Headers
Thread Starter
Pro
Joined: Aug 2004
Posts: 575
Likes: 0
From: Richmond Hill Ontario
Headers
I have a 2001 C5 that I am thinking about putting headers, hi-flo cats and an X pipe on. My questions is, the original system has pre-cats on it and I have heard that if you remove them it may cause the check engine light to come on because of the difference in the O2 readings the PCM is seeing. Does anyone have first hand knowledge whether this mod will do this or what I would need to have done to prevent it if that's the case? Does this require an LS1 edit or is that only necessary when you change the cam?
Thanks,
Thanks,
Le Mans Master
Joined: Mar 2004
Posts: 5,562
Likes: 5
From: South East coast Florida
Originally Posted by creighton
As long as you put the front sensors in the bungs before the cats and the rear sensors in the bungs after the cats you will be fine.
Drifting
Joined: Sep 2000
Posts: 1,456
Likes: 5
From: Bothell WA
I agree with others that you shouldn't have any problems removing the pre-cats. I no longer have the pre-cats in my car and I've not had any problem.
Regarding having the car tuned, I found on my car that it was running leaner after the headers were added. By using LS1 Edit, I could add a little more fuel at WOT and thus make a little bit more power with my car. I don't think its absolutely necessary to have the car tuned, but it will most likely help.
- Mark
Regarding having the car tuned, I found on my car that it was running leaner after the headers were added. By using LS1 Edit, I could add a little more fuel at WOT and thus make a little bit more power with my car. I don't think its absolutely necessary to have the car tuned, but it will most likely help.
- Mark
Le Mans Master
Joined: Mar 2004
Posts: 5,562
Likes: 5
From: South East coast Florida
Originally Posted by Cruzzn
Had no problems with my Dynatech supermax
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Burning Brakes
Joined: Oct 2001
Posts: 1,116
Likes: 0
From: Alhambra Calismognazifornia, in the country everyone comes just to complain but won't go back home!
like with most problems that come up on this board, some people have them and others don't. on this topic, unfortunately i fall in the category of those that do have the problem.
i changed only the mid-section of the exhaust, went to Random Tech x-pipe and hi-flow cats which retained use of all 4 O2 sensors and got rid of the pre-cats (mine is an '02), and i do get the Check Engine light now. Going to try to get a tweaked tune from Diablosport to use with my Predator and see if that goes away.
Now i'm looking at popping on some headers too but worried about how that will affect this issue.
i changed only the mid-section of the exhaust, went to Random Tech x-pipe and hi-flow cats which retained use of all 4 O2 sensors and got rid of the pre-cats (mine is an '02), and i do get the Check Engine light now. Going to try to get a tweaked tune from Diablosport to use with my Predator and see if that goes away.
Now i'm looking at popping on some headers too but worried about how that will affect this issue.
Le Mans Master
Joined: Nov 2003
Posts: 8,003
Likes: 248
From: Tampa Fl
St. Jude Donor '12-'13-'14
i have Kooks, and they have bungs before and after the cats. I did them 4000 miles ago ( last year ) and have had a code. I hooked up the sensers to the headers. I didnt use the simulators
Safety Car
Joined: Oct 2000
Posts: 4,949
Likes: 10
From: Monticello MN
Originally Posted by mowton
If you buy a set of headers without the rear O2 bung's (i.e LGM) then you will need O2 Simulators or have your Tuner handle them.
Ed
Pro
Joined: Jun 2002
Posts: 726
Likes: 45
From: Marquette MI
Originally Posted by vetpet
I have a 2001 C5 that I am thinking about putting headers, hi-flo cats and an X pipe on. My questions is, the original system has pre-cats on it and I have heard that if you remove them it may cause the check engine light to come on because of the difference in the O2 readings the PCM is seeing. Does anyone have first hand knowledge whether this mod will do this or what I would need to have done to prevent it if that's the case? Does this require an LS1 edit or is that only necessary when you change the cam?
Thanks,
Thanks,
Drifting
Joined: Sep 2000
Posts: 1,456
Likes: 5
From: Bothell WA
Originally Posted by cmeflyby
like with most problems that come up on this board, some people have them and others don't. on this topic, unfortunately i fall in the category of those that do have the problem.
i changed only the mid-section of the exhaust, went to Random Tech x-pipe and hi-flow cats which retained use of all 4 O2 sensors and got rid of the pre-cats (mine is an '02), and i do get the Check Engine light now. Going to try to get a tweaked tune from Diablosport to use with my Predator and see if that goes away.
Now i'm looking at popping on some headers too but worried about how that will affect this issue.
i changed only the mid-section of the exhaust, went to Random Tech x-pipe and hi-flow cats which retained use of all 4 O2 sensors and got rid of the pre-cats (mine is an '02), and i do get the Check Engine light now. Going to try to get a tweaked tune from Diablosport to use with my Predator and see if that goes away.
Now i'm looking at popping on some headers too but worried about how that will affect this issue.
- Mark
Safety Car
Joined: Oct 2004
Posts: 4,809
Likes: 236
From: Utah
Originally Posted by Mark VerMurlen
I don't think your problem is related to removing the pre-cats. I think your problem is due to replacing the main OE cats with the hi-flow cats. There have been other reports that these cats don't always clean up the exhaust enough and thus set codes in the computer. Your best bet is to use O2 simulators in your rear sensor locations or disable the cat tests in the PCM.
- Mark
- Mark
Thread Starter
Pro
Joined: Aug 2004
Posts: 575
Likes: 0
From: Richmond Hill Ontario
To everyone that replied, thanks for all of your input. It sounds like I'll need to do a bit more research. I know putting the headers on leans out the engine (always required changing to a richer set of jets in old carburetor days). I think the PCM has a sufficiently large enough fuel map matrix to change the duty cycle of the injectors and add the needed fuel. I've found out that the pre-cats are used to reduce cold start emissions and I guess in those areas that do a cold start emissions check it could be a problem. The headers I've looked at all had bungs for the front O2 sensors and if you keep the stock cats and add an X pipe you would still have the rear O2 bungs. I've also heard from some other sources that people that have used the 02' & up Z06 cats and H pipe on their LS1's, without headers, have run into error codes on and off and under certain circumstances. This also seems to be a hit & miss situation.
