The thermal efficiency of the rotary is bad enough with Iron rotors, with aluminium, it would be even worse, Look at the size of an Rx-7 radiator compared to that of any other small 4 banger, then consider what size it would be if even it had to deal with 10% more heat..The only way around it would be a thermal resistant coating on the face and sides of the rotor..Max

The RX-8 rotors are "normal" (NOT aluminum, etc.)

Weight of the first one we received is 4229 grams, weight of a 93-95 rotor (approximately the same as 89-92's) is 4359 grams (so RX-8 ones are ~130 grams lighter)

They are .004" thinner across the side seal area, .0015 thinner at the first "land" area outside the oil control rings, and equal to earlier rotors across the gear.

We will be doing more measuring -- looks like the face of the rotor is about .005 "smaller" about 1" down from the apex seals -- looks like MAZDA just gave it more clearance about everywhere it needed it.

We are working on determining the casting thickness of the bottom of the apex seal groove -- need to see if it's possible to machine them down to take earlier apex seals. ---- The RX-8 apex seal is considerably smaller in beam height/strength.
We will be finding out soon (week or two?) if the RX-8 apex seal will "fall into" the peripheral exhaust port of the earlier rotor housings (yes, we are going to find out the hard/high$$ way !!).

The "blow-by/scraper" rings should only be needed with the RX-8 side exhaust port side housings.

We are "building/adding to" our RX-8 website almost daily.
http://www.mazdatrix.com/index8.htm

The RX-8 rotors have a stamp by each side seal groove, and there are 4 different side seal lengths covering the 16! different letter stamps for length.
http://www.mazdatrix.com/8engine2.htm

--- Looks like that means you can't really buy side seals before you know the ALL the letter stamps on EACH rotor (that is going to be a real pain!) -- only other solution would be purchase all longest ones, then grind to fit (as we do now).

Weights:
14 grams = stock 2 piece 3mm apex seal
10 grams = stock 3 piece 2mm apex seal
9 grams = new stock 2 piece 2mm seal ***
5 grams = stock 2 piece RX-8 seal
4 grams = 3mm carbon seal
4 grams = 2mm ceramic seal
3 grams = 2mm carbon seal

*** !! We received our first of the new OEM seals this week (they sent 5 !!!!). The 3-piece 2mm seals are being replaced by these new 2 piece ones from MAZDA.

Anyway - LOTS more to look at / measure / etc -- we only received that first rotor yesterday!

Dave Lemon

good stuff :D

So, they should fit into the earlier 13B engine right ?

It would be nice to have a lightweight 10:1 Mazda rotor
right off-shelf instead the 9.7:1 rotor.

"FIT" and "WORK" are two VERY different things --

As I said:
"We will be finding out soon (week or two?) if the RX-8 apex seal will "fall into" the peripheral exhaust port of the earlier rotor housings (yes, we are going to find out the hard/high$$ way !!). "

"Possible/probable" results of the "test" should be:

1) Worked fine - then we continue with testing to see if they make ANY more power.

2) Somewhere in the initial warm-up/break-in period the apex seal center "falls" into exhaust port, catches the top of the exhaust port, gouges the rotor housing, breaks the apex seal into various pieces which those pieces then continue gouging the rotor housing and the face of the rotors - thereby writing off approximately $2500 of parts + labor to assemble an engine.


3) After 6+ hours of break-in!!, on the FIRST hard pull, the apex seal center "falls" into exhaust port, catches the top of the exhaust port, gouges the rotor housing, breaks the apex seal into various pieces which those pieces then continue gouging the rotor housing and the face of the rotors - thereby writing off approximately $2500 of parts + labor to assemble an engine.

3) Initially works "OK", then somewhere down the line, with FULL load on the engine, THEN the apex seal(s) decide to fall into the holes.

I'm putting my money (literally) somewhere between #2 and #3 -- but then, hey, SOMEBODY has to be stupid enough to try it!!

Dave,

I'm not understanding htis comment
"*** !! We received our first of the new OEM seals this week (they sent 5 !!!!). The 3-piece 2mm seals are being replaced by these new 2 piece ones from MAZDA."

does that mean the new apex seals fro the old engines (ie 13-REW, 13BT for FCs) have a new type of 2 peice 2 millimeter apex seals offered by mazda?

Yes, the COUNTRY has been out of the 3-piece 2mm seals for a few months -- just working out of existing inventories. We were seeing a "new" part number listed as a "replacement/option" for them, but there were none available of EITHER type.

The "new" 2-piece 2mm ones are now showing up, and there are still none listed in the country of the 3-pieces. We assume Mazda will do a full "supersession" of the 3-piece # to the newer 2-piece part number fairly soon.

They are "normal" looking 2-piece seals.
We received another 50 or 60 of them today.

Part number is changing from an N3F1 to a N351.

Dave Lemon

hey Mazdatrix, don't forget that the rotors are already clipped on the trailing side to delay intake port closure.

thanks for clearing up the confusions.

You think there going to fall in because the shorter seals wont have enough stiffness to resist bending when the center of the seal isnt supported by the housing? Are you testing them on completely stock housings?

those 1.5 MM Apex seals are gonna do wonders when the boost the rx8.

Um, they are not 1.5mm... they are 2mm... and in fact the RX-8 seals are superceding the 86-02 3-piece seals. Hook on Phonics didn't work for you I take it? :)

I don't understand two things here...

One, if the height of the seals is shorter than the older stuff, how can they be used in the '86-02 rotors? Wouldn't there be not enough preload on the springs, given that the seal groove depths are different? Or am I missing something here (like aternative springs for using the seals in rotors designed for the 3pc seals)

Two, why would there be a problem with falling in the exhaust port? They shouldn't be any flimsier than 3-piece seals, and if anything should be stiffer. My bets are that they'll be fine... after all, they are superceding the 3pc seals so Mazda must trust that they will work OK with peripheral exhausts? (and intakes for that matter)

On another note... thank you for posting the seal weights. That's something I've been trying to find out for months.

Right. I tried to be clear in my explanation for this. Rotaries expel the burning air/fuel earlier than piston engines, hence the hotter tailpipe gasses and louder sound. However, your answer does not address the possibility that the actual combustion temps inside the engine are the same or lower than piston engines. Care to elaborate?

Very good point. Mr. Wankel ruminated on fully ceramic coated rotors and side housings in one of his threads and it sounds like a great idea if the ceramic could be combined with a coating that could sustain constant rubbing of side and apex seals.

there are 3 different ones, we're talking about
n3f1 = 2mm 3peice
n3h1 = 2mm 2 peice renisis (short)
n351? = 2mm 2 peice renisis style tall seal for the 86-02 motors, dave isnt n351 and old number? weird

mike

This picture will help answer questions:

Top seal (thinner one) is the RX-8 apex seal -- it will NOT work in earlier rotors. The apex seal groove is CONSIDERABLY shallower on the RX-8 rotors.

The lower seal in the picture is the "new" 2-PIECE 2mm apex seal from Mazda that will? be replacing the former 3-piece 2mm seals used on 86-95 rotors.

Seeing if the picture shows up in this post --

picture
 

https://www.rx7club.com/forum/attach...postid=2017361

here

Okay, makes more sense now. Thank you.

I *feel* that the RX-8 apex seals should still be fine over the exhaust opening. They appear to be taller than the sealing half of the 3piece seal, and those obviously don't have any problems with "falling in". (especially after trying to disassemble some trashed rotors and seeing just how much those things can flex without breaking!)

Of course, what people think is one thing, what actually happens is a different story...

It's a 13B.

Interesting thing I noticed was that there was a serial number stamped on each housing next to the 13B. (stamped with a hammer driven stamp)

Renesis Rotors
 

I was told that these rotor will fit the 13b engine. They are the same size. They also said that they are 14% lighter that 13b rotors.

the service higlighs book call it the 13b-MSP, presumably its either multi side port, or missing some power, you decide

mike

This is a good thread with damn good info from Mazdatrix. Maybe a possible sticky?

Interesting that the seal is "shallower" than the previous 13B seals.
Is it only done for weight reduction?

It does look more "flexy" than the N351 seal. If it does "fall in" on stock rotor housings, I guess you could always get the RX-8 housings and have smaller exhaust ports :(

J

I imagine that shorter also provides it some additional rigidity due to shallower height.

being a two piece seal it will be thicker though ... that would help with rigidity somewhat (not as much of an effect as changing the depth though)