Exhaust tips protrude more when hot?

XMetal · 10-06-2016, 11:18 PM

My aftermarket exhaust tips always extend about 1/2 an inch further out after a drive. Can someone please help explain why this is happening? Looking at how the x-pipe/resonator is mounted, that portion of the mount shouldn't flex or move? So, I don't understand how the entire mufflers section can just extend out that much more horizontally when heated - where is the movement/expansion coming from? I don't remember seeing this with the OE exhaust, but every aftermarket exhausts that I've owned had done this (Supersprint Race, Remus Sports, and now Eisenmann Sports). Does anyone have a theory on this? Thanks.

Beedub · 10-07-2016, 05:02 AM

heat expansion.... every higher performance car I've had has done this.... the z4m does it to the extreme however they really grow after a blast.

mckenna4978 · 10-07-2016, 10:15 AM

Same here. I have an RPI cat back and the tips after a ride heat up and elongate outward. No big deal. It's the male enhancer...no Viagra needed.

XMetal · 10-07-2016, 03:50 PM

I know this isn't a big deal, but was just curious to know where the expansion would be coming from. I haven't owned any other cars that had done this.

StickMon · 10-07-2016, 03:56 PM

My guess is it comes from the entire run.
Can't imagine that any reasonable percentage growth would gain nearly an inch unless it was a percentage of the entire 8' or so run.
Sure is noticeable, and pretty freaky.

inTgr8r · 10-07-2016, 05:06 PM

Quote:

Originally Posted by Beedub

heat expansion.... every higher performance car I've had has done this.... the z4m does it to the extreme however they really grow after a blast.

The other reason is a Z4m gets happy when driven.

XMetal · 10-07-2016, 06:07 PM

Quote:

Originally Posted by StickMon

My guess is it comes from the entire run.
Can't imagine that any reasonable percentage growth would gain nearly an inch unless it was a percentage of the entire 8' or so run.
Sure is noticeable, and pretty freaky.

That makes sense if it's from the entire 8' or so run since the entire exhaust run is mounted on rubber isolators

Quote:

Originally Posted by inTgr8r

The other reason is a Z4m gets happy when driven.

This is so true

Reborn_ · 10-08-2016, 12:54 AM

Never noticed. I'm going to drive my car tomorrow and look for this.

dc_wright · 10-09-2016, 09:12 PM

Quote:

Originally Posted by XMetal

That makes sense if it's from the entire 8' or so run since the entire exhaust run is mounted on rubber isolators

The extension increase is greater than the thermal coefficient of the stainless steel the exhaust system is made from, so it's possible that the bends are straightening slightly as well. It would be interesting to measure to see if there's vertical travel as well as the extension.
I haven't noted this on my 3.0si, but I'm going to check it out next track day....

Carnifex · 10-10-2016, 07:36 AM

I noticed mine gets longer. The supersprint exhaust gets louder as it gets hotter as well.

XMetal · 10-10-2016, 10:13 AM

Quote:

Originally Posted by Carnifex

I noticed mine gets longer. The supersprint exhaust gets louder as it gets hotter as well.

Yep, same here - all of the exhausts I have/had behave the same as well (gets louder as it gets hotter)

StickMon · 10-10-2016, 03:45 PM

Yep, me too. The RE cans whistle under WOT when cold; almost sounds like a leak.
When hot the whistle turns into rasp, and they get a lot louder.

Nate4641 · 10-19-2016, 09:20 AM

Never noticed it until reading this, but my RPI cans do it too and they're the only exhaust mod I have

inTgr8r · 10-20-2016, 01:32 PM

some cars have a braided flex joint at the manifold connection which helps alleviate this.
Since ours is a hard connection we get the linear expansion pushing the tips out.

Westersund · 10-24-2016, 12:57 AM

Are you guys really talking about the exhaust system growing after a spirited drive or are you talking about the "exhaust".

10-06-2016, 11:18 PM	#1
XMetal Colonel 1128 Rep 2,863 Posts Drives: Anything Join Date: Apr 2010 Location: SoCal iTrader: (0) Garage List 2008 Z4M Coupe [10.00] 2018 Audi S3 [0.00] 2004 X5 [8.50]	Exhaust tips protrude more when hot? My aftermarket exhaust tips always extend about 1/2 an inch further out after a drive. Can someone please help explain why this is happening? Looking at how the x-pipe/resonator is mounted, that portion of the mount shouldn't flex or move? So, I don't understand how the entire mufflers section can just extend out that much more horizontally when heated - where is the movement/expansion coming from? I don't remember seeing this with the OE exhaust, but every aftermarket exhausts that I've owned had done this (Supersprint Race, Remus Sports, and now Eisenmann Sports). Does anyone have a theory on this? Thanks.
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10-07-2016, 05:02 AM	#2
Beedub Major General 423 Rep 5,327 Posts Drives: 2007 Z4 M roadster vt2-500 Join Date: Sep 2007 Location: UK iTrader: (0)	heat expansion.... every higher performance car I've had has done this.... the z4m does it to the extreme however they really grow after a blast. __________________ Z4MR VT2 - Clubsport build. Multi award winning Detailing \| Wrap \| PPF specialists UK based - www.topwrapz.com
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10-07-2016, 10:15 AM	#3
mckenna4978 Private First Class 21 Rep 110 Posts Drives: 07' BMW z4mr-A08 Join Date: Dec 2014 Location: chicago,illinois iTrader: (0)	Same here. I have an RPI cat back and the tips after a ride heat up and elongate outward. No big deal. It's the male enhancer...no Viagra needed.
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10-07-2016, 03:50 PM	#4
XMetal Colonel 1128 Rep 2,863 Posts Drives: Anything Join Date: Apr 2010 Location: SoCal iTrader: (0) Garage List 2008 Z4M Coupe [10.00] 2018 Audi S3 [0.00] 2004 X5 [8.50]	I know this isn't a big deal, but was just curious to know where the expansion would be coming from. I haven't owned any other cars that had done this.
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10-07-2016, 03:56 PM	#5
StickMon My other car is on Mars 636 Rep 3,124 Posts Drives: 2006 MR Join Date: Feb 2011 Location: Lo-Cal iTrader: (1)	My guess is it comes from the entire run. Can't imagine that any reasonable percentage growth would gain nearly an inch unless it was a percentage of the entire 8' or so run. Sure is noticeable, and pretty freaky. __________________ Warning: May contain traces of nuts.
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10-08-2016, 12:54 AM	#8
Reborn_ Lieutenant 295 Rep 410 Posts Drives: 2007 BMW Z4MC Join Date: Dec 2014 Location: SoCal iTrader: (7)	Never noticed. I'm going to drive my car tomorrow and look for this.
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10-10-2016, 07:36 AM	#10
Carnifex New Member 10 Rep 16 Posts Drives: Z4M Coupe Join Date: Nov 2015 Location: Virginia iTrader: (0)	I noticed mine gets longer. The supersprint exhaust gets louder as it gets hotter as well.
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10-10-2016, 03:45 PM	#12
StickMon My other car is on Mars 636 Rep 3,124 Posts Drives: 2006 MR Join Date: Feb 2011 Location: Lo-Cal iTrader: (1)	Yep, me too. The RE cans whistle under WOT when cold; almost sounds like a leak. When hot the whistle turns into rasp, and they get a lot louder. __________________ Warning: May contain traces of nuts.
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10-19-2016, 09:20 AM	#13
Nate4641 Major 151 Rep 1,134 Posts Drives: '07 M Roadster Join Date: Dec 2011 Location: Warner Robins, GA iTrader: (0) Garage List 2007 BMW Z4 M Roadster [0.00]	Never noticed it until reading this, but my RPI cans do it too and they're the only exhaust mod I have __________________ My build/adventure thread
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10-20-2016, 01:32 PM	#14
inTgr8r Lieutenant General 2426 Rep 11,667 Posts Drives: M2 Comp Join Date: Mar 2006 Location: Toronto iTrader: (10)	some cars have a braided flex joint at the manifold connection which helps alleviate this. Since ours is a hard connection we get the linear expansion pushing the tips out. __________________ '21 M2C Hockenheim Silver '18 718 Cayman S Lava Orange (sold) '13 E92 M3 Santorini Blue (sold) '07 Z4 M Coupe Alpine White (sold)
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10-24-2016, 12:57 AM	#15
Westersund Captain 496 Rep 869 Posts Drives: BMW Join Date: Nov 2011 Location: Hallstahammar iTrader: (1)	Are you guys really talking about the exhaust system growing after a spirited drive or are you talking about the "exhaust".
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