BMW i8 Engine Swaps Coming Soon?

Somebody had to do it eventually. The BMW i8 has spent a decade being one of the most visually arresting machines on the road while quietly frustrating anyone who actually wanted to drive hard. Butterfly doors, a carbon fibre tub, a body that looks like it escaped from a Le Mans grid — all wrapped around a 1.5-litre three-cylinder engine making 357 horsepower in a car that weighs almost 1,500 kilograms. The aesthetics wrote cheques that the drivetrain couldn’t cash.

Enter Trevor Elam of Bimmer Network. He looked at that chassis and saw not a hybrid lifestyle vehicle, but a blank canvas. And then he did what most people only theorise about in comment sections: he actually started building it.

When BMW launched the i8 in 2014, the automotive press fell over itself to describe it as a glimpse of the future. The CFRP passenger cell, the plug-in hybrid system, the mid-mounted engine configuration — it was genuinely forward-thinking engineering at a time when most performance cars were still doing things the same way they had for decades.

But the performance was always the caveat nobody wanted to say out loud. Three hundred and fifty-seven horsepower sounds respectable until you consider the car weighs as much as a small SUV and the power figure includes the electric motor contribution. On paper it was quick enough. On road it felt like a very expensive tease — a chassis that clearly had more to give, strangled by a powertrain built around consumption targets rather than lap times.

As these cars have depreciated and hybrid battery packs have begun to age, the question stopped being theoretical: what happens when someone treats the i8 as a chassis rather than a finished product?

BMW’s B58 3.0-litre turbocharged inline-six has earned a reputation that the tuning community tends to describe in the same breath as the 2JZ — and the comparison is not entirely unfair. Closed-deck block. Forged crankshaft. Thermal efficiency that allows the engine to handle serious boost on entirely stock internal components. It is an engine that was over-engineered from the factory for reasons that become obvious when you start turning up the pressure.

Elam is not keeping it anywhere near stock. The build integrates a Dynamic Autowerx upgraded turbocharger with a power target in the 700 to 800 horsepower range — more than double what the i8 left the factory making in total hybrid output. That is not a mild upgrade. That is a different car.

Here is where it gets seriously complicated, and where the people who dismissively say “just swap the engine” in comment sections reveal they have no idea what they are talking about.

The factory i8 is mid-engined. The three-cylinder sits behind the passenger compartment, with the electric motor handling the front axle. The B58 is a longitudinal inline-six — it is physically too long to mount transversely in the rear of the i8’s architecture. The solution, which is either brilliant or insane depending on how you look at it, is to move the engine to the front entirely. Front-engine. Front placement. Longitudinal mounting. On a car that was never designed for any of those things.

What that means in practice:

• The front structure needs to be cut and custom subframes fabricated from scratch — the i8 was not engineered to accept a longitudinal straight-six at the front, full stop.
• The entire hybrid system is stripped out — the high-voltage lithium-ion battery pack, the front electric motor, the rear three-cylinder, and what the build team described as miles of complex hybrid wiring. All gone.
• To handle 800 horsepower, the car adopts an xDrive all-wheel-drive system sourced from an F30-generation M340i — which means fitting a transmission, front driveshafts, and transfer case into a chassis that previously had none of those components. The CFRP central tub either has to be modified or the transfer case mounted significantly further rearward to accommodate the packaging.

This is not a weekend garage build. This is fabrication at a level that requires proper engineering knowledge, machining capability, and the willingness to make irreversible decisions about a carbon fibre monocoque that BMW spent years developing.

There is a certain type of person who watches a build like this from behind a screen and decides their job is to explain why it is wrong. The purists who believe the i8 should remain as BMW intended. The engineers who list every reason it cannot work. The commenters who have never held a spanner in anger telling a builder what is and is not possible.

Trevor Elam is actually doing it. He is cutting metal, fabricating subframes, solving packaging problems that have no off-the-shelf solution, and documenting the process. That is worth more than every opinion offered by someone who has never attempted anything remotely comparable. The criticism is easy. The build is hard. That distinction matters.

The counter-argument to the purists is simple: the i8’s hybrid battery will be dead in most surviving cars within a decade. The three-cylinder is an underpowered engine in a chassis that deserved better from day one. Doing a serious engine swap does not destroy the i8’s legacy — it potentially fulfils it. The body shape always looked like 800 horsepower. It just took someone with the nerve to actually follow through.