Sunday 29 July 2018

porsche cayenne turbo 955 v8 exhaust bypass DIY guide

Love the sound of my cayenne turbo - but it's a pity you can only hear that V8 burble when you're right at the exhaust.

Many people have done an exhaust bypass - it's actually quite a clever and simple (and really cheap!) way to open up the sound of your engine!

What we're doing here is bypassing the rear muffler, by sliding some flexible pipe inside the muffler so the exhaust gases aren't muffled and pass straight through - so tell all your mates you've straight-piped your cayenne!

Tools and parts required

Instead of buying a new exhaust system, all we need for this exhaust bypass is...

  • Gloves and a mat to lie on
  • 15mm socket and/or wrench
  • To clean your exhaust: metal polish, rags, a rotary tool of some kind or wire brush
  • 2" (50mm) internal diameter flexible exhaust hose/pipe, about 1m long in length. A hacksaw or other tool to cut this pipe in half.

So, this is the standard appearance. A bit dirty! I've raised the car up as high as possible on the air suspension which gives plenty of room to get underneath.

Looking up under the exhaust tips, you'll see this clamp with a 15mm bolt on it (Some people have found theirs is 16mm though). Spray a bit of WD40 or equivalent, then crack it open and unbolt this clamp, then remove exhaust tips.

Put your filthy exhaust tips aside for the time being.

Now on my car (Australian spec Cayenne Turbo) there were these little pipe/projections visible in the rear muffler, and I was unlucky enough to have them on both sides. Some people report being able to remove these pipes by sawing away at them with a hacksaw blade - didn't work for me. I tried a dremel with every tool, no good either. Ultimately the only way for me to remove them was with a metal hole-saw attached to an electric drill. The holesaw got destroyed in the process, but at least these pipes came out!

Seriously, getting these little things out was the hardest part of the whole process. You could also use a small reciprocating saw with a long enough metal cutting blade if you have one.

This is the flexible exhaust pipe you'll need. Cost about AUD$50 delivered on ebay for about 1m length. Some people use 2" stainless pipe - that'll work too.

So this is how the flexible exhaust sits inside the muffler. There's a little bit of play, but I'm hoping the length will stop it from moving. If you look at the muffler you'll see two pipes going into the muffler - measure & cut your exhaust hose so that it allows the entrance pipes to be unblocked. I cut mine to about 45cm.

Anyway, now to cleaning the old exhaust tips - don't think it was ever done since the car was new! First sprayed with a lot of degreaser and all-purpose cleaner and rinsed. Used a wire brush on an electric drill to buff off all the old stain and corrosion.

Then used metal polish and rags to try to brighten up the tips a little. They'll never look like chrome exhaust tips due to the brushed metal finish, but they're a lot cleaner at least.

Both done.

Finally, reinstallation of the exhaust tips is the reverse of disassembly.

Of course - you'll want to check out this video for sound before & after!

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