marcjj

Hey guys. I just picked up my 2nd RX8, and this one i'm swapping a K20A to replace the blown up keg. I've tried fixing the 13b, but it's just not meant to be and i'm not sinking another $300 on a futile effort.

SO, I got a K20A given to me for free. and so far this is my shopping list:
STEERING SHAFT EXTENSION 80.00
MAZDA RX8 TO HONDA K-SERIES K24 K20 ENGINE MOUNT BRACKETS $269.99
Honda K24/K20 to BMW M52/N54 RX8 Adapter Plate $389.00

I plan on fabricating brackets to lower the steering rack (looks pretty simple and straight forward).
HOWEVER, I live in Florida so I will go to any length to retain my A/C... so does ANYONE here have experience with customizing A/C lines for an RX8 swap??????????

TeamRX8

iTrader: (25)

you can likely take or send the hoses to a hydraulic hose&rubber company and they can change the hose length to whatever you need, but you’ll need to tell them how much longer they need to be.

where are you getting those parts; kmiata?

marcjj

Colins has a mount kit and adapter plate for K20a to RX8 transmission and mounts. Now I plan on leaving the AC compressor hooked up and I’ll try to make a bracket to keep it that way, but my biggest issue right now is this:

I have a bad left leg (torn ACL) so I need automatic. I’m mating the K20A to the RX8 automatic with the CNC machined plate. So I have to figure out how to make the automatic K20A flex plate and torque converter to match up with the RX8 auto tranny.. with a spacer maybe? Weld a plate?.. any ideas?

marcjj

Mazda RX8 Engine mounts Using Honda K24A2 K24 K20 K24W Engine this is the mounts and you can see the plate on the same page. The kit also has a flywheel that adapts the RX8 5 or 6 speed MANUAL.. so what do I do as an Automatic transmission?

marcjj

Hell, ill pull my rx8 tranny and see how it matches. I could always shave the auto RX8 bell housing and tap new mount points. This should get fun. All the k20a wiring bits and ignition so it runs like stock. I'll leave all the rx8 stuff as well.

TeamRX8

iTrader: (25)

huh, I never saw this before, thanks for the heads up

Honda K-Series to Mazda RX-8 Full Swap


I have no idea about the auto trans, did you ask them about it?

Stubbs

iTrader: (1)

The AC stuff is pretty straight forward. If you're keeping the radiator and stock condenser in the original location it's easier. If you need to use a different condenser make sure it's size correctly. An AC shop make the lines to connect the K series compressor to the evap, and condenser. You'll need the RX8 fittings off the condenser, evap and trinary switch as well as the fittings off the k series compressor. It's a pretty simple job for a competent automotive AC shop, if you have the tools and experience it's doable at home. The RX8 ECU controls the compressor, but you can bypass it by taking AC request wire from the AC amp to a relay and run through the trinary switch to the compressor. Or figure out how the honda ecu controls the ac and run it through that. If you look at my LS build thread, I recently answered a question about wiring the AC in more detail.

Also some food for thought, if you're willing to put in a bit more money and research time you could go with a dual clutch transmission. There are a few guys in Europe that are running BMW Getrag 7 speed DCT transmissions behind K20/24 swapped RX8s. There are adapters available for k series and there are a few ways to control them. Maxxecu has a full standalone ecu that also controls the trans. DKGECU and HGT Tuning have standalone transmission controllers they've developed if you want to use the Honda ecu to control the engine still. I know HTG Tuning has the capability to control the ZF 6 spd and 8 spd autos too. Cost isn't outrageous, at least compared to a T56, but it might be worth considering.
For the RX8 auto you'd need to get an adapter plate, custom flex plate, and figure out electronics to control the RX8 auto. Also you'll need to cut the cowl and firewall if you use the RX8 trans unless you extend the power plant frame forward.
If you already have an auto RX8 chassis it may be simpler, but I don't know how it'll react if the ecu is throwing errors because of missing sensors from the engine. Typically in RX8 swaps the ecu is retained along with oil pressure switch, coolant temp sensor, and RX8 e-shaft trigger wheel and sensor grafted to the new engine. All they are looking to run is the gauge cluster and EPS. The immobilizer is usually bypassed and cooling fans and fuel pump run off the new engine ecu, although some people have left those to the RX8 ecu to control. If you have a manual RX8 chassis, you'll need to source the wiring harness, transmission controller, gauge cluster, and shifter assembly. If you have to get an auto RX8 ECU it probably will need to be re-flashed at the dealer to match the TCM, and immobilizer. I'm not too familiar with the security stuff in the electronics as I eliminated the stock ecu in my swap, but there is some handshaking with the different parts of the canbus network for security. The RX8 transmission controller needs to see a few engine/drivetrain sensors(TPS/APPS, ECT, RPM) and it gets that information through the canbus network. VSS is sourced through the ABS so you'll need to retain that, but if you have a Bosch DSC/ABS unit the ABS and doesn't work. You'll need the base model Sumitomo ABS unit if you want functional ABS. The one that'll be difficult is the TPS/APPS. You could retain the stock throttle pedal and add an extension to actuate a throttle cable for the k20. That'll give you the APP signal, but since the RX8 throttle body can't be used that would likely give you limp mode that could interfere with how the transmission shifts.

marcjj

Great information brother. Thank u so much for the detailed information. I have an automatic RX8 which supposedly works great. I can still shift it in sport mode, so what I need is the K20-RX8 adapter plate, then need to adapt the rx8 torque converter to the k20a plate for the shaft to make a good connection with the rx8 tranny.i have some fabrication skills so I can possibly m(hopefully) make a plate myself. Then like you said I'll emulate the rx8 sensors over to the Honda motor. Maybe investing in AccessPort to control the rx8 ecu would be a good investment. I know eventually I'll need to either upgrade my Megasquirt to v3.0 or purchase a KPrO ecu. For now I plan on running the whole K20 harness, ecu immobilizer, all like it's still in the Acura rsx, just tucked away. The AC looks like it's mounted in the same spot so aside from bending and maybe a custom line, it looks easy to retain. I will be removing the 13b starting today. Gotta get some K20 parts as well. Woohoo

TeamRX8

iTrader: (25)

guess I misunderstood, I thought you were retaining and adapting all of the RX8 A/C components, Well, good luck.

marcjj

I'm doing a whole K20A swap, automatic RX8 with all the OEM features like sport shift and AC. It's going to be a pain but I have a daily to get me around for now. I know I'll need to hammer the firewall, cut cowling, cut cross member, possibly modify k20 oil pan, extend rack and pinion. The uncharted territory is mating an automatic K20 to an automatic RX8 tranny and controllers. I'm guessing I need K20 and rx8 sensors, wiring, immobilizers and ecu, etc.

marcjj

I'll be ordering the adapter plate by Monday. I'll start pulling the 13b and box up all the sensors and EMS stuff (trigger wheel, etc) to adapt on the K20. I haven't had to beat on firewalls since the LS/VTEC CRX days lol

TeamRX8

iTrader: (25)

Are you sure you have a grasp for what’s required on this? I couldn’t find an actual swap using these parts, but judging from the others I saw this is a major project. I don’t see how you’re going to keep the AC with the rear of the engine sitting back that far into the dash. You won’t be beating the firewall. You’ll be cutting a lot of it out as Stubbs noted above.

marcjj

Yeah, this isn't my first project of this type, but I was always working with OBD0 and OBD1 systems, so it was not controlled by 10 computer boxes lol

I ran 11.6 in a Civic coupe w/ a Cummins turbo I fitted onto a dohc 1.6L and had to weld the mounts solid, had a lot more in it too but I was suppose to be going into the Army, so I got rid of it. But yea, this has all been done before, but without AC and working automatic . My hard parts are done (mounts, adapter plate, s2000, manifolds etc)

marcjj

I also have this project.. AE86 GT-S coupe restoration. My baby <3

marcjj

There are some guys on YouTube who have used the same kit as Colin's but manufactured by PMC, it looks like the CAD file was originally open source because a few produce the same kit. https://www.drifthq.com/products/pmc...-k24-mazda-rx8

TeamRX8

iTrader: (25)

yeah, haven’t seen a completed one yet and by all accounts it’s more work than was anticipated

well good luck

marcjj

Got some things disconnected. Still a long way to go. Need parts for the K20a, need mounts, adapter, etc.

marcjj

She looks good too. 86k miles isn't much. She still has another 180k miles of good use!

marcjj

This one is K20A supercharged w/ AC

marcjj

Thanks. There enough resources I shouldn’t have a problem. Hell if I need to I’ll shift the whole mount set forward a bit if need be. I know I’ll need to notch the crossmember, they also make a dummy kit for that as well https://sasautoworks.co.uk/product/r...ame-notch-kit/ like I was saying; most of the hard work is already done and researched. I think I’m going to add another 5 quarts of oil sumped from the K20A pan back into the cylinder head, but that’s on down the road.

TeamRX8

iTrader: (25)

well there were a few done the hard way many years ago, but for current times I’m seeing a few that were started and still not finished along with my previous comments. I’m not saying it can’t be done or you’re not capable. It doesn’t look like a walk in the park. Which you could say about many RX8 swaps, but the K engine swap comes across to me as one of the more difficult ones.

marcjj

I already have the automatic k20a3 that was given to me with a video showing it run, I have the automatic rx8, and people have made the mounts and adapter plates. I'm sure I'll be back here with questions and complaint soon 😂

marcjj

I'm going to go get another hydraulic engine hoist and lift the front end so I can drop the cross member and engine out the bottom.