You Can Fit A B58 Into A BMW E46 3er, But It’s Not Easy

Imagine for a second you’ve just picked up a fairly basic E46 BMW 3 Series and you’re looking to swap in a new engine. What are you picking? An LS swap would be a fairly obvious choice, or you could keep it in the family with an S54 from the M3. Maybe though, you’re feeling brave enough to drop a new B58 in there.

That’s exactly what NV Motorsport UK has done with its latest build. Starting with a basic E46 Touring, it’s managed to successfully stuff the turbocharged 3.0-litre straight-six into the engine bay - and get it running, too.

NV claims this to be the first time the swap has been done. An impressive feat, but as a result has meant no previous support to rely on, throwing up a few headaches among the way.

The biggest of those proved to be getting the new ECU to behave with the E46’s original wiring harness. The relatively simpleton nature of the car’s electronic systems proves a complete mismatch for those the B58 is used to being hooked up to. You could always go down the aftermarket ECU route to lighten the load a little but, if you’re keeping it as OEM as possible like NV has, it’s an option you may look to avoid.

We’ll leave it to them to explain and show the process, but it proves possible to get the two to communicate with each other (eventually), with the E46 finally running with its new lump. A stage that NV says has taken 12 months to get to.

Better still, it’s “highly likely” they’ll offer customers a swap kit once the project is properly finished with a few kinks ironed out.