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DIY - Custom Downpipe back exhaust :'-D

Specific discussion about the E89 2009 Z4 (sDrive35is, sDrive35i, sDrive30i, sDrive23i)
Jonnoh2017
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DIY - Custom Downpipe back exhaust :'-D

Post by Jonnoh2017 » Tue Mar 06, 2018 11:15 am

So I decided a few months back I wanted a bit more noise from the Z 35i..
Quick Video - ( https://www.youtube.com/watch?v=zcmMx8v ... e=youtu.be )

I bought a downpipe back custom exhaust system costing around £500, while it sounded a bit louder, I was still unhappy with the note of the exhaust it also was quite barffy / blowy (too much air going through too smaller tube perhaps?).

I realised the stock system had a X pipe after the secondary cats and I thought seen as the custom system was 2 separate pipes all the way to the exits that this may be the reason for the sound not being so much to my liking.

So I went about getting the car on the ramps at home and started to pull bits off underneath, dropped the custom exhaust and had a good look over it, I wasn't so pleased.
I had asked for a 2.5" system, it was 2.25 up to 2.5 then back to 2.25, with tight compressed bends, and sleeve joints which added lots of turbulence inside and as mentioned no crossover pipe so at the rear it was like listening to 2 X 3cyl turbo engines (in my mind).

So, I started to cut things up (must admit at this point I thought "oh dear, not sure this is a good idea anymore" haha!)

I had ordered some 3.5" stainless tube, a 3.5" muffler , 3.5" 90 degree bends , and 2.75" bends and tubing also.

It took me 3 weekends in total (around 30 hours!) as it was so awkward on the driveway on axle stands, Im 6ft 5" about 16 1/2 stone so it's not so easy to crawl under a car for me lol !

Anyway long story short I managed to complete a full downpipe back system, It's a cheap mig welder and it jammed every half hour so it was a complete nightmare but I'm glad I persevered !.
Also because of this I could only use mild steel wire, not enough oomph to melt the stainless wire properly so I have sprayed it black to help protect the welds!.
Anyway the plan was just to mock a system up and experiment to see what it sounds like, if a joint middle section would sound better etc.

WOW for a driveway bodge I am so pleased with the sound when the taps open :-D !- sounds like a missile or jet!. It really adds to the experience driving it, cant wait for summer!.

I'm yet to decide on the tailpipes to go for, I'm thinking possibly Quad tips, maybe black chrome. not sure so its not got any at the moment , also considering a m sport bumper to surround the exits better.

Potentially, now I'm happy with the sound I will get a proper system tigged up at a later date but this will do for now.

Only Negative is the drone under load at lower RPM... I'm going to try dynamat under the rear section and see if that helps first.
Anyway the noise at higher RPM is epic, half a V12 :-P like a lambos younger brother lol!

Few images attached, I know the welds are gastly this was more of an experiment anyways :-D

Cheers.
Attachments
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28879435_10215978937016248_315553261_o.jpg (324.71 KiB) Viewed 1195 times
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28877263_10215978937096250_1404177219_o.jpg (248.16 KiB) Viewed 1195 times
28822334_10215978936856244_1085075056_o.jpg
28822334_10215978936856244_1085075056_o.jpg (312.51 KiB) Viewed 1195 times
28821752_10215978936616238_1982783756_o.jpg
28821752_10215978936616238_1982783756_o.jpg (327.7 KiB) Viewed 1195 times
28810815_10215978937056249_1287933872_o.jpg
28810815_10215978937056249_1287933872_o.jpg (264.39 KiB) Viewed 1195 times
28810230_10215978936576237_417283933_o.jpg
28810230_10215978936576237_417283933_o.jpg (302.95 KiB) Viewed 1195 times
Last edited by Jonnoh2017 on Tue Mar 06, 2018 9:03 pm, edited 2 times in total.

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Smartbear
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DIY - Custom Downpipe back exhaust :'-D

Post by Smartbear » Tue Mar 06, 2018 3:34 pm

Fair bit of diy there :) , what we really need is a sound clip :thumbsup:
Rob
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e89 Sdrive 20i, plenty of mumbo & good economy-the thinking bears z4
e89 Sdrive 30i, this ones busted, pass me another...
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DIY - Custom Downpipe back exhaust :'-D

Post by dans6490 » Tue Mar 06, 2018 4:29 pm

Smartbear wrote: Tue Mar 06, 2018 3:34 pm Fair bit of diy there :) , what we really need is a sound clip :thumbsup:
Rob
+1.

Jonnoh2017
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DIY - Custom Downpipe back exhaust :'-D

Post by Jonnoh2017 » Tue Mar 06, 2018 5:34 pm

I'll charge up the Go pro and get something posted up soon :-D

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DIY - Custom Downpipe back exhaust :'-D

Post by Fishy Dave » Tue Mar 06, 2018 6:06 pm

Well done for giving it a go, particularly working on your back under the car. :thumbsup:
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DIY - Custom Downpipe back exhaust :'-D

Post by mcbutler » Tue Mar 06, 2018 6:41 pm

Jonnoh2017 wrote: Tue Mar 06, 2018 11:15 am So I decided a few months back I wanted a bit more noise from the Z 35i..

I bought a downpipe back custom exhaust system costing around £500, while it sounded a bit louder, I was still unhappy with the note of the exhaust it also was quite barffy / blowy (too much air going through too smaller tube perhaps?).

I realised the stock system had a X pipe after the secondary cats and I thought seen as the custom system was 2 separate pipes all the way to the exits that this may be the reason for the sound not being so much to my liking.

So I went about getting the car on the ramps at home and started to pull bits off underneath, dropped the custom exhaust and had a good look over it, I wasn't so pleased.
I had asked for a 2.5" system, it was 2.25 up to 2.5 then back to 2.25, with tight compressed bends, and sleeve joints which added lots of turbulence inside and as mentioned no crossover pipe so at the rear it was like listening to 2 X 3cyl turbo engines (in my mind).

So, I started to cut things up (must admit at this point I thought "oh dear, not sure this is a good idea anymore" haha!)

I had ordered some 3.5" stainless tube, a 3.5" muffler , 3.5" 90 degree bends , and 2.75" bends and tubing also.

It took me 3 weekends in total (around 30 hours!) as it was so awkward on the driveway on axle stands, Im 6ft 5" about 16 1/2 stone so it's not so easy to crawl under a car for me lol !

Anyway long story short I managed to complete a full downpipe back system, It's a cheap mig welder and it jammed every half hour so it was a complete nightmare but I'm glad I persevered !.
Also because of this I could only use mild steel wire, not enough oomph to melt the stainless wire properly so I have sprayed it black to help protect the welds!.
Anyway the plan was just to mock a system up and experiment to see what it sounds like, if a joint middle section would sound better etc.

WOW for a driveway bodge I am so pleased with the sound when the taps open :-D !- sounds like a missile or jet!. It really adds to the experience driving it, cant wait for summer!.

I'm yet to decide on the tailpipes to go for, I'm thinking possibly Quad tips, maybe black chrome. not sure so its not got any at the moment , also considering a m sport bumper to surround the exits better.

Potentially, now I'm happy with the sound I will get a proper system tigged up at a later date but this will do for now.

Only Negative is the drone under load at lower RPM... I'm going to try dynamat under the rear section and see if that helps first.
Anyway the noise at higher RPM is epic, half a V12 :-P like a lambos younger brother lol!

Few images attached, I know the welds are gastly this was more of an experiment anyways :-D

Cheers.
If you had ordered a 2.5 system and got a 2.25 system why did you not simply return it and get a better one!!!
Mark
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DIY - Custom Downpipe back exhaust :'-D

Post by Machine monkey » Tue Mar 06, 2018 8:07 pm

Well done OP having built my own exhaust system a few times I know how rewarding it is. And also how difficult it is doing it under the car.

Also what you really don’t want on a turbo engine. Is any restriction after the turbo causing turbulence and back pressure. It will kill spoll and power and also make the turbo work harder and hotter. Basically all bad things.

Go get a cheeky remap and I bet there will be really noticeable improvement.
My little blue zed is in lots of bits. With lots of things started and not many finished! I may have found the limits of my time and ability!!

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DIY - Custom Downpipe back exhaust :'-D

Post by Jonnoh2017 » Tue Mar 06, 2018 8:16 pm

Fishy Dave wrote: Tue Mar 06, 2018 6:06 pm Well done for giving it a go, particularly working on your back under the car. :thumbsup:
Thanks pal :-)

Jonnoh2017
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DIY - Custom Downpipe back exhaust :'-D

Post by Jonnoh2017 » Tue Mar 06, 2018 8:17 pm

mcbutler wrote: Tue Mar 06, 2018 6:41 pm
Jonnoh2017 wrote: Tue Mar 06, 2018 11:15 am So I decided a few months back I wanted a bit more noise from the Z 35i..

I bought a downpipe back custom exhaust system costing around £500, while it sounded a bit louder, I was still unhappy with the note of the exhaust it also was quite barffy / blowy (too much air going through too smaller tube perhaps?).

I realised the stock system had a X pipe after the secondary cats and I thought seen as the custom system was 2 separate pipes all the way to the exits that this may be the reason for the sound not being so much to my liking.

So I went about getting the car on the ramps at home and started to pull bits off underneath, dropped the custom exhaust and had a good look over it, I wasn't so pleased.
I had asked for a 2.5" system, it was 2.25 up to 2.5 then back to 2.25, with tight compressed bends, and sleeve joints which added lots of turbulence inside and as mentioned no crossover pipe so at the rear it was like listening to 2 X 3cyl turbo engines (in my mind).

So, I started to cut things up (must admit at this point I thought "oh dear, not sure this is a good idea anymore" haha!)

I had ordered some 3.5" stainless tube, a 3.5" muffler , 3.5" 90 degree bends , and 2.75" bends and tubing also.

It took me 3 weekends in total (around 30 hours!) as it was so awkward on the driveway on axle stands, Im 6ft 5" about 16 1/2 stone so it's not so easy to crawl under a car for me lol !

Anyway long story short I managed to complete a full downpipe back system, It's a cheap mig welder and it jammed every half hour so it was a complete nightmare but I'm glad I persevered !.
Also because of this I could only use mild steel wire, not enough oomph to melt the stainless wire properly so I have sprayed it black to help protect the welds!.
Anyway the plan was just to mock a system up and experiment to see what it sounds like, if a joint middle section would sound better etc.

WOW for a driveway bodge I am so pleased with the sound when the taps open :-D !- sounds like a missile or jet!. It really adds to the experience driving it, cant wait for summer!.

I'm yet to decide on the tailpipes to go for, I'm thinking possibly Quad tips, maybe black chrome. not sure so its not got any at the moment , also considering a m sport bumper to surround the exits better.

Potentially, now I'm happy with the sound I will get a proper system tigged up at a later date but this will do for now.

Only Negative is the drone under load at lower RPM... I'm going to try dynamat under the rear section and see if that helps first.
Anyway the noise at higher RPM is epic, half a V12 :-P like a lambos younger brother lol!

Few images attached, I know the welds are gastly this was more of an experiment anyways :-D

Cheers.
If you had ordered a 2.5 system and got a 2.25 system why did you not simply return it and get a better one!!!
If only it were that easy, old system was on the car 6 months, not going to return it after that.

Fancied a challenge anyway and for £200 max cant go wrong :-D

Cheers

Jonnoh2017
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DIY - Custom Downpipe back exhaust :'-D

Post by Jonnoh2017 » Tue Mar 06, 2018 8:19 pm

Machine monkey wrote: Tue Mar 06, 2018 8:07 pm Well done OP having built my own exhaust system a few times I know how rewarding it is. And also how difficult it is doing it under the car.

Also what you really don’t want on a turbo engine. Is any restriction after the turbo causing turbulence and back pressure. It will kill spoll and power and also make the turbo work harder and hotter. Basically all bad things.

Go get a cheeky remap and I bet there will be really noticeable improvement.
Cheers mate :-)

I agree , still got the cats in the downpipe so some backpressure there but I've carried out all other mods for around the quoted "420 BHP" from MHD tuner - Not sure how close to that figure it is.
But it sure goes well :-D

Thanks,

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DIY - Custom Downpipe back exhaust :'-D

Post by Mr Tidy » Tue Mar 06, 2018 8:38 pm

Impressive bit of DIY there OP. :thumbsup:

And the best bit is you like how it turned out - result!
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Jonnoh2017
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DIY - Custom Downpipe back exhaust :'-D

Post by Jonnoh2017 » Tue Mar 06, 2018 8:42 pm


Jonnoh2017
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DIY - Custom Downpipe back exhaust :'-D

Post by Jonnoh2017 » Tue Mar 06, 2018 8:44 pm

Mr Tidy wrote: Tue Mar 06, 2018 8:38 pm Impressive bit of DIY there OP. :thumbsup:

And the best bit is you like how it turned out - result!
Cheers Mr Tidy!.

Will get an external Video up at some point when its drier

Cheers

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DIY - Custom Downpipe back exhaust :'-D

Post by Machine monkey » Tue Mar 06, 2018 8:50 pm

Jonnoh2017 wrote: Tue Mar 06, 2018 8:19 pm
Machine monkey wrote: Tue Mar 06, 2018 8:07 pm Well done OP having built my own exhaust system a few times I know how rewarding it is. And also how difficult it is doing it under the car.

Also what you really don’t want on a turbo engine. Is any restriction after the turbo causing turbulence and back pressure. It will kill spoll and power and also make the turbo work harder and hotter. Basically all bad things.

Go get a cheeky remap and I bet there will be really noticeable improvement.
Cheers mate :-)

I agree , still got the cats in the downpipe so some backpressure there but I've carried out all other mods for around the quoted "420 BHP" from MHD tuner - Not sure how close to that figure it is.
But it sure goes well :-D

Thanks,
420 is health I am aiming for similar with my e85
My little blue zed is in lots of bits. With lots of things started and not many finished! I may have found the limits of my time and ability!!

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Jonnoh2017
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DIY - Custom Downpipe back exhaust :'-D

Post by Jonnoh2017 » Tue Mar 06, 2018 9:05 pm

Machine monkey wrote: Tue Mar 06, 2018 8:50 pm
Jonnoh2017 wrote: Tue Mar 06, 2018 8:19 pm
Machine monkey wrote: Tue Mar 06, 2018 8:07 pm Well done OP having built my own exhaust system a few times I know how rewarding it is. And also how difficult it is doing it under the car.

Also what you really don’t want on a turbo engine. Is any restriction after the turbo causing turbulence and back pressure. It will kill spoll and power and also make the turbo work harder and hotter. Basically all bad things.

Go get a cheeky remap and I bet there will be really noticeable improvement.
Cheers mate :-)

I agree , still got the cats in the downpipe so some backpressure there but I've carried out all other mods for around the quoted "420 BHP" from MHD tuner - Not sure how close to that figure it is.
But it sure goes well :-D

Thanks,
420 is health I am aiming for similar with my e85
Nice :-D ! - I held a meet in Bucks, doesnt seem youre too far, tag along next time ?

Whats yours running now ?

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