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M2 Technical Topics > S55 Engine / Drivetrain / Exhaust / Bolt-ons / Tuning > X pipe, H pipe or straight pipe

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      12-19-2019, 08:58 AM   #1
Fahidm2comp
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X pipe, H pipe or straight pipe

Was thinking of removing the OPF filters and replacing with either a x pipe or h pipe instead of just a straight pipe.
I have a custom OPF back valved system but will be getting it custom tuned with Litchfield (UK) and therefore I want to remove the restriction of the filters. I won’t have to worry about the CEL either as this will be taken care of as part of the tune.
I was wondering if anyone has done this setup, and if there are any advantages of any 1 over the other, and also the difference that can be expected in the sound.. if any.

Thanks
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      12-19-2019, 09:16 AM   #2
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If your custom OPF back exhaust replaced the resonator, I recommend you a resonated midpipe to avoid any drone.
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      12-19-2019, 09:28 AM   #3
Fahidm2comp
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Quote:
Originally Posted by _RS4_ View Post
If your custom OPF back exhaust replaced the resonator, I recommend you a resonated midpipe to avoid any drone.
Yes it was replaced with equal length pipes, I previously had a milltek system which was a bit quieter and kept the midpipe resonator intact, but this current system doesn’t drone at all as it is now.. will the drone be increased excessively with the OPF delete?

I want to avoid excessive drone and therefore if so, any recommendations on the resonator to shortlist?
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      12-19-2019, 02:24 PM   #4
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If you equalized the pipe length, go all out and do an x-pipe to capture the higher pitched howls that equal-length pipes can deliver.
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      12-20-2019, 12:54 AM   #5
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Quote:
Originally Posted by Fahidm2comp View Post
Yes it was replaced with equal length pipes, I previously had a milltek system which was a bit quieter and kept the midpipe resonator intact, but this current system doesn’t drone at all as it is now.. will the drone be increased excessively with the OPF delete?

I want to avoid excessive drone and therefore if so, any recommendations on the resonator to shortlist?
I'm afraid so, I do not recommend straight pipes in that case. I don't know which resonator could fit into your custom rear section.
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      12-20-2019, 04:54 PM   #6
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Quote:
Originally Posted by _RS4_ View Post
If your custom OPF back exhaust replaced the resonator, I recommend you a resonated midpipe to avoid any drone.
that is correct.
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      12-20-2019, 04:56 PM   #7
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Quote:
Originally Posted by _RS4_ View Post
I'm afraid so, I do not recommend straight pipes in that case. I don't know which resonator could fit into your custom rear section.
it depnds on how they did the job. Anyway a custom solution i believe will be the only way for your application
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      12-21-2019, 08:32 AM   #8
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Quote:
Originally Posted by Big Fabri View Post
it depnds on how they did the job. Anyway a custom solution i believe will be the only way for your application
Thanks guys.. basically I’m going to be going for a resonated section to replace the OPF’s, not a box but instead 2 high flow cylinder resonators, followed by an x pipe just before the diff section where the pipes would naturally diverge. It already sounds insane as it is, but I’m wanting a lot more flow for when the tune is operational. I’ll be glad to showcase the setup once all done!
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      12-21-2019, 02:49 PM   #9
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The factory centre silencer is already a H pipe inside the resonator case. Have you removed that?

So have you not any crossover at all?
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      12-21-2019, 03:46 PM   #10
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Quote:
Originally Posted by Fahidm2comp View Post
Thanks guys.. basically I’m going to be going for a resonated section to replace the OPF’s, not a box but instead 2 high flow cylinder resonators, followed by an x pipe just before the diff section where the pipes would naturally diverge. It already sounds insane as it is, but I’m wanting a lot more flow for when the tune is operational. I’ll be glad to showcase the setup once all done!
i would'nt do that. just replace the opf with nothing. in case you need you can always put something
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      12-21-2019, 04:28 PM   #11
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Quote:
Originally Posted by doughboy View Post
The factory centre silencer is already a H pipe inside the resonator case. Have you removed that?

So have you not any crossover at all?
Unfortunately I can’t post videos on here to show you as i don’t have a laptop and I’m using an iPhone. Basically everything from the OPF backwards is custom, resonator has been removed, and then it has a muffler custom made to integrate the original valves from the stock exhaust to make it quieter and louder when going through the modes and opening and closing the flaps. The stock resonator was completely removed in order to lengthen the shorter pipe and make them equal length.
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      12-22-2019, 01:59 AM   #12
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I'm not a fan of custom exhausts, wouldn't it be easier to buy a complete exhaust system like Milltek, since you live in the UK? You can choose the valved race version (louder) with OPF bypass pipes and won't have any fit issues, it's really plug and play.
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      12-22-2019, 02:59 AM   #13
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Quote:
Originally Posted by _RS4_ View Post
I'm not a fan of custom exhausts, wouldn't it be easier to buy a complete exhaust system like Milltek, since you live in the UK? You can choose the valved race version (louder) with OPF bypass pipes and won't have any fit issues, it's really plug and play.
I had that exhaust initially, it’s been sold, this a far cry from a milltek exhaust, I’m sure big fabri can chime in as he’s seen it and heard it.
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      12-22-2019, 06:23 AM   #14
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Quote:
Originally Posted by _RS4_ View Post
I'm not a fan of custom exhausts, wouldn't it be easier to buy a complete exhaust system like Milltek, since you live in the UK? You can choose the valved race version (louder) with OPF bypass pipes and won't have any fit issues, it's really plug and play.
No such thing as an after market equal-length exhaust, it's in another league of its own.

Congrats O/P on a beautiful sounding exhaust and not the usual S55 exhaust note! I have a custom equal-length exhaust myself.
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      12-22-2019, 08:46 AM   #15
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An x-pipe generally will outperform an H or straight pipes. But that's assuming equal length at the merge.
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      12-22-2019, 03:42 PM   #16
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Quote:
Originally Posted by Fahidm2comp View Post
I had that exhaust initially, it’s been sold, this a far cry from a milltek exhaust, I’m sure big fabri can chime in as he’s seen it and heard it.
haha, me too, had milltek, sold it.

equal length coming in the new year.

I'll be aiming to replace mid silencer with two single resonators then squeeze an x pipe in behind the diff, after the length equalisation..

im keeping sec cats for UK mot test as ill be be runniing decat dps.
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