E39 Exhaust Cutout

[rk11]

I want to buy a cutout for my 2003 525i, and I just wanted to double check that I had the outer diameter right before buying one. I measured the outer diameter of my exhaust at 2.5" inches. Please let me know if that's right. And does anyone know where near the battery I can get key on only constant power for it?

[JimLev]

I have a QTP electric cutout on my 540.
Depending on where you put it the pipe could have a double wall.
I cut a hole in the dead leg of the Y resonator then welded on a short section of pipe and a flange for the cutout.
Yes I know my welds look like crap, that was the second time I used a TIG welder.
The intention was to run it back to the bumper for a dual exhaust setup that I haven't done yet.

Dual_5.JPG

Dual_7.JPG

Dual_11.JPG

[rk11]

The welds aren't horrible and I was planning on putting mine in a similar spot. What size cutout did you need to order?

[JimLev]

Those welds are crap, at least they don't leak.
I used a 2 1/4" QTP, had to keep it on the small side, there isn't a lot of clearance under the car.

These are good TIG welds.
Header34.JPG

[jicaino]

Jim that's one nice placement for that cutout, as the other branch that normally acts as the tailpipe would sort of take up the function of a resonator if you have a muffler in place. How does it feel with that cutout? Also, the valve you're using looks extra nice, as everthing in your car. Where did you get it?

[MotorMouth93]

JimLev what kind of sound do you get with the cutout at that location? I've been thinking of doing an electric cutout too.

[JimLev]

Don't expect and seat of the pants gains, I did this as the beginning of a dual exhaust setup but as usual something else got in the way (LS3 '33 Ford build).
The left side has a nice small Vibrant dual tip muffler. I wasn't going to put a muffler on the right side, just some matching dual tips that I had that are now on the '33.
I corrected the post above, I used a 2 1/4" QTP, this one.
https://www.summitracing.com/parts/q...c225/overview/

I like that I can control how much it opens/closes to control the amount of deep tone from it at the low/mid RPM's.
With it full open at 5-6500 RPM it sounds more like a 12 cyl European car.

[bossman1]

Just curious does all the exhaust go through the cutout once full open? Or does some of it still go through the muffler?

Don't expect and seat of the pants gains, I did this as the beginning of a dual exhaust setup but as usual something else got in the way (LS3 '33 Ford build).
The left side has a nice small Vibrant dual tip muffler. I wasn't going to put a muffler on the right side, just some matching dual tips that I had that are now on the '33.
I corrected the post above, I used a 2 1/4" QTP, this one.
https://www.summitracing.com/parts/q...c225/overview/

I like that I can control how much it opens/closes to control the amount of deep tone from it at the low/mid RPM's.
With it full open at 5-6500 RPM it sounds more like a 12 cyl European car.

[JimLev]

JimLev what kind of sound do you get with the cutout at that location? I've been thinking of doing an electric cutout too.

It's a pretty deep mellow tone unless you wind it out to redline.
I'll see if I can find a short clip of it.

25% open clip
https://1drv.ms/u/s!ApkTIzHhyMd5mBH2EymidsHS_85c

When it's 100% open it's louder and has a slight rasp only when cold if you goose it, it goes away after the 1st mile.
I think it's the internal perforated section in the resonator that you can see in the post 2 pic above.
The next time I have it apart I'll put a tack weld on it and the internal pipe so it won't vibrate.

[JimLev]

Just curious does all the exhaust go through the cutout once full open? Or does some of it still go through the muffler?

It's about 50/50 when wide open.
You can see straight thru my Vibrant muffler. Much smaller than the OE twin scuba tanks and 37 lbs less.

Inlet
VIB2.JPG

Outlet
VIB3.JPG