[gT-BMW]

sup e90 anybody here still running a stock intake manifold on a 325i but with a custom tune? Ive read on here that the 325i is detuned from the factory and that the n54 manifold with a bcp tune with headers and secondary cat delete produces some decent top end.just curious has anybody tried that tune with the stock 325i intake manifold?

[W37V]

Originally Posted by gT-BMW

sup e90 anybody here still running a stock intake manifold on a 325i but with a custom tune? Ive read on here that the 325i is detuned from the factory and that the n54 manifold with a bcp tune with headers and secondary cat delete produces some decent top end.just curious has anybody tried that tune with the stock 325i intake manifold?

BPC did. They had a post where documented their tune development and their experiments with various parts (n54 manifold etc). In short, no you will not / can’t make the same power with stock manifold unless you chop it off. BPC produced the most power with the stock manifold cut in half. I wish they didn’t delete that thread as it was super interesting.

In order of power you got following:
1. N54 manifold gets you most top end power. You lose lots of torque at the bottom end, but it allows car to breathe better in high rpm range. This setup yields smooth power across entire rpm range. This intake allows engine to spin up to and use higher rpm range. With this setup you will be making power up to 7500rpm.
2. 3IM manifold yields more power at the bottom end. It operates by directing air in the most efficient way for the rpm. You get a lot of tq at the bottom end. Setup is still more powerful than single stage intake. However due to “limit” of the intake, you will be making power up to 6800rpm (perfect for automatic).
3. Single stage (stock) intake is very limited. The most I have seen people getting from this one was up to 10hp with a tune. And that was pushing it.

[E92William]

This chart should give some interesting insight into the different options and their performance. ( I'm not sure if the blue line for the stock car was tuned or a baseline run) but red is n54 and green 3 stage.

The single stage manifold I think is molded from factory into the 2nd stage of the 3 that the shape provides for the 3 stage version so you will always be compromised between lacking torque and top end. It doesn't seem to have the proper runner length to provide power at those rpms.

Didn't know BPC had deleted that thread it was very interesting, there is however a guy in the 128i forums who did attempt this and is currently driving it around! Here's the link:

The old cut up manifold into trumpets idea https://www.1addicts.com/forums/show....php?t=1789646