Are downpipes worth it if ...?

StartupJunkie · 02-10-2009, 02:00 PM

Hi Folks,

I'm under the belief that if you improve airflow in and out of the motor, that you can get more power.

If I upgrade my intake system, is there any benefit of replacing the downpipes without replacing the rest of the exhaust system (midpipes, mufflers)? I cannot find any conclusive evidence from past posts.

I have no interest in making any more noise than stock (kids+wife factor).

thanks,

Junk

ar design · 02-10-2009, 02:10 PM

Downpipes help significantly with both spoolup as well as power!

rcracer_tx · 02-10-2009, 02:13 PM

Quote:

Originally Posted by StartupJunkie

Hi Folks,

I'm under the belief that if you improve airflow in and out of the motor, that you can get more power.

If I upgrade my intake system, is there any benefit of replacing the downpipes without replacing the rest of the exhaust system (midpipes, mufflers)? I cannot find any conclusive evidence from past posts.

I have no interest in making any more noise than stock (kids+wife factor).

thanks,

Junk

Are you tuned? If not, you actually get more gains than if you were. You can easily make 20whp more with catless downpipes on stock exhaust without a tune...I say go for it

You will hear the turbos more though...

enrita · 02-10-2009, 02:26 PM

i have the AR catless DPS and axleback Bastuck and the sound its intoxicating. Secondary cat is still there. The car is more responsive with the dps and more willing to Rev. The turbos sounds really nice too:-) AR are great Dps you wont regreat ;-)

Gen_E92 · 02-10-2009, 02:45 PM

Quote:

Originally Posted by enrita

i have the AR catless DPS and axleback Bastuck and the sound its intoxicating. Secondary cat is still there. The car is more responsive with the dps and more willing to Rev. The turbos sounds really nice too:-) AR are great Dps you wont regreat ;-)

post some sound clips!

ar design · 02-10-2009, 02:48 PM

Quote:

Originally Posted by enrita

i have the AR catless DPS and axleback Bastuck and the sound its intoxicating. Secondary cat is still there. The car is more responsive with the dps and more willing to Rev. The turbos sounds really nice too:-) AR are great Dps you wont regreat ;-)

enrita · 02-10-2009, 03:24 PM

Quote:

Originally Posted by Gen_E92

post some sound clips!

Will try, i have become an expert in finding tunnels lately , even with minus 10 i have to pull down the window and do a WOT in the tunnel

ramorendez · 02-10-2009, 03:28 PM

Quote:

Originally Posted by enrita

Will try, i have become an expert in finding tunnels lately , even with minus 10 i have to pull down the window and do a WOT in the tunnel

Just don't step outside to do any recording!

NM_BMW · 02-10-2009, 03:30 PM

+1 AR pipes are great. You won't reap the benefits of downpipes and intake unless you have a tune. FWIW, I have a fully catless setup, AR Downpipes with the Vishnu Exhaust. I love the way my car sounds. It doesn't smell bad at all like some others have complained about a catless setup. The only way I can smell it is if your standing right behind the car.

StartupJunkie · 02-10-2009, 03:32 PM

Has anyone flowbenched the various sections to figure out what the most restricted section is? As you fix one area, a different will be the new constraining factor.

So is there concensus that a downpipe replacement doesn't add much noise in terms of exhaust note? I don't mind hearing a little "woosh" of the turbos.

Any posts with exhaust note would be greatly appreciated.

Thanks,

Junk

enrita · 02-10-2009, 03:34 PM

the main restriction are the DPs and i dont think it sound that much more with stock exhaust , maybe between 4-6K is more noticeable :-)
I am installing JB3 1.22 chip this weekend and i will definetely go in some tunnels since its better traction there as well to do WOT . Will definetely do a little video.

tibra1 · 11-18-2010, 11:17 PM

Can anyone give me more feedback on how bad it smells fully catless?

I got the AR Dps and AE exhaust for an e92...Im not sure if i should go ahead and order some HFCs or run it full catless..the smell does worry me

BrianMN · 11-18-2010, 11:24 PM

Woh old thread! It only smells when the car is stationary...and smell is subjective...I personally don't mind it one bit, but the next guy might gag.

tibra1 · 11-18-2010, 11:40 PM

Quote:

Originally Posted by BrianMN

Woh old thread! It only smells when the car is stationary...and smell is subjective...I personally don't mind it one bit, but the next guy might gag.

LOL..yeah reviving old threads but im desperate..dont know whether to weld the HFCs before I put it on..or try it fully catless and then see..

It is subjective, but there is no denying there is a smell..last thing i want is a nice car that stinks..its embarrasing..

themyst · 11-18-2010, 11:42 PM

Quote:

Originally Posted by rcracer_tx

Are you tuned? If not, you actually get more gains than if you were. You can easily make 20whp more with catless downpipes on stock exhaust without a tune...I say go for it

You will hear the turbos more though...

lol... startupjunkie now has the 2nd fastest 6AT on dragtimes

he's beyond tuned!

Forcefed3 · 11-18-2010, 11:43 PM

Quote:

Originally Posted by tibra1

LOL..yeah reviving old threads but im desperate..dont know whether to weld the HFCs before I put it on..or try it fully catless and then see..

It is subjective, but there is no denying there is a smell..last thing i want is a nice car that stinks..its embarrasing..

Try catless first.

tibra1 · 11-19-2010, 12:10 AM

Quote:

Originally Posted by gbreeE90

Try catless first.

Yea i will ,,thx

Bimmer This · 11-19-2010, 01:07 AM

Junk, a nice set of DP's will net you another 3 mph in the 1/4 mile.

tscdennab · 11-19-2010, 02:09 AM

I installed 2.5" catless DPs on a stock tune and BMW Performance Exhaust and I gained a lot of power, more than when I had the Power Kit installed. This is with the secondary cats in place.

The exhaust sounds significantly louder with the catless DPs.

I think the ideal setup would be catless DPs and high-flow secondary cats.

BrianMN · 11-19-2010, 06:59 AM

Quote:

Originally Posted by tscdennab

I installed 2.5" catless DPs on a stock tune and BMW Performance Exhaust and I gained a lot of power, more than when I had the Power Kit installed. This is with the secondary cats in place.

The exhaust sounds significantly louder with the catless DPs.

I think the ideal setup would be catless DPs and high-flow secondary cats.

Dyno for this?

**335i** · 11-19-2010, 08:14 AM

Quote:

Originally Posted by enrita

i have the AR catless DPS and axleback Bastuck and the sound its intoxicating. Secondary cat is still there.

why u still have second cats? delete them and u will get even better gains

about mufflers i think even u can leave all stock exhaust only delete second cats and then install catless dps also leave stock mufflers and u save $$$ instead of buying exhaust

all gains will be the same as you bought new exhaust

adrianBMW99 · 11-19-2010, 08:40 AM

Downpipes are generally the single most restrictive point of an exhaust. Yes, you will have power gains, more so than if you replaced any other part of the exhaust. On the sound note, DP's are a smart way to go as the car will be considerably quieter than installing a cat-back.

02-10-2009, 02:00 PM	#1
StartupJunkie First Lieutenant 30 Rep 314 Posts Drives: 07 BMW 335i Sedan+2 Baby Seats Join Date: Feb 2009 Location: SF South Bay Area, CA iTrader: (0)	Are downpipes worth it if ...? Hi Folks, I'm under the belief that if you improve airflow in and out of the motor, that you can get more power. If I upgrade my intake system, is there any benefit of replacing the downpipes without replacing the rest of the exhaust system (midpipes, mufflers)? I cannot find any conclusive evidence from past posts. I have no interest in making any more noise than stock (kids+wife factor). thanks, Junk
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02-10-2009, 02:10 PM	#2
ar design 302 Rep 4,408 Posts Drives: 04 M3 Join Date: Jan 2008 Location: Denver, CO iTrader: (9)	Downpipes help significantly with both spoolup as well as power! __________________ -Critter
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02-10-2009, 02:26 PM	#4
enrita Major General 161 Rep 7,377 Posts Drives: 335i - Big turbos Join Date: Sep 2008 Location: Italian in Sweden iTrader: (0)	i have the AR catless DPS and axleback Bastuck and the sound its intoxicating. Secondary cat is still there. The car is more responsive with the dps and more willing to Rev. The turbos sounds really nice too:-) AR are great Dps you wont regreat ;-) __________________ 07 335i AT - MOTIV 750 - MHD E85 BMS flash - BMS PI - JB4G5 - Okada Coils - NGK 5992 Plugs - Helix IC - Snow Stg. 3 - Stett CP - Custom midpipes with 100 HJS Cats - Bastuck Quad - PSS10 - QUAIFE LSD - BMS OCC - Forge DVs - AR OC - ALCON BBK - M3 Chassi - Dinan CP - Velocity M rear Toe arms - Advan RZ-DF - LUX H8 - Level 10 AT upgrade
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02-10-2009, 03:30 PM	#9
NM_BMW Vishnu Powered 74 Rep 2,205 Posts Drives: 335xi, S1000RR Join Date: Nov 2007 Location: Proceding iTrader: (7)	+1 AR pipes are great. You won't reap the benefits of downpipes and intake unless you have a tune. FWIW, I have a fully catless setup, AR Downpipes with the Vishnu Exhaust. I love the way my car sounds. It doesn't smell bad at all like some others have complained about a catless setup. The only way I can smell it is if your standing right behind the car. __________________ 2008 335xi Sedan \| Titanium Silver \| Black Dakota PROcede v5 \| Vishnu Exhaust \| BMS DCI \| AR Catless DPs \| Helix FMIC \| Stett Charge w/ Tial BOV \| MORR VS8s \| KWv3
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02-10-2009, 03:32 PM	#10
StartupJunkie First Lieutenant 30 Rep 314 Posts Drives: 07 BMW 335i Sedan+2 Baby Seats Join Date: Feb 2009 Location: SF South Bay Area, CA iTrader: (0)	Has anyone flowbenched the various sections to figure out what the most restricted section is? As you fix one area, a different will be the new constraining factor. So is there concensus that a downpipe replacement doesn't add much noise in terms of exhaust note? I don't mind hearing a little "woosh" of the turbos. Any posts with exhaust note would be greatly appreciated. Thanks, Junk
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02-10-2009, 03:34 PM	#11
enrita Major General 161 Rep 7,377 Posts Drives: 335i - Big turbos Join Date: Sep 2008 Location: Italian in Sweden iTrader: (0)	the main restriction are the DPs and i dont think it sound that much more with stock exhaust , maybe between 4-6K is more noticeable :-) I am installing JB3 1.22 chip this weekend and i will definetely go in some tunnels since its better traction there as well to do WOT . Will definetely do a little video. __________________ 07 335i AT - MOTIV 750 - MHD E85 BMS flash - BMS PI - JB4G5 - Okada Coils - NGK 5992 Plugs - Helix IC - Snow Stg. 3 - Stett CP - Custom midpipes with 100 HJS Cats - Bastuck Quad - PSS10 - QUAIFE LSD - BMS OCC - Forge DVs - AR OC - ALCON BBK - M3 Chassi - Dinan CP - Velocity M rear Toe arms - Advan RZ-DF - LUX H8 - Level 10 AT upgrade
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11-18-2010, 11:17 PM	#12
tibra1 Banned 132 Rep 6,773 Posts Drives: 2011 ZCP M3 - 2007 335i crashd Join Date: Apr 2009 Location: NYC iTrader: (4)	Can anyone give me more feedback on how bad it smells fully catless? I got the AR Dps and AE exhaust for an e92...Im not sure if i should go ahead and order some HFCs or run it full catless..the smell does worry me
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11-18-2010, 11:24 PM	#13
BrianMN Banned 117 Rep 2,428 Posts Drives: 4 Door Family Sedan Join Date: Sep 2009 Location: Minneapolis iTrader: (7)	Woh old thread! It only smells when the car is stationary...and smell is subjective...I personally don't mind it one bit, but the next guy might gag.
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11-19-2010, 01:07 AM	#18
Bimmer This Major General 103 Rep 6,473 Posts Drives: 2007 BMW 335i Join Date: Nov 2008 Location: Westminster iTrader: (3)	Junk, a nice set of DP's will net you another 3 mph in the 1/4 mile.
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11-19-2010, 02:09 AM	#19
tscdennab Banned 156 Rep 1,809 Posts Drives: BMW 335i Join Date: Oct 2010 Location: Europe iTrader: (0) Garage List 2008 BMW [6.24]	I installed 2.5" catless DPs on a stock tune and BMW Performance Exhaust and I gained a lot of power, more than when I had the Power Kit installed. This is with the secondary cats in place. The exhaust sounds significantly louder with the catless DPs. I think the ideal setup would be catless DPs and high-flow secondary cats.
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11-19-2010, 08:40 AM	#22
adrianBMW99 First Lieutenant 95 Rep 327 Posts Drives: BMW Join Date: Aug 2010 Location: FL iTrader: (0)	Downpipes are generally the single most restrictive point of an exhaust. Yes, you will have power gains, more so than if you replaced any other part of the exhaust. On the sound note, DP's are a smart way to go as the car will be considerably quieter than installing a cat-back.
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