Question re: Muffler Cut-outs

[Bob B]

I have watching a show called Bitchin' Rides. One of the cool things they do when customizing a vehicle is to install muffler cut-outs. This allows the driver to hit a button and open a port in the muffler thereby making a more throaty sound.

View: https://www.youtube.com/watch?v=Oyjdnj5I3dE


I love my BMW Z3 M Roadster, but it's sound is what I would call European "civil." It would be nice to have more of a muscle car sound now and then. However, I am concerned that muffler cut-outs might change the back-pressure and adversely affect performance.

If you have installed cut-outs, what has been your experience?

 

[Pingu]

Just remember to swap back to standard for the MOT.

https://zroadster.org/threads/pingus-m-roadster.17767/page-2

 

[Bob B]

[Yeah, they would probably not pass inspection here in Maine, USA. They might even be illegal. 'Will have to check.

From your response, may I assume that you have cut-outs on your own Z and they do not affect performance?

 

[Pingu]

They do affect performance .

Fuel economy goes from 15mpg-27mpg to 11mpg-37mpg.

If I take it easy on a motorway (60-70mph), I've measured 37mpg (fill-to-fill).

If I do some trackday-type driving, I can get it down to 11mpg.

Best of both worlds .

 

[Dino D]

I’ve got a cut out on another car (single pipe so just one).
It quite far back and bypasses the rear silencers and exits under the car via a downturned pipe in an area not close to anything that can get damaged (ie fuel tank!)

The advice was to go for vacuum operated ones over electric motors as the motors get too hot over time sitting on the exhaust and fail.

The vacuum operated one has been reliable - only failure was the electronic control unit - dry soldier joints and its probably robustly enough built for living in the engine bay for years (in the this case by the battery).

I’d say if possible put the control unit inside the car and run the electrical wires through the bulk head so it lasts longer. Either way open it up and check the quality of the soldering before installing.
All it does is take the remote signals and sends current to a vacuum solenoid that diverts vacuum.
The solenoid itself was decent and the same as used for turbo pipe work so not issue with that living in the engine bay.

It’s a huge issue as it lasted a few years first round and was quite cheap to buy but as you’ll need two for the M it’ll add up.
Also not sure if you’ll need two remotes or can make work on a single remote. It’s just a garage door remote with open close function.
Would be quite neat if it was wired to the controller with modified OEM button on the dash like for the soft top…

Another thing is that sometimes it doesn’t close tightly enough so let’s a little blow by when in the closed (quite position). Probably needed cleaning up carbon build up which might be the cause.

Great solution to keeping stock exhaust and sound and having a louder sound and performance when needed hence I’ve done it to a family car but for a BMW straight six a well made exhaust with a nice sound all the time is fine as it not a commuter car.




ps set up so that ‘failure’ mode, ie when no vacuum is applied is quiet mode, so if does fail it’s still quite!