[stilov]

So, in the beginning, I read and searched and came to the conclusion catback was mostly for noise... (and maybe a couple hp)

Personally I couldn't justify the cost v. hp. I would rather spend money on mods that have substantial gains.

Now I sit, 3in dps, 2nd cats gone, dci, FMIC, JB4, and meth.

Am I missing out on power now? Has anyone done dyno testing on catbacks once all the other mods are done?


To give you an idea where I am coming from...I had an E39 M5 before. Mods were so much money for so little. Exhaust was similar...not too much to gain, unless you did headers.

So I cut out my cats, kept the stock resonator and put some magnaflow mufflers on it...It sounded great and I always got compliments on cruises, etc. I got all the sound benefit for a total of like 300 bucks.

[rader1]

There is a difference between "cat back" and "axel back." Deleting the secondary cats and resonator will yield a few hp, but just the axel back(muffler) is pretty much just noise

[stilov]

My 2ndary cats are already gone...

so do I have much to gain at this point? Not sure on my rwhp...gonna slap it on the dyno soon enough.

[Zeph]

Originally Posted by stilov

My 2ndary cats are already gone...

so do I have much to gain at this point? Not sure on my rwhp...gonna slap it on the dyno soon enough.

I think the 2ndary cats are the only power gain remaining after the DP's. The stock mufflers really aren't restricting flow enough to make or break HP numbers.

Zeph

[thebigragu99]

Originally Posted by Zeph

I think the 2ndary cats are the only power gain remaining after the DP's. The stock mufflers really aren't restricting flow enough to make or break HP numbers.

Zeph

Exactly the rear cats is where the power is made !

[stilov]

well then...check

[PlutoniumTans]

Has anyone opened stock mufflers to see how restrictive they are ? NO ! I think they are restrictive , def. not straight through, plus the piping diameter after 400 whp you'd want to go 2.5 on a double pipe setup.

[Brey335i]

You will gain 1 hp from going straight pipe from your current setup. Idk how you can comfortably leave that horsepower on the table

[PlutoniumTans]

Originally Posted by Brey335i

You will gain 1 hp from going straight pipe from your current setup. Idk how you can comfortably leave that horsepower on the table

I'm sure you'll gain good 10 - 15 whp

[PlutoniumTans]

it's not worth the money, you're not missing out on POWER really, I know others must be telling you turbo cars need super flow exhaust, but on our cars it's just FINE

[Jeff@TopGearSolutions]

If your looking for every last drop there is power. I havnt seen enough significant evidence to suggest an actual HP gain figure though.

[tofu-]

how much power is to be gained by deleting secondary cats? i thought it was negligible?

[thebigragu99]

Originally Posted by PlutoniumTans

Has anyone opened stock mufflers to see how restrictive they are ? NO ! I think they are restrictive , def. not straight through, plus the piping diameter after 400 whp you'd want to go 2.5 on a double pipe setup.

I know on a 135 the muffler has been cut open and the found out it's a resonator with a little packing stuffed in it..I'm not to sure about the 335,but I have heard it flows extremely well for a stocker.Spend you money on something else.gl

[Jeff@TopGearSolutions]

Originally Posted by thebigragu99

I know on a 135 the muffler has been cut open and the found out it's a resonator with a little packing stuffed in it..I'm not to sure about the 335,but I have heard it flows extremely well for a stocker.Spend you money on something else.gl

The 135i stock exhaust is a bottleneck as it goes from 2 to 1. The 335i does flow better in stock form then a 135i.

[merchomini]

so if you replace the 2ndary cats with straight pipe, this is as much gain as you would get from an exhaust.....does this throw any codes??

[thebigragu99]

Originally Posted by merchomini

so if you replace the 2ndary cats with straight pipe, this is as much gain as you would get from an exhaust.....does this throw any codes??

I felt it

[Jeff@TopGearSolutions]

Originally Posted by merchomini

so if you replace the 2ndary cats with straight pipe, this is as much gain as you would get from an exhaust.....does this throw any codes??

You still have any restriction in the muffler.

[merchomini]

Originally Posted by Jeff@topgearsolutions

You still have any restriction in the muffler.

what about it throwing codes?

[stilov]

Well I am sure there is a little power, but the noise plus cost, I consider those negatives and it doesn't sound like there is enough left to justify it.

[Jeff@TopGearSolutions]

Originally Posted by merchomini

what about it throwing codes?

Dont know of any codes for aftermarket catback.

[Beemw335]

Not worth it power wise, strictly for sound.
I say forget it, you wont feel the extra 5 hp andthats 5 hp at the most!

[chrisw335i]

if your completely catless then your not missing out