Question about tune with header's?
06-24-2004, 10:56 PM
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Question about tune with header's? Is it a must to have a good tune if you put header's on a ls1? Just curious because I will be putting header's soon and need to know if I will need a tune also.
06-24-2004, 10:58 PM
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Originally Posted by 2_wacko
Is it a must to have a good tune if you put header's on a ls1? Just curious because I will be putting header's soon and need to know if I will need a tune also.
06-25-2004, 09:07 AM
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My theory is this:
think of a balloon that has a constant volume of air, the intake is filling the the balloon at a constant preasure and the exhaust is leaking it out, if you make the exhaust bigger, in order to keep the same balloon volume you have to blow in more air and pressure stays the same. So we have more air going through the same volume. VE or volumetic Efficiency goes up with headers.
Under Open Loop or Power Enrichment or WOT or when you are peddle to the metal, You MAF will notice more air flow and add fuel accordingly. Your volume is still the same so more fuel in the same volume is a richer condition.
Under Closed Loop or Part Throttle or cruising, the narrow band O2 sensors are controlling everything so the header should not affect the fueling, except that headers run cooler than a cast exhaust and can reduce the performance of the sensors.
The car will run rich with Headers, once you tune this condition using a wideband O2 you will have more power. In Open Loop you would lean out and add 1 or 2 degrees of timing, which is were the additional power comes from.
But then again I could be wrong
think of a balloon that has a constant volume of air, the intake is filling the the balloon at a constant preasure and the exhaust is leaking it out, if you make the exhaust bigger, in order to keep the same balloon volume you have to blow in more air and pressure stays the same. So we have more air going through the same volume. VE or volumetic Efficiency goes up with headers.
Under Open Loop or Power Enrichment or WOT or when you are peddle to the metal, You MAF will notice more air flow and add fuel accordingly. Your volume is still the same so more fuel in the same volume is a richer condition.
Under Closed Loop or Part Throttle or cruising, the narrow band O2 sensors are controlling everything so the header should not affect the fueling, except that headers run cooler than a cast exhaust and can reduce the performance of the sensors.
The car will run rich with Headers, once you tune this condition using a wideband O2 you will have more power. In Open Loop you would lean out and add 1 or 2 degrees of timing, which is were the additional power comes from.
But then again I could be wrong
06-25-2004, 11:05 AM
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Depending on the design and makeup of the headers will effect what the O2s report which can be a false rich or lean condition
Taking a stainless steel header and heat coating them can make the exhaust hotter then it was with stock exhuast manifold and report lean where as using like a LGM LT where S1 O2s are now 1 1/2 feet further back not only would cause the O2s to report false rich but also effect cold start, O2s getting to proper operating temps and can trip false CAT errors and may effect the O2 heater or its I/M smog test.
Mild steel header will transfer heat differently and thus also effect what the O2s report.
Also in some headers the stock O2 wires are now too short and splicing, longer wires, etc will effect/change the output voltage going to the PCM.
I've seen headers where two primaries come together as a pair and the O2 is mounted to that pair thus now the exhaust temps are different then if all pipes come to 1 collector so again the O2 can only report as to the conditions it is in and the end results is much more then a minor change of the commanded AFR.
If headers are being added for performance then the PCM should also be tuned/calibrated to assure a correct AFR for the exhaust design.
Taking a stainless steel header and heat coating them can make the exhaust hotter then it was with stock exhuast manifold and report lean where as using like a LGM LT where S1 O2s are now 1 1/2 feet further back not only would cause the O2s to report false rich but also effect cold start, O2s getting to proper operating temps and can trip false CAT errors and may effect the O2 heater or its I/M smog test.
Mild steel header will transfer heat differently and thus also effect what the O2s report.
Also in some headers the stock O2 wires are now too short and splicing, longer wires, etc will effect/change the output voltage going to the PCM.
I've seen headers where two primaries come together as a pair and the O2 is mounted to that pair thus now the exhaust temps are different then if all pipes come to 1 collector so again the O2 can only report as to the conditions it is in and the end results is much more then a minor change of the commanded AFR.
If headers are being added for performance then the PCM should also be tuned/calibrated to assure a correct AFR for the exhaust design.
Originally Posted by billc5
My theory is this:
Under Closed Loop or Part Throttle or cruising, the narrow band O2 sensors are controlling everything so the header should not affect the fueling, except that headers run cooler than a cast exhaust and can reduce the performance of the sensors.
The car will run rich with Headers, once you tune this condition using a wideband O2 you will have more power. In Open Loop you would lean out and add 1 or 2 degrees of timing, which is were the additional power comes from.
But then again I could be wrong
Under Closed Loop or Part Throttle or cruising, the narrow band O2 sensors are controlling everything so the header should not affect the fueling, except that headers run cooler than a cast exhaust and can reduce the performance of the sensors.
The car will run rich with Headers, once you tune this condition using a wideband O2 you will have more power. In Open Loop you would lean out and add 1 or 2 degrees of timing, which is were the additional power comes from.
But then again I could be wrong
06-25-2004, 06:30 PM
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I know i installed my Coated Jet Hots and Y-pipe and lost 3 hp , tq i do not remember i am thinking a tune will do some good so did everyones opinion
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06-25-2004, 10:24 PM
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A tune will always help with any mods. If your not concerned with getting peak performance and drivabilty then you can just put them in and drive around and see how it is. IMO a predator is not going to help you much since it has only a very narrow adjustment, unless you get a custome tune for it.