ideal x-pipe positioning for performance gain?
 

I've read through a ton of x-pipe threads but none seem to indicate what the best positioning would be for maximum performance gain - not talking sound here, just added hp/torque. I have a 3.0 engine, just wondering if anyone could be more specific than just placing it where the resonator is. I know we are not talking huge gains here, and I know sound is the main draw, but wanted to do this mod right, and based in performance gain. Thanks!

I would say right at the resonator is just fine. You won't even feel a difference in throttle with that x pipe alone.

Best hp gain is with it on the bench. No location in the exhaust is going to give you any measurable gain, but putting it in the wrong place will reduce power. Your exhaust is already optimized.

Exactly!

As I've said previously, I lost so much power replacing my center resonator with a Magnaflow x-pipe and straight pipes that I had to tow in a lower gear all the time. This is not a simple change, there's a lot of science involved. And all my research says that the length of pipe ahead of the x must be equal for the pulses to cross properly in the x. And at least on the 4.4 V8, the length of the left cylinders is longer than the right because of the positioning of the exhaust to clear the trans and transfer case.

I pulled out my x, replaced it with a simple H-pipe and the performance immediately was back to where it was stock and maybe slightly better.

Thanks for the feedback guys. Really appreciate it. Not sure yet if I will do this mod but trying to understand more about it. I know that the performance gains will not be as "significant" as claimed but every bit helps (especially with an '01 3.0 with 160k :D).

TowX, interesting that the H-pipe worked better for you. I have read that although it works in similar fashion, the exhaust does not even out both pipes as with an x, hence the preference for most to pass on it. I'm glad it worked for you. Definitely worth looking more into it.

Right now I have a CAI and, although I'm likely way off the mark on this, felt that perhaps a slight mod on the exhaust (via x/h pipe) would further improve and help along the gain via the intake. Again, just an educated guess on this. :rolleyes:

A tuned exhaust is designed with specific lengths of pipe to manage the pressure waves from the exhaust manifold. You don't need to even out the flows to gain power, you actually need to manage the pressure waves to help extract the exhaust, thus flowing more. It is not reasonable to expect any horsepower gain at all from an x pipe. Where you place it is a sort of a lottery; get it right, and it won't hurt too much, get it wrong and you will reduce your power. Claims of horsepower gains with an x-pipe are not founded on science and engineering. What you will get is more noise, and to many it is a good tradeoff to get a louder exhaust without much performance drop. If that is the goal, have at it.

The claims you are reading are likely from internet vendors. Back before there was the internet, these types of claims were made by door to door sales reps selling miracle cures, hence the term snake-oil salesman. Same thing.

Your intake is in the same category. The standard intake is not restrictive, and is a CAI. Buying a new CAI for underhood jewelry is fine. Buying one with the plan to gain power is not logical. The most it can do is shift the power curve left or right, through unintentional intake tuning. That can give you a couple of hp at one rpm, at the cost of a few hp at a different rpm. Usually the gains are within the accuracy range of any dyno the vendor is using, ie they are on paper only.

If you want more power for your 3.0, you need a forced induction system. Nothing else makes an appreciable difference, because you are simply trading BMW engineering for internet sales company engineering.

If you do want to modify your 3.0 without forced induction, then you would need a CAI, a larger exhaust, smaller pulleys, a chip tune to remove speed limiters, possibly headers, and so on. All together, you could get a few hp that way, let's assume 5% or 10 hp. I challenge you to even notice that in a 5000 lb vehicle. This is why most X5 mods are focused on aesthetics (tires, wheels, wheel spacing, tints, etc); there simply isn't much to be had by modding for power, unless you go the forced induction route, and that is cost-prohibitive. It makes more sense to buy a new vehicle.

Good luck.

Thanks JCL. This is exactly why I love this site. Really appreciate the invaluable insight. Again, just to educate myself further, but what do you mean by a "larger exhaust?"

A larger diameter, to reduce restriction and flow more. That assumes you need to flow more; the standard exhaust isn't particularly restrictive IMO. If you combine a larger diameter exhaust with free-flowing catalytic converter and a free-flowing muffler, you can gain a few hp. Wouldn't be worth it (hp/$) but it is technically possible.

Got it. Thanks!

:iagree: When I put mine on I did not notice much of a gain........maybe just a little tiny bit more at lower rpm. But the sound was much better! And that is what I was going for. Best of luck.