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Naturally Aspirated Performance ForumDiscussion of naturally-aspirated rotary performance. No Power Adders, only pure rotary power!
From the "12A" to the "RENESIS" and beyond.
Part 1: Mazda. i got sent a link the other day to some housings for sale that turned out to be aftermarket (stock housings modified to P Port), which was a surprise. we thought a thread was in order with pics and stuff.
Mazda has made several variations over the years, i found a couple doing the research for this:
The beginning, Mazda has racing housings at the very start, 1968, the pic is teeny, but for the 110 Cosmo they had a "cross port" engine, its the normal primary intake port with peripheral secondary ports
Part number unknown. just as a note the 110 Cosmo engine was quite different, it had aluminum side irons and different passages to try and get the rotor housing temperature more uniform, stuff that was dropped for the R100
Housing number 2, was for the R100's in 1969. Its broadly the same 10A engine, but full PP instead or a semi
Part number 3883-10-100? 3883-78-100?
For the Rx3 in 1972-1976, the Sports Kit is a 12A Bridgeport engine, the JAF had banned the peripheral port. This 12A BP engine is 225ps@8500rpm, later to get to 235ps with a real Weber http://foxed.ca/rx7manual/manuals/Rx...%20(70-73).pdf
its pretty neat how detailed this manual is.
for 1977 the P Port is back. Between the R100 and the 1977 Rx3, the road going 12A had been updated quite a lot. These Rx3 housings are sand cast in the 74-85 style to match the then current engines.
This engine features a Round intake port, and was rated at 250ps@9000rpm. The 13B version, was the same port timing and was rated at 280ps@9200rpm
i've got no worthwhile pics of these, the 12A part number was 1058-78-100A
For the then new Rx7 the housings were again revised. still sand cast, the intake port keeps the same port timings, but becomes rectangular instead of round.
http://foxed.ca/rx7manual/manuals/comp.manual.pdf
the 12A is 4352-10-100, and the engine was rated at 270ps@9000rpm
the 13B is 4801-10-100 and it was rated initially at 280ps@9000, but with dry sump in 1980 and mechanical fuel injection it goes to 290 and then 310ps
There are many differences between a stock housing and the PP housing, the exhaust port is larger at the Trochoid, but smaller at the header flange, essentially its just a round pipe vs the stock housing where it tapers. also the top header stud is lowered, its a small thing, but the header ends up fairly close to the intake, and not lowering the stud actually makes it harder to get to. as can be seen in the pics the port is cast in, and the casting quality is very different from a stock housing.
Also these PP housings have no sheet metal insert like a stock housing, its just the chrome sprayed on the aluminum.
The next iteration of the P port housing is for the Multi Rotor engines in 1986, it is somewhat confusing because there is a competition 3 rotor engine, the 20B, and the JC Cosmo engine, also the 20B, which share very few parts, but have the same name. the competition engine has a number of differences, different bearing sizes, rotors, the irons bolt to a Hewland instead of a Mazda transmission. Since this is dry sump the housing legs get smaller, as they aren't needed.
the over the counter engine was rated at 450ps@8500 so its a big step up, EFI by now, slide throttle and dry sump.
the casting finish looks way better (no longer sand cast?), but the water seals still live in the rotor housings like the 74-85 engines.
ZR03-10-B10, port timing is unknown
There are some iterations to get to the R26B. The 3rd spark plug is added. To do this the dowel pin moves. The port timings and runner sizes have been revised, but its unclear what they actually are
This wasn't sold to muggles, part numbers unknown. It can't be seen in the pics, but at this power level i would imagine the sheet metal insert is used, like a stock housing
Part 2: Everyone else. Everyone else modifies a stock street car housing, and fall into basically three styles.
Racing Beat, Racing Beat bores basically 1 big hole, threads a sleeve into the housing and through the Trochoid, then you need to finish the end, seal it, and the intake just gets a hose barb.
There are some tradeoffs to this. The hose barb intake is actually pretty convenient, and since it angles up, the top header bolt can stay where it is. The downside is that there is a lot of finish work on the sleeve, as the Trochoid is curved where the sleeve comes through, so it ends up in a fish-mouth shape. The angle of the port could go either way, its probably not as good entering the engine, although the intake system is probably more straight.
RB does turbo and non turbo, and 74-85 with the N304 casting, or 86-95 with the water seal in the irons, so they have something for everyone
The Japanese style. The Japanese style P port housing is a closer copy of the Mazda housing, and it looks like it is setup to be able to run the Mazda intake manifolds.
With this style, there are two cuts to the housing, a small one that is the ID of the sleeve, and a big one with the OD of the sleeve. The sleeve actually ends up sitting on a flat part of the inner Trochoid, so the sleeve is simpler (the end can just be flat) , and there is less hand finishing required. The flanges are floating on the end of the sleeve, so they can tolerate some misalignment, they do still need a support for the intake though.
Since the Japanese housings are so uniform, it seems like they are all made by the same guy, although they are sold by several shops, ARF, Revolution, Jackpot, etc
Generally round port, apparently round port is more mild mannered, which is nice in a street car. Both 74-85 and FC/FD housings get used
also there are three plug versions, Revolution
and then Jackpot does these. It seems really extreme
When I put something in the shopping cart like the 13B MFR housings 4801-10-100 ----> 0000-01-9001 supersession there isnt a button to check availability/stock anymore?
Do you have to call on each part or is there a reality check as part of the check-out process now.
*edit*
Parts availability is in the check out screen
When I put something in the shopping cart like the 13B MFR housings 4801-10-100 ----> 0000-01-9001 supersession there isnt a button to check availability/stock anymore?
Do you have to call on each part or is there a reality check as part of the check-out process now.
*edit*
Parts availability is in the check out screen
surprisingly it’s indicated as being in stock there too
although I was told it doesn’t have the port shape that is now preferred and shown to make more power, considering what a pro built engine costs it’s two drops in the bucket
will just drop these here from about 12 years ago; ~350 bhp, ~220 ft-lbs was typical for these 13B road race engines
I really dont know anything about p-port housings, but its an interesting topic to me that I want to learn about...
It was my understanding that the MFR p-port castings/porting is the most mild configuration (since you cant go back) and its up to individual teams to develop the ports to their needs.
From what I hear the as supplied MFR p-port housings are basically streetable.
Or was there something else about the port than sizes/shape/timing that you meant Team?
my understanding is that the preferred intake PP port tapers from the large entrance diameter down to a smaller size, but have no recollection of the size or shape. Which made sense to me from a momentum/resonance perspective.
the one thing about the engine above is it’s not made from a production automotive engine, but from an industrial 13B propane generator (?) engine that I believe has since been discontinued by Mazda.
Of course now with the CNC billet stuff that would likely be the choice unless the rules specifically dictate OEM/Production parts.
.
From what I hear the as supplied MFR p-port housings are basically streetable.
we have some data points on this. first the idle speed in the manual is 900rpm, which is lower than most of the ******* with street ports (you could go lower but the carb doesn't really work well)
second, when i started at Almaden Mazda in 1997, i got to hear about Rob Goldens REPU, which apparently he still has. from the U turn, it would do 0-100 in the length of the Chevy dealership
and third, watch this, its got kind of an intense idle, but they just drive it away from stops like a regular car. and this is 1983, so its a 13B with injection, dry sump and all the other tricks.
actually #4 is the 787B, it starts with something resembling a key, and then runs on its own the rest of the time. i've seen them use it to haul stuff around, its like the pickup truck of race cars.
(the start and idle for ~45 seconds at 1100rpm, and then surge from 1100-2500 for another 45 seconds is the ECU relearning its idle after shutting the battery power off, and not something the engine needs)
Is there an MFR P-port rotor housing that doesnt have the coolant seal groove on the rotor housing?
Or are we expected to only use the old style side housings?
so there are a bunch of differences in the irons, but the competition 20B actually might predate the FC engines by just a bit. also the multi rotor race engines have different castings, and along with the vestigial intake ports, the narrower oil pan legs, they also have the bolt pattern for a Hewland transmission, instead of the Mazda transmissions.
the later engines like the R26B, has different dowel pin locations, the coolant comes in the center, and then it also has the bosses for the Carbon Fiber supports they used to make it a stressed member of the chassis
You are probably using the term "vestigial" loosely?
*edit* nvm, your use of term matches the definition- small remnant of formerly larger thing. Definition does not denote a lack of purpose/function as I commonly think of.
I have read (and it makes sense in my head) that the shallow imprints of the side intake port on the side housing wear surface serves an important function and that is why they are present even on sidehousings that never had side intake ports.
That function is rotor seal pressure blow-down for lower seal wear rate and carbon/contamination migration out of the seal grooves.
The mechanism is the side intake port face volume and path into the intake stroke allows the gas sealing pressure behind the side seals and corner seals and in the volume on the rotor face between the side seals and oil seals from combustion pressure to blow-down into the intake stroke as the intake port interrupts the rotor flank sealing grid momentarily.
Or are there MFR side housings that dont have the side intake port imprint on the wear surface?
This is Neato Dorito. I’ve always found the port size, shape and indexing location ( port timing ) to be really interesting. I remember some ten years back when race P port 13b’s were making 330 ish hp like teamrx8 said. Man those things would make some noise.
I grabbed a few of these pictures off of chips motorsports Instagram. It seems like he’s doing a few of these in both the two bolt flange and the wiggins clamp for intake attachment. Not sure about his port shape tho after the threaded insert.
first of all, thank you! your threads like this are always the business. you will always have audience with me. peripheral ports are a world, i have always wanted to be a part of, but somehow keep coming up short.
you cleared up the 10A questions i have always had and never really got answers to.
Originally Posted by j9fd3s
The next iteration of the P port housing is for the Multi Rotor engines in 1986, it is somewhat confusing because there is a competition 3 rotor engine, the 20B, and the JC Cosmo engine, also the 20B, which share very few parts, but have the same name. the competition engine has a number of differences, different bearing sizes, rotors, the irons bolt to a Hewland instead of a Mazda transmission. Since this is dry sump the housing legs get smaller, as they aren't needed.
the over the counter engine was rated at 450ps@8500 so its a big step up, EFI by now, slide throttle and dry sump.
the casting finish looks way better (no longer sand cast?), but the water seals still live in the rotor housings like the 74-85 engines.
ZR03-10-B10, port timing is unknown
... and here is another group of questions i've always had, so hopefully you can shed some light. so my question is nomenclature ... were the terms 13G and 13J official from Mazda - maybe just internal? i know you said they called both engines 20B, but i'm just trying to find out where those other names came from if i can.
I recently had the pleasure of dynoing an MFR based 12A on my engine dyno. Ports massaged by Roger Mandeville back in the day, made a bonkers 298+ at the crank but unfortunately has a compromised water jacket that I'm looking to have repaired. Also this was as raced and delivered, turns out it needs more carb:
I also have a few other MFR housings worked over by Drummond and a few other OG builders if people are curious. No other engines though.
were the terms 13G and 13J official from Mazda - maybe just internal?
yes and its super confusing, to me anyways; it is neat to watch the progression though, they make a lot of progress really fast
1986-87, they have the 13G, 3 rotor, 450hp@8500, also sold over the counter as 20B engines, but share no parts with the 20B in the Cosmo
1988, 13J-M, this is a 4 rotor, 500hp@8500
1989; 13-JMM, 4 rotor, ceramic seals and coatings, the early 2 position variable intake, 630hp@9000
1990: there are two, the 13J-L, which i have no info about and the R26B, which is shorter, three plugs, i think this has a 4 step intake? they claim 700hp@9000rpm.
1991: R26B, i guess version 2, fully variable intake, and the ceramic coating that stayed on, 700hp@9000.
the R26B's also went into the 792P and a couple other cars, they actually ran LeMans again in 1994
was always curious which engine they ran in the S5 GTO car. i had suspected it may have been the 13J (though i had no idea that there was more than one version of it), but according to the chart you posted, it may have been a version of the R26B. i think this is the closest i've come to finding out.
this also puts the development from 757B to 787B into perspective, and you're absolutely right, they made VERY quick progress!
from that pic you can also see how the factory 4 rotor engines have a different cooling and oiling system path than a 2 rotor.
they both feed and exit the center iron (the oil probably drains the same as normal, through the "center" irons).
so the rear two rotors basically stay the same, but the front two rotors get fed from the other side.
its one of the differences between the Mazda 4 rotors and everyone else
06-18-22, 11:38 AM
