Originally Posted by JCL

I don't agree that a turbocharged engine will always be less reliable. I also think it is important to separate the concepts of reliability and durability. They are very different things.

If you take more horsepowerpower out of the same engine, by forced induction or other mods, you will reduce durability, since the engine is being worked harder. If you design an engine for that power, however, the same is not necessarily true. All heavy truck engines are turbocharged, and they are very durable. One million miles is not unusual. The engine is simply designed for the power that is being taken out of it. Same with the rest of the powertrain.

Same with BMW, they are not just adding turbos to naturally aspirated engines. They are engineering in the turbos. So I don't think there is any effect on durability, ie how long it will last, unless they decide to design it to wear out sooner. Haven't seen any evidence of that yet.

The second topic is reliability. Reliability (incidence of breakdown) will typically be reduced with added complexity. Turbos do add another thing to fail. However, BMWs don't typically fail mechanical engine components, whether they be pistons, cranks, or turbos. They fail electrical and control components much more often. One of the only control items that gets added to the mix with a BMW turbo (apart from a revised control software) is the wastegate actuator. Guess what rattled on early 3 series turbos? And before worrying about adding a component to a modern BMW, think about how many parts are already on the vehicle. If you want the best reliability, it would make more sense to buy a turbo model with fewer options, ie no NAV, cameras, HUD, LDW, etc. Those are the items that are more likely to fail than the turbochargers, IMO.

I had a 2008 535i for nearly four years. No problems whatsoever with the turbochargers. I had a fuel pump problem, but the same could have happened with an NA version. I would have no hesitation to buy a turbocharged BMW over a naturally aspirated one. In fact, I think it is going backwards to buy one of the last NA versions. You are buying last generation technology, it is already obsolete.

This same discussion happened when fuel injection came out. Some people bought the last models with carburetors. Same when alternators came out, some liked the simplicity of a DC generator, even if it didn't do as good a job of charging the battery. Same with double overhead camshafts. And electric fuel pumps. There are many more examples.

German engineers have been designing forced induction passenger vehicles since the 1920s. BMW introduced a production turbocharged vehicle in 1973, almost 40 years ago. This isn't exactly a new concept.

We have the four cylinder 28i available here in Canada now. Family member just bought an X1, I will drive it in a few days. He says it runs great. My next vehicle will be turbocharged, just because I want the thermodynamic efficiency gains that come with forced induction.

Jeff