bkey71 is correct about the battery air intake. In addition,the cover apparatushelps keep the battery very clean, which helps avoid dust accumulation - dust is bad because itcan significantly reduce the cranking power of the battery. It also helps ensure the battery and connections stay dry, reasons why this is good should be obvious.

BTW, some people remove the engine top cover, which can be a bad thing to do. It will extend the time your engine takes to reach the optimum operating temperature range, especially during the winter... while the engine is warming up, it is much less fuel efficient. And, that plastic cover can protect your hood from getting repeatedly heated to a high temp, which can help protect your paint.

Triangle side mount? Snorkel? You lost me with the slang. What are you fellas talking about?

 

I've heard the battery intake called a snorkel before (Mz3forums,) and it seemed to fit, so I use it.
The triangle-side mount is that uselessPOS that is supposed to hold the snorkel in place. But as I found out is not really necessary as the batt box and rad support do that just fine w/o it, and only makes accessing the battery/air filter box/lights and ???that much harder. Plus as 2.0(?) mentions, those plastic screws/clips are not only aPITA, but stupid.

 

Thanks V. Makes sense. Though I have experience with fixing and replacing this and that on many cars over the years, I have not touched much of anything in my M3 engine compartment. I have accessed the battery a couple of times to reset the CEL light, and therefore I know what you mean by snorkel. I have not removed anything from my engine compartment. To be honest, modern cars are so electronic (versus being very mechanical in the late 1970s and earlier ... I in my past owned some POS 1979 and older vehicles ...), I'm almost scared to touch anything in the engine area, other than to check fluids, for fear of Fing something up.

 

Believe me, I know what you mean.
I have been trying to update my info and learn some new tricks on these forums for a few years now... trying to get a feel for what can and cannot be done from the young techno-geeks w/these modern computer controlled cars.
It used to seem hard to come up with new and wonderful ways of improving power and mileage, but that was nothing compared to todays cars.