headers and high flow cats
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 980
Likes: 12
From: Clayton, NC
headers and high flow cats
Is it necessary to install high flow cats with long tube headers? What would be the difference with the cats installed and not installed if it is not necessary.
Happy New Year to all
Happy New Year to all
Le Mans Master
Joined: Oct 1999
Posts: 8,205
Likes: 40
From: Tucson AZ
Safety Car
Joined: Mar 2006
Posts: 3,946
Likes: 263
From: Cedar Falls Iowa
Installing the high flow cats with the headers is no big deal.
They:
1. don't create any real significant loss of horsepower (maybe 5 hp or less).
2. allow you to pass emissions testing.
3. allow you to run without switching off or tuning out the O2 warning sensors, and
4. help in minimize nasty emissions smells that can be sucked into the cabin while cruising.
They:
1. don't create any real significant loss of horsepower (maybe 5 hp or less).
2. allow you to pass emissions testing.
3. allow you to run without switching off or tuning out the O2 warning sensors, and
4. help in minimize nasty emissions smells that can be sucked into the cabin while cruising.
Instructor
Joined: Apr 2007
Posts: 200
Likes: 0
From: Hawthorn Woods Illinois
Guys,
I had LT Kooks and the Hi-Flo cats installed on my '07 A6 and honestly I have not had, nor any of my family ever smelled anything at all. If I did not see them installed I would not know they are there....EXCEPT that I also had the Corsa Sport cat back exhaust installed as well at the same time and MAN, it sounds luverly. LOL
I am aware that they can indeed increase emissions, but it is my hope that the tuner can do some magic before the test. I had to do the same thing years ago with my '69 Hemi Charger (before the laws changed) and had to IMMEDIATELY change back to a more streetable tune. But seriuosly with about 2500 Summer and Fall miles since that work and NO smell whatsoever. Honest INJUN!
Fran
I had LT Kooks and the Hi-Flo cats installed on my '07 A6 and honestly I have not had, nor any of my family ever smelled anything at all. If I did not see them installed I would not know they are there....EXCEPT that I also had the Corsa Sport cat back exhaust installed as well at the same time and MAN, it sounds luverly. LOL
I am aware that they can indeed increase emissions, but it is my hope that the tuner can do some magic before the test. I had to do the same thing years ago with my '69 Hemi Charger (before the laws changed) and had to IMMEDIATELY change back to a more streetable tune. But seriuosly with about 2500 Summer and Fall miles since that work and NO smell whatsoever. Honest INJUN!
Fran
Drifting
Joined: Nov 2004
Posts: 1,923
Likes: 62
From: California
Installing the high flow cats with the headers is no big deal.
They:
1. don't create any real significant loss of horsepower (maybe 5 hp or less).
2. allow you to pass emissions testing.
3. allow you to run without switching off or tuning out the O2 warning sensors, and
4. help in minimize nasty emissions smells that can be sucked into the cabin while cruising.
They:
1. don't create any real significant loss of horsepower (maybe 5 hp or less).
2. allow you to pass emissions testing.
3. allow you to run without switching off or tuning out the O2 warning sensors, and
4. help in minimize nasty emissions smells that can be sucked into the cabin while cruising.
#2 and #3 isnt correct..
Hi flow cats are 2-way cats and you will not pass smog, will fail the NOx sniff test. With high flow cats your 02 sensors will pick it up and WILL trigger the Check Engine Lights, not right away but eventually it will.
Team Owner
Joined: Jan 2007
Posts: 22,136
Likes: 23
From: In the woods looking for my thrown putter.
St. Jude Donor '13, '15
I know people with high flow cats that passed the sniff test. I passed it with a 406 carburated small block with headers and NO cats.
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Tech Contributor
Joined: Mar 2003
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From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
My 2001 had them and passed the sniffer. NY now has no sniffer and its just a PCM ready test. With all codes intact, I passed.
Tech Contributor
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From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
Safety Car
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From: Cheektowaga NY
St. Jude Donor '08
Instructor
Joined: Apr 2007
Posts: 200
Likes: 0
From: Hawthorn Woods Illinois
I had CEL about 20 miles after I had my Kooks, Hi-flo cats and Corsa cat back installed. I was told to expect it and that it would not harm anything. After my tune, (a couple of days later) including TM turn off I have gone 2500 or so miles and I have not gotten any CEL yet.
Fran
Fran
Tech Contributor
Joined: Mar 2003
Posts: 12,094
Likes: 197
From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
I had CEL about 20 miles after I had my Kooks, Hi-flo cats and Corsa cat back installed. I was told to expect it and that it would not harm anything. After my tune, (a couple of days later) including TM turn off I have gone 2500 or so miles and I have not gotten any CEL yet.
Fran
Fran
The CEL would be from it not being tuned. They lean out the car too much in closed loop.
Last edited by SpinMonster; Jan 4, 2008 at 05:39 AM.
Drifting
Joined: Nov 2004
Posts: 1,923
Likes: 62
From: California
Let me know when mine will trigger the CEL. I have had high flow cats on both of my vettes with a running total of 7 years and did all my own tuning and have never bypassed a single code ever. No CEL. Every car I tune with them has the codes intact too...no CEL.
My 2001 had them and passed the sniffer. NY now has no sniffer and its just a PCM ready test. With all codes intact, I passed.
My 2001 had them and passed the sniffer. NY now has no sniffer and its just a PCM ready test. With all codes intact, I passed.
Im talking about the CEL being on when your car isnt tuned. Also here in CA, when your car is being smogged, your cars OBD port is connected to the smog machine and will detect any pending code. Now, I dont know how strict NY sniffer test is, but here in CA, I doubt it if you can pass the sniff test with high flow cats
Tech Contributor
Joined: Mar 2003
Posts: 12,094
Likes: 197
From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
Im talking about the CEL being on when your car isnt tuned. Also here in CA, when your car is being smogged, your cars OBD port is connected to the smog machine and will detect any pending code. Now, I dont know how strict NY sniffer test is, but here in CA, I doubt it if you can pass the sniff test with high flow cats
Some think even tuned, the CEL would appear and that is not true. Many tuners just turn off the CEL code for the rear cats instead of tuning it properly to have the codes intact in case of a real cat issue. So for the benefit of those not reading through and not to annoy you: a properly tuned car should have no codes bypassed and there will be no check engine lights even with high flow cats.
In NY the inspection is also connected to the OBDII port and the car with all codes intact with high flow cats will have no codes pending (actually called 'immature' in the scans) with any properly tuned cat, high flow or other. A as per my friends in the republic of Khali-phor-Nia, who share my love of DIY tuning (yes you Alex and Steve), their cars pass the sniffer but fail the visual inspection, but eyesight is usually not so good in the presence of dead presdients. I have tuned enough cars here with H/C and good sized cams to know it can be done. My car is a prime example. I dont even know if my CEL light bulb works. Just kidding of course since it turns on when you start the car as a test.
Safety Car
Joined: Dec 2004
Posts: 3,565
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From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
I keep reiterating the reason for the CEL not for you but for the readers that skip though threads without seeing what was stated before. Some think even tuned, the CEL would appear and that is not true. Many tuners just turn off the CEL code for the rear cats instead of tuning it properly to have the codes intact in case of a real cat issue.
So for the benefit of those not reading through and not to annoy you: a properly tuned car should have no codes bypassed and there will be no check engine lights even with high flow cats.
In NY the inspection is also connected to the OBDII port and the car with all codes intact with high flow cats will have no codes pending (actually called 'immature' in the scans) with any properly tuned cat, high flow or other. A as per my friends in the republic of Khali-phor-Nia, who share my love of DIY tuning (yes you Alex and Steve), their cars pass the sniffer but fail the visual inspection, but eyesight is usually not so good in the presence of dead presdients. I have tuned enough cars here with H/C and good sized cams to know it can be done. My car is a prime example. I dont even know if my CEL light bulb works. Just kidding of course since it turns on when you start the car as a test.
Some think even tuned, the CEL would appear and that is not true. Many tuners just turn off the CEL code for the rear cats instead of tuning it properly to have the codes intact in case of a real cat issue. So for the benefit of those not reading through and not to annoy you: a properly tuned car should have no codes bypassed and there will be no check engine lights even with high flow cats.
In NY the inspection is also connected to the OBDII port and the car with all codes intact with high flow cats will have no codes pending (actually called 'immature' in the scans) with any properly tuned cat, high flow or other. A as per my friends in the republic of Khali-phor-Nia, who share my love of DIY tuning (yes you Alex and Steve), their cars pass the sniffer but fail the visual inspection, but eyesight is usually not so good in the presence of dead presdients. I have tuned enough cars here with H/C and good sized cams to know it can be done. My car is a prime example. I dont even know if my CEL light bulb works. Just kidding of course since it turns on when you start the car as a test.
No tune, No Codes. (Doesn't mean she wouldn't benefit from a tune though)
Safety Car
Joined: Dec 2004
Posts: 4,276
Likes: 8
From: Tucson AZ
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
...can't imagine a situation where cats aren't necessary - required by law. Like others have stated, I've been running by Kooks w/hfc for 3-years and absolutely no problems - no emissions issues, etc.