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911 SC Exhaust Mod


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Hey guys and girls,

Could someone help me identify what muffler/exhaust set up I'm running. Ultimately I'm trying to work out what muffler I have so that I can work out if blocking an outlet will cause any issues. 

My plan is to fit a remote exhaust cut off valve to the driver side exhaust pipe so that I can close during highway driving/cruising and open when I want to hear the insane noise that comes from this car :P Any help would be much appreciated! From what I can tell it's a 2 in 2 out design. 

Here are some photos:




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1 minute ago, 81SC said:

The heat exchangers look like SSI. The muffler appears to be a Monty, judging by the shape of the end section.

You're correct about it being 2 in 2 out.

Thank you for your reply. The monty images I found online are all ridiculously shiny - mine looks very dull.. Could it just be wear?

The muffler looks like a banana :P

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Looking at the photos and the location of the spot welds indicates the location of the internal baffles are slightly different between the one outs and the two outs.

Enought to cause a problem?  I wouldn't think so as you'll have both outlets open at WOT and actuated by throttle bell rank mounted micro switch or low manifold vacuum.

If you're curious you could try two dyno runs, first both open, second one temporarily capped and just check you AFMs while you're at it.


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Looks like you're right :) As per your recommendation I sent Monty and email.

His reply was that it was his M22. In response to it being capped, he said:

The left and right sides meet and mix in the middle, then split . 
If you cap one side , not all the muffler is getting used, but all the gases will extract on one side.  
It will work, but the left and right side will not be balanced. 

Monty Manufacturing Pty Ltd
Email: sales@montymufflers.com
Mobile: 0427 814 824
Therefore my next step will be buying one of these (https://www.ebay.com.au/itm/3-76mm-Mannal-Electric-Exhaust-Catback-Downpipe-E-Cut-Out-Valve-System/152928459599?epid=25015833235&hash=item239b3f1b4f:g:ZPYAAOSwMgZamQfF) and placing it on the drivers side pipe for early morning/late night drives out of my area :P
Thanks for your help guys! Out of curiosity though - has anyone else done something like this on theirs?
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Before you go to the expense and effort of installing the valve, I suggest you block one outlet off with rag and tape as there is a fair chance that the reduction in noise might be a whole lot less than you think and the only answer is to replace the Monty with a Dansk version of the earlier style Porsche muffler.

As an ex Monty muffler owner, quiet wasn't a word I'd use to describe them.  Nice noise though!

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I literally just gave that a go but used a beetroot can with a worm clamp! haha the drone disappeared and everything was a lot less eventful... Idle noise wasn't reduced that significantly though... I'll take some noise measurements next chance I get. 

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