I was wondering how much of the BMW 535I engine is actually made by BMW? I know that the turbochargers are not made by BMW but rather by Mitsubishi and the fuel injectors by Piezo. BMW is a company that started business by making engines so when I bought the car I figured I was getting an engine made by the best. This is probally still true but I don't know how much of it is really BMW and how much is from other companies supplying parts that they threw in there. It may be an odd question but does anyone have an idea?

 

Obviously, many components like turbo's and sensors are bought from automotive suppliers, BMW does not design those themselves. More than 75% of the automotive industry consists of suppliers, only a relatively small part of the engineering is done by the OEMs (in this case BMW). However, BMW is in charge and has endresponsibility for teh design, so they determine which components to buy.

The real important/differentiating components are designed (& often manufactered) by the OEMs themselves. In case of BMW, it's things like for example the cylinder head and other engine elements that they're really good at, that's why they make those themselves. And of course they do the "overall design" or "system design" of the car and make all the important choices.

Your E60 consists of components from over 200 different subsuppliers.


P.S.: Piezo is not a company, the injectors use piezoelectrical technology vs the electromagnetic principle. Advantage is that it's much faster, allowing the engine control unit to inject fuel multiple times for each stroke (small amounts of pre-injection & post-injection can make the engine run smoother and it can help reaching the emission goals). Disadvantage is teh risk of drift over life, which means that less fuel may be injected in 5 years or so causing the engine to run differently.