Messed up on point 1 the valve must be open for peak engine performance (exhaust gas flow) no question at all so we agree. Closed it stops the booming at low rpm and keeps regulatory agencies happy and it must be open for max power. After market exhausts designed for racing or max power agreed no flap required and don't need the extra weight

Mine is a 525 baby 2.5l engine. I will try and see my old boss and get a run on the dyno if I can arrange it and will up date ASAP Side Note I read and did a lot of exhaust work in the mid 80's based on a book
Scientific Design of Exhaust and Intake Systems (Engineering and Performance) by Philip Hubert Smith just googled it and its still available. Have a read, I got some amazing results with pipe length, megaphones and intake length ( 40mm tubes on each of 4 barrels on Webber carbs with different lengths)

 

Sounds like my kind of book. Ill look it up. If you do ever get a chance to dyno it, post the results. Id definitely like to see them. The 525 is a nice car. What kind of mileage do you get? I was getting pretty good mileage for a while, but now that Ive done some stuff to it, the highest I see is 20, unless Im at idle. To be fair though, I should be making close to 300 whp. As of now I've done a Dinan Ecu, full exhaust, and intake. Im trying to use as much Dinan as I can, since they work so closely with BMW. Funny some guys all the way in California could do all that. They know their stuff too.

 

Also Ozi5Msport, Ive added you in case we end up having any more of these discussions. I've enjoyed it.

 

Anyone esle get a check engine Light after doing this mod?

 

Don't see how you could get a CE light for this.. it's a vacuum controlled flap.. I don't think it even has feedback. Did you mess up the electrical connector for the solenoid?

 

OK,OK the (check engine light "C,E,L") was from the gas cap not being tight... we got gas and my kid
filled her up....

 

Thank you vkhong, I followed your instructions and the result is as you described. However, for my car I had to use a straight vacuum connector with 3/16 inlets made by DORMAN, part # 47303. Maybe you can add 2012 550i (F10) to your list if you like. Now the exhaust butterfly is open at engine start and I can hear the V8 engine a little better.

 

I need to do this asap!

 

A quick update, I traded in my 2012 for a 2015 and I did the same thing to it last week as well. Nice little rumble at idle

 

I swear the hoses are glued on there, I can not get them off!!!!