Originally Posted by Munit
These are one of those situations that if you simply step back and use common sense you will see that its really not sensible that bmw M would use a restrictive elbow if there was 10hp on the table from using a slightly larger diameter pipe. The diamter being smaller is not necessarily more restrictive. Its likely calculated based on desired intake air velocity whichi requires a certain diameter. Larger diameter means slower moving air. So while it may move "more" air, the air is slower and would take more time. This intake does not have a restriction for air in totally stock form.
Evidence is in the GTS 4.4 stroked engine which uses the identical intake box as the stock s65 m3. Clearly a 4.4L if anything requires more air and the stock setup provides enough air for that so our stocker engine has more than enough air.
I think a dyno gain is for the filter only but to each his own. M would not leave 10hp on the table if it were a matter of tweaking the intake elbow diameter. Just makes zero sense
Auto manufactures leave HP on the table all the time. They decide what is their desired performance number is and what will meet Global needs/laws/standards and stick with that. I have been adding HP to cars since I was 16 and this has always been the case.
Let's look at the m3. Why did BMW make a heavy ass muffler when we know it could be made much lighter reducing weight which will make the car quicker. Couldn't BMW make a filter which is more like after market versions to get 1-2 more HP? Couldn't BMW software tune more HP out of these cars? Couldn't BMW install higher flow cats while still passing all emissions. If all these things were done and the car can produce say 430-440 HP stock instead of 414, why did BMW not do this? If the car had 25 more HP but cost 1k more would it sell less or more?
If you can answer why BMW did not do the above and BMW can only get 414 out of the S65 motor then I will retract my questions and admit you are the BMW master