Derestricted Exhaust Stage 2

Tyres, exhausts, suspension, strut braces, air filters, brake pads/rotors and anything else for 'dawn raiders'.

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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Derestricted Exhaust Stage 2

Post by pingu » Sun 20 Apr, 2014 13:38

Quoted from here: http://www.zroadster.net/forum/viewtopi ... 15&t=31684

pingu wrote:I had a spare exhaust system, so I thought I'd have a look inside. The first thing to note is that it's a double-skin exhaust.

Under the double skin was this...

Image (RH Silencer)

Here's a diagram showing how the exhaust flows...

Image (RH Silencer)

Main entry pipe is fully open in Chamber 1, perforated in Chamber 2 and sealed from Chamber 3.

Secondary pipes are perforated in Chamber 1, perforated in Chamber 2 and fully open in Chamber 3.

Exit pipes are sealed from Chamber 1, sealed from Chamber 2 and perforated in Chamber 3.

---------------------------

I have de-restricted the exhausts by removing the secondary pipes and removing the perforations on the exit pipes...

Image (LH Silencer)

Here's a diagram of the new exhaust flow...

Image (RH Silencer)

The inner cut-out was welded back in place, then sealed with exhaust repair paste. The system was tested to a pressure of 8 bar. The outer cut-out heat shield was attached using exhaust repair paste, then painted using high temperature exhaust paint.

Finished result...

Image (LH Silencer)

All the modification has been done to the top of the silencer and none of this can be seen from under the car.

I can't objectively tell you what the improvements are, but it does sound slightly "fruitier" and a little bit less of a screamer at mid-revs.

There is less engine braking and the engine seems to rev more freely.


Inside the original box, the exhaust flow was ...

Image



I've decided to go onto "Stage 2" and totally derestrict the back box...

Last time, I used mild steel wire to weld the box and corrosion had started (as you would expect) ...

Image

I cut the top off the box using plasma cutting blades as they are thinner than normal metal cutting blades...

Image

Inside the "Stage 1" back box, the exhaust flow was ...

Image


After a lot of cutting and worn down discs, the inside now looks like this ...

Image


The exhaust flow will now be ...

Image

A bit different to the original, and much less reverse flow :) .


This time I used stainless steel welding wire, the downside being that stainless is very hard. This makes it difficult to grind to a pretty finish. Even though I used thin plasma disks, there was a gap of about 3mm all around, so bridging the gap took a lot of time. Again, I tested with compressed air and talcum powder.

Image


I've only done one box so far, and I'm waiting to get my car back from the spray shop before I fit the boxes, so I can't comment on performance or noise yet.
Last edited by pingu on Wed 23 Apr, 2014 23:51, edited 1 time in total.
Pingu

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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Re: Derestricted Exhaust Stage 2

Post by pingu » Wed 23 Apr, 2014 23:44

Both done now. Tested at 8 Bar and no leaks.

3kg saved :D .

Original = 15.5kg

Modified exhaust = 14kg

Another massive improvement in the Power-to-Weight ratio :) .

Can't wait to try them.
Pingu

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Althulas
Joined: Fri 13 Feb, 2009 00:55
Posts: 809

  M roadster S50

Re: Derestricted Exhaust Stage 2

Post by Althulas » Thu 24 Apr, 2014 03:49

Can you post a you tube video of the sound you achieve, be nice to hear a comparison to OEM.
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Deano1712
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Joined: Sat 05 Aug, 2006 13:56
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  M roadster S50
Location: Leeds

Re: Derestricted Exhaust Stage 2

Post by Deano1712 » Thu 24 Apr, 2014 06:19

Nice job. Some extra power and noise for free. Let us know the difference it makes.

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Silverlady
Joined: Tue 22 Apr, 2014 12:31
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  Z3 roadster 2.2i

Re: Derestricted Exhaust Stage 2

Post by Silverlady » Thu 24 Apr, 2014 09:40

Terrific stuff : we need blokes, boldly going, like Pingu !

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pingu
Joined: Fri 30 Apr, 2004 17:01
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  M roadster S50

Re: Derestricted Exhaust Stage 2

Post by pingu » Thu 24 Apr, 2014 12:15

I won't be able to test them for a while as the car is away getting sprayed and it's a "take your time" price, so it might not be back for some time.

I've got a standard set of rear boxes on the car at the moment and I'll do a sound test when I get the car back.

Ideally, I'd join the pipes with a Y pipe, but access is very limited (as you can see). The only way to do it would be to completely dismantle the back boxes, but I don't want the evidence to be visible, so that's out of the question.
Pingu

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aceman
Joined: Sun 01 Jun, 2008 12:16
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  M roadster S50
Location: Wakefield

Re: Derestricted Exhaust Stage 2

Post by aceman » Thu 24 Apr, 2014 21:24

Hey Pingu I didn't realise you were on with this job too otherwise I would have had a natter with you at Billz cruise earlier this month. I also have a spare set of silencers that I have totally gutted and removed all the baffles from inside so mine will be interesting when fitted. :wink: I have welded up one box so far although need to check it for leaks and I have also polished up the end plates which when fitted to the car should look quite nice, the rest of the box will be painted VHT black.

One question when you leak tested the box what did you use to plug the ends up as I have been thinking what would be the best way but like the idea of talc over the weld to spot any leaks.
Aceman

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pingu
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  M roadster S50

Re: Derestricted Exhaust Stage 2

Post by pingu » Fri 25 Apr, 2014 14:23

Wobbly Handcam Productions are proud to present...



Remember to clean off all the Vaseline and talcum powder, and take the paper towels out of the outlets.


(Daddy, why is that man putting Vaseline on that exhaust pipe?)
Pingu

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aceman
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Location: Wakefield

Re: Derestricted Exhaust Stage 2

Post by aceman » Fri 25 Apr, 2014 22:40

Cheers :D
Aceman

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Rocking seats ? You need seat bushes click HERE

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kruisn
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Re: Derestricted Exhaust Stage 2

Post by kruisn » Sat 04 Oct, 2014 23:15

Hey there Pingu. Have you got your rear box sorted yet? Or have I missed the sound file you were going to post?. I hope it all went well. Looking forward to the sound. Regards Kruisn.
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pingu
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Re: Derestricted Exhaust Stage 2

Post by pingu » Sun 02 Nov, 2014 21:17

Phone video of the car starting from cold...



Gets the juices flowing every time :).
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Althulas
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Re: Derestricted Exhaust Stage 2

Post by Althulas » Sun 02 Nov, 2014 22:31

Nice can you do a longer one and rev it a bit to? Gosh I sound like a kid but it does get the juices flowing.
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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Re: Derestricted Exhaust Stage 2

Post by pingu » Mon 03 Nov, 2014 01:59

Althulas wrote:Nice can you do a longer one and rev it a bit to? Gosh I sound like a kid but it does get the juices flowing.
It's SORN'd for a while. I'll do it after I've changed the clutch and done the gearbox shift pins - so it won't be soon :( .
Pingu

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