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Some 3d printing material has a higher melt temperature, you can even print with kevlar/titanium/... in it or even metal for a one off is not that bad.
Trow it in 3dhubs or other 3d printing service and see what it costs.
all the stock OE intakes are nylon 6 if memory serves.
Just read this entire thread this weekend. Quite a journey and project. I'm sure after this amount of time you get fatigued with the project and turn your attention to other things like the E30, 96 FD, home renovations etc.
With all the effort and time invested I wish you the best on completing the project with success.
Seeing all this R&D it helps explain why these 4 rotors being sold cost an arm and a leg. Keep living the dream John!
Well it could work. But I think that, by the time the stock piece has been cut and machined flat, that the wear face probably isn't perfectly straight anymore, so it would need flattening and nitrating anyway. So maybe easier to start from a new piece of material. And finding good end housings is getting harder around here.
Could actually work. Heating a rotor housing to about 300 deg C will cause it to expand about 0.8mm so it can be expanded to fit over a small dovetail. The outside perimeter isn't the problem though, because if the wear plate is a little bit thicker than the pocket in the machined piece, than the rotor housings will clamp it in place. I was wondering about how to fix it in place a the inside bore, This seems like a simple solution:
So, after looking into casting some more, I figured that maybe it's better to spend some more on billet material and just machine it. I think the chances of succeeding are better and it's probably takes less time. It's a pretty complex looking piece, but most of the machining operations are not that difficult, lot's of 2D contours and some boring. I drew up this for now:
I think I will try and do the 2 intermediate housings and the center housing first. They are pretty much the same, the center one just has the mounting for the stationairy gears and an added oiling hole. I designed it so modified stock rear stationairy gears can be used. This will be more rigid and better than the usual solution which uses a key and a circlip to keep the stationairy gear in place. The housing itself will be a simple 6082-T6, and cast iron for the wear plate. The stock wear surface is a simple cast iron, which is about 400HV after nitrating. I think it's GG25 or similar. I think I will try and use GGG60, a ductile iron with a higher tensile strength. It's about 600-650HV after nitrating.
The front cover is starting to shape up aswell. Need to machine the front face and the mounting points, and then machine the tensioners. Almost done
I would definitely DLC the iron inserts after lapping them to perfect straightness, will last forever and reduce friction a lot. Nitriding will not be neccesary anymore from wear aspect view.
We had a aluminum side housing (weak cast alu) of a 250cc Aixro DLC'd, worked perfect.
In industry, we've DLC coated nitride for extra wear safety. We've also TiN over DLC regardless of nitride, not so much for the extra wear, but as an indicator of wear. When the gold is gone and it's black, you know where you're at. same goes for silver instead of black. It's always up to the customer on what to do, but it is a nice indication method.
all the stock OE intakes are nylon 6 if memory serves.
nice to see you back at it John!
Hmmm, Isn't just the upper intake manifold plastic?
Originally Posted by TonyD89
In industry, we've DLC coated nitride for extra wear safety. We've also TiN over DLC regardless of nitride, not so much for the extra wear, but as an indicator of wear. When the gold is gone and it's black, you know where you're at. same goes for silver instead of black. It's always up to the customer on what to do, but it is a nice indication method.
That's really neat , I'll see if I can get a quote for DLC coating, but to be honest, if I can get similar wear as stock then I'm already more than happy.
Today was a good day, The cnc was plowing through aluminium, ran perfect all day, no issues Got the 2 other intermediate plates roughed in. Lot's of machining still to do, but making progress
While that was running I did all sorts of stuff. I did a few spherical shock top bearings things for a friend, and messed around in cad with the intake manifold thing. I tried some more designs, and couldn't think of anything I liked. Someone here mentoned a split design with a lower intake manifold and an upper. I thought it was difficult, and not as compact, but I drew it in, and it looks like it will work really well
Nice thing is that because it's only a 50deg. bend, I won't need to do multiple pieces and welding. This can be machined from one 4x4" bar, with one easy fixture I can get 95% of the port cnc-ed, with only a small amount of hand finishing needed. Unless I think of something better it looks like a winner
I know I mentioned it and that is exactly as I imagined it.
Originally Posted by John Huijben
While that was running I did all sorts of stuff. I did a few spherical shock top bearings things for a friend, and messed around in cad with the intake manifold thing. I tried some more designs, and couldn't think of anything I liked. Someone here mentoned a split design with a lower intake manifold and an upper. I thought it was difficult, and not as compact, but I drew it in, and it looks like it will work really well
Nice thing is that because it's only a 50deg. bend, I won't need to do multiple pieces and welding. This can be machined from one 4x4" bar, with one easy fixture I can get 95% of the port cnc-ed, with only a small amount of hand finishing needed. Unless I think of something better it looks like a winner
This last 2 part design you have done is by far the neatest and well thought out. Sometime you just need to take a step back as the obvious is steering you right in the face. Loving how the irons are coming along too!
I noticed the O-ring encompasses both ports without a divider, is that intentional? Would that cause fueling issues with air leaking between the ports?
Not sure. There just isn't enough room for an o-ring in between there. Maybe lose the o-ring and use a paper gasket?
Update
Todays update is a sad one :-(.
I'm swapping the white chassis for another one.
Reason is that when I build the chassis, My goal was to do time attack racing... but now, two years later my goals are a little different. Now I want something that I can use on the street, and maybe do a few track days per year for fun. This is also why I'm changing the engine to side ports. Now modifying the white chassis to do this isn't that easy. It doesn't have a title anymore, it's beginning to get a little rusty from sitting around and getting an interior in there is tricky. I think it's just easier to cut my losses and start with another chassis.
So after going back and forth I got another one, it's also S4, same year and everything so all the parts swap over, and yesterday I removing everything from the white chassis (and I mean everything, it's just metal now).
The chassis I got is actually a complete car, It doesn't run but everything is there. the PO started modifying it, but never finished it, outside of the car is not so good, it's got S5 doors in a different colour, paint is faded, but the inside is a nice! It's got a black turbo interior. Engine is a stock 6-port, I actually plan to get it running with this engine first, so I can drive it around while working on the awesome engine :-).
So today I started work, I wanted to swap both the front and rear subframes entirely, but after taking a closer look, I found new poly bushings everywhere, fresh calipers with race pads and braided lines, adjustable links, and more nice stuff, so I just put the S4 diff with modified LSD in there, and the coilovers.
After that I pulled out the engine. Car has been sitting for a while, and I wasn't sure about the condition, so I want to open it up, and check everything out. Probably put in some 2-piece apex seals and viton waterseals while I'm in there. Wierd thing is that I don't think it's the stock engine. It's got the rotating aux sleeves, which I don't think the euro cars got, I've never seem them anyway. Hopefully I can open up the engine tomorrow :-).
Last edited by John Huijben; Mar 4, 2017 at 06:08 PM.
Indeed. there are more differences, this one has a crank angle sensor and seperate coils, normally there is a distributor. exhaust is different and the ecu and some of the wiring is different aswell. When I got the car the plugs that matched were plugged in, but the ones that are different weren't. maybe partly why the project stranded?
Anyway, got the engine cleaned and disassembled. No surprises, engine looked unopened with normal wear. Ordered 2 piece apex seals and some gasket stuff, so the engine can go back together soon.
All of them have the aux sleeves.. Is it a late 87' model? some of those do not have the distributor, at least the turbo models. Im not sure about the egr valve, i think mine also had it, can't tell, i also had a usdm model
Good luck with the new chassis!
I believe the early euro S4 engines used throttle valves instead of sleeves in the aux ports and the early ones did have a distributor instead of waste spark coils.
John, I know this is a process and you are learning as you go. With as few 4 rotor builds that are out there; have these engines been proven for any length of longevity?
Other than a 24hr race. Has anyone street driven a 4 rotor for any significant length of time with significant mileage of 10k, 15k or more without bearing failure or other engine failures?
Maybe it's a stupid question as most people wouldnt consider a 4 rotor build at the expense verses an LS Swap that would provide cheap reliable power.
But for those after more then just power. Is the 4 rotor anything more than just a race motor? Is it realistic to think you could buy a 4 rotor and put it in a street car and expect to get a favorable result?
I'm not John, but I do know the price of admission to a 4-rotor is steep. I think when people buy them, they do not have longevity in mind. I believe that Zach is the only one who will try to get some miles out of his, but that is a TBD issue. I suppose for $30-50k, you expect the engine to last as long as a regular 13B PP engine.
I'm not John, but I do know the price of admission to a 4-rotor is steep. I think when people buy them, they do not have longevity in mind. I believe that Zach is the only one who will try to get some miles out of his, but that is a TBD issue. I suppose for $30-50k, you expect the engine to last as long as a regular 13B PP engine.
I appreciate the reply. Yes the price is steep when you match up the power with other comparable offerings like LS swaps, 13 and 20B turbo builds.
There is something inherently special about the 4 rotor. It came so close to going into a street car when Chevy tested one in a Corvette several years ago. It has that sound that is the epitome of engine sounds. Without buying an exotic with a flat plane crank you aren't getting close otherwise.
Having owned an LS3 Swapped FD, Single and twin Turbo 2 rotors I like the linear power of NA engines as well as the typical reliability of an NA rotor motor. The promise of the 4 rotor is the power of a turbo rotary without the turbo and the linear power all with the bonus of the F1 sound. Maybe it's asking too much of these Bespoke engines? Figured I would ask here if it's being done.
The other consideration is that you can get 400hp/400tq out of a V8 NA, where you will struggle with a rotary engine that is not turbo. Also, a V8 RX7 can get upwards of 30mpg. A 4 rotor will get probably a third of that at best. There is a reason so many people go V8, but you can't deny that sound and the bragging rights a 4 rotor gives you.
I appreciate the reply. Yes the price is steep when you match up the power with other comparable offerings like LS swaps, 13 and 20B turbo builds.
There is something inherently special about the 4 rotor. It came so close to going into a street car when Chevy tested one in a Corvette several years ago. It has that sound that is the epitome of engine sounds. Without buying an exotic with a flat plane crank you aren't getting close otherwise.
Having owned an LS3 Swapped FD, Single and twin Turbo 2 rotors I like the linear power of NA engines as well as the typical reliability of an NA rotor motor. The promise of the 4 rotor is the power of a turbo rotary without the turbo and the linear power all with the bonus of the F1 sound. Maybe it's asking too much of these Bespoke engines? Figured I would ask here if it's being done.
In context, high strung rotaries(even pport) are more reliable in racing than their piston counterparts. There are side-port 4 rotors, like scoot. And, I don't see why you couldn't expect reasonable longevity out of one, assuming you're not driving it at 10/10ths its whole life. v8's have plenty of reliability issues when driven at the edge.
I think the reason no one gets any real longevity out of the 4 rotors (main bearing wear) is that it is critical to line up the 4 eccentric shaft bearings perfectly and keep them in line and the Mazda stacking rotary is the worst possible design when trying to achieve this.
Then you have the added issue that when the engine does flex from combustion pressure, the stack does not flex along the eccentric shaft center line.
There is a reason Mazda stuck to 2 bearings in the 13B (any 2 points creates a straight line for the eccentric shaft)
And a reason the 20B had factory recall to replace all the eccentric shafts with a new design with an updated coupling (on a very minute level the 20B front shaft has to be semi-floating between the taper on the main shaft and the front bearing on the slip-over shaft.)
Same reason the R26B used a 2 rotor eccentric shaft with a slip-over shaft front and rear.
You can actually see the wear on the taper of a used 20B eccentric shaft coupling, my guess is Mazda's design change was the angle between the male and female sections are not 100% the same to allow slight "float" when it has to.
I don't know how John's eccentric shaft will cope with this. The 2 rotor plus 2 rotor slip over design uses the same idea of any 2 points creates a straight line, but it will have to have twice the clearance between the main shaft and the slip over shaft to have the same "float".
The Western mind thinks of rigidity as strength, the Eastern mind knows that flexibility overcomes rigidity.
以柔克剛
4 rotor is like a flat crank V8 in more ways than one. Good for racing and "reliable" with the proper rebuild schedule. That is race reliability, but not longevity in terms of 100,000 or 200,000 miles.
Since you have to cut the firewall to keep a 4 rotor RX-7 from handling like an inline 6 Supra anyways I am thinking I might do the tried and proven method of coupling two 13Bs together with a flexible coupler for a budget 4 rotor on my RX-8.
Well most 4-rotors aren't build to run like stock and last a long time. At least I haven't seen any. I think there isn't really a point in that (Says the guy who is converting from PP to side port ), because by the time it's de-tuned enough so it runs 80000 or so miles it probably doesn't make that much hp, or sound that cool anymore, so whats the point?
It's really expensive aswell. Not just building it, but think of all the fuel needed to actually run that much miles
I'm not sure the main bearings being out of alignment is that big of an issue. When all is machined well it should be concentric within 0.01-0.02mm's or so, and it really doesnt take any effort to "bend" an e-shaft that much, you can do it with one finger.
Anyway hope to get back to that soon. Really need to get that thing going again. Stuff is getting in the way again though. I'm currently getting that stock US 6-port back together so I can at least drive a rotary on the track, but ehhmm.. yeah It got a bit out of control... again. It's still a 6-port though
for a one off is not that bad.
, I'll see if I can get a quote for DLC coating, but to be honest, if I can get similar wear as stock then I'm already more than happy. 
