Why Choose the GM LFX 3.6L Engine for Your Mazda RX-8 Swap?
Photo Credit: rx8club.com
Introduction
The Mazda RX-8 is beloved for its unique style, incredible chassis balance, and spirited driving experience. Which is exactly why I choose this platform over others. However, the 13B-MSP RENESIS rotary engine is notorious for reliability issues, expensive maintenance, and poor fuel economy (this is the least important factor but, still one none-the-less). As an RX-8 owner myself, I wanted reliability without sacrificing performance, leading me directly to the GM LFX 3.6L V6 engine swap. Found in vehicles like the Chevrolet Camaro and Cadillac ATS and even the GMC Terrain, the LFX delivers excellent power, improved reliability, better fuel economy, and plenty of potential for future modifications; to an extent. In this post, I'll share exactly why the LFX is becoming a popular engine swap for RX-8 enthusiasts, covering everything from performance and practicality to challenges you'll face along the way.
Now, if you’ve been following this mess of an RX-8 build, you’ll know the plan wasn’t always to go the GM route. At one point, I was all-in on a K20Z3 swap. I even got the motor for free; how could I not consider it? High-revving, lightweight, tons of aftermarket support. It checked a lot of boxes. But here’s the reality: after looking at the fab work involved, the firewall clearance, and the overall complexity, I hit pause. That doesn’t mean the K20 is dead though. It’s still sitting in the garage, and I’ve got this idea in the back of my head for a stripped-down, budget Honda time attack build. Something light and fast; with as little money into and lowest consumables as possible. But for now, the RX-8 is taking a different path, a more refined one if you will. With the help from the Keisler Automation Totality RX-8 Swap Kit.
Why Consider the LFX 3.6L Swap for Your RX-8?
- Reliability: Greater dependability and simpler maintenance compared to rotary engines.
- Performance Gains: Over 300 horsepower stock, smooth torque delivery.
- Fuel Economy: Noticeable improvement over rotary engines.
- Affordability & Availability: Easy to source from multiple GM vehicles.
Performance and Technical Advantages
The LFX is not just reliable; it enhances the RX-8 driving experience significantly. Due to its aluminum construction, the LFX offers excellent weight distribution, maintaining the RX-8’s legendary handling characteristics. The modern ECU allows for tuning (typically through HPtuners), further enhancing power output and efficiency. Plus, the aftermarket support is growing rapidly, offering supercharging, turbocharging, and bolt-on modification options.
Challenges and Considerations
Despite its advantages, the LFX swap isn't without challenges. You'll need custom or aftermarket engine mounts, solutions for drivetrain compatibility (often adapting the Camaro or custom transmission options), and a reliable wiring harness or standalone ECU setup. Legal considerations, like emissions and state registration compliance, must also be carefully considered before starting your project.
When undertaking an LFX swap into your Mazda RX-8, one of the most significant hurdles you'll face is integrating the modern GM V6 powertrain seamlessly into the RX-8’s chassis. This is where the Keisler Automation RX8 Totality LFX Swap Kit truly shines. Designed specifically for RX-8 enthusiasts, Keisler Automation's kit simplifies many of the challenges DIY enthusiasts commonly encounter. The kit addresses critical components like motor mounts, transmission adapters, wiring harnesses, and ECU programming, effectively removing much of the guesswork and fabrication typically required in engine swaps. This swap is in fact, a total swap kit; hence the name.
Choosing the Totality Swap Kit is instrumental because it streamlines the entire swap process, significantly reducing the complexity, downtime, and potential for costly mistakes. Beyond just mechanical integration, the kit also ensures reliable electronic communication between the GM LFX engine and the RX-8’s factory systems, preserving functionality like gauges, air conditioning, and emissions compliance (where applicable and if you care about that, well rather your county).
Why I Chose the Keisler Automation Totality RX8 Swap Kit
Let’s be real, this RX8 build was never going to be easy. I could have gone full DIY on the LFX swap: custom mounts, wiring spaghetti, and hours of forum deep dives. But after digging into what the Keisler Automation Totality Kit actually offers, I realized I would be fighting problems that someone else already solved, and solved way better than I could.
This kit is not just “some parts to make it work.” It is purpose built for the RX8 chassis. It handles the engine and trans mounts, includes a baffled oil pan that clears the subframe, comes with LFX specific headers that do not need a Sawzall to fit, and even accounts for driveshaft and shifter alignment. Like, someone actually looked at an RX8 engine bay and said, “Yeah, let’s make the LFX fit like it belongs here.”
Another big reason I went with this kit is that it lets me keep factory style heat and AC. And yeah, I know some people strip that out to save weight or whatever, but I live in the armpit of Texas. Having working AC and heat in this car is not optional. I am not trying to cook in traffic or freeze my face off during one of those weird surprise cold snaps. Comfort matters, fight me.
Also, I have owned rotaries. Had an FC back in the day. Loved the style, hated the motor. The thing looked amazing and handled great, but I never really trusted it. You never knew if it was going to start, overheat, or explode into a fine vapor of oil and apex seals. That stuck with me.
The 13B MSP has its fans, and I respect the cult, I really do, but at this point in my life I just want modern reliability. I want to drive the car. Not babysit it. Not carry a fire extinguisher and two spare coils in the trunk just in case. The LFX gives me that. It is newer, proven, and actually comes with things like working DBW throttle and OEM sensors that play nice with real world stuff.
I am going with this kit because I did not want to spend six months fabricating brackets, second guessing every weld, or constantly wondering if I forgot some small detail that would ruin the car. I wanted something that made this swap feel intentional, like it was built for it. For what it includes, it is actually pretty fair. Is it cheap? No. But neither is redoing everything because your budget swap turned into a nightmare. This kit saves time, sanity, and probably a couple of late night rage quits. That is worth something.
Real-World Examples & Testimonials
I'm currently documenting my own LFX RX-8 build right here on the Weekend Wrencher blog, sharing detailed insights, costs, and progress. Additionally, several RX-8 community members have successfully completed the LFX swap, praising its reliability, performance, and cost-effectiveness over rotary rebuilds or more expensive swaps.
Conclusion
The GM LFX 3.6L engine is rapidly becoming one of the best swaps for RX-8 enthusiasts seeking reliable, powerful, and practical performance upgrades. Despite the complexities involved, the benefits far outweigh the challenges, especially if you’re already a hands-on, DIY automotive enthusiast.
Have you considered or started your own LFX RX-8 swap? Let me know in the comments below!