What size cats to use?
Thread Starter
Senior Member
Joined: May 2014
Posts: 414
Likes: 11
From: Victoria, Australia
04 E55
What size cats to use?
Hey all,
I'm in the process of ordering a set of EC mids, and will be removing the primary and secondary cats. So, I'm also sourcing a pair of 100 cell cats here in Oz. I've essentially chosen my brand (Venom), but now it is the size. I've tried to search but it seems a bit conflicting.
Most of what I have read has people using 3" cats, however I believe the stock exhaust is only 2.5"? Are people referencing the cat body?
I'm after the inlet and outlet size of the cats everyone uses on the stock piping. I believe I need 2.5" inlets, and will get a 4.25" body on the cat. Is this suitable?
Or, due to the EC mids being a 3" collector, I also have the option of getting 3" inlet 4.25" body, 2.5" outlet is this is an even better option? I will be able to get a boiler maker at to do all of the fab work for me, so that part shouldn't be an issue. Thanks for any help.
I'm in the process of ordering a set of EC mids, and will be removing the primary and secondary cats. So, I'm also sourcing a pair of 100 cell cats here in Oz. I've essentially chosen my brand (Venom), but now it is the size. I've tried to search but it seems a bit conflicting.
Most of what I have read has people using 3" cats, however I believe the stock exhaust is only 2.5"? Are people referencing the cat body?
I'm after the inlet and outlet size of the cats everyone uses on the stock piping. I believe I need 2.5" inlets, and will get a 4.25" body on the cat. Is this suitable?
Or, due to the EC mids being a 3" collector, I also have the option of getting 3" inlet 4.25" body, 2.5" outlet is this is an even better option? I will be able to get a boiler maker at to do all of the fab work for me, so that part shouldn't be an issue. Thanks for any help.
MBWorld Fanatic!
Joined: Dec 2011
Posts: 1,226
Likes: 24
Mercedes
Why not keep the secondary cats? It'll clean up the exhaust stink much better than dinky little 100 cell race cats.
I had just 200 cell cats with my long tubes, and the exhaust stink was bad enough that I had my secondaries reinstalled.
I had just 200 cell cats with my long tubes, and the exhaust stink was bad enough that I had my secondaries reinstalled.
Super Member
Joined: Feb 2007
Posts: 530
Likes: 109
From: Atlanta
2016 AMG GTS
I got these
http://performance-curve.com/3thunde...ter415300.aspx
not sure yet how well they work as I just got the car back on the road with headers, two of these, x pipe and 3" pipe to the stock mufflers. but seat of the pants dyno says its pretty insane.
http://performance-curve.com/3thunde...ter415300.aspx
not sure yet how well they work as I just got the car back on the road with headers, two of these, x pipe and 3" pipe to the stock mufflers. but seat of the pants dyno says its pretty insane.
Thread Starter
Senior Member
Joined: May 2014
Posts: 414
Likes: 11
From: Victoria, Australia
04 E55
I want to free up the exhaust as much as possible. If the secondaries are any where near as good as 200 cells I may look into it, but from my internet searches it doesn't appear so.
MBWorld Fanatic!
Joined: Dec 2011
Posts: 1,226
Likes: 24
Mercedes
When I had just 200 cell cats, the exhaust stink was pretty bad at times (especially cold startup, which the secondary cats are designed to handle best). Secondaries are efficient enough to pass emissions sniff test too, which 200 cell race cats barely can do.
I did notice a seat of the pants loss when putting my secondaries back on, but that may have just been the noise that gave a false sense of power.
I did notice a seat of the pants loss when putting my secondaries back on, but that may have just been the noise that gave a false sense of power.
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Thread Starter
Senior Member
Joined: May 2014
Posts: 414
Likes: 11
From: Victoria, Australia
04 E55
Hmm, interesting. I'd really like to know what CPI the secondaries are, and how much difference in rwhp high flow cats make compared to deleted primaries and stock secondaries. If it is ~5-10hp I might save the $400 and live with it.
Is a 4.25" cat BODY too large to fit in our cars?
Is a 4.25" cat BODY too large to fit in our cars?
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Thread Starter
Senior Member
Joined: May 2014
Posts: 414
Likes: 11
From: Victoria, Australia
04 E55
Headers have arrived, and I'm organising the 3" piping now. I can either buy it in a 6m - 20' length, or in 'off cuts'. Is 6m excessive, or about the right length for both sides, to go from mids to (perhaps a resonator delete) rear section? Thanks, and Merry Christmas.
