I really really have to start hanging out here more often!



I've learned a lot but I'm confused as well, mostly concerning the square vs round port that Judge Ito was talking about. I'm very unclear in terms of what we're referring to here....



Judge Ito, you mentioned your cosmo motor. Two or three rotor? I'm about to disassemble, port, and rebuild a two rotor. Unsealed from Japan with about 40K on the clock. Originally I had planned on dropping in the motor as is, but the thought of building and porting my first rotary engine kept me from doing it. I have Vosko's turbo (T78) with a larger compressor, a Garrett GT79. Spool up isn't fantastic with most happening from 4K and above. I don't want to make it worse. I guess what I'm looking for is a few pointers with this engine.



I've thought about polishing up the intake runners, leaving the port shape as is, and concentrating on the exhaust side which is smaller than the FD's. Thoughts? Now that I've read this post, my motivation to port the intake side of things has quadrupled! I like what you said about being mild on the primary side and wild on the secondaries. Anything special associated with the Cosmo ports?



Thanks for this thread (and any advice you can provide). I'm fully digital photographically, so I'll take lots of images as I go along.

 

Michel thanks for adding to the thread. Any imagery that you can capture would be great.

Please feel free to use my password on nopistons.net if you need to host the pics.

I try to keep everyone from attaching them so that the page always loads nice and fast.

PM me if and when you need that.

-Dave

 

Ok, took apart the engine today. The Cosmo engine is very interesting. It seems to be a match of old and new. Corner seal springs are of the old type and apparently are better than the newer ones. The main bearing, just like the 3-rotor, is similar in design to the Turbo II but uses a bearing with a deeper oil groove (which I believe Racing Beat sells if you're interested in them and it comes in a Mazda box w/Mazda part number but Mazda USA can't get them). The motor was just about immaculate (or as good as one could expect) Everything was good and I could have easily thrown this motor right in. Definitely a low mile engine. Housings were exceptional. We'll check the side plates tomorrow. Anyway, I have two replacement cameras coming from NPS tomorrow morning so I'll be fully digital again and will post pictures of the stock ports tomorrow :-) I'm extremely excited about this endeavor, but I'll need help from you guys!

Michel

 

I was under the impression that mazda redid the corner seal springs becaus ethe old ones were no good.

Where did you hear that the older ones are better?

I would replace them either way if i were you. They are cheap anyway and that wouldn't save you much to reuse them.

 

I've always heard that the FD corner seals and corner seal springs should be used when rebuilding. Hence, they're better

 

Yep, FD ones are better and they are only about a $1 each...

 

Oh no, I'm replacing all the springs regardless. They commented that the '79 type springs were superior (stronger?) than the later versions but I believe we're using REW stuff. Replacing all the necessary stuff and the Apex seals too. I'll probably just use the OEM seals although the shop is high on Atkins seals....

Michel

 

Your talking about the small little round rings right.

The newer ones are flat and not round.

 

Ok, everything has arrived and I began porting the intake runners late this evening. I'll really dive into it tomorrow. I do not have any templates so I'm being a bit cautious as I have no desire to break through into a water jacket or oil passage. Anyway, I'll post two images and tell me what you guys think. It's hard to see the track lines so I drew them in on the computer.

 

Here's the secondary. Seems like there's only room to go up/down on it. I'm comfortable with porting the runners, but not doing the port face shape. I have a friend who may be able to loan me some templates however, and I may wait for those before attempting anything drastic. I'm really itching at the bit. Pun intended The Cosmo ports are already quite a bit bigger than the FD's. Trying to keep the primaries "reasonable" and go pretty close to all out on the secondaries.



I'll post a bunch of pics tomorrow when the light is better. Promise! What does eveyone think? Judge?