how much power can be gained from removal of secondary cats

Riceball777 · 08-29-2015, 03:31 AM

my car 335i has all the basic bolt ons running 91 octane. how much power can getting rid of the secondary cats free up? how much louder will it be? I have the stock exhaust with catless downpipes.

csu87 · 08-29-2015, 07:59 AM

Anywhere from 1 to a jiggawatt...

LQQKOUT · 08-29-2015, 08:11 AM

From what I was reading the rear cats are high flow, so removing them does little for power. By removing them you'll get a louder exhaust tone but that's about it.

infidel335 · 08-29-2015, 08:17 AM

Louder exhaust and a gas-like odor so consider that if this is your daily driver.

Jnat · 08-29-2015, 08:23 AM

Anything that removes back pressure will help with power in a turbo car to some degree. I would think no more then 5whp.

Antetokounmpo · 08-29-2015, 08:29 AM

Probably 300-400 hp.

Stucks · 08-29-2015, 12:54 PM

At lower power levels under 450whp, you wont see much of a gain, maybe a couple of whp. At these new higher horsepower levels that cars are making these days (550+ whp), youd prob see around 10whp from removing the secondary cats.

Riceball777 · 08-30-2015, 04:45 AM

so for a full bolt on stock turbo car running straight 91 octane it pretty much not worth it i suppose for only a few HP. I do plan on installing inlets soon as wekk a flashing in a e85 back end flash and i'll start running 50% e85.

JDuke335i · 08-30-2015, 03:12 PM

If you only gain 1 hp , it all counts in the end .

techwhiz · 08-30-2015, 11:52 PM

Not worth the trouble for the gas smell and other things.
The exhaust on the 335i is pretty well designed and you get noise, but no real HP.

CalmLikeABomb · 08-31-2015, 12:19 AM

The car sounds better and you will loose close to 45 lbs depending which brand. Not to mention some minor gains.

08-29-2015, 03:31 AM	#1
Riceball777 Lieutenant 163 Rep 466 Posts Drives: S2000 618whp/ e90 335i Join Date: Jul 2012 Location: Los Angeles iTrader: (0)	how much power can be gained from removal of secondary cats my car 335i has all the basic bolt ons running 91 octane. how much power can getting rid of the secondary cats free up? how much louder will it be? I have the stock exhaust with catless downpipes.
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08-29-2015, 07:59 AM	#2
csu87 Banned 2134 Rep 3,554 Posts Drives: 09 335xi Join Date: Nov 2013 Location: Northern Colorado iTrader: (0)	Anywhere from 1 to a jiggawatt...
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08-29-2015, 08:11 AM	#3
LQQKOUT Lieutenant 102 Rep 416 Posts Drives: 335XI Join Date: Jul 2011 Location: United States iTrader: (4)	From what I was reading the rear cats are high flow, so removing them does little for power. By removing them you'll get a louder exhaust tone but that's about it.
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08-29-2015, 08:17 AM	#4
infidel335 Lieutenant 29 Rep 454 Posts Drives: 2009 335xi Join Date: May 2012 Location: NoVA iTrader: (0)	Louder exhaust and a gas-like odor so consider that if this is your daily driver. __________________ 335xi: JB4 G5 \| KW V1s \| muffler delete \| BMS DCI \| VRSF 7" FMIC \| VMR v703 18x8 \| and your mom
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08-29-2015, 08:23 AM	#5
Jnat DisplacementReplacement 409 Rep 1,100 Posts Drives: 2020 X3M Join Date: Sep 2012 Location: Jersey Shore iTrader: (0)	Anything that removes back pressure will help with power in a turbo car to some degree. I would think no more then 5whp.
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08-29-2015, 08:29 AM	#6
Antetokounmpo Brigadier General 1550 Rep 3,475 Posts Drives: E90 6MT FBO; '18 F150 Platinum Join Date: Jul 2013 Location: WI iTrader: (3) Garage List 2018 Ford F-150 Pla ... [0.00] 2008 BMW 335xi [0.00]	Probably 300-400 hp. __________________ 2008 335xi 6MT \| VRSF Catless DP \| VRSF 7" FMIC \| VRSF CP \| TIAL BOV \| DCI \| MHD 2+ BC Racing BR \| Stoptech 600 \| Firehawk Indy 500 255 Square \| Atric Altimax 225 Sq. 2018 F-150 Platinum 701A \| FX4 \| 3.5 EcoBeast
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08-29-2015, 12:54 PM	#7
Stucks Lieutenant Colonel 172 Rep 1,909 Posts Drives: 2017 F30 340i Xdrive Join Date: Oct 2010 Location: Montgomery County, MD iTrader: (12)	At lower power levels under 450whp, you wont see much of a gain, maybe a couple of whp. At these new higher horsepower levels that cars are making these days (550+ whp), youd prob see around 10whp from removing the secondary cats. __________________ Current: 2017 F30 340i xdrive Previous: 2008 e92 335i coupe: RB turbos, mach 116 race fuel, methanol, alot of boost. Previous: 2003 Honda Accord V6 coupe: AEM V2, zex 75 wet shot (sold)
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08-30-2015, 04:45 AM	#8
Riceball777 Lieutenant 163 Rep 466 Posts Drives: S2000 618whp/ e90 335i Join Date: Jul 2012 Location: Los Angeles iTrader: (0)	so for a full bolt on stock turbo car running straight 91 octane it pretty much not worth it i suppose for only a few HP. I do plan on installing inlets soon as wekk a flashing in a e85 back end flash and i'll start running 50% e85. __________________ 2007 e90 335i pure stage 2 DD turbos, rb inlets
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08-30-2015, 03:12 PM	#9
JDuke335i Second Lieutenant 57 Rep 272 Posts Drives: 2009 335i , Alpine white Join Date: Aug 2014 Location: Bmw Land , sims (nc) iTrader: (0)	If you only gain 1 hp , it all counts in the end . __________________ FBO , MHD , tuned
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08-30-2015, 11:52 PM	#10
techwhiz Colonel 453 Rep 2,973 Posts Drives: e90 335i Sedan - Arctic Join Date: Feb 2012 Location: Bay Area, Ca iTrader: (4)	Not worth the trouble for the gas smell and other things. The exhaust on the 335i is pretty well designed and you get noise, but no real HP. __________________ Arctic Metallic\CF Splitters, Spoiler, Mirror Covers\LED Tails\LSD\Tinted\Coded\Apex Square SM10-19"\LED Angel Eyes\Gloss Black Grill\Integrated V1 & Galaxy Tab\M-Performance Brakes\Cobb Tuned\xHP Flash\Resonator Removed and -> is your friend.
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08-31-2015, 12:19 AM	#11
CalmLikeABomb Private 12 Rep 77 Posts Drives: 2009 e90 335i Join Date: Feb 2014 Location: San Diego iTrader: (0)	The car sounds better and you will loose close to 45 lbs depending which brand. Not to mention some minor gains.
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