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RXBeetle Reader
4/18/19 1:06 p.m.

Good news to report, it's only minimally berked. Even better I picked up a parts engine that has all I need to get my engine back together. 

Engine came out pretty quick Saturday and I broke the engine down Sunday.

Broken here:

Scuffed here:

And here:


The rotor and housing may be reusable with some clean up with some abrasive stones but I'll hold off on decisions until I get some measurements. The teardown also revealed the Devcon smoothing my aux ports was starting to let go at the edges. It's not bad yet but I'm not waiting for that day to come.  I'm not impressed with how fast the Atkins solid corner seals are wearing my side housings. I don't have many miles on them after lapping and plasma nitriding them and I can already feel some slight wear. I think I'll be going back to stock for those. None of the apex seals (RA classic seals) were damaged luckily so I'll probably be reusing them. 


Some FB marketplace scouring, a trip to Detroit, and $300 returned me a pretty complete engine and trans drop out.

If anyone is intered in the trans ('86 S4 N/A) or other parts give me a shout. 




The spare engine had all the apex seals still in it with one broken corner seal that chewed up the rotor groove pretty good. Side plates looks in good shape, no cracks in the coolant seal groove, I'll just have to check it for wear and port the front one to match my rear iron. Luckily I still have my mazdatrix template hanging on the wall.  The housings are in pretty good shape with just the normal ~3mm of flaking on one edge in the exhaust area. One has a loose exhaust sleeve.  I don't need that housing for the build but it's fixable if needed. The good rotor is 1 letter (weight) off my good rear rotor, close enough. 


I ordered some LS2/truck coil packs that will hopefully resolve my misfire issues. I'm going to dop down to 7psi wastegate springs as well and sneak it up higher with electronic boost control as I get the fuel and spark dialed in well. The plan is to finish cleaning and measuring parts this weekend and get any seals/parts ordered asap. 

Truth be told, until I snagged the spare engine I was pretty seriously considering an LS swap. The rotary parts, even used, are skyrocketing in price and my sourced BOM for a L33 mated to T5 was ringing in at $2500. I don't play this game to make smart choices though; I want to have fun playing with engines and make loud turbo rotary noises. 



Bent-Valve Reader
4/19/19 10:37 p.m.

In reply to RXBeetle :

I love the Renesis engine in my RX-8. Yes, I'm borked in the head. But I understand the LS comment.

The car handles so nice if I couldn't fix the rotary I would consider a piston engine.


bruceman Reader
4/20/19 4:38 p.m.

Thank you for documenting this. I'm not building another Renesis for my Rx8, it will be replaced with an REW.

RXBeetle Reader
4/23/19 12:05 p.m.

At least I'm in good company here. 

I've cleaned and checked clearances on the old and "new" parts from the donor motor. Nothing concerning on the old parts, which is good considering I didn't have very many miles on them since the full rebuild years ago. 

I've been slowly chipping the Devcon epoxy out of my aux port and reapplying the old nasty methylene chloride paint stripper to break it down. I'm not sure how much power is gained by smoothing the port but its not worth risking.    

The biggest pain was pulling the blind roll pins to swap the exhaust sleeve into the replacement housing. The N/A sleeves have a nasty diffuser stuck in the middle for noise reduction. I've got a little bit of porting work to do on the replacement housing and iron to match my old parts but if all my parts come in I should be reassembling this weekend.    

Parts on order:

  • Side seals (OE Mazda)
  • Rotor bearing for the donor engine rotor
  • Coolant seals and other o-rings
  • Exhaust manifold gasket
  • Low boost wastegate springs
  • LS coils and harness




RXBeetle Reader
11/24/19 12:38 p.m.

Keeping with past updates, this is long overdue. 

Following up from last post:

  • Side seals (OE Mazda)  - Side seals ground / clearanced. Blow-by is almost zero so I'm happy with the time spent getting this right.
  • Rotor bearing for the donor engine rotor - old one pressed out, new one pressed in
  • Coolant seals and other o-rings - Atkins set  covered all the bases there
  • Exhaust manifold gasket - I tried a thick Remflex gasket, so far no leaks 
  • Low boost wastegate springs - Some measuring and math got me some springs that get me down to 7psi, this caused some issues...
  • LS coils and harness - $40 for four with the harness used OE from eBay

While I had the engine apart and ported the "new" front iron to match the rear, I ported and clearanced the oil pump which picked up some pressure. Engine assembly was uneventful.

Until I went to install the oil pump drive the next day and realized I had made the most boneheaded mistake at step 1....

Those famaliar with rotary engine assembly will recognize that the oil pump is not at the back of the engine and the flwywheel is not at the front of the motor. I had built the engine with the eccentric shaft in backwards... This took another night to disassemble and reassemble correctly. I was lucky the coolant seals hadn't swelled or anything. Test fit everything one last time and in she goes. 


RXBeetle Reader
11/24/19 12:39 p.m.

With it back up and running I had a few issues, summer was in full swing and cooling was adequate at best. The turbo was really slow to spool. Way lazier than even this 83mm compressor should be. Turns out those 7psi springs weren't enough to hold the gates shut. An electronic boost controller plumbed to the top of the gate really helped with that but it also showed that I was running out of injector. I band-aided that with a base fuel pressure bump and  sent my primaries out to Injector Rehab for a dec-cap and cleaning.  

The biggest issue with the cooling system is low speed stop ang go. I couldn't cram much fan on the short Sciricco style radiator and I'm a big fan of having cooling overhead. I had largely copied the RX8 radiator placement previously but I found I could put a pretty big radiator vertically. A big "hot rod" 2-1/4" thick two pass radiator. It required some modification (remove rad cap bung and lower hose barb. The results are great. I can sit in traffic on a 90F day and the single 12" Spal fan is enough to keep it cool. This meant that I could get it down to the dealership to have the airbag recall done. My wife was not a fan of me driving around with a grenade in front of us. Good to have someone looking out for you. 


RXBeetle Reader
11/24/19 1:30 p.m.

Somewhere in there I rerouted the filter to get it in front of the radiator and plumbed the blow off valve into the intake.


I fabbd up a new 3" exhaust system that splits into 2x 2.5" mufflers in place of the stock muffler. This proved to be a little obnoxious for my liking so I stuffed a magnaflow I had from ages ago right behind the down-pipe. That required some massaging to get in there but tamed it down significantly. 


I took it to a work car show and spotted (heard from a mile away) a fellow GRMer fidelity101's rally RX7.


So now I'm running about 10psi of boost and ripping the 255 RE-71Rs off it. Just taking my time dialing in the calibration and having some fun taking the long way home back and fourth to work now and then. Well, ok, not now. It's Michigan and terrible out. Project car hibernation time.


slowbird Dork
11/24/19 2:02 p.m.

This is awesome. I love the idea of keeping it rotary but going back to the old-school version.

Bent-Valve HalfDork
11/24/19 7:27 p.m.

Im glad is back up. I'll be driving mine to work tomorrow, might be one of the last drives this winter depending on the weather.

RXBeetle Reader
5/15/20 9:45 p.m.

Time for more progress reports. Summer ended with some terrifying sticking throttle. A little stuck is a big problem with a 92mm throttle. My budget ebay throttle let a screw go which let the plate slide and wedge. Terrifying. Lucky for me I was able to keep things under control and get it parked before entering low earth orbit. My intercooler plenum saved my engine from munching the screw and I was able to fish it out and reinstall the screw with the tools I had on me. I have since gone back and hit it with thread locker too.

Winter set in and I got to work on the longer term projects. Lots of power on tap, more than my 255 RE71Rs will hold, leads to wheel hop. The diff mounts were trashed so I upgraded those with some Whiteline urethane jobbies. I have yet to get miles on these but I'm hoping it doesn't make for too much harsh NVH. The car is pretty comfy and tolerable as a daily. 


Tolerable except for 2 things, exhaust leaks and lack of AC. I have been hanging onto the RX8 AC compressor and it looks like the suction line and expansion valve will work as well. So I still need a condenser, dryer, and a couple custom lines to connect the dots. Oh, and a crank pulley that won't hit the water pump pulley... Small issue, the 13B water pump housing puts the pump pulley too close to the RX8 AC pulley so I spent the better part of a night searching through rockatuo to find just the right size 4 rib pulley to get the clearance I needed. It will run the compressor a few % slower but that's better than hard parts hitting. I turned the RX8 pulley off the hub and welded on the donor 90s Jeep Cherokee power steering pump pulley. 

This jungle gym mess of a bracket bolts to the engine in 4 places and mounts the alternator, AC compressor, and RX8 tensioner. The AC pump and alternator keep the RX8 axial position if I ever feel like swapping to a shiny underdrive crank pulley, this was really protection for the possibility that I would screw up the frankenstein pulley job. 

Condensor from a PT Cruiser tucked up nicely on the radiator bracket I had fabbed up. That was more luck than forethought I'll admit. I still have to finish the lines but I have some time. It snowed last week...

Can't really see it in there, but it doesn't need to be see, just work. 



Fixing the exhaust leaks were a hell of a job. I am really space constrained with a big S300 turbo mounted really close to the engine and twin wastegates mounted low to keep them cool. My gates were hard plumbed back to the downpipe which made leaks pretty inevitable with heat cycling. It's not the prettiest or most flow efficient solution but it fits, seals, and has a little flex. 

The end result - NASA downpipe

Fits, ship it! Let's drive!

I think that covers all the snow weather efforts. Now it's time to throw insurance back on it and find an excuse to take some drives. My work commute has gone from a 40+ mile round trip to topping off my coffee as I shuffle to my garage workbench makeshift home office. Can't really take the RX8, it's already there. 

Bent-Valve (FS)
Bent-Valve (FS) HalfDork
5/16/20 2:05 p.m.
RXBeetle said:

The end result - NASA downpipe

My dad worked for NASA as an engineer, I got see lots of rocket parts, and yup, it looks like a NASA rocket engine pipe! LOL.

Now will it make it rocket around? cheeky

Nice work!


Truthfully it does look like the piping that goes from the turbine pumps to the combustion chamber or exhaust from those pumps.

Doesn't it go here and connect there?

bgkast (Forum Supporter)
bgkast (Forum Supporter) GRM+ Memberand PowerDork
5/16/20 2:17 p.m.

This is awesome. That wire printer is the best thing I have seen all week.

bonylad GRM+ Memberand Reader
5/16/20 4:19 p.m.

In reply to bgkast (Forum Supporter) :


The work on the whole car makes me feel inadequate with my little thread. Amazing work and I agree. The wire printer is the highlight. Have a problem? Hell I just make a machine!  Impressive either way!

RXBeetle Reader
5/17/20 9:05 p.m.

Thanks all. Bonylad, I feel the same way looking at half the builds on here as well. Consider this has been almost 5 years working on the car, and the original motor work was over 10yrs ago. It also helps that I probably have as mure fun designing/building than running or racing car. 

Bent-Valve, nailed it! Space hardware always blows my mind. You get the full spectrum of incredibly detailed spare no expense materials and machining and tin shed. The Saturn V looks like a manager said, "listen we can't just leave the tanks showing, make it look like a rocket by Friday!" and wrapped some metal roof tin around it. The lunar rover and lawn chairs have far too much in common to be a coincidence.  

And thanks for the reminder - I really do need to get a writeup on the wire printer. It's the cheapest laser engraver I could find (search 500mW NEJE) and the most crude methods to get an arduino to automate advancing the wire and clicking print. Really, I butchered a mouse to have the arduino "click" print in the software. There's a real possibility that I spent more time automating the process than if I had just sat there and done done the pull/click work, but what's the fun in that?

engiekev Reader
8/13/20 8:59 a.m.

The fab work on this build is crazy impressive! Do you have a background in fabrication?

Also very interested in the wire printer!

I think I have seen you fly by our house on Davisburg Road a few times in Clarkston, may be another black RX8 however.

RXBeetle Reader
8/13/20 8:04 p.m.

In reply to engiekev :

There is a 99% chance that was me, I'm up in Ortonville. Thanks for the compliments. I pretty much grew up in a machine shop, tack on a welding class and 4.5 formula SAE builds and I guess that counts as background. Now work is all keyboard wrangling so my build projects keep me sane. 

Latest progress has been a better boost solenoid and rerouted lines. A lot more fine resolution. Junkyarding was a welcomed trip out of the house as the lockdown orders eased up. I snagged a bunch of AC line ends and connected all the dots save for the suction line and high pressure line off the compressor. I found a local shop that crimped them up using my ends. The last obstacle was faking a coolant temp sensor with a resistor to get the stock ECU to kick the compressor clutch on. As of today I have my first project with AC! That won't last long though. One of the high pressure line crimped ends is leaking. sad I'll have to see if the shop can give it a little extra squish or something. 


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