Mike Haecker

This is probably the most popular example. There’s also a twin turbo j32 s2000 making over 1000whp if I remember correctly. It also had mostly stock internals. (Edit, I found the video. It’s got aftermarket rods and a home made block fill, so not as stock as the one in the civic)


He never said he lost HVAC, so don’t assume. Obviously he had to cut some of the firewall. Big deal? You’d rather reengineer the steering geometry, than to trim the firewall? I’d cut the firewall any day to preserve the steering geometry that Mazda gave us from the factory. The hole could be patched too, if thats a concern. Not to mention how much less the v6 weighs compared to an LS, and how it’s weight is shifted further back.

Obviously this swap is for people who care to preserve the stock handling as much as possible, while still gaining more reliability and power than stock.

RX8J35

Been a long time since I was on the forum. To clarify I did consider an LS swap but the aluminium blocks with a t56 would run $6k plus cdn. This entire swap was much less than that. Also Mike nailed it with the last comment.

LS aluminium block fully dressed as my v6 is 100lbs plus,

I did not have to trim the firewall. I chose this so I can keep the motor as far back as possible. Trimming the curve in the firewall gave me 2 inches to move the motor back.

I also did this to reuse as much of the OEM parts on the car. Steering rack to the front bumper was unchanged.

Yes I still have my heater core I could have still kept my AC but just wasn't worth the hassle to me as our summer in Calgary isn't unbearable.

Been driving the car with the same setup and haven't had to fix anything yet.

Boost will be coming this winter! Now that i have added TCS.

furansu

Do you mind posting fresh images -- I'd like to see more, and know a bit more about the driveline changes and adaptations made.

J-series motors sound great and rev way better than you'd think a SOHC motor would -- not a bad choice in keeping to the spirit of the car.

rytomi

I'm curious about two things on your build...

Did you keep the stock diff or did you replace the gears? I would think the gearing would be awful on an engine that revs lower.
Also how do you control the engine? Did you adapt a Honda ECU to use the RX-8 instruments, or somehow reprogram the RX-8 ECU to handle the Honda engine?

RX8J35

Funny enough no i have not changed the rear diff. It is a 4.44 I have been looking for a 3.9 but difficult to find. I agree on the highway the gearing sucks i never need to downshift out of 6th gear to overtake though . Mpg was 9L/100km on a 50-50 city hwy drive.

I don't usually hwy drive the car so another reason I haven't rushed. With this gearing acceleration is good so once more no rush.

I orginally had the Honda ecm with an interface board to the Mazda ecm but now I run a MS3X and share oil pressure, coolant temp signals, wired the power, aux, and immobilizer outputs appropriately to get it all to work like factory. Used the rotary crank wheel and sensor for the steering rack.

Engine check light reconfigured to come on through the MSX3.

Used signals from front and rear abs sensors for the TCS controlled by the MS3x.

rytomi

That's pretty amazing. I didn't even know there was a box you could get to translate the protocols. You must have put a lot of planning into this swap.

JeffreyyyD

I’m actually looking to do this same swap over the summer, just wondering mainly about your intake solution/ trans adapter. The throttle body faces the flywheel on the stock J35, so how did you solve that? Also, if you have any information on your flywheel/ clutch setup, I would greatly appreciate it.

RX8J35

Hi, the intake runners and manifold easily rotates 180deg. If the motor is not mounted low enough the TB will require a bit of an angle to clear the hood. Trans adapter was a 2 piece total 1.5inch thick aluminum. The flywheel adapter was custom as well aluminum. I used a rx8 chromoly flywheel to fit into the adapter.

JeffreyyyD

Thanks for the reply. The transmission to engine adapter plate seems to be fairly straight forward I have started working on it a bit, it is mainly the flywheel adapter that is confusing me a bit. Do you have any pictures/sketches of it? I'm guessing you spaced out the flywheel adapter so that it retains its stock position?

RX8J35

yes you are correct I spaced it out. Check out my Instagram "wmscalgary" I have the pics there just easier.

Adonilan

Just like many here, I have been thinking about this very swap for a couple of years now. Glad to have found your instagram and posts here.

I picked up an RX-8 this Christmas and plan to do this swap. My plan is similar to yours and I plan to have this swap running as if it was factory. I plan to use a MicroSquirt to run the engine and the factory computer for everything else.

Any reason for the change of engine?
I am also looking to get a j32a2 since they are $200-$300 here but wonder what would be the advantage that got you to change yours.

also, could you share/email me the drawings for the flywheel spacer/adapter? I know I will have to modify the thickness of it depending on the thickness of the transmission adapter, but everything else should be the same (my car was automatic so I already have the lightweight flywheel from when the manual conversion was made).

RX8J35

Hi,

I swapped to the 3.5 as I got a deal on it and swapped the j32a2 heads on yo it as it has a slightly better cam and valves are 1mm bigger. Also just due to future plans I have for the car.

I'll have to dig up my dwgs. As that was since 2013 and a one off. I recommended to another member to look into the miata jswap kit with a miata trans in the 8. As it has all the parts and saves a lot of time. But its up to you.

As a heads up, I had reworked the firewall to keep my engine as far back as possible, basically removing the curvature of it. This allowed the steering rack to remain in its original position. And I didn't have to lenghten the driveshaft.

message me on instagram on Monday for the dwg.

dkslp

I’m also interested in this swap. Did you ever have any luck finding the drawings?