line.

I have another question regarding a full bridge. I was under the impression that full bridges with notched housings work with 2-piece seals, since there are rebuild videos of "RX7 Specialties" and "FullBOOST" that did just that. However there are some old threads on here where people argued that when this is done, the triangle piece will cause problems. The seals I bought are regular Atkins 2-piece seals, I have read that appearently they are engineered slightly differently to allow for a bigger bridge. Not sure how big of a bridge I can build on the triangle-piece side.

Here is the car in its current condition:
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