High-Flow Cats Sizing
#1
Senior Member
Thread Starter
Join Date: Aug 2011
Location: Richmond BC
Posts: 338
Likes: 0
Received 0 Likes
on
0 Posts
2011 C63 Calcite White
High-Flow Cats Sizing
Anyone know the proper sizes high-flow cats we need to replace the stock secondary cats?
will these sizes fit?
2.5" inlet-outlet
4" body diameter
11" length or 12" length?
Also is 200CEL a big difference compare to the 300CEL? I kinda want the 300CEL for less fuel smell unless the 200CEL has a much noticeable gain.
Thanks for your helps
will these sizes fit?
2.5" inlet-outlet
4" body diameter
11" length or 12" length?
Also is 200CEL a big difference compare to the 300CEL? I kinda want the 300CEL for less fuel smell unless the 200CEL has a much noticeable gain.
Thanks for your helps
#2
Senior Member
Join Date: Jul 2002
Location: Bay Area, CA
Posts: 375
Likes: 0
Received 0 Likes
on
0 Posts
2010 C63, 2007 X5
Most people just remove the 2nd cats, kept the primary cats and replaced it straight or x-pipe. When I removed my 2nd cats, it only had a minor fuel smell. You also will gain about 5-10 hp by removing the 2nd cats.
#4
Senior Member
Thread Starter
Join Date: Aug 2011
Location: Richmond BC
Posts: 338
Likes: 0
Received 0 Likes
on
0 Posts
2011 C63 Calcite White
I don't really mind the fuel smell, but gf is sensitive to it and hate it . It would also be much less hassle to just put an xpipe on.
#5
Super Member
I think I'm one of the few running high flow cats (300cel if I remember right) with the long tube headers as most delete them, but even with the cats I noticed a bit more gas smell after the mods. No, it is not noticeable inside the cabin, and outside the car it doesn't bother me but there is a noticeable increase.
If you still have your primary cats in place, then I would say without hesitation just delete the secondary cats, because all of the above I referenced was without primary cats.
And I would say there is a minor hp loss with the cats, 5-10hp sounds about right as BO Knows pointed out. But at the track and in real world conditions as you can imagine, it's almost immeasurable on a 450-550hp car depending on mods.
If you still have your primary cats in place, then I would say without hesitation just delete the secondary cats, because all of the above I referenced was without primary cats.
And I would say there is a minor hp loss with the cats, 5-10hp sounds about right as BO Knows pointed out. But at the track and in real world conditions as you can imagine, it's almost immeasurable on a 450-550hp car depending on mods.
#6
Senior Member
Thread Starter
Join Date: Aug 2011
Location: Richmond BC
Posts: 338
Likes: 0
Received 0 Likes
on
0 Posts
2011 C63 Calcite White
I think I'm one of the few running high flow cats (300cel if I remember right) with the long tube headers as most delete them, but even with the cats I noticed a bit more gas smell after the mods. No, it is not noticeable inside the cabin, and outside the car it doesn't bother me but there is a noticeable increase.
If you still have your primary cats in place, then I would say without hesitation just delete the secondary cats, because all of the above I referenced was without primary cats.
And I would say there is a minor hp loss with the cats, 5-10hp sounds about right as BO Knows pointed out. But at the track and in real world conditions as you can imagine, it's almost immeasurable on a 450-550hp car depending on mods.
If you still have your primary cats in place, then I would say without hesitation just delete the secondary cats, because all of the above I referenced was without primary cats.
And I would say there is a minor hp loss with the cats, 5-10hp sounds about right as BO Knows pointed out. But at the track and in real world conditions as you can imagine, it's almost immeasurable on a 450-550hp car depending on mods.
-Put my resonators back on and straight-pipe the 2ndary cats.
or
-Keep straight pipe in place of resonator and xpipe the 2ndary cats.
or
-Keep straight pipe in place of resonator and straight pipe the 2ndary cats. (I suppose this option will lose power, but will be be bad for the engine?)
Thanks
#7
I think I'm one of the few running high flow cats (300cel if I remember right) with the long tube headers as most delete them, but even with the cats I noticed a bit more gas smell after the mods. No, it is not noticeable inside the cabin, and outside the car it doesn't bother me but there is a noticeable increase.
If you still have your primary cats in place, then I would say without hesitation just delete the secondary cats, because all of the above I referenced was without primary cats.
And I would say there is a minor hp loss with the cats, 5-10hp sounds about right as BO Knows pointed out. But at the track and in real world conditions as you can imagine, it's almost immeasurable on a 450-550hp car depending on mods.
If you still have your primary cats in place, then I would say without hesitation just delete the secondary cats, because all of the above I referenced was without primary cats.
And I would say there is a minor hp loss with the cats, 5-10hp sounds about right as BO Knows pointed out. But at the track and in real world conditions as you can imagine, it's almost immeasurable on a 450-550hp car depending on mods.
Do you have a sound clip or a video of your car running? I am curious as to how much the 300 cell cats quietened the exhaust.
Trending Topics
#8
Senior Member
Join Date: Jul 2002
Location: Bay Area, CA
Posts: 375
Likes: 0
Received 0 Likes
on
0 Posts
2010 C63, 2007 X5
Oh thanks for the info and yeah I got my primaries on, do you know which set up would be better sounding, i don't really care for performance as I only drive around the city.
-Put my resonators back on and straight-pipe the 2ndary cats.
or
-Keep straight pipe in place of resonator and xpipe the 2ndary cats.
or
-Keep straight pipe in place of resonator and straight pipe the 2ndary cats. (I suppose this option will lose power, but will be be bad for the engine?)
Thanks
-Put my resonators back on and straight-pipe the 2ndary cats.
or
-Keep straight pipe in place of resonator and xpipe the 2ndary cats.
or
-Keep straight pipe in place of resonator and straight pipe the 2ndary cats. (I suppose this option will lose power, but will be be bad for the engine?)
Thanks
http://www.mbhmotorsports.com/C63-OEM-X-pipe.html
It will give you a bit more performance and better sound. If it's still not loud enough for you, then remove the resonator and straight pipe it. None of this will lose power, in fact it will only increase power and does no harm to your engine. Also no Check Engine Light.
#9
MBWorld Fanatic!
You should not get any gas smell if you remove your secondary cats. The primary cats do all the work needed to pass smog regulations. The secondary cats are there adhere to the 100,000 emissions warranty required in the US should a primary cat start to deteriorate but not to the point of throwing a CEL. If you're thinking of replacing you primary cats with after market a 100 cell cat of the same diameter will flow better but may throw a CEL. Europipe (Porsche exhausts) focuses on total catalyst surface area to produce a 100 cell cat which has the same catalytic surface area as a 400 cell cat. Hence you get the higher flow while still meeting the emissions standard. BTW If you want to know what real exhaust gas smells like, stand behind something with an LS7 crate motor in it, Holley dominator, headers, and straight pipes and remember not to smoke.
Last edited by DuaneC63; 08-25-2012 at 02:54 AM.