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      10-18-2017, 02:16 PM   #1
kmarei
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Question Straight Exhaust vs. H-Pipe vs. X-Pipe!

saw this today
pretty interesting

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      10-18-2017, 02:51 PM   #2
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X pipe sounds better, do you have stock in Amsoil?
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I was thinking of foaming that hole as well.
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      10-18-2017, 03:10 PM   #3
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Very interesting. What they're saying about H pipes easier to be installed isnt necessarily true for bmw's where a lot of the dual pipes run next to eachother (on a lot of i6 engines)

As for NA engine tuning on european cars I always have the rule of thumb that every extra HP is allowed to cost around $50-$75. So if you're building a new exhaust system, adding an x piece inbetween is allowed to cost about $150 (and that is usually possible, a generic x piece isnt very expensive)
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      10-18-2017, 04:07 PM   #4
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X pipe sounds better, do you have stock in Amsoil?
I wish
I spend all my money on cars
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      10-18-2017, 04:27 PM   #5
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The issue is that the best exhaust for a naturally aspirated car is vastly different than what is best for a turbo car.

In a turbo car, the absolute best exhaust is one with minimum restriction and turbulence, as in a X-pipe or many bends/changes in flow.

Why companies make "high performance" exhausts for these cars and use X-pipes is ridiculous....
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      10-18-2017, 05:55 PM   #6
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Then why does the S63TU come with an x-pipe yet the S63 doesn't? Either way, I'm adding an x-pipe and putting Vibrant resonators (same ones M6Beast uses on his custom M6 systems, it'll look like the last picture) in place of the stock muffler that has two sharp turns inside the muffler itself.
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      10-18-2017, 06:34 PM   #7
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^the theory on either x and h pipe is that it creates a scavenging effect where the air in the adjasent pipe is sucked out creating a slight underpressure.
This would help sucking the combusted air out of the other cylinder bank when the exhaust valves in that bank open.
If this is still effective in a turbo engine I dont know. There a turbo wheel/wastegate blocking that underpressure.
Its something that should be measured. Still even in a turbo car the exhaust air is still pulsated, so resonant adaptations can influence that.
Maybe they added the x-pipe mainly for sound experience; that was another benefit concluded in the video
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      10-19-2017, 09:53 AM   #8
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Factory X5M/X6M exhaust has a H-pipe built in, albiet very small diameter, and most probably for acoustics, rather than performance.
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      10-19-2017, 10:27 AM   #9
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now the question remains
what happens if you add an X-pipe AND an h pipe
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      10-19-2017, 10:32 AM   #10
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Originally Posted by kmarei View Post
now the question remains
what happens if you add an X-pipe AND an h pipe
Do we really think that BMW isn't hiring engineers smart enough to figure out the proper exhaust setup for each car and what they do for one model doesn't necessarily mean the same will improve the performance of another model?
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      10-19-2017, 10:38 AM   #11
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Originally Posted by omasou View Post
Do we really think that BMW isn't hiring engineers smart enough to figure out the proper exhaust setup for each car and what they do for one model doesn't necessarily mean the same will improve the performance of another model?
are you implying that the highly skilled BMW engineers know more about this than the people on the off topic forum???

this is the same team that brought us LOL thread vol1, 2 and 3!!!
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      10-19-2017, 01:32 PM   #12
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Originally Posted by kmarei View Post
are you implying that the highly skilled BMW engineers know more about this than the people on the off topic forum???

this is the same team that brought us LOL thread vol1, 2 and 3!!!
So I watched the video and the conclusion is that I just lost 15 minutes of my life that I will never get back, only to learn that an H or X pipe may give me a 0.28% increase in HP, which is probably w/in some margin of error and not of any statically significant value. I also learned that an X pipe may sound cooler if the under carriage allows me to properly place it but would still be better off installing a cat back muffler if I want an improvement in sound
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      10-19-2017, 07:37 PM   #13
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If you're interested in the raw sound pre-muffler, here's a short clip I took to demonstrate.
Driving-wise, there's significant drone at 1280rpm, but this will change with lengthened exhaust section to tailpipe.

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      10-19-2017, 07:51 PM   #14
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Originally Posted by protecon View Post
Factory X5M/X6M exhaust has a H-pipe built in, albiet very small diameter, and most probably for acoustics, rather than performance.
The picture above on the left is a stock X*M exhaust and there's no crossover at all. Does yours have one then?
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      10-19-2017, 07:57 PM   #15
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Quote:
Originally Posted by omasou View Post
Do we really think that BMW isn't hiring engineers smart enough to figure out the proper exhaust setup for each car and what they do for one model doesn't necessarily mean the same will improve the performance of another model?
BMW also engineers exhausts to be quieter for the mom's that may drive a car...that doesn't mean it's best for performance. While the S63 and S63TU aren't the same internally, architecturally they are the same and I'd be a fool to not believe that if the M5 benefits from an X-pipe that I could benefit from it as well. If BMW engineering was the greatest end all be all of things, there wouldn't be a billion dollar aftermarket industry. BMW can't even engineer plastic intake and cooling parts that last longer than 50k, injectors that don't cause complete engine failures, etc etc...shall I keep going? BMW may engineer the shit outta their cars, but there's also bean counters saying that corners need to be cut to stay within budget, manufacturing timelines, etc.
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      10-19-2017, 08:01 PM   #16
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Quote:
Originally Posted by omasou View Post
So I watched the video and the conclusion is that I just lost 15 minutes of my life that I will never get back, only to learn that an H or X pipe may give me a 0.28% increase in HP, which is probably w/in some margin of error and not of any statically significant value. I also learned that an X pipe may sound cooler if the under carriage allows me to properly place it but would still be better off installing a cat back muffler if I want an improvement in sound
On a stock engine, your point is valid. Once modified, that changes completely and then you're simply wrong. So you think 1k+ F10 M5's, Supras, Gallardos, GTRs, etc are running stock exhaust?
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      10-19-2017, 09:35 PM   #17
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Quote:
Originally Posted by m5james View Post
Quote:
Originally Posted by omasou View Post
So I watched the video and the conclusion is that I just lost 15 minutes of my life that I will never get back, only to learn that an H or X pipe may give me a 0.28% increase in HP, which is probably w/in some margin of error and not of any statically significant value. I also learned that an X pipe may sound cooler if the under carriage allows me to properly place it but would still be better off installing a cat back muffler if I want an improvement in sound
On a stock engine, your point is valid. Once modified, that changes completely and then you're simply wrong. So you think 1k+ F10 M5's, Supras, Gallardos, GTRs, etc are running stock exhaust?
Yes, they are running the "stock" exhausts the engineers design for that engine. That doesn't mean taking that strategy and applying it to a different car will produce a benefit.

The point of the video was on the same engine there was a negligible benefit and slight sound improvement. The latter is option, the former was fact.
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      10-19-2017, 10:16 PM   #18
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The picture above on the left is a stock X*M exhaust and there's no crossover at all. Does yours have one then?
Yeah they all do - it's built into the muffler section, and you'll never see it unless you chop the top off like I did.

Keep in mind, I said it was tiny - I'm talking no more than 20mm ID.


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      10-20-2017, 09:32 PM   #19
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Ahh, I see. I just wanna hear the turbos more, so those two turns within the muffler can't be helping. I read about allmotor2000 on the F10 boards and he created a table on what lengths are needed to make a Helmholtz resonator to stop the drone.
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      10-21-2017, 03:03 AM   #20
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Ahh, I see. I just wanna hear the turbos more, so those two turns within the muffler can't be helping. I read about allmotor2000 on the F10 boards and he created a table on what lengths are needed to make a Helmholtz resonator to stop the drone.
Yeah I found the original formula it was based on, and built a calculator in Excel so I can plug in the exact RPM.
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      10-23-2017, 11:18 PM   #21
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Well feel free to email that to me at m5james@yahoo.com :-)
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      10-26-2017, 06:01 AM   #22
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Well feel free to email that to me at m5james@yahoo.com :-)
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