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      04-04-2013, 03:13 AM   #1
System Of A...
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Thoughts on secondary cat delete? (already catless)

Hey guys, so I currently have turner test pipes (primary cat delete), no resonators, and a gintani race exhaust. Its shriekingly loud, but I thought why not remove the secondary cats as well? Might as well.

Will I notice a significant increase in smell if I do this? Will there be any power gain whatsoever? I noticed a niceeee increase in power around 4k with the test pipes. And ofcourse, how much of an increase in sound will I get? 20-30%? Thanks!

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      04-04-2013, 07:05 AM   #2
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Dont think you will get any power increase but it should be a decent amount louder
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      04-04-2013, 07:17 AM   #3
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Aren't the secondary CATS already HFC essentially? If said statement is true, you wouldn't really see much different once removing them.
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      04-04-2013, 09:22 AM   #4
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Even secondary cats are a restriction. Certainly less of a restriction than 400 cell cats, but also certainly more of a restriction than a resonator.
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      04-04-2013, 09:30 AM   #5
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It is to my understanding from trolling the forums that the 200 cells are ceramic OEM?
... and "HFC"s are metallic?

Even then, I suppose there would be a 5-7whp difference throughout the power band between the two setups or so. That said, the lower smell and db would definitely warrant KEEPING them if its a DD. Thoughts?
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      04-04-2013, 11:41 AM   #6
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Removing them to gain 5 whp on a 4000 lb car is a waste of time. It will smell more, and that coupled with a loud exhaust is just asking to get pulled over even more in CA.
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      04-04-2013, 11:45 AM   #7
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Quote:
Originally Posted by SYZ View Post
Removing them to gain 5 whp on a 4000 lb car is a waste of time. It will smell more, and that coupled with a loud exhaust is just asking to get pulled over even more in CA.
strong
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      04-04-2013, 11:58 AM   #8
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Why not replace the secondaries with a pair of resonators or high flow cats. Gain the 5hp without the added noise.
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      04-04-2013, 04:21 PM   #9
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Its actually worth less than 5rwhp, the dyno I saw done, it averaged 1.8rwhp over the setup with the rear cats still in.

To the OP it will smell a lot more and be raspy as hell. You will want to put the resonators back in.
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      04-04-2013, 06:31 PM   #10
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Do it. It will only smell for the ppl behind you haha
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      04-04-2013, 06:34 PM   #11
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Quote:
Originally Posted by JAM3S View Post
Do it. It will only smell for the ppl behind you haha
Not always...depending on wind and so on. Been in a few catless cars and as a passenger I could smell it sometimes.

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      04-05-2013, 12:38 AM   #12
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Quote:
Originally Posted by JAM3S
Do it. It will only smell for the ppl behind you haha
I smell my Akra when in garages and in reverse with windows open. There is definitely a difference for the driver IMO but totally worth it because its not overbearing.

But I think just removing secondary cats is not really much of a difference because you still have the 400 cel primaries doing most of the work.
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      04-05-2013, 01:31 AM   #13
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He is already catless/ test-pipes

IMO this is a bad idea. First it is illegal to go catless. Secondaries, for the 1.8 hp gain and mild gain in sound, you are going illegal which to me ain't worth it, nor do I want the smell to be that obvious when your sitting at a traffic light with a cop near by-just silly in my view.

Sounds like your car is obnoxiously loud and unfortunatly gives m3 drivers a bad name.
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      04-05-2013, 01:34 AM   #14
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Quote:
Originally Posted by M3takesNYC View Post
He is already catless/ test-pipes

IMO this is a bad idea. First it is illegal to go catless. Secondaries, for the 1.8 hp gain and mild gain in sound, you are going illegal which to me ain't worth it, nor do I want the smell to be that obvious when your sitting at a traffic light with a cop near by-just silly in my view.

Sounds like your car is obnoxiously loud and unfortunatly gives m3 drivers a bad name.
You're on the wrong forum. We love trouble, fast cars, and everything illegal. Op please post a video clip ASAP
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      04-05-2013, 07:14 AM   #15
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Quote:
Originally Posted by Lute View Post
As everyone has echoed

- Minimal gains
- Increased volume
- Largely increased smell
Time for this:

/thread.
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      04-05-2013, 09:40 AM   #16
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Quote:
Originally Posted by M3takesNYC View Post
He is already catless/ test-pipes

IMO this is a bad idea. First it is illegal to go catless. Secondaries, for the 1.8 hp gain and mild gain in sound, you are going illegal which to me ain't worth it, nor do I want the smell to be that obvious when your sitting at a traffic light with a cop near by-just silly in my view.

Sounds like your car is obnoxiously loud and unfortunatly gives m3 drivers a bad name.
Uh oh, Contrarian douche alert.

First you said he was catless then you said he wasn't. So anyone with test pipes gives M3 drivers a bad name?

I'm enjoying my catless IPE setup, maybe a 328i is more your speed if the sound of the V8 is too much for you.
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      04-05-2013, 01:46 PM   #17
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Thanks for all the input guys. I guess I won't move forward with this yet as the gains (sound/power) are not worth the time and money being spent to get them
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      04-05-2013, 02:14 PM   #18
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Not worth it. I've had catless cars before and you will end up smelling like exhaust when you get out of the car.
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      04-05-2013, 05:10 PM   #19
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Quote:
Originally Posted by SYZ View Post
Removing them to gain 5 whp on a 4000 lb car is a waste of time. It will smell more, and that coupled with a loud exhaust is just asking to get pulled over even more in CA.
great post. +1
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      04-05-2013, 07:22 PM   #20
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I gutted my secondary cats and modded my stock muffler. I love the sound and I can't smell any difference from before. A lot of people say you won't feel a gain or it's pointless. I say if you have the means to do it for free or on the cheap it's a good mod. I felt a increase in the power from it.

Originally I did this to see if I would be happy with this and if not I would fork out the cash for aftermarket. I'm happy with my $88 exhaust and best of all I can just tell people it's stock.
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