Valved exhaust modification.

[JordanTurbo]

Alright guys, posted this in the BMW section but thought id get the opinions of this corner of the forum too..

As you may know, the standard exhaust on the BMW e36 328 is valved. The valve stays closed until 3.5k revs and opens above that giving a nicer sound.

A popular modification is the "golf tee" which involves removing and plugging the vacume line to the valve and thereby keeping it open all the time.

I have done the above mod which is great but wanted some more. Searching has revealed people, mainly in the US, that have opened the back box up and removed the pipework to make it a straight through system like below. (Not a 328 box but you get the idea)



I have taken this idea but plan to take it a step further and be a bit smarter about what I remove.

Removed my rear box today and opened it up like so.





Looking at the pipework it workes like this:

• Valve closed - air takes a long trip round the box.

• Valve opened - air can take a more direct route.

My plan is to modify the pipework between the dashed white lines in the below picture so that when the valve is open gasses can exit straight out of the back of the box.



Using the above method should achieve the results I want, while leaving the "valve closed" sound relativly unaffected as it still has to go through all the other pipework. (I will reverse the golf tee mod)

Thoughts?

[chriz1]

That can't be helping for bhp, I'd go get a custom back box made

[Talkwrench]

It can only help but I doubt it'll make too much difference to the sound level. The 2.8 is not an inherently "noisy" engine from an exhaust perspective. While you have the back of the system off, whip off the middle box too and put straight thru pipes in. That'll make it sound a whole lot better without being too noisy, hollow or droning. It'll be far less restrictive as well.