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RXBeetle Reader
3/5/16 7:36 p.m.

This project started about the same as my FB RX7, smokey. I've had my RX7 for 4 years and daily drove it for 80,000+ miles. I bought the RX8 for just over challenge $$ with a blown engine. The RX8 started and "ran" but the engine was toast, likely an oil control ring failure and a bad oil metering pump sensor that kept throwing it into limp mode. I've had a 6-port 13B sitting on an engine stand for years with the intentions of putting it in a few different chassis over the years. I bought the 13B off John Brown, and rebuilt it along with street porting the intake and exhaust.

The goal is to match the power of the Renesis with the ported 13B. I built the engine with the intent of turboing it but that's down the road. The Renesis engine came out pretty easily despite my HF engine hoist being delivered sans caster... wtf

The 13B mounts right up to the trans but after that its time to get creative with the welder. There are some real nice (pricey) mounts for the 13B-RE engine. I don't have an RE but I like the mount design.

Why are there a bunch of welded up holes you ask? I drilled the whole thing backward... weld weld weld, redrill redrill redrill.

I started with some steel angle iron, I'm also running a 12A front cover so the fabbed pan seals that up as well. I made a baffle to cut down on slosh, the oil pan is deeper than the RX8 but shallower than the S4 pan but still holds 4 quarts. Teadplate because why not

The crossmember replaces the stock stamped unit. 2 urethane mounts connect the dots between the pan and the crossmember. After some POR15 engine paint:

It fits!!! Kinda, the header (cheap-o OBX stainless) needed a ~10-deg cut/weld at the flange to get it to clear the crossmember.

A little Tractor Supply black paint on the engine bay before the engine went in. A few more engine details:
-ACT streetlight flywheel and clutch -JW Performance 4 barrel intake manifold -Speedmaster 4 barrel throttle body

I've got some more progress I'll post pics on soon. Lots of little things that eat up hours. injector bungs, throttle pedal, cable, coil mounts, etc.

chandlerGTi UberDork
3/6/16 6:58 a.m.

Nice work, looks like fun.

JtspellS SuperDork
3/6/16 7:11 a.m.

Nice!! It looks odd to see a carb in an 8 chassis though lol.

RossD UltimaDork
3/6/16 7:25 a.m.

Nice work.

RXBeetle Reader
3/6/16 6:01 p.m.
JtspellS wrote: Nice!! It looks odd to see a carb in an 8 chassis though lol.

I had a chuckle at it as well. I seriously considered throwing the 12A dizzy and a 600cfm Holley I have on there to get it running but decided against it. I am topping it off with a big round air filter. The 4 barrel stuff makes it cheap and easy and I get more surface area cheaper than a cone filter. The intake manifold clearance is a challenge and the 4 barrel intake clears with just enough wiggle room.

MS3 will run the engine but I have to keep the stock ECU for now to keep the electric power steering and some body control stuff functional.

BoxheadTim GRM+ Memberand UltimaDork
3/6/16 6:20 p.m.

Nice work. I especially like the creative use of diamond plate for the oil pan.

RXBeetle Reader
3/31/16 12:12 a.m.

Some more no-particular-order updates. Exhaust is 95% there. I'm using a cheap-o stainless OBX header and a magnaflow 6" round muffler, after that it's just the factory RX8 exhaust. I reused the doughnut flange from the stock exhaust. Only problem was the inside was so caked with carbon and oil it ignited when I welded it to the muffler... The header is for an FC and didn't clear the new crossbrace/engine mount. I had to cut the primaries off the engine flange and hack at it with the angle grinder to rock the header up and closer to the engine. I welded in a couple of EGT bungs and moved the O2 bung to the collector.

The coil bracket has taken me way too much time but floating 4 big bricks (FC trailing coils) in space and connecting all the dots didn't turn out too bad. The coils just didn't seem to have a happy place they wanted to be in the engine bay. (Lokar throttle cable poking through the fire wall under the coils)

The pulley alignment was a hot mess. I wanted to use the RX8 AC pump and alternator, but none of this bolts to the FC block. I welded up some monkey bars off the side of the engine to hit all the points which let me move the alternator over to the driver side to make room for some future induction plans.

That all went great but I realized the water pump was way out and the RX8 pulley was too shallow with the FC pump. High rpm and rotary water pumps aren't a good combo so I wanted to stuff the biggest pulley I could in the space I had. I found a Jones Racing pulley that seemed like it would save me from doing any machining, almost... I turned a little sleeve to hold it all concentric and still had to take a mm off the back of the pump housing to get everything lined up.

The intake manifold is a disaster. It's a JW 4-barrel intake and I'm sure it flows a ton but the runners took a lot of cleaning up with the ole Dumore. The flange matches the engine ports well but the hardware doesn't have a finished face to snug against. More buzzing to do there. I poked a couple holes in the secondary runners and welded in some bungs. I have a pair of ASNU 1000cc injectors to fit there, still need to make the secondary fuel rail.

I've done quite a bit of work on the fuel system but need to snag some pics. I have a 340L/hr Aeromotive drop in pump and I'm doing a lot of mods to the fuel module with the goals of increasing the bowl capacity (remove filter and replace with external) and get the siphon jets to flow more (plumb in parallel instead of series. Should I have just picked up the improved S2 fuel module? probably, but I'm stubborn and like the challenge.

Other odds and ends include oil filter bypass (remote filter), mold almost done for an fiberglass air cleaner base, welded up a throttle pedal, and fabbed a crank position sensor bracket. It's getting warm out and I'm getting anxious. As soon as I finish the fuel system it's on to cooling and ECU.

RXBeetle Reader
7/22/17 12:55 p.m.

Well I guess this is a long overdue update. She runs! Here's a bunch of pictures from some of the more fun projects involved.

Splitter - The OE radiator ducting was missing and the cooling could barely keep up with 70F cruising without good inlet ducting.

ECU Harness - I'm half color blind and wanted a solution that didn't involve buying dozens of different color spools of wire I could barely distinguish. Winter is cold and my basement is warm so I took the time to cobble up a wire printer from an ebay laser printer, a servo, a gutted mouse, and an arduino.

20AWG, no problem

Back in my FSAE days A buddy and I designed a daughter board that fits in the MS3 case and handles all the drivers and signal conditioning routed through a nice sealed Molex connector. I had a few more boards printed up and got to soldering.

Fuel - I've got overhead for E85 and a turbo because RX8 450cc primaries and 1000cc ASNU secondary injectors. I gutted the stock pump module filter for more volume and put an F250 inline filter down stream. The pump is a drop in Aeromotive 340L/hr. All of the return flow goes through a couple venturis to draw fuel from both sides of the saddle tank into the pump cup. It's really clever but it's not designed for 3x the flow so I opened up the venturi nozzles.

I've hit a lot lot of snags along the way and I still have a lot of little things to do but the basics are working really well. More updates to follow, hopefully more frequently.

JamesMcD SuperDork
7/22/17 1:14 p.m.

I love this. Being able to see the top of the "keg" in an RX8 is awesome.

stuart in mn
stuart in mn UltimaDork
7/22/17 3:00 p.m.

Labeling the wires is a genius move.

fidelity101 SuperDork
7/22/17 7:47 p.m.

good damn this is clever! i have had similar ideas but I like your execution a lot!

appliance_racer Reader
7/23/17 7:52 a.m.

I'm concerned your splitter may be creating a lot of lift as it seems to be floating in mid air on its own.

Excellent work on the car!

RXBeetle Reader
7/23/17 12:37 p.m.
appliance_racer wrote: I'm concerned your splitter may be creating a lot of lift as it seems to be floating in mid air on its own. Excellent work on the car!

Thanks! The hovering splitter is upside down, just flip it over for downfarce.

RXBeetle Reader
12/14/18 12:07 p.m.

The latest progress was supposed to be a (last) winter project but life/work/house/death/family have been a higher priority for much of the year. I did finally get the car back on the road with the addition of a lot of cut, ground, bent, and welded aluminum and steel. Oh and a Borg S360 turbo.  I managed to get out for one test drive. I live on  dirt road and really dont want to spend the winter playing with a salty muddy mess. I had a really rich swag tune on it causing missfires above ~7psi but man was it good to get that one drive in and hear the turbo spool. 


This started with the idea that I would build a turbo manifold and downpipe and plumb that up to a water-to-air intercooler hat for my 4150 4 barrel manifold and throttle body. Simple right? Well project creep hit me hard and I made some real good excuses to re-do all the little things I didn't like.

I'll add some details on the build shortly.


FunkyCricket Reader
12/14/18 2:56 p.m.

Oh, i just made this.. no big deal... 


what ever, that is redonkulous. thanks for sharing. It's a really cool build.

RXBeetle Reader
12/14/18 5:57 p.m.

I started with the exhaust manifold as turbo placement seemed like might tightest constraint. That was true, but getting the hung off some weld ells was pretty much tipping the first domino.

-Jigging flanges for turbo placement-


-Cut grind, cut grind, cut grind-

-Welding happened somewhere in there and the resulting flange warp had to be made flat again-

-V-band the the turbine housing to replace the wonky OE flange-


APEowner GRM+ Memberand Dork
12/14/18 6:09 p.m.

Cool car but I really dig the laser wire printer. I don't suppose you've got a build thread on that somewhere, do you?

RXBeetle Reader
12/14/18 6:35 p.m.

This is about when I realized intake wouldn't go on/off without the turbo making way. I weighed my options and started in on what was probably the most time consuming part of the project. I had the original manifold so I buzzed the flange off that and started ordering mandrel bends and running the numbers to get the geometry that would give me the runner length I wanted while having all 4 tubes end in teh same plane. 1.5" primaries and 2" secondaries. I picked up the intercooler from a friend years ago with the intention of getting it on this engine at some point. I'm not real sure how much effect having the intercooler post throttle will effect response but it's pretty common on a lot of production cars. 

-Carboard Aided Design-

-Cardboard traced and buzzed out of aluminum. I debated machining some bellmouths but I was worried it would put them too close to the intercooler. A friend has a speed/resto shop that let me use his dimple dies to form some pretty nice radiuses that I welded and blended into the runners. You may recognize some of his paint work from enginerd's ACR neon.

-weld inside and out-

-Had to make a tool to bend the edge up to get a little more rigidity and nicer look-

yes this was done on my counter while my wife was away... 

-connect the dots-

-wash rinse repeat with some hammering, torching, and clamping mixed in-

-Throttle body goes here-

-Injectors here-


All this work left me with a long list of issues. The turbine housing was a fingers width from a brake line. The t-stat outlet was pointed at the charge pipe, the water pump inlet was pointed at the turbo, the radiator and oil cooler would be a wise idea but not worked out yet. 

RXBeetle Reader
12/14/18 6:36 p.m.
APEowner said:

Cool car but I really dig the laser wire printer. I don't suppose you've got a build thread on that somewhere, do you?

No build thread, but I should do that. 

wheelsmithy GRM+ Memberand SuperDork
12/15/18 8:41 a.m.

Yowza!, this is way cool. 


JtspellS SuperDork
12/18/18 2:55 p.m.

Still love everything here, good luck!

RXBeetle Reader
12/19/18 5:55 p.m.

A little background on the old 6-port keg. I had to look back at old rx7club posts, apparently I started building this engine back in 2005... 

The street port is from racing beat templates if I remember correctly. I pulled the sleeves and filled the aux ports with Devcon epoxy to blend it in. I also ground the and lapped the irons myself and sent them out for ion nitriding along with the stationary gears.  

-Primary port-


-Exhaust port with the N/A diffuser ground out-


The N/A rear iron has a pretty flimsy dowel pin land so I added 2x 9/16" OD tension bolt sleeves on the rear housing.

 I think the 4-port has proven to be a better starting point but I'm working with decisions I made over a decade ago. 

Today I'm working on plumbing intercooler heat exchangers. $40 ebay AC condenser sectioned in half makes for two 9"x12" cores T-ed to run in parallel. I welded on a bracket to bolt these in place of the stock oil coolers. I'm using a 500gph "tsunami" bilge pump. No idea how well this will work but I've got some months to find out. 



Rain and snow in the forecast, no joy.

RXBeetle Reader
4/12/19 12:03 p.m.

I spent the winter making a 3" exhaust into 2x 2.5" mufflers where the stock one was as well as doing little detail work and correcting things I had rushed through earlier. The  results seemed worth it. The weather broke, my road were freshly graded and it was turbo time. 


I worked my way up through the fuel map letting autotune pull back the fat base map I had. unfortunately I kept getting a bad missfire/backfire around 5000rpm at full boost (~15psi). The logs showed I had a bad transition on my staged injection transition, a carry over from N/A. I fixed that but no joy. My next theory was a rich misfire causing a negative feedback loop causing a worse rich condition. I was seeing low 9s for AFR. I leaned out the high load map based on the lower kPa cells and gave it another go. 5000rpm came up real quick followed by the loudest backfire I've ever heard. I hit the clutch and brake and watched the tack drop to 0. I popped the hood after coasting onto a side road. Oil was everywhere on the drivers side and the silver engine paint made a large crack in my front side plate very obvious. Two things were in my favor, I was close enough to home for the free AAA tow and they had me and the RX7.9 back in the garage in time for SWMBO's tacos. 


I pulled the plugs last night with no sign of detonation and my bore-scope shows all 6 apex seals, at least what is in view of the plug hole. It's been a rough week. Time for a tear down. 

I am kicking myself for neglecting to put the SD card in so no log of the event. The relationship to speed and load suggest an ignition issue. That seems to be a common theme for backfire/broken front irons. 

BirgerBuilder Reader
4/12/19 3:02 p.m.

Hopefully it's not too berked. This build is sick! 

Bent-Valve Reader
4/12/19 3:50 p.m.

As I reread this entire thread I got the full range of emotions. From a goofy smile looking at the carb to a bummed frown looking at the cracked plate.

BirgerBuilder said it best "Hopefully it's not too berked."


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