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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > any one thought of gutting downpipes?



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      05-04-2007, 10:15 PM   #1
jerrygarcia
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any one thought of gutting downpipes?

the b5 s4 guys do this a lot and it produces pretty good gains, comparable to aftermarket dps. Wondering if anyone has looked into doing this. I know nothing about the process of actually gutting it, just that the s4 guys do it.
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      05-04-2007, 10:18 PM   #2
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dp? dps??
downpipes? diapers? you never know with the audi guys...

ditch the abriviations, just type out the words already... unless you like seeing people ask "what is a dp"

isnt it the pre-cats that they gut???
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      05-04-2007, 10:22 PM   #3
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hes probably talking about gutting the cats out, ive heard of people doing this

but i think they are dumb, who wants shitty smelling gas and a back bumper with a nice soot stain on it?
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      05-04-2007, 10:48 PM   #4
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Quote:
Originally Posted by 533ogetnom View Post
hes probably talking about gutting the cats out, ive heard of people doing this

but i think they are dumb, who wants shitty smelling gas and a back bumper with a nice soot stain on it?
They probably think your an idiot. If you take the cats you can gain up to an extra 20-30whp and not only that but you can run c16 fuel and a map made for it and gain anywhere up to another 80-100whp, then your talkin about a 450-500whp 335i with god knows how much torque. Does that sound dumb to you?
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      05-04-2007, 11:37 PM   #5
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Originally Posted by SoCal335i View Post
They probably think your an idiot. If you take the cats you can gain up to an extra 20-30whp and not only that but you can run c16 fuel and a map made for it and gain anywhere up to another 80-100whp, then your talkin about a 450-500whp 335i with god knows how much torque. Does that sound dumb to you?
yea, yea actually it does
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      05-05-2007, 12:54 AM   #6
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yea, yea actually it does
Then keep your car slow. Thats not what im about. Remember if you're not first, you're last!
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      05-05-2007, 12:55 AM   #7
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Quote:
Originally Posted by 533ogetnom View Post
hes probably talking about gutting the cats out, ive heard of people doing this

but i think they are dumb, who wants shitty smelling gas and a back bumper with a nice soot stain on it?
hahahahah you again......are you serious?

I have ran no cat on my big turbo A4...have been through plenty of C16, 109, 103,100, and 91 octane..... and never once got a "nice soot stain".

C16 on straight pipe will make your exhaust tips like a powder white, but then whipes right off. you might get a different smell, and i dont know about you but straight pipe, no cat and race gas is the BEST SMELL EVER!!!

who would want 30-40hp and a "smell" of gas......shit sign me up.
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      05-05-2007, 01:17 AM   #8
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its not just that, its the simple fact that its highly illegal, and for a reason, the diffrence in pollutants is like the diffrence between the country dumping their oil into the nearest lake and recycling it.

its a shitty thing to do plain and simple.
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      05-05-2007, 01:44 AM   #9
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I have downpipes on mine... we will be selling them and full cat-less and cat-back exhaust systems shortly
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      05-05-2007, 01:45 AM   #10
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Quote:
Originally Posted by 533ogetnom View Post
its not just that, its the simple fact that its highly illegal, and for a reason, the diffrence in pollutants is like the diffrence between the country dumping their oil into the nearest lake and recycling it.

its a shitty thing to do plain and simple.
Its not a big deal in some states.
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      05-05-2007, 03:58 AM   #11
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Not to mention in Cali. you won't pass emissions again.
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      05-05-2007, 07:39 AM   #12
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Quote:
Originally Posted by 533ogetnom View Post
hes probably talking about gutting the cats out, ive heard of people doing this

but i think they are dumb, who wants shitty smelling gas and a back bumper with a nice soot stain on it?
With the B5 S4 reference he is referring to the pre-cats; the main cats remain intact. In fact, emissions also remain fully intact while gaining 20+ WHP and about the same in torque. This is all without soot build-up or any change in smell.

Now, not having been under this car yet as mine is due to arrive in a week, I do not know for sure how many cats are on this vehicle. From what I have gathered there would be only one per bank so two in total and in parallel. So there is no pre-cat to gut. The only option would be to gut the main cats which I would take not suggest for a road going vehicle. Plus, the location of the cat for bank 1 would make it nearly impossible to gut. As such and if that extra power is needed, built downpipes would be a better option.
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      05-05-2007, 07:41 AM   #13
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Its not a big deal in some states.
But it is against federal regulations. While the lack of emissions testing in some states allows this to be easily done; it is still against federal law.
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      05-05-2007, 11:07 AM   #14
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I had a serious cat-less soot stain on the rear of my s2k, I would wash the car and drive around the block and it would be back! I think that was more of a tuning issue with running too rich and the fact that the muffler was too close to the bumper though. The cat-less smell is really no big deal though IMO. Just slap a lot of wax on your rear bumper.

As far as gutting the cats goes, I think that I would just wait for an aftermarket downpipe to come out (I mean other then supersprint who makes some, but they are retardedly expensive). Another problem is going to be tricking the ECU into thinking that they are still on there. No one has been able to say if a simple mechanical o2 simulator would work for the 335.
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      05-05-2007, 12:38 PM   #15
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I'm waiting for someone to make a bolt in offroad down pipe.
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      05-05-2007, 03:12 PM   #16
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I'm waiting for someone to make a bolt in offroad down pipe.
If the stock units are not double walled then they are extremely large and aftermarket units may not provide any benefits. The bends are not too bad either...
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      05-05-2007, 03:16 PM   #17
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Quote:
Originally Posted by BoostedBMW View Post
I had a serious cat-less soot stain on the rear of my s2k, I would wash the car and drive around the block and it would be back! I think that was more of a tuning issue with running too rich and the fact that the muffler was too close to the bumper though. The cat-less smell is really no big deal though IMO. Just slap a lot of wax on your rear bumper.

As far as gutting the cats goes, I think that I would just wait for an aftermarket downpipe to come out (I mean other then supersprint who makes some, but they are retardedly expensive). Another problem is going to be tricking the ECU into thinking that they are still on there. No one has been able to say if a simple mechanical o2 simulator would work for the 335.
A previous Acura CL Type-S 6MT I owned would get some soot in stock form. This was compounded when the blower and my custom liquid/air IC was installed. It was definitely tuning related. I had to run near 11:0.1 to keep knock at bay.
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      05-05-2007, 03:23 PM   #18
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If the stock units are not double walled then they are extremely large and aftermarket units may not provide any benefits. The bends are not too bad either...
True it's hard to say, but dumping the cats and cleaning up the bends a little might make a big difference. The closer to the turbo, the higher flowing your exhaust needs to be! Let's just say I'm very optimistic a good downpipe will be worth around 15-20rwhp in a high boost car.
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      05-05-2007, 03:29 PM   #19
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Quote:
Originally Posted by Terry335 View Post
True it's hard to say, but dumping the cats and cleaning up the bends a little might make a big difference. The closer to the turbo, the higher flowing your exhaust needs to be! Let's just say I'm very optimistic a good downpipe will be worth around 15-20rwhp in a high boost car.
Without the cats I would definitely agree. Especially once some laregr snails are attached.

However, I would love to see a catalytic converter pressure drop test to get an idea on the potential bottleneck of the stock cores.
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      05-05-2007, 03:31 PM   #20
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Without the cats I would definitely agree. Especially once some laregr snails are attached.

However, I would love to see a catalytic converter pressure drop test to get an idea on the potential bottleneck of the stock cores.
Yeah same here. Maybe everyone can ship in $10 and I'll gut my cats/dyno to see the difference?
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      05-05-2007, 03:34 PM   #21
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Yeah same here. Maybe everyone can ship in $10 and I'll gut my cats/dyno to see the difference?
PETA may get involved once they hear of this cat gutting fund.
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      05-05-2007, 04:15 PM   #22
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Quote:
Originally Posted by 533ogetnom View Post
its not just that, its the simple fact that its highly illegal, and for a reason, the diffrence in pollutants is like the diffrence between the country dumping their oil into the nearest lake and recycling it.

its a shitty thing to do plain and simple.
your realy going to say this about a BMW with no cat that honeslty is not even much difference than running a cat as far as smog goes.....seroiusly it is not much different. but your going to gripe about a BMW vs a schoo. bus, city bus, big rig, tractors, etc?

hate to break it to you but state cars are doing it 50 tmes more than motor vehicles are!

and im not trying to start an argument, its just the simple truth
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