rx7turbo1

welp. here is what I did over the weekend... It's a cosmo 13bt with S5 rotor housings. I'm happy with it. Just curious how it will perform. Any recommendations? I still have time before re-assembling..



Secondaries.









Primaries. Just went with the flow.

rx7turbo1

Exhaust. I wanted it to be D shaped. squared at the bottom and rounded up top.





Final product.

kahren

very nice for the first time, cant tell if u put a chamfer on top of the exhaust port if you didnt do so.

rx7turbo1

After looking at this stuff, I wish I had done a few things differently.



- keep the primaries smaller

- close the secondaries just a tad earlier

- keep the top of the exhaust port at the same angle as the exhaust sleeve and close it earlier. Then port downwards to open earlier instead. I definately like the port shape, just think it could be timed differently..



What do you think about all this? Do you think the exhaust port matches the intake ports for a high boost application?



I tried to keep everything proportionally larger, but haven't a clue about correctly matching port timings. In my mind, this engine will need a lot of boost to recover from the lost velocity. The intake runners are about 1.5x the size of FC runners. And now the ports primaries went from 30mm to 40mm and the secondaries went from 50mm to 60mm.The exhaust was ported about 3mm up, 1.5mm down, and 2mm on each side. I noticed the cosmo exhaust ports are 2mm wider than FC ports, however have the same timing. This drove me to widen mine further. without worries...

rx7turbo1

Thanks!



yeah, I angled the closing edge, but could prolly go more. It's about 1.5mm in width and the angle is unknown. I tried to match it to the stock mazda chamfer. It was smoothed and polished.

t210thanniv

just courious, what type of bit did you use to polish the exhuast porting?

rx7turbo1

I used a cross cut carbide in a die grinder for the cutting, then did the final grind with a tree shaped stone bit in a dremel, and polished it off with a 1/4" shank 80 grit flapper.









it was included with a kit like this, but you can pick up the flapper wheels anyhwere.