How useful is this thing?

[aramis]

Mine is a 6-potter E46, there is a valve in one of the exhaust tip, how useful is it actually? AFAIK (correct me if I am wrong), it will open when the car reaches certain RPM, just like the DC5 ori muffler.

 

[DiNAN.328i]

"At idle and engine speeds up to 2500rpm, the flap is held closed (vacuum applied to the actuator). This allows exhaust gasses to flow through the open pipe only, reducing low frequency noise which maybe generated.

Above 2500rpm, the exhaust flaps is open (no vacuum applied to the actuator) which allows exhaust gasses to flow through the short pipe for maximum performace in the mid to high rpm range."

 

[BMW9700]

this is for noise reduction, i have removed the vacuum pipe from the actuator so it is always open.. the exhaust note is more bassy when idling and at low revs..there is no difference to the performance..

regards

Mine is a 6-potter E46, there is a valve in one of the exhaust tip, how useful is it actually?

AFAIK (correct me if I am wrong), it will open when the car reaches certain RPM, just like the DC5 ori muffler.

 

[aramis]

so, it is only for noise reduction and not for performance, right?

 

[DiNAN.328i]

pretty much

 

[Daniel]

I believe an exhaust valve is to help improve torque on the lower rev range by increasing back pressure and later opening up to allow maximum gas flow of exhaust gases. It 'tunes' the exhaust to cater for the different amounts of gas flow.

Is can be compared to that of the VTEC in Honda engines, but in this case its for the exhaust.

 

[Vanquish]

Guys,

Which brings us to the next question - does the removal of that valve affect the low rpm response of the engine ? BMW9700, care to share your own experience after the removal of the flap, bro ? How loud are your stock exhaust now after the removal of the flap? I'm thinking of removing mine to fit a pair of larger diameter twin pipes since the stock ones are rather smallish. Appreciate your thoughts ...

Cheers,
VaN.

 

[BMW9700]

Guys,

Which brings us to the next question - does the removal of that valve affect the low rpm response of the engine ? BMW9700, care to share your own experience after the removal of the flap, bro ? How loud are your stock exhaust now after the removal of the flap? I'm thinking of removing mine to fit a pair of larger diameter twin pipes since the stock ones are rather smallish. Appreciate your thoughts ...

Cheers,
VaN.

Hi bro Van

i did not remove the flap but just disconnected the vacuum hose at the tip..it can be inserted back..I dont find any gain/loss in performance but the exhaust note has become deeper and more bassy..i prefer that the valve is disconnected..please do try and post your findings..btw you can use a larger screw to tap the hose while not being used to prevent dirt from being sucked in..


regards

 

[Daniel]

mmmm , that flap is suppose to help the drivability of the car. but since its on a 'large' motor, anything noticiable would be very small.

 

[Vanquish]

Thanks BMW9700 / Daniel ...

Rite ... so the flap stays then. I'll remove the vacuum hose and let it run for a couple of days to gauge it. Looks like I gotta stick to the stock rear tail pipes then .... Too bad!

Cheers,
VaN.

 

[Slide]

Only for noise and below is the link for the proof. Pages 9-11.

http://www.landrover.ee/est/files/manuals/engine/BMW_M52_engine.pdf

 

[Daniel]

Throttle response with fuel injection has been somewhat of a chore to get right by all the manufacturers. Various styles of exhaust valves, flaps in airboxes and servomotors whirring and whizzing away have only gotten close to the Holy Grail of throttle response. To date, engineers got the bright idea to make fuel injection work like a carburetor by employing a CV carburetor slide controlled by vacuum created by the engine, just like on CV style carbs. This ensures that the motor only gets as much fuel as it can handle for a given rpm. On the exhaust side, the valve aids the smoothing and organizing egress of spent air and fuel mixtures.

This valve also constantly adjusts the internal diameter of the exhaust to match engine rpm.

 

[Vanquish]

Yeah,

That's why it's also refered to as an Active Silencer in a number of Beemer forums which pretty much clears up the confusion about it. I just disconnected mine a while ago and took the car for a quick spin. Apart from a nice bassy rumble while idling and driving below 2K+ RPM, there is almost no difference in performance at all thru the usual RPM range . The rumble, thankfully is not as loud/intrusive as it was on my pal, Roland1888's previous ride - an E46 328i which also had the flap deactivated. All in all, a free mod for those who who wants a bit of noise but still keen on keeping their stock rear box on their ride.

Cheers,
VaN.

 

[aramis]

thanks guys for the great posts!

 

[3er]

The 325i doesnt have the active muffler bit. Its meant to rumble away! A true 325i indeed when you hear one.

Of course if you add the ACS.....

 

[omegaoracle]

The 325i doesnt have the active muffler bit. Its meant to rumble away! A true 325i indeed when you hear one.

Of course if you add the ACS.....

No wonder i couldn't find it...
thanks bro