BMW's M42 Vs. M44 Engine: What's The Difference Between These Four-Cylinders?

BMW has quite a few engines worth checking out for a potential swap, and the M42 and M44 are two decent four-cylinder picks. They aren't known as the most reliable BMW engines ever built, but that doesn't mean they are complete duds either. On the surface, the pair of motors appears to have a lot in common, and that's because they do. Still, despite the similarities, the M44 is the more powerful of the two. That means if you're looking to squeeze out as much performance as you can from your swap, that's your pick.

The M42 dates back to 1989, but if you can find one in good shape, it's a reliable and solid engine. The 1.8L engine can produce up to 134 horsepower, or 138 if you have the second-gen E36 version of the motor. While the M42 is a serviceable engine, it's essentially a stripped down version of 1996's M44. As expected, the M44 is an improvement over the previous generation, and that makes it a better pick for a lot of people looking to perform a swap.

The M42 is very solid engine if you can get your hands on one. After all, it powered the awesome BMW E30. With it being slightly less powerful than its successor, you can typically find one at a cheaper price as well. The first-gen E30 model of the engine can be sourced for a little over $1,000, making it an affordable engine to find — at least at the time of this writing. As time goes by and engines become rarer, prices typically change with them.

Although it's not as prevalent on the market as the popular LS engine, it's still a good pick for a project car. The M42 is a versatile engine that offers a lot of performance at stock value. If you want to get more out of it, you could add a lightened flywheel that increases throttle response or install a turbo. Keep in mind, though that those will drive up the price further and give you more work to do. Regardless, the only thing really working against the M42 is that its M44 successor simply has a better performance for not that much higher of a price.

The M44 is the evolution of the M42, and it's an overall more durable engine. It slightly increased in size from 1.8L to 1.9L, but the durability comes into play with the cast iron crank replacing a forged steel one. Performance at the top end between the two engines is the same, but the M44 is able to hit its max torque at a lower RPM: 4,300 compared to the M42's 4,500. The improvements from engine to engine aren't massive, but the M44 is a solid engine that boasts good performance. 

Although the M42 is a cheaper engine, the M44 is still very affordable as you can pick one up for around the $2,000 ballpark. Some drivers report rough idling as an issue with both the M42 and M44 engines, though, so don't think going with the M44 will fix everything. Of course, your mileage may vary and you may be able to find a good engine without these problems.