What do you typically see in a scan after headers?
It seems to me that people would sometimes not add headers because they want to avoid a check engine light. I must admit, I have been one of them until I started to do some tuning and have a much better understanding of how the computer works. Now I have flipped on that view and am trying to figure out what adding headers could actually do to cause a problem. I could see if there is a routine looking to make sure that the cats heated up in a specific amount of time would cause a CEL since you move the cats back farther but what about headers making it run lean or rich. The function of CL should accomodate that, should it not? Or, is it that it changes it so much that you max out the LTFT boundaries?
I was told that after adding headers, the engine is making more hp and running lean. That is one reason why a check engine light would come on. A tune will correct this.
When you add headers to an LS1, it wont throw a code cause its running lean, if it throws a code its cause the long term fuel trims exceed 14% for more than 10 minutes. The computer will compensate for the need for more fuel and keep the motor from going lean.
PO171-"Fuel trim lean", PO172-"Fuel trim rich"--these codes refer to the fuel trim settings in the computer and not the A/F ratio in the motor. Theres another code "lean fire bank one/bank two"-refers to the same condition but both banks are involved. However, the A/F ratio in the motor is adjusted by the computer to prevent an actual lean condition.
Headers aid in the evacuation of spent gases from the cylinder. By clearing out more exhaust, there is more room in the cylinder for incoming air and this will cause a lean condition until an adjustment is made to allow more fuel to be injected. The computer will adjust on its own until programming can be done.
Last edited by leojnknsC5; 03-04-2007 at 08:27 AM.
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What do you typically see in a scan after headers?
