What Are The Best Motor Swap Alternatives For A Mazda RX8?

The RX8 was the last Mazda (and production car, in general) to be powered by a rotary engine. While it was supposed to be a swan song, in practice, the dinky little RENESIS wasn’t the end-with-a-bang kind of engine, in the same vein as the legendary RX7. But, if you have the technical know-how and patience, the Mazda RX8 is the ideal platform for a motor swap.

Still, with the ability to rev up to 10,000 RPM, the RENESIS rotary motor in the RX8 was certainly a unique and lovable engine. So much so, that it *almost* made up for its horribly poor unreliability, particularly among the earlier examples of the RX8. This included, but wasn’t limited to, engine failure, excessive oil consumption, and bad quality control.

While diligent and very regular maintenance can make the RENESIS quite a reliable motor, what can’t be helped is the poor fuel economy. Besides low MPGs, emissions weren’t a strong suit of the RENESIS. On top of that, with a fairly limited amount of headroom for how much power you can really get out of the RENESIS, there’s only one viable option; a motor swap.

But, what with, you might ask? Well, the Mazda RX8 is incredibly versatile if you need to do a motor swap, and it’s quite receptive to varying engine types. LS and JZ swaps are awesome picks for a motor swap project on the RX8, if you need the extra horsepower. Or, you could also consider a Nissan SR swap, or with a fellow rotary engine, the 13B-REW.

What Are The Best Motor Swap Options For A Mazda RX8?

Before you commit to a motor swap project on your RX8, there are some things to be wary of. For starters, while the RX8 does have a long hood and a lot of space to fit a bigger engine in there, you’ll probably muddle the stock handling dynamics. This is because Mazda tucked the small RENESIS far back in the engine bay to ensure optimal weight balance.

On top of that, a Mazda RX8 motor swap project isn’t as straightforward, either. The RX8 can be quite tricky to work with, especially with it being a newer car. As such, it has a CAN bus, and you’ll need to sort out the gauge cluster, electric steering, ABS, sensors, and ECU while making these compatible with the new motor. Still, once that’s done, it should be easier.

The LS V8 is the most commonplace and most well-documented RX8 motor swap option. Otherwise, if you can’t get an LS or just don’t want it, the icons of JDM, both the JZ and RB series of motors, are compatible options. Inline-4 engines are another popular choice for swapping into the RX8, especially the SR20DET. You could even swap in an RX7 rotary!

With that in mind, here are some of the best motor swap options for a Mazda RX8…

1. General Motors LS V8 Swap

Possibly the most ubiquitous Mazda RX8 motor swap candidate, it’s no small wonder that the LS V8 is amongst the first swaps to be conducted successfully for the RX8. Not to mention, it’s also one of the easiest to perform, and most well-recorded. The LS family is broad, but the 5.7-liter LS1 and 6.2-liter LSx are ideal for the RX8, but any LS will work.

The LS V8 motors enjoy the distinct benefit of being extremely prevalent, so parts are readily available. It’s also relatively powerful; at least 300 horsepower. But, more importantly, it has lots of torque down below. Despite boasting a much larger displacement, the LS motors can be pretty economical, even more so than the RENESIS. 25 mpg is entirely possible!

Of course, if you feel that it lacks zest, the LS enjoys a massive aftermarket. Of course, there are lots of different transmissions available for it, depending on how much power you want and what you prefer. The T56 is typical for manual drivers. Depending on how much you’re willing to spend, 450-500hp is realistic with basic forced induction or an N/A build.

There’s also no need to cut into the firewall. With lots of guides to work with, it’s possible to build up your own swap kit. However, third-party kits are also available for it. They may not be completely plug-and-play but do cut down on required fabrication work. It also sits well back, but the motor does hang over the front wheels.

2. Toyota UZ Series Swap

If you want to deviate from the norm, the Toyota’s V8 option offers a feasible RX8 motor swap to make. The disparity between the UZ and LS families is that the UZ motors are DOHC or QOHC, rather than pushrod. While many believe that the UZ engine won’t fit inside the RX8, people have managed to accomplish this, some even tucking the motor neatly inside.

The UZ, like the LS, spans a long period but has a much smaller family. While the 2UZ-FE will be easiest to find, it’s more suited to brutish SUV implementation due to its low-revving design with a durable but heavy cast-iron block. Therefore, either a post-95 1UZ-FE or a 3UZ-FE will be ideal. These are all aluminum, with forged rods and high compression.

Post-97 1UZ-FE received VVT-i too. Nevertheless, the 4.0-liter 1UZ-FE will at least yield 256 hp and 353 Nm of torque, while the newer 4.3-liter 3UZ-FE should provide 282 hp and 417 Nm of torque minimum. Either way, Toyota is known for overbuilding motors, and the 1UZ-FE is especially rugged. Both the 1UZ-FE and 3UZ-FE are noted for their reliability, too.

While performance mods aren’t as broad for the UZ motors compared to the LS, people have commonly incorporated forced induction for extra verve. For extra headroom, you’ll want the 1UZ-FE with its smaller bore, which means thicker cylinder sleeves. With a mild supercharger with a modest boost of 6 psi, 350 horsepower is more than possible.

3. Toyota JZ Series Swap

Possibly one of the most exalted motors of all time, the JZ family needs a minimal introduction. It’s also one of the more common conversions made to the RX8. Keep in mind that with one of these, your RX8 will most likely turn into a drag car or cruiser rather, than a time trial virtuoso. The big question is whether to go for the 2.5-liter 1JZ or the 3.0-liter 2JZ.

The 1JZ is a more realistic choice, being lighter and more affordable. Both have similar potential, but in terms of brute force, the 2JZ is difficult to argue with. Of course, there are different types of 1JZ and 2JZ, but if you’re not going for the GTE, it really is nonsensical to make the swap. You can expect at least 276 hp and 363 Nm of torque for the 1JZ-GTE.

And, 276 hp and 435 Nm of torque for the 2JZ-GTE. But of course, these numbers mean little considering that the JZ motors are almost always modified to some extent. There are stories of the non-VVTI motors running routinely at over 400 hp, without breaking a sweat. You could also pair the 1JZ-GTE and adapt it to match the RX8’s manual.

The 5-speed will be a better choice, with the same bolt pattern but stronger overall. And, with a better gear ratio for forced induction. Otherwise, a late model (~09) 6-speed can work. With an adapted bell housing, you can avert a whole lot of fabrication and extra expense. For context, the 5-speed R154 can sustain around 600 Nm of torque on stock internals.

4. Nissan SR Swap

Yes, it’s yet another Japanese motor, but there’s a reason for this. Nissan’s SR motors are one of the most well-known performance 4-cylinders out there. For any small front-motored, rear-wheel-drive platform projects, the SR motors will be given a thought. The most prominent SR motor is probably the SR20, though multiple variants of it do exist.

The most performance-oriented production variant is the SR20DET, perhaps most recognizable as the engine of the Nissan Silvia. While there is technically a more powerful variant, the SR20VET, it’s exclusive to Japan and super rare. Depending on where you sourced your SR20DET from, you can expect around 200 horsepower and 270 Nm of torque.

But the well-thought-out design of the SR20DET means that it can be taken to 400 horsepower on a stock block, with good cooling and stronger internals. While it’s a full alloy motor, the DET is still relatively heavy. For transmission options and compatibility, you can find aftermarket bell housing adapters to match the SR20DET to the RX8’s motor.

Otherwise, the SR20DET is often paired with the RB25 5-speed manual transmission, which can withstand mild modifications. If you’re bold, there are other inline-4s you can choose from. This includes the Volkswagen AG 1.8t 20v and the Cosworth YB 2.0-liter turbo. Alternatively, you could even swap in the Honda S2000’s F20C VTEC motor.

5. Mazda 13B-REW Swap

In the end, the best option may be to stick with what you’ve got. The RENESIS and the 13B-REW may have the potential to generate impressive power figures. But, if you can find the 13B-REW that came from the original poster child, the RX7, you can swap that in. The main advantage is that the 13B-REW enjoys a larger aftermarket appeal than the RENESIS.

Of course, the 13B-REW needs no introduction. It’s the sequentially turbocharged 2-rotor found in the 3rd-gen RX7. Emitting 255 hp and 294 Nm of torque, it was one of the first rotaries to put Mazda on the map. With stock internals, it’s known to have gone well over 400 hp. For extra speed, you’ll probably have to convert to a single turbo since a twin won’t fit.

The oil filler neck on the 13B-REW also won’t fit. And, you’ll have to shrink the lower intake manifold, using a power tool. If you want to maintain the spirit of the RX8, combined with the soul of the original, there are plenty of awesome threads online that you can check out. There’s one that’s powered by a big BorgWarner S466, currently producing over 500 hp.

Or, you could opt for a more humble, everyday 300 hp build. Other than that, give Rotary Works (US) and Promaz (AU) a look. They both manufacture kits for an RX7 13B swap. Or, if you’re insane enough, you could even consider a three-rotor, the 20B. Or even, you can technically even fit the four-rotor 26B, found in the rare Mazda Eunos Cosmo.

6. Some Honorable Mentions…

While the options we mentioned earlier are some of the more popular options, there are other, quirkier alternatives, too. The 4.4-liter M62B44 and 4.0-liter M60B40, both pulled from older big BMWs have been swapped into the RX8, with some success. That said, they’re going to be expensive to maintain. Not to mention, they’re harder to source and are low on power.

Or, you could downside even further, as there’s a lot of interest in a 6-cylinder-powered Mazda RX8. Narrow-angle V6s can be installed and tucked away neatly in the RX8. Perhaps the most intriguing among these, is the LFX swap, a 3.5-liter 54-degree V6 found in many Cadillacs. Then, there are the more creative, and less practical options around for a motor swap.

Enthusiasts have somehow managed to insert a 5.9-liter 6BT Cummins turbo engine into the RX8, affectionately granting it the RX-Hate moniker. It makes no sense but provides light relief. Or, how about the supercharged, fire-breathing M113 5.4 Kompressor which emits nearly 500 horsepower and over 500 Nm of torque (with the firewall cut)?

And, maybe even the Ford Windsor 351 V8, which is the predecessor to the current Ford Modular V8s. I’ve also seen photos of a Nissan 4.5-liter VH45DE-powered RX8 making the rounds. All in all, when it comes to planning a motor swap for an RX8, the sky’s the limit. V8, V6, inline-4, rotary, no matter which you prefer, with some ingenuity, you can make it work.