Headers, CAI and No Tune?
Melting Slicks
Joined: Oct 2006
Posts: 2,905
Likes: 1
What should you expect...a code being thrown. A tune will help tons and get rid of the majority of torque management.It'll really wake the car up and you won't have to worry about CELs illuminating, burning into your forehead like Terry Bradshaw.
Thread Starter
Melting Slicks
Joined: Mar 2007
Posts: 2,002
Likes: 2
From: Carlsbad CA
TIA
Melting Slicks
Joined: Feb 2004
Posts: 3,307
Likes: 111
From: Tucson AZ
O2 Sensor codes with long tube headers
Chevy uses a dual O2 sensor system on each side to test the Cats. The front O2 sensor inputs AFR changes and the rear should be flat as the CATS burn any excess fuel. However, for the Cats to light off, they must reach a very high temperature. You will recall that C4 vettes have a single Cat that is halfway down the exhaust pipe and only one O2 sensor, whereas C6 cars have the Cats up front bolted directly to the cast iron exhaust manifolds. This is so they heat up almost immediately after startup.
Now, you install long tube headers and a hi-flow X pipe and the Cats are down wind a lot further and it takes them longer to fire up. The second O2 sensor output is not flat when this happens and this sets a P0430 or P0420 code meaning the Cats are not working. The car will still run fine, you will just be staring at the check engine light periodically.
Most tuners can tune out the rear O2 sensor or supress the Cat codes. You can also do this yourself with a hand held Predator.
Now, you install long tube headers and a hi-flow X pipe and the Cats are down wind a lot further and it takes them longer to fire up. The second O2 sensor output is not flat when this happens and this sets a P0430 or P0420 code meaning the Cats are not working. The car will still run fine, you will just be staring at the check engine light periodically.
Most tuners can tune out the rear O2 sensor or supress the Cat codes. You can also do this yourself with a hand held Predator.
Last edited by Vito.A; Apr 3, 2008 at 01:29 PM.
Thread Starter
Melting Slicks
Joined: Mar 2007
Posts: 2,002
Likes: 2
From: Carlsbad CA
Nice clear explanation ... thanks! So, does the code go away when they do reach temp? Or does it remain until it cycles so many times? I take it that also clarifies that it is the headers that result in a code and not the CAI?
This is important but could anyone shed any light on performance?
This is important but could anyone shed any light on performance?
Last edited by Poppy's Vette; Apr 3, 2008 at 01:56 PM.
Safety Car
Joined: Mar 2005
Posts: 3,639
Likes: 8
From: Madison Wisconsin
St. Jude Donor '08
I'd like to know more about this too.Those of us that want to retain our warranties but still be able to do some mods without tuning. What can we do without having a CEL on all the time?
Burning Brakes
Joined: Jan 2003
Posts: 1,150
Likes: 2
From: League City tx
Actually, they will only void the warranty if they can prove that the part caused the failure. The only thing it WILL void for sure will be your cats/exhaust/mufflers.
This is quoted from the SEMA website. their website is
http://www.sema.org/main/semaorghome.aspx?ID=50096
Quote: The Law
Federal law sets forth requirements for warranties and contains a number of provisions to prevent vehicle manufacturers, dealers and others from unjustly denying warranty coverage. With regard to aftermarket parts, the spirit of the law is that warranty coverage cannot be denied simply because such parts are present on the vehicle, or have been used (see Attachment A).The warranty coverage can be denied only if the aftermarket part caused the malfunction or damage for which warranty coverage is sought. Disputes in this area usually boil down to arguments over facts and technical opinions, rather than arguments over interpretations of the law.
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Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
It's hard to say how much you're leaving on the table. I have seen bone stock '08's that are ~10.5:1 AFR on the dyno so right there you're leaving a lot on the table. Hard to say what the CAI and exhaust mods will do to the motor without tuning/logging it.
You may or may not throw a code with the headers and CAI.
You may or may not throw a code with the headers and CAI.
Last edited by 5 Liter Eater; Apr 3, 2008 at 04:37 PM.
Racer
Joined: Dec 2006
Posts: 343
Likes: 1
From: Houston TX
I picked up 18 rwhp with a tune. Why spend 2k on exhaust/headers/intake and then worry about $500 for a tune. Just keep writing the checks and it will go faster 
Oh yeah and get a 160 stat to go with it.
For what it is worth, my LS2 M6 with a callaway intake, headers, 160 stat, exhaust made 393rwhp on the valvoline mobile dyno at the NHRA races last week. That is a solid 40-50rwhp over a stock LS2 M6
Oh yeah and get a 160 stat to go with it.For what it is worth, my LS2 M6 with a callaway intake, headers, 160 stat, exhaust made 393rwhp on the valvoline mobile dyno at the NHRA races last week. That is a solid 40-50rwhp over a stock LS2 M6
Safety Car
Joined: Mar 2005
Posts: 3,639
Likes: 8
From: Madison Wisconsin
St. Jude Donor '08
Safety Car
Joined: Jul 2001
Posts: 4,609
Likes: 490
From: Houston, Texas
St. Jude Donor '20-'21-'22-'23
Is the computer not "smart" enough or self adjustable enough to learn and adjust fuel mixture over a period of time?
In other words, without touching the factory OE ecm calibrations, wouldn't the ecm learn and adjust a/f ratio properly over a period of time...just as it would properly adjust itself when the car is driven in the mountains at 13,000 ft and adjust itself properly back down at sea level, and vice vera?
.
In other words, without touching the factory OE ecm calibrations, wouldn't the ecm learn and adjust a/f ratio properly over a period of time...just as it would properly adjust itself when the car is driven in the mountains at 13,000 ft and adjust itself properly back down at sea level, and vice vera?
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Race Director
Joined: Jan 2006
Posts: 18,396
Likes: 169
When my C6 was delivered, within 3 months I installed DynaTech coated headers, cats, and x-pipe, along with a VaraRam. The car threw a code within the first 50 miles. I reset the code, and it never returned. My theory is that the ECM is designed to run the engine in varied enviroments. Below sea level in Death Valley to altitudes as high as 12,000 ft, and temps that vary as much as 150 degrees. I think it will, over a short period of time, compensate for the increade in flow and air fuel requirements resulting from the installation of the headers and CAI. Granted, a tune may give you a few more horses, but, IMO, it's not completely necessary. My car ran fine with the stock tune.
"AlohaC5" Senior Member
Joined: Jun 2003
Posts: 3,562
Likes: 44
From: Madison, AL
The most significant downside to not getting a tune after installing headers and a CAI is the lack of horsepower and torque you'll have after installing those mods - especially with long tube headers. The deletion of codes, CEL, etc. are all important, but you're doing it for power. Here's an example: I installed LG performance headers and gained only 7 hp without a tune. I gained 28 hp and lots of torque with a tune. Your car will run fine without a tune for daily driving, but you won't realize the cost/benefit of the upgrades.
Le Mans Master
Joined: Oct 2007
Posts: 6,149
Likes: 11
From: Greater Detroit Metro MI, when I'm not travelling.
My experience: you are leaving 30HP on the table.
Then another 30HP on top of that with a tune.
DEFINITELY get a tune; it will net you better gas mileage, better driveability and MUCH more power...
Here is my before/after dyno with CAI/Headers/Catback and then the same mods + a tune:
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
No. The PCM looks at the injector flow table, MAF flow table and PE (power enrich) table to determine WOT fueling. It ignores the oxygen sensors. The only "learning" it does is if your setup is running lean in closed loop (cruising, part throttle) it will add fuel via positive fuel trims. If you have positive fuel trims because the PCM is having to add more fuel than the table say to then it adds fuel above what the tables say to in WOT. It does not work the other way around though. If the car is too rich and the PCM is having to take fuel out (negative fuel trims) it will not subtract fuel in open loop (WOT) for fear of creating a lean condition.
Burning Brakes
Joined: Feb 2008
Posts: 988
Likes: 2
No. The PCM looks at the injector flow table, MAF flow table and PE (power enrich) table to determine WOT fueling. It ignores the oxygen sensors. The only "learning" it does is if your setup is running lean in closed loop (cruising, part throttle) it will add fuel via positive fuel trims. If you have positive fuel trims because the PCM is having to add more fuel than the table say to then it adds fuel above what the tables say to in WOT. It does not work the other way around though. If the car is too rich and the PCM is having to take fuel out (negative fuel trims) it will not subtract fuel in open loop (WOT) for fear of creating a lean condition.
So when I tuned mine the first time for a 12.4 AFR, then drove around, suddenly that AFR became 13.2+....
Last edited by AndrewZPSU; Apr 4, 2008 at 10:53 AM. Reason: little more detail...
Thread Starter
Melting Slicks
Joined: Mar 2007
Posts: 2,002
Likes: 2
From: Carlsbad CA
Some great responses guys ... thanks very much. The issue isn't cost at all. I was considering the loss of power train warranty with a tune. I'm also not concerned about losing warranty for issues directly related to the headers or CAI. I think GM will use the position of a tampered ECM to void almost anything and everything. On the other hand, short of a catastrophic failure of the engine, tansmission or rearend, I wouldn't let a dealer touch my car anyway.
Burning Brakes
Joined: Jan 2003
Posts: 1,150
Likes: 2
From: League City tx
Some great responses guys ... thanks very much. The issue isn't cost at all. I was considering the loss of power train warranty with a tune. I'm also not concerned about losing warranty for issues directly related to the headers or CAI. I think GM will use the position of a tampered ECM to void almost anything and everything. On the other hand, short of a catastrophic failure of the engine, tansmission or rearend, I wouldn't let a dealer touch my car anyway.
Also, as long as the tuner keeps your stock tune, you can reflash it back to stock and they will never know it was there.
