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Old 12-12-2007, 11:28 AM   #1
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Default What causes popping/"clapping" in the SRT4

I've been wondering for some time what causes the burble and pop on decel in an SRT4, it's very pronounced and Mopar even claims that their staged kits are tuned to increase it, so there must be a method to it. It's not quite as loud as ALS but it's definitely distinctive.

Just curious really, this isn't my "How do I get that sound in my Miata" thread
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Old 12-12-2007, 11:31 AM   #2
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Its unburnt fuel in the exhaust system igniting.
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Old 12-12-2007, 11:43 AM   #3
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yup, ignition cut i think
you can do that to your miata with MS i believe
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Old 12-12-2007, 11:52 AM   #4
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that thing must go through turbos and cats like mad. I do know there is also no muffler..
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Old 12-12-2007, 11:57 AM   #5
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Well, I'm at 65k and no problems with cats or turbos...
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Old 12-12-2007, 12:35 PM   #6
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Quote:
Originally Posted by Stealth97 View Post
I do know there is also no muffler..


There it is.

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Old 12-12-2007, 12:45 PM   #7
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Quote:
Originally Posted by BenR View Post
There it is.

Damnit you beat me to it.

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Old 12-12-2007, 12:59 PM   #8
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even a lean condition can cause the popping. my car does it too. it's definitely not rich on decel.

if you want it to make a lot of noise, drill a 1" hole in your downpipe.
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Old 12-12-2007, 03:21 PM   #9
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put the cat as far upstream as possible and add a very long, free flowing exhaust behind it. I was doing some reading on this a while back and retarding your timing 10-15 degrees under decel (more vac than idle) will make it much more pronounced. So on MS add a line in under the idle row and retard the timing 10 degrees from the idle value. That should do it.
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Old 12-12-2007, 08:32 PM   #10
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I don't want to make a bunch of noise, I'm just curious what makes the noise in my SRT4. Of course I know it doesn't have any mufflers, what the stock duals (long gone btw) look like, etc.

It got me thinking because a buddy of mine has a near identical SRT w/ side exit exhaust, Stage 3 ECU, catless DP etc. and his backblast on decel scares pedestrians.

Some of you are saying it's because it's rich, others that it could be lean, that there's an ignition cut involved.. so many theories.
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Old 12-12-2007, 08:42 PM   #11
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everything i own with non-stock exhuast has has a slight burbling noise when engine braking
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Old 12-12-2007, 11:54 PM   #12
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Quote:
Originally Posted by kotomile View Post
It got me thinking because a buddy of mine has a near identical SRT w/ side exit exhaust, Stage 3 ECU, catless DP etc. and his backblast on decel scares pedestrians.
I want mine to sound like that! we need to find out exactly what does this...
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Old 12-13-2007, 01:30 AM   #13
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judging by the color of the bumper, i'd say extra fuel
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Old 12-13-2007, 02:09 AM   #14
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i run no muffler and get it a LITTLE bit... IMO it's kind of a mean sound when u roll down to a stop and u get a bap bap bap every few rpms

as far as the gurgle sound, i believe it's the cams design in the srt-4, not 100% sure tho so don't hold me to it
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Old 12-13-2007, 02:19 AM   #15
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If you like noise enable launch control. You can just hold the throttle while you slow down with the clutch in.
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Old 12-13-2007, 02:22 AM   #16
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lol... that's not the same sound as an srt.... unless ur car's set up for it?
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Old 12-13-2007, 10:40 AM   #17
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I dont think it's the lack of mufflers. it's running super rich from all the pc-pros hidden under the dash.
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Old 12-13-2007, 10:52 AM   #18
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Just like was said above...
The reason it happens on the SRT OEM is the free flowing exhaust system and the car is is factory tuned a little rich.

When MS cuts fuel when I pull off the pedal and I get some gurgle/popping in my miata. Take off the muffler and I'm sure you'd have a nice loud afterfire.
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Old 12-13-2007, 11:17 AM   #19
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it does it on my miata, i think because i am running 9mm plugs and 87 octane should i be running 91 to stop the popping?
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Old 12-13-2007, 11:21 AM   #20
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Mine does it to, but it's because I cant get my dick out of the tailpipe.

Last edited by Braineack; 12-13-2007 at 11:42 AM.
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