So I've been reading up on the 20B engine and various swaps that have been performed with it. I've spent most of my time here and over at RX7Club's 20B forum and then browsing around the internet trying to soak up what little knowledge there is to be had.

As a disclaimer, I'm a car newb. I'm learning and researching all that I can (currently deployed with the USAF, nothing else to do) so that I won't be going into this blind. I don't plan to do the swap for a good while yet anyway (at a minimum 1.5 years after I get back home) and when I do it's going to be a project for me and my good friend who has a lot of experience with rotaries (he's completely redone his RX7 into a 600HP beast). So, with that out of the way and hopefully warding off any flames, onto my questions.

1. I read that the 20B requires a 4" exhaust system in order to handle it's increased flow over my Renesis. Is this true? If at all possible I'd like to keep my current 3" exhaust (Mazdaspeed) but if a larger exhaust system will improve performance/reliability then that's what it'll have to be.

2. I've read that the T56 is being used because our OEM transmission can't handle the 20B without desintegrating. I found that there's a T56 Magnum? Is this the same transmission people are talking about usually or this perhaps an upgraded version? I also read about a T606 (or something) but haven't researched it at all yet, will get to that after my lunch break.

 

4" is the usual minimum on a 20B. Most turbos used also have a 4" discharge. I would go full 4". Performance and reliability will be higher with the 4" over the 3".

In the middle of a 4" downpipe to twin 3" midpipes/catbacks...