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Old 08-30-2021, 01:27 PM
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bcredliner bcredliner is offline
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It is possible that the length of headers can decrease torque. It largely depends the overall length and if they are equal length. Torque is what gets you going. Be sure headers for the 3.0 do not reduce torque. Claims of increase HP and TQ by owners are hardly ever backed up by dyno runs, the butt dyno means nothing.

I wouldn't add headers unless they were a name brand that lists gains. It doesn't mean the claims will be accurate but that is why they build headers. The gain with the right exhaust isn't much. As an example the Dinan free flow muffler for a 3.0, when it was available, increased the HP by 5 at 6500 RPMs and TQ 4 also at 6500 RPMs.

If you are after better sound I would install electric cutoffs equal length from the exhaust manifolds and past the first O2 sensor. The cutoffs should increase performance but I don't know how much. Based on Dinan only offering the muffler for the 3.0, a low restriction muffler should be beneficial.

Before modifying the 3.0 exhaust I think I would start with letting more and cooler air in as happens with a cold air box. Once you have more air going in letting more exhaust out should help a little more. If you then get it tuned to match up with the changes you should get yet a little more improvement.

In short, I would add an air box, a low restriction muffler and electric cutouts and call it a day. Both the muffler and air box will improve the sound of the engine and cutouts are great fun if nothing else.
X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
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