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Author Topic: Loud POP on gear change after pre cat removal, will it do any damage?  (Read 3094 times)

Offline sideshowfred

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Loud POP on gear change after pre cat removal, will it do any damage?
« on: May 25, 2012, 07:37:42 pm »
If this is the wrong section please feel free to move it.

Removed the pre cat from the downpipe last weekend and ever since within the first 10 mins of driving I get a loud, sometimes VERY loud, pop from the exhaust just after I slot into the next gear. It only happens at 3k rpm or there abouts. Whilst I really like the sound and intend on making it as often as possible i'm a little concerned it might be doing damage to either the turbo or cat?

Secondly, why is it making this pop? Like i say, i really like the sound  :driver:

Has anyone else had the same thing happen? Manual box, rest of the exhaust is standard as is engine other than a Pipercross panel filter.

Your thoughts please
  :smiley:
« Last Edit: May 25, 2012, 07:54:04 pm by sideshowfred »
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Offline jhtrophy

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #1 on: May 25, 2012, 07:53:09 pm »
dsg?
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Offline sideshowfred

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #2 on: May 25, 2012, 07:53:42 pm »
No, manual, forgot to add that bit
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Saintsteve

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #3 on: May 25, 2012, 08:03:47 pm »
It's un- burnt fuel in your exhaust.. You will get this being audible because you've now removed the pre cat.

you've removed the designed pre cat, which reduces the back pressure of the exhaust gases, so, it's part and parcel with your modification you've made.

Apart from giving you a possible emission failure at your MOT it shouldnt damage anything..
« Last Edit: May 25, 2012, 08:05:29 pm by Saintsteve »
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Offline Marshall

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #4 on: May 25, 2012, 09:51:43 pm »
I have a Pipewerx downpipe connected to original catback and after a cold start for the first few minutes if you rev to say 3000 rpm it sounds like it backfires like hell on lift off.
Perfectly normal once there's no pre cat


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Offline Shorty

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #5 on: May 25, 2012, 10:10:41 pm »
Yeah its normal, enjoy it.  :smiley:
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Offline -blade-

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #6 on: May 25, 2012, 10:45:22 pm »
..........and along with the pop you can sometimes see the unburnt fuel flash out of the exhaust when it ignites.... i guess the more straight and unrestricted the exhaust system the more likely the flame will show ( i had a skyline a while back that would get me in trouble in pedestrian areas  :stupid: plus the cars behind flashing at me due to the foot long flame coming thier way  :laugh: )

but no, no damage will be caused by your popping
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Offline sideshowfred

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #7 on: May 26, 2012, 09:08:09 am »
Cheers guys. I will now enjoy it fully knowing it won't damage anything.  :driver:
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Offline Dan.b

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #8 on: May 26, 2012, 10:09:23 am »
Video of said noise please  :happy2:
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Offline GrayMK5GTI

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #9 on: May 26, 2012, 10:55:18 am »
Quote from: Saintsteve on May 25, 2012, 08:03:47 pm
It's un- burnt fuel in your exhaust.. You will get this being audible because you've now removed the pre cat.

you've removed the designed pre cat, which reduces the back pressure of the exhaust gases, so, it's part and parcel with your modification you've made.

Apart from giving you a possible emission failure at your MOT it shouldnt damage anything..

Wrong. Pre cat is to aid cold start emissions which isn't tested on the UK MOT  :grin: also, as the Miltek, blue flame exhausts etc don't have a pre-cat. . . .

Several of us have passed MOT without the pre-cat in place (me included)

Wish mine did those pops  :happy2:
« Last Edit: May 26, 2012, 10:57:44 am by GrayMK5GTI »
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Saintsteve

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #10 on: May 26, 2012, 02:37:47 pm »
My Dsg does pop, with it's non res milltek installed.

I'm guessing the main Cat is still keeping the emissions under control if that's the case?
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Offline biffobear

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #11 on: May 26, 2012, 03:29:53 pm »
mine passed mot 3 weeks ago no problem with pre cat removed.
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Offline sideshowfred

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #12 on: May 26, 2012, 07:15:08 pm »
I'll try and get a video done in the morning guys. Took my mate out in the car earlier and he was surprised how loud they were!!
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Offline GrayMK5GTI

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #13 on: May 26, 2012, 07:40:13 pm »
Quote from: Saintsteve on May 26, 2012, 02:37:47 pm
My Dsg does pop, with it's non res milltek installed.

I'm guessing the main Cat is still keeping the emissions under control if that's the case?

Yeah the main cat is 800CEL so that will keep the emissions down  :happy2:
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Offline RetroRaz

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Re: Loud POP on gear change after pre cat removal, will it do any damage?
« Reply #14 on: November 18, 2013, 12:13:38 pm »
sorry for reviving an old thread, but has anyone else experienced these pops? or any other problems from removing the pre cat?
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