2.25" vs. 2.5" X-Pipe?
 

Any benefit in one vs. the other?

Word on the street has it both will work. Also, any specific brand? eBay one for 40$?

Big Difference …..you'll be happy...

what engine? what's your intent?

you could always measure the pipe where you plan on installing it and then just match that size. could also be about the same price to have a decent local exhaust shop make/install one for you.

.... I went in to my muffler shop and asked them how much it would be for an X pipe for the x5 he said around 4 to 500 is that normal

Sorry guys car is a 6/06 4.8is!

We have the same go 3" if u want much better


Heres my Exhaust stages, different setups give u an idea

BMW X5 Exhaust stages - YouTube

Thats a liiiiiitle too much for me. Id like to keep the stock mufflers and everything else. I'm just looking to slap in an X pipe.

Could you post a link for the ebay xpipes?

The 4.8 has 2.5 exhaust. To maximize the performance benefit the X pipe should be 2.5.

Anything larger will be larger than the existing exhaust and won't work.

2.25" inlets, 2.5" outlets. Recommend Dr. Gas x-pipe

Yea that is a lot to install an x pipe. I payed 80 bucks to install mine

yeah... i believe it... we pay stupid prices when it comes to anything labour related...

Does the X pipe replace the H pipe and is the pipe 2.5" at that point?

I think its because of your spelling of 'labor'. Fancy spelling means fancy prices.

Looking at the comparisons of Hpipe vs Xpipe, I think I'd stick with the better rumble sound of the Hpipe for driving around town. Unless someone can show that MPG increases with the Xpipe.

4.8is X5 with x-pipe - YouTube
better throttle response at higher rpm is noticible
hwy more power that you can feel
havnt noticed loss of torque

Just talked to my muffler shop today... they said around $250 to fabricate a custom x-pipe... or around 100 - 150 to install one if you bring your own... so it should be not more than $300 all in...

thing is what X pipe should we go with, cheap 60$ ebay one or 150 megna flow one lol

cost mee 300 inckuding xpipe and new hangers

I was quoted 175 for a resonator delete. No X pipe and he told me that he would cut the flanges off. I take it these $40-$60 x pipes (which I still can't find) don't come with flanges. I would love to find an x pipe with flanges so I could do the install and be able to take it back out.

Can someone please post a link to these $40-$60 x pipes.

Edit: I searched again and found a bunch non specific to BMW. So looks like the flanges must go unless you have one custom made with flanges which doesn't sound like a bad idea. The muffle shop wouldn't have to touch the X or know what it's for. Might be able to save a few bucks if you told them it was going on a 1982 chevy truck:)

If your goal is a 'better' sound by way of an X pipe, it won't matter which X pipe you choose, assuming the diameters are the same. As far as longevity, it might matter how it is built and the thickness of the tube walls.

If you want or also want to improve performance, "theoretically", the X pipe will increase scavenging. The greatest benefit of scavenging is a lower RPMs. As the RPMs increase scavenging decreases. I think the scavenging benefit will be minimal. Greater scavenging is not always good.

I think the best route to improve the sound and gain performance would be to remove or replace the resonators or mufflers with less back pressure versions. Less back pressure is always good.

There is the potential, no matter what you choose to do, that the change will create a drone in the cabin. Over time or when driving a longer distance the drone can be very annoying. To be sure that didn't happen I would do something someone else has already done so I would know what my X would sound like and if there was any resulting drone.

Scavenging is ALWAYS good. Where the xpipe is installed (collector LENGTH) will greatly affect how it works. Properly fitted will make the exhaust QUIETER and SMOOTHER. Not drone. If adding an xpipe only creates drone you're doing something wrong. There are no "kits" though so you'll have to get busy with a welder yourself. Make sure the collector lengths leading to the X are EQUAL and short as possible. Having the X before the cats works REALLY GOOD but makes it harder for the cats to work.

Proper construction will mean a GUSSET plate top and bottom joining the two parts of the X. Here is a pic of a Dr. Gas xpipe that I have for example. I have not tweaked the inlets and outlets YET. In fact it is still sitting in a box in the garage.

http://img.photobucket.com/albums/v1...X-pipepic1.jpg

What H-pipe? 60mm at that point. A slight neck down inlet then expansion after the X helps velocity (scavenging)

I disagree that increasing scavenging is always good to achieve improved performance.

Scavenging works best at low RPMs when there is the greatest exhaust pulse gap that creates more following vacuum. As RPMs increase the pulse gap decreases and the benefit of scavenging reduces. Scavenging benefit increases if the exhaust pipes are smaller because the smaller pipes increase the exhaust velocity which creates a greater pulse and corresponding vacuum that follows.

The problem is that the smaller the pipe the greater the back pressure. When scavenging is not good is when scavenging increases back pressure. In the case of forced induction such as turbo charging that use the exhaust to function, the pulse is already smoothed out so the pulsing necessary to create the vacuum needed for scavenging benefit is gone.

Drone is caused by resonate frequency. A change in resonance can result in drone. I agree that drone should not be due to the installation of an X pipe but there is that potential. That's why my suggestion is to do something that someone else has done with no drone outcome. FYI-I thought an X pipe made the exhaust louder. My only reference were Youtube videos that sounded louder to me but could easily been where the microphone was placed. I agree, it would be far less likely to create a drone if the result of an X pipe is a quieter and smoother sounding exhaust.

I think, if you can achieve the sound you want by lowering back pressure it is always a better route.

In our cases, yours because of the supercharger and mine because of nitrous, we have too much back pressure even with the Dinan exhaust. I have decided electric cutouts are my best investment. It will result in a greater performance gain due to decrease in back pressure. I won't get the 20% increase that could come from headers but it will be far more than I could expect from an X pipe even if I don't fully open the cutout flaps. Good cutouts will cost about $450, the welding about the same as an X pipe but I think the cost benefit ratio will be far better than an X pipe.

I love the sound of Dinan exhaust and don't want to change that. Not saying the X pipe is not a significant benefit to a closed exhaust system but since I have not read anything that reported any significant measurable improvement in performance my conclusion thus far is that the cost benefit outcome is not good.

It's always been my understanding that equal tube length (left/right) are a MUST to get an X-pipe to function correctly. The V8 E53 has longer exhaust tubing from the left cyl bank to the X-pipe location then the right cyl bank. This causes L/R pulses at certain RPM to reach the merge point at the same moment, causing a high pressure spike (the exact opposite of scavenging).

Unequal length exhaust tubing means H-pipe is the go-to for better sound and no power loss.

For an X-pipe to function correctly, the exhaust path from every exhaust valve to the merge point MUST BE IDENTICAL. That means equal length headers, collectors and exhaust tubing upstream of the X-pipe. Anything short of that, and the X-pipe is more likely causing a power LOSS.

That seemed logic to me but tech information that I have found indicates equal length tubing is not necessary in 2 planed V8s.

I have spent some time this afternoon getting more informed concerning X pipes. What I found to be important is an X pipe that has smooth inside walls, the optimum size is 2.75" but 2.25" to 2.75" is nearly as effective, in 100% of applications the sound is reduced and smoother as mentioned. 60% realize some gain in HP, the average being 5-8HP. In 40% of the cases HP did not change either way. The best location is as close to the engine as possible so the scavenging effect happens sooner but that won't matter if rest of the exhaust will not handle the increased velocity and it won't matter that much anyway.

Regardless, I wouldn't install the pipe in between the exhaust manifold and O2 sensors even if I could. The X pipe is better but the choice to use an X pipe or an H pipe is often governed by where it will fit, ground clearance etc. Scavenging increases velocity of the exhaust which means narrowing down the exit tubes out of the X pipe reduces the benefits. This is all based on engines producing less than 600HP. My sources were aftermarket exhaust companies, and printed articles in well known car magazines.

The design of an exhaust system is complex. I found it is possible to achieve better performance results with a well designed performance exhaust system than open headers-that was news to me and a big WOW. To do so it is necessary to know the maximum flow of the heads and construct a system that matches that flow--that would include an X pipe. The result would be maximum velocity from engine to tailpipe. I don't know of anyone that has verified the outcome of specific exhaust changes on an X. Until there is we are assuming results measured elsewhere are applicable. I think that makes some sense to do so but I would make the purchase of an X pipe solely with the goal of a quieter and smoother sounding exhaust.

FYI-I don't consider seat of the pants endorsements. I might if I found a few that started with OMG you won't believe the difference, I wish I had done this years ago.

If we consider horsepower and reduced noise the X pipe is always effective as it always reduces noise and never decreases HP.

You mention equal length tubing. From what I have gathered in the 4.6is the shorter run has a smaller diameter (50mm) vs the longer run (55mm). I believe this was to make the two equivalent in length.
This is for the downpipes to the resonator.

If that is the case the differences in tube diameters would not make them equivalent in length. The smaller side would produce a greater velocity which would be a bad thing to do.

I should have ended the sentence in post #23 ....."X-pipe is more likely causing a power LOSS"..... with, across the RPM range.

Many exhaust manufacturers that use X-pipes with unequal length tubes and report HP gains have dyno tested the X-pipe location so the scavange effect is occurring right at peak HP RPM.

These manufactures usually will not provide full RPM pull sheets comparing straight pipe vs H-pipe vs X-pipe results. In most tests the X-pipe will show a few more hp at peak RPM but an actual DROP in HP/torque at lower RPMs (peak HP #s sell exhaust systems/exhaust parts. Few buyers look into average HP/torque thru the RPM range) .

On tracked vehicles an X-pipe tuned for peak HP is a plus (the engine is kept near the optimum RPM to use the HP peak). Street vehicles operate thru the RPM range, a loss of HP/torque at lower RPM for a few more HP near redline is not a tradeoff I would accept.

Lots of bad information. Not going to argue, pointless. Ultimately it's a "feel good mod" for most anyhow.

The general consensus is that an H-pipe equalizes exhaust pulses. A X-pipe both equalizes the exhaust pulse and improves scavenging. Depending on the application and the rest of the exhaust system components, the addition of an X pipe may, can, might improve torque and or horsepower. The following video provides a demonstration: The XPipe Explained by Ed Hanson at Ed Hanson's Muffler Service. - YouTube

There are some applications like a low torque high winding engine, where the addition on an X pipe may decrease the performance of an application. Since getting from point A to point be is a combination of torque and horsepower the X-pipe could decrease torque even when it increases horsepower resulting in it taking longer to get to point B.

Since a H-pipe does not improve scavenging, an X pipe, assuming on that particular application it improves performance, will generate better numbers than a H-pipe, except in low torque and high winding application where the X-pipe is more likely to be a negative. There are also cases where a H-pipe will generate lesser numbers in those same applications.

The benefits of scavenging depend on the pressure of the exhaust flow combined with the amount of vacuum that follows an exhaust pulse. As RPMs increase the pulses are closer together resulting in decreasing vacuum. Less vacuum means less scavenging which means any benefits of scavenging decrease as RPM increase. At the top of the RPM range a X-pipe is the least, if at all, beneficial.

The best numbers because of an X-pipe will come from the farthest upstream the exhaust system it is possible to install the X-pipe.

It is important to know how exhaust changes impact torque and horsepower as the best changes will be those that are most effective where you need improvement, i.e--torque get you going, horsepower keeps you going.

I have been unable to find dyno numbers that are meaningful. The ones I found either changed more than just the X pipe between runs or the difference was within normal dyno error.

:iagree: the only thing I would count on is that it will change the sound.

If you are saying the information I am posting is bad, I think you should explain what and why the information is bad. I don't see differences as arguing unless someone gets angry.

The vid demonstrates the scavenging operation of the X-pipe when only one side is moving exhaust gasses (out of phase), this will ONLY happen thru the RPM/throttle position/load range with equal length tubing upstream. The X5 has about 2' more exhaust length from the left cyl bank to the X-pipe vs the right cyl bank, this will cause some RPM/throttle position/loads to deliver the pulses in phase.

I'm all for everyone modding to personal taste, I just point out the flaw when it's passed off as a "performance enhancing mod".

I did it for the loud factor. Reading all this info convinced me that i had no clue what i was doing and took a shot in the dark. The end result was successful, im the neighborhood alarm clock

I know this is a big boy v8 thread but for someone like me who might want a bit smoother exhaust flow, and a slightly different tone to the stock exhaust this is why I would personally do an X pipe on my 3.0.

So from what I gather here the x pipe should be installed as far forward as possible to the factory mounting flanges of the factory resonator for best performance?

Without spending 1400 on aftermarket mufflers for increased sound which I don't really want anyway, I'd rather just do an X pipe and delete the factory resonator if I'm able to do so with no ill effects and a couple hours of time at the shop installing it.

The video is only to show that an H pipe has little to no scavenging capability.

I spoke with Magnaflow tech. He didn't come across as an expert though he didn't hedge or sound like he was making stuff up so he might have been. He said there is an insignificant difference in the scavenging performance with equal or unequal tubes from the exhaust manifolds.

Per the X-pipe information I have wadded through my take is a performance exhaust system designed from the manifold to the exhaust exit to maximize scavenging capabilities of an X-pipe will result in better performance than if it is not included. How much depends on a specific application and it is a small compliment to the rest of the system. Other than that it is a shot in the dark that will sound better.

Here's Lingenfelters data on H-pipes, page 132. Lingenfelter has spent thousands of hrs dyno testing.......

John Lingenfelter on Modifying Small-Block Chevy Engines: High Performance ... - John Lingenfelter - Google Books

Additional torque below peak torque RPM with no loss of HP. Just what you want on a streeted SUV.

John Hennessey tested X-pipes on the Jeep SRT V8 (same unequal length exhaust config as the V8 X5s) and found there was a power loss across most of the operational RPM range. X-pipe was tossed.

Great shot!

Yes, the closer to the exhaust manifold the better but not between the exhaust manifold and O2 sensor. If sound is your only goal it won't matter where you install the X pipe. However, I would try to find a place to put it before the mufflers as you may get some performance benefit. The X-pipe results in a different sound than the H-pipe. The H-pipe results in a lower sound, toward a American muscle car sound while the X-pipe change is more toward the exotic car sound. You can find some comparisons on Youtude.

I think just the X-pipe alone would give me the slight tonal change in the exhaust that I would be looking for, and be a little more free-flowing than factory resonator.

No need for increased loudness (it is a 3.0), and the only way to achieve that is either deleting or replacing with aftermarket mufflers. Too much work for me lol.

Everything I have posted I noted as the general consensus of current information or it might, could, may or may not deliver a particular result of horsepower and/or torque.

The older the articles I found the more likely there were several schools of 'expert' conclusions. There are still anecdotal 'expert' counterpoints or particular applications that don't hold true to the general consensus. I am not going to challenge the findings of Lingenfelter or Hennessey. I have read other similar test findings from reputable organizations.

It is important to note the Lingenfelter article is about conclusions drawn in 1996 derived from a small block Chevy. It could well be that the H-pipe delivered in that particular application. The X-pipe was not a consideration then. This following are their current offerings: Akrapovic Stainless Evolution Exhaust ZO6 ZR1 Corvette 2006-2012 - Lingenfelter Performance Corsa Camaro SS Stainless Steel Cat Back Exhaust 6 Speed AT 2010-2013 - Lingenfelter Performance While neither look like the X-pipe pictured in this thread, both merge the two sides to equalize the exhaust and contribute to scavenging.

I assume this article was before X-pipes were a factor. Meaning, there is no comparison where Lingenfelter might conclude--don't bother with and H-pipe if performance is the goal.

The phrase you mention read-- additional torque was at or below peak torque. That doesn't mean to you the gain is very near peak torque? If that was the case, per my chevy small block days, the torque peak was at 3500 to 4000 RPMs and wouldn't be usable normal street driving for me.

The majority of current findings are that the H-pipe measured performance benefits are within the range of dyno error or the variables in other conditions that impact torque and horsepower from one dyno run to the other. As I mentioned in previous posts, results vary per the application. Since an H-pipe does equalize the exhaust the Lingenfelter testing base may be one of those applications that the H-pipe is a performance benefit. On the other hand the increase in exhaust velocity or scavenging via a H-pipe is very little to none so my guess any increase was very small.

I have not seen the Hennessey information you reference. Does it say the unequal length was the reason they scrapped the X-pipe? The impact on X-pipe performance with unequal exhaust lengths from the exhaust has been a specific question I have asked. Both performance exhaust makers clearly said it does not. The exhaust is still equalized and the level of scavenging does not change.
The following is the current SRT8 exhaust offering which includes and X-pipe but not the components that would be unequal length: MagnFlow Stainless Steel Cat-Back System Performance Exhaust | 2006 - 2010 Jeep SRT-8 Parts & Accessories | Hennessey Performance

I think the only conclusions of this discussion that is worthwhile is that either route will change the sound, the X-pipe will very likely result in an improvement of how long it takes from point A to point B and how you get the best performance may be different for a 3.0, 4,4, 4.6 4.8 and also different depending on what engine mods or exhaust system mods one has already done.

IMO,if you want the biggest improvement of A to B performance of a X5--reduce the back pressure rather than a H,Y,X or whatever pipe. That was the first thing we did in the good ol' days. It still holds true for the vast majority of applications, the X5 not being a part of the few where it is detrimental.