RX8 LS Swap – Which LS Engine Fits The RX8 Best?

If you are the owner of an RX8 with an engine failure, fret not, you’re not the sole person. In fact, the RENESIS found in the RX8 is an engine known to fail. This is especially true when the owner doesn’t pay enough attention to care for it.

It’s important to note that the failure rate of the RENESIS is exaggerated. It was an entirely new engine with design oversights, just like many other first-gen engine innovations. Being such a common sports car riddled with rumours of constant flooding and premature engine failure, it’s also a very accessible platform.

Thanks to that, RX8 prices have been driven way down. And new owners of the RX8 may not understand how to maintain the RENESIS properly. In fact, the low barrier of entry often end up with new owners downplaying the care the RENESIS needs. Therefore, this typically results in a painful lesson in the way of a cooked RENESIS.

Whether if your RX8 engine failed on you or if you bought one as an empty canvas, an engine swap might be a viable solution. RX8s are some of the most common platforms people used to perform engine transplants and for good reason.

It’s a rear-wheel-drive platform, opening it up to an eclectic range of engine options. It also has a generously proportioned engine bay that can accept different engine configurations without needing major bodywork. Finally, it’s a relatively recent, common, and affordable car to buy with a rather taut chassis.

One of the most common engine swaps carried out for the RX8 is the LS swap. The primary reason being that many RX8s are bought over to the US and the LS engine is ubiquitous there. It’s also such a well-understood engine that commonly receives the engine swap treatment.

It’s a joke that everything that has been brought to the US will have an LS engine swapped into it at some point. However, there are many qualities that people adore in the LS, and for those handy at fabricating an LS engine might be easier to source than the RENESIS.

Thanks to that, the LS swap for the RX8 is regarded as the simplest and easiest engine transplant. The difficulty is relative of course. It’s still an engine transplant, which is a major job by any metric. However, it’s the most well-documented swaps, and there are swap kits available to reduce the fabrication work. If you have a good spec RX8 then a new engine can put new life into the car.

Even General Motors understands the popularity of the LS as a donor powertrain It’s even sold as a crate engine for keen modders in their project cars. That said, what does the swap entail, and why is the LS engine so revered?

LS Engine Information

LS Generation 3 (1997 – 2007)

For the rest of the world, other than Australia, the LS engine is largely unknown. LS refers to the nomenclature used by General Motors for their post-97 small-block V8 engines. GM refers to the prior and latest generation of their V8 as the LT.

It’s a bona fide clean sheet design forsaking the ageing LT engines. The idea is simple –  make a reliable, compact and lightweight V8 engine that produces good power and torque. It’s an all-new engine powering and introduced alongside the all-new Chevrolet C5 Corvette.

Because the LS family is absolutely massive, the engines are colloquially referred to as LSx engines. The x refers to the specific configuration of the engine, but because nomenclature consistency is somewhat blurry here, it can be perplexing for outsiders to understand the family.

The major departure for the LSx family of engines is the fact that it utilises aluminium cast blocks. This massively cut down the weight of the powertrain when paired with the aluminium cylinder heads. GM has also ditched the distributor ignition in favour of the modern direct ignition system.

Despite technically being from the same family, the LSx engines can vary significantly in terms of displacement, output and characteristic depending on its application. That said, the most common LS engines are actually the iron blocks Vortec engines that were put in trucks and SUVs. These have very rigid engine blocks, albeit with much more weight too.

It’s recommended that you stick with the LS series, as you’d want to reduce as much weight from the nose as possible. The Gen-3 engines are down to the LS1 and LS6, both are 5.7-litre V8s. The LS1 is most commonly found in the C5 Corvette and post-refresh fourth-gen Camaro. The Corvettes had the LS1 with the most output though, at 350 horsepower and 475 Nm of torque.

The Z06 C5 Corvette and CTS-V received the mighty LS6. It’s a very different beast altogether, with numerous modifications made to improve output. You can expect around 400 horsepower and 522 Nm of torque from the LS6. This is the most powerful variant of the 3rd-gen LS.

Generation 4 (2005 – 2020)

By 2004, GM realised the need for further modernised and higher output V8s. The main purpose of the gen-4 engines is to refine and innovate upon a solid foundation. Thus, GM incorporated VVT and cylinder-shutoff technology into the gen-4 engines.

This proved important, as these engines had provisions to support up to 7.4-litre of displacement. Electronic throttle bodies are also standard on the gen-4 LSx. The first to spearhead the new generation is the LS2 engine. It’s once again introduced alongside the then-new C6 Corvette.

The LS2 is a direct successor to the LS1. It had more displacement (6.0-litre), similar head casting to the LS6 and a higher compression ratio. This pushed output to 400 horsepower and 542 Nm of torque. GM also improved torque delivery throughout the engine operating range.

By 2008, Chevrolet knew the Corvette needed more grunt to remain competitive. Introducing the LS3 as the new Corvette default engine, it featured a larger bore to displace 6.2-litres. Along with revised, tougher block casting, larger rectangular ports, and multiple other performance enhancements. This pushed power output to 430 horsepower and 575 Nm of torque.

There’s also the LS7 engine, which is an absolute behemoth with 7.0-litres of displacement. GM sold aftermarket-purpose LS7s as the LSX crate engines. These produce over 500 horsepower and 637 Nm of torque. And while it seems quite unfeasible, people from Dyno Torque have fitted the LSX454 into an RX8 before. But they are some of the best in the business of V8 conversions.

Despite that, Chevrolet deemed the LS7 to be inadequate at propelling their halo Corvette. The manic Corvette ZR1 received the elusive LS9. It’s based on the LS3, which had thicker cylinder walls appropriate for forced induction. Displacement remained at 6.2-litres, but now supercharged with a sizable 2.3-litre Eaton Roots-type supercharger. This pushed horsepower all the way to 638, and torque to 819 Nm.

It also developed a variation of the LS9 dubbed the LSA specifically for the Cadillac CTS-V, HSV models and Chevrolet Camaro ZL1. Intriguingly, GM also sold the LS9 as a crate engine, but in limited numbers.

So Which LS To Buy?

It’s fair to say that I’ve barely scraped the surface of the LSx family of engines. People on a tighter budget have gone with the truck engines, but these are actually bulkier and require more work to fit in the RX8. The generation 5 LT engines can also fit the RX8. But prices of LT engines are quite high, and it’s more work to fit one in the RX8.

Commonly, people go for the LS1 or LS2, which are easier to source. These swaps are also well documented. That said, most agree that the engine you go for depends on your budget. All the LS engines have great potential to make a lot of power, so if you find a great deal for an LSx/transmission set, go for that one. You’re going to need the rest of your budget for the swap.

The T56 6-speed manual is the default transmission of choice for most folks. If more power is intended, the T56 can be built to handle it. You can also source a TR-6060 6-speed which supersedes the T56. The TR-6060 also features external shifter linkages that can be made to fit the stock RX8 shifter location.

That said, if you’re keen on building your RX8 into a cruiser, automatic transmissions can be used as well. The 4-speed 4L60 is a common candidate for that, but even the 6-speed 6L80 has been made to fit the RX8. It all boils down to your personal goals.

Things To Consider Making The Swap

Once you’ve found your engine and transmission, you now have to decide on the differential. If you’re sticking to the LS1 engine, then there’s the option to use the stock Mazda differential. It’s going to weigh less, free up much more space for exhaust routing, and should be more affordable.

However, if you decide that you’re going to need more power, then you have to ditch the stock Mazda differential. The Ford 8.8 differential is the default option. It’s commonly used for LS swaps, it has been proven to survive nearly 1000 horsepower and it’s quite common. As a bonus, the gearing is appropriate for a torquey V8 engine, which translates to better fuel economy and drivability.

Swap Kits

Unless you intend to make all the fabrication work yourself, there are a multitude of swap kits available to make your life easier. You’re still going to need to make modifications for the install, but it’s going to save you hours of labour.

Two of the earliest kits sold are from V8Roadsters and LS1RX8. Both are well regarded and reputable kit suppliers. V8Roadsters is known for its very well-built kit that’s been proven countless times. Their kit is more appropriate for late-gen LSx engines. V8R has built their reputation in supplying quality swap kits for MX-5s.

LS1RX8 specialises in RX8 LSx transplants and boasts a community solely for its LS swap kits. Its kit is based on the early Camaro LS1 engines. Either will require you to find the specific parts or make modifications needed to fit the engine though.

Depending on which kit you go with, you might need to find additional parts to make the LS fit properly. You only need to tell your kit supplier what exact drivetrain configuration you have, and they should be able to advise you on that. V8Roadsters also offers a complete turn-key package that includes everything you need aside from the drivetrain.

RX8 Steering Rack Relocation

A hurdle that you will encounter is the oil pan. The LSx oil pan will protrude over the RX8 steering rack, thus requiring a relocation. There steering rack relocation kits out there that drops the steering rack about 2 inches to clear the oil pan. With this method though, you’re going to affect the steering geometry. Therefore, you need a bump steer kit to correct that, which LS1RX8 sells.

The other method is to go for a hydraulic power steering rack conversion. In the V8Roadsters kit, the steering rack from the NC Mazda MX-5 is used in lieu of the stock electric unit. This saves approximately 35 lbs in weight. With their core conversion, the rack can be made to fit under the oil pan with the stock fluid ports.

Front Sway Bar Spacers

Next on the agenda is the front sway bar. The stock RX8 sway bars won’t clear the ancillaries of the LSx. LS1RX8 offers sway bar spacers to relocate the sway bar. The V8Roadsters kit has integrated sway bar mounts designed to work with CTS-V accessory drives.

Delete The Stock RX8 Power Plant Frame (PPF)

By switching to the LSx transmission, you’re going to need to delete the stock RX8 power plant frame (PPF). The stock RX8 transmission and differential are mounted with the PPF as a single rigid unit. Deleting the PPF means you’re going to need custom transmission and differential mounts. Both kits have provisions for the transmission mount but sell the differential kit separately.

Custom Propeller Shafts

You’re going to need custom propeller shafts to mate the transmission to your differential of choice. Fortunately, it’s possible to make your own measurements and have a propeller shaft made to fit your needs. It’s also possible to buy it straight from the kit providers. They both provide ready-made driveline kits for 8.8 Ford differential conversions.

Fuel Pump Upgrade and Headers

Another important supporting mod to note is the fueling system. The stock Mazda fuel pump will not adequately provide for any LSx engine. You can seize the opportunity to upgrade to a beefier aftermarket fuel pump that’ll provide room for upgrades. Also, the stock LSx headers will not fit into the RX8. You’ll either have to mock up one yourself or purchase one from the kit suppliers.

Wiring Harness

Furthermore, you’ll have to figure out the wiring harness for the car. It’ll be a lot of reading and time spent figuring out how to mate the LS PCM to RX8 electronics. You’ll most likely have to retain the stock RX8 ECU with its sensors so the instrument cluster works. The kit suppliers also sell a pre-built wiring harness that can save you time, and a crank trigger mounting to retain the Mazda crank angle sensor for the gauges.

Battery Relocation To Trunk

Because the LSx engine takes up so much more real estate than the RENESIS, you have to reposition the battery. Typically, people move the battery to the trunk, as it’s the only other sensible location. You can wire up your own battery relocation or just buy a relocation kit from the kit suppliers.

Cooling, Fans, A/C, Brakes

Then you just have a few remaining sundry items you’re going to need. You need wires, coolant hoses, heater hoses, cooling fans, and custom A/C lines. The LSx is a heavier engine, albeit not by much. Thus, it’s recommended that you upgrade your suspension setup to handle the additional power and increased heft. Bigger brakes are also recommended for more stopping power.

You Will Be Cutting Into Your Car

If you really intend to swap an LSx into your RX8, know that it won’t remain in a complete piece. For the manual, you need to enlarge your clutch master cylinder hole some. The front battery brace and ABS pump mounting brackets have to be cut. You’re going to need to cut the shifter hole too. New holes also have to be drilled into the vehicle frame to install the transmission subframe.

Engine and Transmission Go In Separately

It’s tricky to install the engine and transmission together at once. Therefore, it’s recommended for you to segregate them and install them separately. If you have a 2-post hoist, then you can install the engine and transmission into the subframe first, then drop the car onto it.

Keep The Stock Radiator and Oil Cooler

Surprisingly, the stock RX8 radiator provides sufficient cooling efficiency for the LSx. You can keep the stock radiator and just modify the hoses to fit the LSx engine. You can also repurpose the stock RENESIS oil cooler for the LSx engine. Though an oil cooler isn’t essential for those who don’t intend to track their car.

RX8 LS Swap Overal

Overall, swapping the LSx into an RX8 isn’t exactly a simple task. However, if you have done major repair work before and are handy with tools, then it’s not too difficult. Being well-documented is an enormous advantage too. You’re not treading new ground here, so there are people out there to answer your questions and provide pointers. Engine swaps are also an excellent opportunity to hone your fabrication skills.

Those who are interested in the swap should also search for build threads. This post and this post provide an insight on what’s involved in one of these swaps. And we have a big post on all the popular RX8 engine swap options.

Why choose the LS over a RENESIS?

The easiest engine swap to carry out for an RX8 is another RENESIS. However, there are valid reasoning behind a V8 powered RX8. And the thing is that it’s not an entirely performance-driven decision. Believe it or not, there is pragmatism behind a V8-powered RX8.

For one, it’s broadly agreed that the LSx engine is more reliable than the RENESIS. Being an engine that requires a lot of attention, RENESIS failure tales are what drive most people to perform an engine swap. People like the rest of the RX8 and its availability, but not the engine.

Thus, it only makes sense that one wants to replace the RENESIS with the venerated LSx engine. It’s not as frail, with many people reporting an excess of 300,000 miles on their stock LS performing only basic maintenance. Parts are also readily available and affordable.

Moreover, the LSx engines provide more performance than the RENESIS. Being a big displacement V8, it has loads of torque down low which is what rotary engines struggle with. Swapping to the LSx drastically transforms the RX8 into an effortless 4-door sports-cruiser. It can also feel more refined, as the RENESIS requires you to strain it to be rewarding; while the LSx can supply torque-on-demand.

If you demand more performance, then the LSx is also a very mod-friendly platform. As opposed to the RENESIS, which even now has a relatively experimental aftermarket scene. People have done pretty much everything with the LSx engines and made all sorts of power. The recipe is time-proven, so there’s little new ground that needs to be tread. It’s even possible to twin-turbocharge an LSx and fit it into the RX8.

Finally, the LSx addresses another issue of the RENESIS. There’s no way around it, the RENESIS is still a thirsty engine despite Mazda’s effort to remedy it. Rotary engines burn a lot of fuel to make power. The LSx meanwhile paired with the long gearing can greatly improve the RX8’s fuel efficiency. LS1RX8 reports peak mpg at 26 highway with a double-overdrive T56 transmission.

That said, the LSx swap is not one to be downplayed. It’s not exactly the easiest job, and you have to commit fully to the swap. This means properly budgeting for the entire swap, accounting for everything involved in an engine swap. Most projects are abandoned halfway through simply because conditions changes and people discover they’ve bitten off more than they can chew.

Crucially, if you want your RX8 to remain a genuine sports car, then the RENESIS is still the better option. It both weighs less and positions better in the RX8’s engine bay. Swapping the LSx into the RX8 will turn it into a front-engine rear-wheel-drive sports-tourer. And without the proper supporting handling mods, an LSx-powered RX8 might feel lazy.

Did you notice the body kits in the videos above? We have a full guide on which body kit is best for your RX8, check it out.

Why not use other V8s?

The other side of the coin is always this, why not use other V8s? It’s definitely plausible, as people have fitted other V8s into the RX8 before. The common alternative being the Toyota 1UZ, which is commonly found throughout the world.

The brief answer is that the LS engine provides a good compromise between weight, dimensions, availability, power, and reliability. The 1UZ is a respected engine in its own right, but it’s a taller engine because of its quad-cam setup. This means that more work is required to tuck it underneath the low-slung bonnet.

The tuning potential of the LSx engines is also frankly startling. Very few other engines are as mod-friendly as the LSx engines and that’s why it’s the performance engine of choice for many. However, outside of the US, the availability of the LSx engines is dubious.

Hence, the UZ engines are alternatives that most European and Asian countries end up with. The tuning potential isn’t up to par compared to the LS, but the UZ has all the V8 characteristics. And you can find a UZ for not much money these days. It’s also spectacularly reliable for a V8, as per classic Toyota fashion.

RX8 LS Swap Conclusion

Some would argue that replacing the rotary engine with a piston engine is sacrilege. But other than rotary enthusiasts, most would think that the RENESIS is more hassle than it’s worth. Some goes as far as replacing the RENESIS with the 13B-REW from the RX7, the engine it’s supposed to supersede.

For me though, I reckon the RENESIS gives the RX8 its flair as an affordable sports car. Ridding the RX8 of a RENESIS means discrediting Mazda’s effort to make the RX8 drive like it should. If you are looking for another rotary try and get hold of the R3 engine. However, I also think that a V8 powered RX8 is splendid, and I understand the rationality behind it. If you’re up for the project, have the time and money to spare, it’s a journey that will prove most rewarding nevertheless.

If you decide not to swap your engine in the end you can also look at a turbo kit for your RX8.

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