Custom X Pipe with an OEM mod

BDO · 10-22-2014, 12:23 PM

I've been running the OEM modded backbox on my M3 pretty much since I bought it, so I am used to the deep, guttural growl at low rpm, eventually giving way to the engine induction noise as the revs climb over 4500rpm.

Last week I installed a catless (both primary and secondary cats deleted) x pipe, with a stage 2 tune. Power and torque improvements are awesome (around 30whp).

Sound wise, there are some problems. The first thing I noticed is that the deep rumble at low rpm (<3000) that I got with the OEM mod is gone. As in, totally gone. Next, I noticed a very loud, high pitched "rasp" between 3000 and 4000 rpm. With the first version of the x pipe, using "small" resonator boxes, this was just too loud and there was a fair whack of resonance too.

A bigger set ("medium") of resonators cured this, and brought the pitch and the volume of the "rasp" down to pleasant levels.

However, the low rpm sound is still MIA. Why is this, and what can I do to get it back?

grantmax · 10-22-2014, 12:31 PM

Catless and OEM Mod? You sir, did not do your research.

One does not simply remove cats with the OEM Mod. As you found out, it's one or the other.

BDO · 10-22-2014, 12:35 PM

Quote:

Originally Posted by grantmax

Catless and OEM Mod? You sir, did not do your research.

One does not simply remove cats with the OEM Mod. As you found out, it's one or the other.

Tell me more, please. And yes, I did all the research post the mods.

Damn my impulsive streak.

What actually happens when cats are removed and the OEM mod is present? Why is there such a marked difference in the sound?

Would I get better results by going back to the original (unmodded) backbox (which I still have)?

edwinm3 · 10-22-2014, 01:54 PM

Quote:

Originally Posted by BDO

Quote:

Originally Posted by grantmax

Catless and OEM Mod? You sir, did not do your research.

One does not simply remove cats with the OEM Mod. As you found out, it's one or the other.

Tell me more, please. And yes, I did all the research post the mods.

Damn my impulsive streak.

What actually happens when cats are removed and the OEM mod is present? Why is there such a marked difference in the sound?

Would I get better results by going back to the original (unmodded) backbox (which I still have)?

You'll still get rasp even with the unmolested muffler.

BDO · 10-22-2014, 02:34 PM

Quote:

Originally Posted by edwinm3

Quote:

Originally Posted by BDO

Quote:

Originally Posted by grantmax

Catless and OEM Mod? You sir, did not do your research.

One does not simply remove cats with the OEM Mod. As you found out, it's one or the other.

Tell me more, please. And yes, I did all the research post the mods.

Damn my impulsive streak.

What actually happens when cats are removed and the OEM mod is present? Why is there such a marked difference in the sound?

Would I get better results by going back to the original (unmodded) backbox (which I still have)?

You'll still get rasp even with the unmolested muffler.

I can live with the rasp as it is now. I want to do something to restore the deep rumble at low revs. Is that possible? What would the sound be like if I returned the old, stock backbox?

grantmax · 10-22-2014, 02:41 PM

Quote:

Originally Posted by BDO

I can live with the rasp as it is now. I want to do something to restore the deep rumble at low revs. Is that possible? What would the sound be like if I returned the old, stock backbox?

Best to swap to a different muffler. Megan, Corsa, and CNT all do a decent job of cleaning up the sound. Dinan too.

Rasp is great in moderation. Rasp with the OEM Mod is ruthless.

MTrezzz · 10-22-2014, 02:47 PM

Challenge Street X-pipe with OEM MODDED REAR sounds really good and for a DD it's great!

Not loud! Like ACM Test Pipes and ACM REAR.

BDO · 10-22-2014, 02:50 PM

Quote:

Originally Posted by MTrezzz

Challenge Street X-pipe with OEM MODDED REAR sounds really good and for a DD it's great!
Not loud!

Like ACM Test Pipes and ACM REAR.

My setup is not loud at all, and the rasp is not bad. I actually want a louder low rpm sound.

MTrezzz · 10-22-2014, 02:53 PM

Mastermind x-pipe with OEM REAR?
Challenge RACE plus maybe? with OEM REAR

s85e90 · 10-22-2014, 03:33 PM

Quote:

Originally Posted by MTrezzz

Mastermind x-pipe with OEM REAR?
Challenge RACE plus maybe? with OEM REAR

You're mentioning x pipes with no resonators at all that will sound like crap.

Dave07997S · 10-22-2014, 03:43 PM

Just have a couple of resonators welded into place, it will go along way in cleaning it up.

Thats why Borla and Dinan have catless xpipes but with resonators in place.

Dave

BDO · 10-22-2014, 03:54 PM

Quote:

Originally Posted by Dave07997S

Just have a couple of resonators welded into place, it will go along way in cleaning it up.

Thats why Borla and Dinan have catless xpipes but with resonators in place.

Dave

So another pair of resonators?

Dave07997S · 10-22-2014, 03:56 PM

Quote:

Originally Posted by BDO

So another pair of resonators?

You should get buy with just one set (pair).

I had a Riss racing xpipe with no cats or resonators and it was so raspy even with just the OEM box. I welded in 2 resonators and it sounded actually pretty good.

Dave

BDO · 10-22-2014, 04:11 PM

It already has a pair of resonators... And the rasp is not a problem. The lack of sound under 3000 rpm is.

Dave07997S · 10-22-2014, 04:53 PM

Quote:

Originally Posted by BDO

It already has a pair of resonators... And the rasp is not a problem. The lack of sound under 3000 rpm is.

Sorry misunderstood.

Dave

BDO · 10-23-2014, 02:54 PM

Quote:

Originally Posted by Dave07997S

Quote:

Originally Posted by BDO

It already has a pair of resonators... And the rasp is not a problem. The lack of sound under 3000 rpm is.

Sorry misunderstood.

Dave

Any pointers on my conundrum? I'm eyeing an Eisenmann Race backbox, what's your opinion on that setup with my x pipe when it comes to low rpm sound?

10-22-2014, 12:23 PM	#1
BDO Lieutenant 276 Rep 536 Posts Drives: 2016 X6 40d M-sport Join Date: Feb 2011 Location: Citizen of the World iTrader: (0)	Custom X Pipe with an OEM mod I've been running the OEM modded backbox on my M3 pretty much since I bought it, so I am used to the deep, guttural growl at low rpm, eventually giving way to the engine induction noise as the revs climb over 4500rpm. Last week I installed a catless (both primary and secondary cats deleted) x pipe, with a stage 2 tune. Power and torque improvements are awesome (around 30whp). Sound wise, there are some problems. The first thing I noticed is that the deep rumble at low rpm (<3000) that I got with the OEM mod is gone. As in, totally gone. Next, I noticed a very loud, high pitched "rasp" between 3000 and 4000 rpm. With the first version of the x pipe, using "small" resonator boxes, this was just too loud and there was a fair whack of resonance too. A bigger set ("medium") of resonators cured this, and brought the pitch and the volume of the "rasp" down to pleasant levels. However, the low rpm sound is still MIA. Why is this, and what can I do to get it back?
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10-22-2014, 12:31 PM	#2
grantmax Lieutenant Colonel 142 Rep 1,637 Posts Drives: 2011 M3 ZCP Join Date: Mar 2011 Location: LA iTrader: (1)	Catless and OEM Mod? You sir, did not do your research. One does not simply remove cats with the OEM Mod. As you found out, it's one or the other.
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10-22-2014, 02:47 PM	#7
MTrezzz Major 198 Rep 1,406 Posts Drives: Lime Rock Edition Join Date: Jan 2013 Location: Long Island iTrader: (1)	Challenge Street X-pipe with OEM MODDED REAR sounds really good and for a DD it's great! Not loud! Like ACM Test Pipes and ACM REAR.
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10-22-2014, 02:53 PM	#9
MTrezzz Major 198 Rep 1,406 Posts Drives: Lime Rock Edition Join Date: Jan 2013 Location: Long Island iTrader: (1)	Mastermind x-pipe with OEM REAR? Challenge RACE plus maybe? with OEM REAR
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10-22-2014, 03:43 PM	#11
Dave07997S Brigadier General 736 Rep 3,976 Posts Drives: 2020 Ford Mustang GT Join Date: May 2009 Location: El Segundo, CA iTrader: (1)	Just have a couple of resonators welded into place, it will go along way in cleaning it up. Thats why Borla and Dinan have catless xpipes but with resonators in place. Dave __________________ 2020 Ford Mustang GT 6MT PP1 444rwhp (Sold)2013 M3 Coupe-MR/BLK ZCP, 2011 M3 Coupe-MR/Blk 2007 Porsche 997C2S Speed Yellow/Blk sport seats 2004 BMW M3 Imola/Blk
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10-22-2014, 04:11 PM	#14
BDO Lieutenant 276 Rep 536 Posts Drives: 2016 X6 40d M-sport Join Date: Feb 2011 Location: Citizen of the World iTrader: (0)	It already has a pair of resonators... And the rasp is not a problem. The lack of sound under 3000 rpm is.
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