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Discussion Starter · #1 ·
Do you think moderate modifications like cold air intake & headers significantly add power by themselves. Is a DYNO Tune with a computerized reprogramming of the chip mandatory to take advantage of the mods? What kind of power would be added without Dyno tuning on the average? How much power could be expected after a Dyno tune?
 

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It depends on the specific changes. The LSx engine management system is adaptive. If it can *see* the effect of the mods, it will adjust appropriately. Unfortunately, the system makes built-in assumptions about some parameters, principally those related to airflow through the motor. When you make modifications that improve breathing, performance does improve in the short term, primarily because the mix gets leaner as a result of the improved flow. But the PCM doesn't know that you've improved the flow, and it sees the mix get leaner at the O2 sensors, so it adjusts to compensate for what it perceives as a lean condition. This can ultimately result in the car running richer than it has to.

Mostly, when you're running at partial throttle, the PCM is doing what it has to to keep the mix at the target A/F ratio and the Mods don't matter, the O2 sensors dictate how much fuel and air pass through the engine and the PCM will work to keep that ratio the same as before the Mods. You're flowing more air, the PCM adds more fuel, but the O2 sensors dictate the mix and they "see" the added airflow and the engine does perform better. But, when you go to WOT, the PCM goes open-loop and uses the LTFTs to control the mix. Those LTFTs will have adjusted "up" because of the leaner condition the PCM has been seeing at partial throttle. As a result, WOT could end up being too rich and the engine might actually perform poorer at WOT than it did without the Mods.

The ultimate answer to your question is more straightforward than it might seem, though. You need to get a peek at the LTFTs. Your local dealer can do this for you with their Tech-II. If the LTFTs are up around 10 or higher, you could probably derive some measurable benefit from a Tune. If they're less than that, there's no point in spending the money to lean it out since the most you'd squeeze out is a few more HP.
 

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I have never seen a post of a member that did not gain HP/TQ from a DYNO tune after installing Headers. A Dyno tune is usually worth about 10 HP in addition to what the Headers give. You can probably pick up some HP from a Dyno tune in conjunction with a Air Intake change. IMO Dyno tunes are very expensive so I suggest you do several mods like Headers and Air Intake in conjunction with the Dyno Tune. :cheers:

.
 

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Discussion Starter · #4 ·
Thanks RocketSled & I L GO. What you have both said helps alot. I put stepped headers, cold air, thermostat corsa tit comp exhaust, wires & plugs in my 02 Z06. The car sounded better but didn't feel any faster. I was still running 12.4's at the track and lost 2 mpg on the highway. I just did a Dyno Tune on the car Thurs. at The Vette Doctor's and the car feels great but it's too early to tell in NY this time of the year. At 30 degrees or so I might as well put bicycle tires on it. I can't hook up at all. It feels great but I need A little heat to really know for sure.
 

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POWERTOWEIGHT said:
At 30 degrees or so I might as well put bicycle tires on it. I can't hook up at all.
Tell me something I don't know! I live in central Mass = colder than you!

From late November to early April, it's partial throttle only.
 

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Discussion Starter · #6 ·
I had a further thought tuning. It just occured to me that my overall philosophy of always trying to maximize my midrange and torque my not be the best idea. Even under ideal conditions, traction is my biggest problem when doing 0 - 60 or 1/4 mile runs. My car might actually run better by trying to maximize hosepower at the top as that is where I can really put it on the ground. Any further thoughts?
 

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RocketSled said:
It depends on the specific changes. The LSx engine management system is adaptive. If it can *see* the effect of the mods, it will adjust appropriately. Unfortunately, the system makes built-in assumptions about some parameters, principally those related to airflow through the motor. When you make modifications that improve breathing, performance does improve in the short term, primarily because the mix gets leaner as a result of the improved flow. But the PCM doesn't know that you've improved the flow, and it sees the mix get leaner at the O2 sensors, so it adjusts to compensate for what it perceives as a lean condition. This can ultimately result in the car running richer than it has to.

Mostly, when you're running at partial throttle, the PCM is doing what it has to to keep the mix at the target A/F ratio and the Mods don't matter, the O2 sensors dictate how much fuel and air pass through the engine and the PCM will work to keep that ratio the same as before the Mods. You're flowing more air, the PCM adds more fuel, but the O2 sensors dictate the mix and they "see" the added airflow and the engine does perform better. But, when you go to WOT, the PCM goes open-loop and uses the LTFTs to control the mix. Those LTFTs will have adjusted "up" because of the leaner condition the PCM has been seeing at partial throttle. As a result, WOT could end up being too rich and the engine might actually perform poorer at WOT than it did without the Mods.

The ultimate answer to your question is more straightforward than it might seem, though. You need to get a peek at the LTFTs. Your local dealer can do this for you with their Tech-II. If the LTFTs are up around 10 or higher, you could probably derive some measurable benefit from a Tune. If they're less than that, there's no point in spending the money to lean it out since the most you'd squeeze out is a few more HP.

That is a darn good explanation! :thumb:
 
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