Go Back  Miata Turbo Forum - Boost cars, acquire cats. > Performance & Tuning > Supercharger Discussion
Reload this Page >

What to expect after removing catalytic converter?

Supercharger Discussion For all you misguided souls.
Sponsored by:
Sponsored by:

What to expect after removing catalytic converter?

 
Old 08-27-2016, 07:53 AM
  #1  
Junior Member
Thread Starter
 
Join Date: Dec 2010
Posts: 477
Total Cats: 10
Default What to expect after removing catalytic converter?

Gents,

I needed to pull the header to get it welded--the EGR tube fitting cracked. While I had it out, I decided to inspect the cat. The metal spiral core had separated from the case and was fairly loose inside. I had the core removed and I've remounted the empty cat. I drove it a short distance to work--I wanted to make sure the header welding was okay. AFRs seemed fine around town, so I took it on the highway on the way home. Nothing out of the ordinary.

Is there anything I should expect, like lower boost levels, from running without the cat? Do I need a retune for track use? Should I just get another hi-flow cat?

Thanks,
poormxdad is offline  
Old 08-27-2016, 10:39 AM
  #2  
Elite Member
iTrader: (17)
 
Join Date: Aug 2007
Location: Knoxville, TN
Posts: 2,902
Total Cats: 171
Default

I wouldn't expect a change in boost level, especially with a blower. Keep an eye on AFR's under acceleration. Reducing exhaust restriction should pick up some power and lean out your tune. You may need to add a little fuel to the top of your VE table.
pdexta is offline  
Old 08-27-2016, 12:42 PM
  #3  
VladiTuned
iTrader: (76)
 
18psi's Avatar
 
Join Date: Apr 2008
Posts: 35,141
Total Cats: 3,141
Default

its gonna sound nasty/raspy and stink a little
otherwise no issues.
18psi is offline  
Old 08-27-2016, 02:55 PM
  #4  
Junior Member
Thread Starter
 
Join Date: Dec 2010
Posts: 477
Total Cats: 10
Default

Originally Posted by 18psi View Post
its gonna sound nasty/raspy and stink a little
otherwise no issues.
It sounds stupid. Would I be better off with a new high flow cat or a straight pipe?
poormxdad is offline  
Old 08-27-2016, 03:25 PM
  #5  
Ich verstehe nur Bahnhof
iTrader: (4)
 
psyber_0ptix's Avatar
 
Join Date: Mar 2012
Location: Northern VA
Posts: 4,471
Total Cats: 487
Default

Expect to save 15% or more by switching to Geico.
psyber_0ptix is offline  
Old 08-27-2016, 03:47 PM
  #6  
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago. (The non-murder part.)
Posts: 28,934
Total Cats: 2,807
Default

Originally Posted by poormxdad View Post
It sounds stupid. Would I be better off with a new high flow cat or a straight pipe?
A straight pipe won't meaningfully change the sound relative to the gutted shell you have now. Might be a tiny bit louder (as you'd be removing what is effectively an expansion chamber), but it's definitely not going to improve things.
Joe Perez is offline  
Old 08-27-2016, 05:17 PM
  #7  
Elite Member
iTrader: (17)
 
Join Date: Aug 2007
Location: Knoxville, TN
Posts: 2,902
Total Cats: 171
Default

Adding a resonator... or a turbo... will help the rasp a lot.
pdexta is offline  
Old 08-27-2016, 05:35 PM
  #8  
Junior Member
Thread Starter
 
Join Date: Dec 2010
Posts: 477
Total Cats: 10
Default

It sounds like a garage door spring being hit by a clown with a maraca.
poormxdad is offline  
Old 08-27-2016, 06:21 PM
  #9  
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago. (The non-murder part.)
Posts: 28,934
Total Cats: 2,807
Default

Originally Posted by poormxdad View Post
It sounds like a garage door spring being hit by a clown with a maraca.


That just made a little bit of expensive scotch go through my nose. Burns like hell, in case you were wondering.


What does the rest of the exhaust system look like?
Joe Perez is offline  
Old 08-27-2016, 07:26 PM
  #10  
Elite Member
iTrader: (13)
 
Join Date: Sep 2010
Posts: 2,019
Total Cats: -113
Default

Originally Posted by Joe Perez View Post
That just made a little bit of expensive scotch go through my nose.
What were you drinking? I like scotch.
thumpetto007 is offline  
Old 08-27-2016, 11:57 PM
  #11  
Junior Member
 
Join Date: Jan 2015
Location: Spokane, WA
Posts: 150
Total Cats: 13
Default

Originally Posted by thumpetto007 View Post
What were you drinking? I like scotch.
Balvenie 21yo or GTFO.
Dann0 is offline  
Reply
Leave a poscat -1 Leave a negcat
Old 08-28-2016, 09:46 AM
  #12  
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago. (The non-murder part.)
Posts: 28,934
Total Cats: 2,807
Default

Sorry, just a 15 year Glenlivet.
Joe Perez is offline  
Old 08-28-2016, 11:17 AM
  #13  
Ich verstehe nur Bahnhof
iTrader: (4)
 
psyber_0ptix's Avatar
 
Join Date: Mar 2012
Location: Northern VA
Posts: 4,471
Total Cats: 487
Default

No love for the Lagavulin 16?
psyber_0ptix is offline  
Old 08-28-2016, 12:17 PM
  #14  
Elite Member
iTrader: (13)
 
Join Date: Sep 2010
Posts: 2,019
Total Cats: -113
Default

Haha good stuff! We are all manly men. We drink scotch and drive silly little cars. We know we are men, we dont need to prove to the world!
thumpetto007 is offline  
Old 08-28-2016, 10:08 PM
  #15  
Junior Member
Thread Starter
 
Join Date: Dec 2010
Posts: 477
Total Cats: 10
Default

Originally Posted by Joe Perez View Post
: What does the rest of the exhaust system look like?
Seems to be in pretty good shape. I got everything from Jason at Enthuzacar. I have the longest Magnaflow resonator that will fit, and a Borla Pro something muffler. If I were to do it again, I'd get a four inch or so shorter resonator and have it welded up so the can was as far away from the back of the seatwell as possible.

Although I'm partial to anything from The Macallan or Laphroaig, I have recently been enjoying Alberta Blended Rye Whisky Dark Batch from Canada. Just a little sweet.
poormxdad is offline  
Old 08-30-2016, 12:44 PM
  #16  
Goin Innnnn!!!
iTrader: (7)
 
Chooofoojoo's Avatar
 
Join Date: May 2014
Location: Denver, Co.
Posts: 458
Total Cats: 40
Default

Originally Posted by psyber_0ptix View Post
No love for the Lagavulin 16?
Oh there is love. Distillers Edition or regular Lagavulin 16 all day.
Chooofoojoo is offline  
Old 08-30-2016, 12:52 PM
  #17  
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago. (The non-murder part.)
Posts: 28,934
Total Cats: 2,807
Default

Originally Posted by poormxdad View Post
(...) and a Borla Pro something muffler.
Well there's your problem.

Most of the exhaust systems that Enthuza builds use straight-through mufflers, and the Borla Pro is one of those. These mufflers are basically just a huge glasspack- they do not have any internal baffling.

This is ideal for turbocharged engines, since the turbo itself happens to be a very good muffler. But for supercharged or naturally-aspirated engines, they're not much better than an old-school cherry bomb in terms of quieting the high frequencies.
Joe Perez is offline  
Old 08-30-2016, 12:56 PM
  #18  
VladiTuned
iTrader: (76)
 
18psi's Avatar
 
Join Date: Apr 2008
Posts: 35,141
Total Cats: 3,141
Default

Originally Posted by Joe Perez View Post
Well there's your problem.

Most of the exhaust systems that Enthuza builds use straight-through mufflers, and the Borla Pro is one of those. These mufflers are basically just a huge glasspack- they do not have any internal baffling.

This is ideal for turbocharged engines, since the turbo itself happens to be a very good muffler. But for supercharged or naturally-aspirated engines, they're not much better than an old-school cherry bomb in terms of quieting the high frequencies.
Chambered mufflers are not any better, but also kill flow, so they suck twice as hard.

You want the bestest quietest high flow setup? big maggie with a cat. done

I learned a long time ago that resonators don't quiet down an exhaust. I've gone as far as running 2 21" resonators (think about that for a second), and it still wasn't "quiet". you want a big, thick, (that's what she said) muffler. the bigger in girth, the better (again, what she said)
18psi is offline  
Old 08-30-2016, 01:30 PM
  #19  
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago. (The non-murder part.)
Posts: 28,934
Total Cats: 2,807
Default

There's a difference between a huge resonator and a baffled muffler.
Joe Perez is offline  
Old 08-30-2016, 01:36 PM
  #20  
Senior Member
iTrader: (1)
 
Join Date: Nov 2010
Location: Marylandistan
Posts: 970
Total Cats: 74
Default


Just install some whistle tips and win.
stratosteve is offline  

Thread Tools
Search this Thread
Quick Reply: What to expect after removing catalytic converter?


Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.