[darkpuppet]

hardk0re,Dec 12 2006, 06:22 PM Wrote:Why is it hard to believe, when you tune the parameters you have to work with aren't directly affected by your exhaust.  The exhuast not flowing well would create backpressure and take more power from the engine.

When you have a free'd up exhaust you can re-tune but theres no real benefit, you won't really be able to add more spark, fuel, etc.. because your initial input parameters are the same.

edit: I would assume if your turbo things change, your exhaust flow directly relates to how well your turbo spools, etc  but most tunes probably wouldn't need to be modified even in this case if they were done correctly.
[right][snapback]219859[/snapback][/right]

wellllll... there's a couple of caveats to that.

If you have an aftermarket MAF... the more the car can breath, the higher the load scalars can go..if you can confirm the load scalars are fine, you're good to go.

For equipment using the stock MAF.. it's gonna peg, which means that the tune will take into account the current airflow characteristics of the car. Update the exhaust, and it'll lean out because the car is consuming more air than before, but the tune is assuming the usual amount for the pegged MAF at given rpm/throttle position.

However, most tunes I've seen are safely rich, which means that a simple visit to a dyno after the parts are put on is all that's usually needed to ensure you're not running too lean.

There's usually a 10-15% margin of safety, so adding something like an exhaust (which could net you 20HP), wouldn't necessarily need a retune, tho it's more desireable to be tuned for it.