http://cgi.ebay.com/ebaymotors/Mazda-RX-7-...emZ380020057566



I'll host the pics too so they dont disappear when the auction is terminated



Attachment 18278



Attachment 18279



Also does anyone know the reason for the different casting around the "MAZDA 13B" area? I've seen that casting on a few housings and haven't figured out where they came from.

I saw these a couple days ago and wondered the same thing. Im not sure how well that Batman port would work.

it says there TII housings and thats for the knock sensor...



dont know...never seen porting like this. dosnt make it bad though. i like it...lol



maybe some of the porting pros on here can explain it...?

Hello Kitty https://www.nopistons.com/forums/pub...#>/biggrin.gif

i wrote the guy on eBay who is selling these, cause i was curious...



this is what i got back.



"I never seen these kind of ports myself. They were in S4 Turbo (Side Plates with huge port too). I have no idea about the HP # nor the benefit. Thanks"

I lol'd

GSL-SE housings are recessed like that, but they aren't as scalloped.



Very interesting.

I've seen S4 NA housings with that casting, and also S5 T2.

ive seen a similar exhaust port used before, but instead of 2 lines on the outer edge of the port it was one single in the middle,



as for the pros and cons of the port , your going to start to loose some compression from your power stroke earlier but given the areas volume it has to escape from the gases are going to be moving fast but with a low volume before it meets with the majourity of the port.



have seen this in aussie abit,

Earlier opening with some support in the middle for the apex seals? An exhaust port with a bridge? https://www.nopistons.com/forums/pub...1047683561.gif



I had housings like the one on the left with the casting recessed around the 13B and the nicely radiused lower leg in the S4 motor I got with my '88 SE. On the tops of the housings there were little cast letters identifying it as coming from Mazda's very own Hiroshima foundry, Licensed by NSU Wankel. Pretty neat... I sent them out for Cermet coating and got some S5 housings back instead. https://www.nopistons.com/forums/pub..._DIR#>/sad.gif Mazda contracted out housings to different foundries to keep up with demands and the design was obviously simplified. More info on casting differences between years and different foundries is needed. The "in house" housings are definitely more appealing to look at IMO.



Now that I just got done talking about them, I just found a couple photo's...



http://img259.imageshack.us/img259/4...g014ol5.th.jpg



http://img153.imageshack.us/img153/7...g019sr4.th.jpg







I have a feeling someone really wanted the best looking housings for their pet project. I wasn't too upset about getting the stronger S5 housings in exchange.