F20 exhaust material question?

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steve o
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F20 exhaust material question?

Post by steve o » Fri Apr 06, 2018 11:37 am

Hi,

does anyone know the exact material used on the 120d F20 stock exhaust?

Looking to do a M135i split exit modification and the £300 powerflow want to cut off the back box and clamp on a split piece of pipe seems a ridiculous amount to me.

So, you can get all the pieces readily online to DIY it for around £60 / £70, I just wondered what the OEM exhaust material is incase I choose to DIY weld directly to my existing system.

Any input appreciated.

Cheers.

Bob R
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Re: F20 exhaust material question?

Post by Bob R » Mon Apr 09, 2018 12:08 am

'Split exit modification' ?
Is this the process of cutting open the back box and welding the perforations ?
Either way I would expect most exhaust systems to be mild steel unless aftermarket.
M135i, Estoril Blue, 4 door, Pre LCI, Auto, Black Leather, Pro Nav, H+R springs 15mm spacers, Bluespark, modded back box :drive:

steve o
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Re: F20 exhaust material question?

Post by steve o » Tue Apr 10, 2018 8:13 am

There's several options yes, I'm just weighing up the cheapest way.

I could:
1) open the existing exhaust and weld on a second branch inside the back box to exit on the right side.

2) try to weld a second branch externally on the existing back box to exit on the right side.

3) cut off the back box and weld up my own bespoke boxless end. So a y piece and some bends to exit both left and right.

4) find a suitable standard m135i back box, cut mine off, sleeve connect to the new box and weld open the sports flap.

Final option is the easiest and probably neatest solution, but not the cheapest with back boxes averaging around the £150 Mark.

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marco_polo
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Re: F20 exhaust material question?

Post by marco_polo » Tue Apr 10, 2018 8:17 am

My standard exhaust seems to be some kind of low-ish grade stainless. Cutting it (removing the tip alignment pins) gave me a bit of a workout.

Is yours rust-free?
Silver F21 M135i - ManBox - HK - Adaptive + Eibach Pro's - BBS CH-R's - BMWP Drexler LSD - TMC Piggyback - M4 LCA's - aFe Dry Filter

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steve o
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Re: F20 exhaust material question?

Post by steve o » Tue Apr 10, 2018 8:33 am

Yeah my hunch is it's stainless of some grade but I can't tell what for sure.

Bob R
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Re: F20 exhaust material question?

Post by Bob R » Wed Apr 11, 2018 6:34 pm

I was reading another forum about modifying back boxes and the general consensus was that it is Aluminium.
Apparently Aluminium isn't magnetic so may be worth trying a magnet on it to confirm.
M135i, Estoril Blue, 4 door, Pre LCI, Auto, Black Leather, Pro Nav, H+R springs 15mm spacers, Bluespark, modded back box :drive:

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Re: F20 exhaust material question?

Post by marco_polo » Wed Apr 11, 2018 7:05 pm

Bob R wrote:
Wed Apr 11, 2018 6:34 pm
I was reading another forum about modifying back boxes and the general consensus was that it is Aluminium.
Apparently Aluminium isn't magnetic so may be worth trying a magnet on it to confirm.
Stainless isn't magnetic either, so a magnet won't confirm much.
Silver F21 M135i - ManBox - HK - Adaptive + Eibach Pro's - BBS CH-R's - BMWP Drexler LSD - TMC Piggyback - M4 LCA's - aFe Dry Filter

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steve o
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Re: F20 exhaust material question?

Post by steve o » Wed Apr 11, 2018 9:27 pm

Don't worry guys. I've managed to source a 135 box cheap and local so it's a simple case of a stepped sleeve adaptor and cut old one off, bolt new one on. No welding needed anymore.

Ta.

Bob R
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Re: F20 exhaust material question?

Post by Bob R » Wed Apr 11, 2018 9:34 pm

marco_polo wrote:
Wed Apr 11, 2018 7:05 pm
Bob R wrote:
Wed Apr 11, 2018 6:34 pm
I was reading another forum about modifying back boxes and the general consensus was that it is Aluminium.
Apparently Aluminium isn't magnetic so may be worth trying a magnet on it to confirm.
Stainless isn't magnetic either, so a magnet won't confirm much.
Too much arsing around in school physics.
M135i, Estoril Blue, 4 door, Pre LCI, Auto, Black Leather, Pro Nav, H+R springs 15mm spacers, Bluespark, modded back box :drive:

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Re: F20 exhaust material question?

Post by chinskee » Fri Apr 27, 2018 1:10 pm

steve o wrote:
Wed Apr 11, 2018 9:27 pm
Don't worry guys. I've managed to source a 135 box cheap and local so it's a simple case of a stepped sleeve adaptor and cut old one off, bolt new one on. No welding needed anymore.

Ta.
Hello Im looking at installing the m135i box on my car. Its a 116i so not sure if exhaust diameters are the same, but do you know roughly where you cut etc and what reducer/adapter you used?
13 116i MSport - Alpine White
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