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      10-06-2020, 07:49 PM   #23
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Originally Posted by super51fan View Post
Routing the downpipe under the transmission is very strange to me. It almost looks like the M5 midpipe setup. I wonder if they are planning for a V engine configuration down the road. I know that sounds farfetched but I do not see why else they would do it this way.
Not as far-fetched as you may think. Remember, they had tested a V6 earlier in the development of the F8X.
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      10-06-2020, 08:32 PM   #24
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Originally Posted by CanAutM3 View Post
Hmmmm, interesting. I wonder if it is an attempt at making an equal length exhaust system.
I believe so.
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      10-06-2020, 08:43 PM   #25
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Originally Posted by autoart View Post
Could it be in the yellow circles those are braided exhaust pipes?
No they are not flex joints, they are cats.
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      10-06-2020, 08:52 PM   #26
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Originally Posted by F85MTuNED View Post
I believe so.
Kinda confirmed in post #19
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      10-06-2020, 09:58 PM   #27
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Sorry equal-length guys, in the pic right behind the skid plate is a 18-24in section running sideways. This makes the length unequal. The short side runs rearward immediately, but the long side routes around the gearbox/trans (?) in the middle.

This is yet another thing on the new Gs that make no sense...like the big honker, and locked ECUs.
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      10-07-2020, 05:08 AM   #28
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Quote:
Originally Posted by TopJimmy View Post
Sorry equal-length guys, in the pic right behind the skid plate is a 18-24in section running sideways. This makes the length unequal. The short side runs rearward immediately, but the long side routes around the gearbox/trans (?) in the middle.

This is yet another thing on the new Gs that make no sense...like the big honker, and locked ECUs.
It’s not obvious if you don’t speak German, but the BMW ///M employee in the video is quite specific about how they equalized the exhaust lengths to obtain balanced exhaust pulses and achieve the desired sound.

Based on this, I am one to believe the G8X will sound much better than the F8X.
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      10-07-2020, 07:28 AM   #29
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      10-07-2020, 07:40 AM   #30
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This is how they are getting equal length exhaust now ?
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      10-07-2020, 07:55 AM   #31
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Quote:
Originally Posted by CanAutM3 View Post
It’s not obvious if you don’t speak German, but the BMW ///M employee in the video is quite specific about how they equalized the exhaust lengths to obtain balanced exhaust pulses and achieve the desired sound.

Based on this, I am one to believe the G8X will sound much better than the F8X.
In the StraightPipes video posted in one of these threads, they rev both cars pretty aggressively in various modes (starts at the 7:35 mark and again at 24:50), and they do seem to sound a bit better than the F8x, right out of the box (not under load at least). Some of the F8x raspiness is still present but overall it seems to have a deeper, smoother tone.
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      10-07-2020, 10:33 AM   #32
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Quote:
Originally Posted by JTO24 View Post
In the StraightPipes video posted in one of these threads, they rev both cars pretty aggressively in various modes (starts at the 7:35 mark and again at 24:50), and they do seem to sound a bit better than the F8x, right out of the box (not under load at least). Some of the F8x raspiness is still present but overall it seems to have a deeper, smoother tone.
AND the guys were filming with an iPhone on YouTube live so not exactly an optimal setup for audio recording
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      10-07-2020, 12:05 PM   #33
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There could be more than one answer, packaging aspects could have been the trigger and when the idea was out there why not spend the effort to achieve EL when you’re at it. Or vice versa.
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      10-07-2020, 12:26 PM   #34
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I don't speak German, so don't know precisely what was said about the exhaust lengths. But could be that the engineer is confirming exhaust lengths to achieve a particular sound, not that they are equal.

The sound of the car in the video sounds very unequal exhaust phasing to me.

Then there the 'a picture is worth a thousand words' . Take a look at how much deviation there is in the two pipe runs in the OP, and then look at this pic of the turbo layout on the S58. Notice how they stagger horizontally to get them as close to each other as they can. The outlets are far closer than they are on an S55. Look at how far forward the rear turbo is.

Nothing equal length about that setup in my opinion. The sound in the video shouts unequal.
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      10-07-2020, 01:15 PM   #35
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Quote:
Originally Posted by IS3andME View Post
Not as far-fetched as you may think. Remember, they had tested a V6 earlier in the development of the F8X.
Sounds like a perfect opportunity for a certain model on the CLAR platform to use Toyota's V35a
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      10-07-2020, 01:17 PM   #36
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Quote:
Originally Posted by NISFAN View Post
I don't speak German, so don't know precisely what was said about the exhaust lengths. But could be that the engineer is confirming exhaust lengths to achieve a particular sound, not that they are equal.

The sound of the car in the video sounds very unequal exhaust phasing to me.

Then there the 'a picture is worth a thousand words' . Take a look at how much deviation there is in the two pipe runs in the OP, and then look at this pic of the turbo layout on the S58. Notice how they stagger horizontally to get them as close to each other as they can. The outlets are far closer than they are on an S55. Look at how far forward the rear turbo is.

Nothing equal length about that setup in my opinion. The sound in the video shouts unequal.
I am fluent in German.

When the Youtuber comments that the exhaust sounds very "clean", the BMW ///M employee clearly states that they made the two exhaust pipes the same effective lengths so that the exhaust pulses alternate nicely for it to sound like a more typical inline-6.
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      10-07-2020, 02:48 PM   #37
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Quote:
Originally Posted by CanAutM3 View Post
I am fluent in German.

When the Youtuber comments that the exhaust sounds very "clean", the BMW ///M employee clearly states that they made the two exhaust pipes the same effective lengths so that the exhaust pulses alternate nicely for it to sound like a more typical inline-6.
Well there is something amiss.

You can clearly see from the turbine positions on the S58 pic I attached, that there isn't much difference in length to address to achieve an equal length system.
The airborne pic shows a big diversion by crossing one pipe over the gearbox, adding much more than the turbo spacing difference.

All the data given in this thread cannot all be true.
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      10-07-2020, 03:18 PM   #38
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Quote:
Originally Posted by NISFAN View Post
Well there is something amiss.

You can clearly see from the turbine positions on the S58 pic I attached, that there isn't much difference in length to address to achieve an equal length system.
The airborne pic shows a big diversion by crossing one pipe over the gearbox, adding much more than the turbo spacing difference.

All the data given in this thread cannot all be true.
The turbo spacing shouldn’t be the measure, right? It should be the distance from the manifold exits to the exhaust tips, not the turbos to the exhaust tips that determine EL or not?
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      10-07-2020, 05:21 PM   #39
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Quote:
Originally Posted by CanAutM3 View Post
It’s not obvious if you don’t speak German, but the BMW ///M employee in the video is quite specific about how they equalized the exhaust lengths to obtain balanced exhaust pulses and achieve the desired sound.

Based on this, I am one to believe the G8X will sound much better than the F8X.
Makes sense - the sound of the S55 was criticised vs. older M's so they have done something about it for the S58. Not much of a conspiracy there.
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      10-07-2020, 05:33 PM   #40
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Quote:
Originally Posted by solstice View Post
Quote:
Originally Posted by NISFAN View Post
Well there is something amiss.

You can clearly see from the turbine positions on the S58 pic I attached, that there isn't much difference in length to address to achieve an equal length system.
The airborne pic shows a big diversion by crossing one pipe over the gearbox, adding much more than the turbo spacing difference.

All the data given in this thread cannot all be true.
The turbo spacing shouldn’t be the measure, right? It should be the distance from the manifold exits to the exhaust tips, not the turbos to the exhaust tips that determine EL or not?
In an ideal setup, yes. But these cars use a log manifold which gives different lengths for each cylinder. They also tend to keep the runner lengths fairly consistent for each turbo, meaning turbine outlet becomes as good as it gets.
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      10-07-2020, 05:56 PM   #41
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Very curious to see how they route the exhaust (driver vs passenger turbo) and if they truly flipped it on the G8x like they did on the X3M vs the S55., or if they kept the rear bank turbos routed to the passenger side ("short" side) because they are on slightly different platforms.

If they kept the S55 set-up, I can see why they did they piping. But if they kept the S58 X3M set-up, they may have been doing something unusual but effectively equal-length but in a different cylinder pulse spacing method.

The videos posted sound decent over the S55 thus far, even compared to my CS when it was stock and not customer equal-lengthed.
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      10-28-2020, 02:27 PM   #42
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I'm no engineer, but learned as much about the science of tuning as I could when I was younger and have always been into physics and chem and spent a few years 15 years ago building some pretty wild cars...

I mean it seems like common sense, maybe I'm wrong but wouldn't you really need equal back pressure for bank 1 and bank 2, as cam phasing for peak HP would vary slightly on back pressure? And as far as I know VANOS doesn't allow different phasing or varied lift/duration for each individual cylinder?

Maybe they engineered it to be as close to equal as possible and use other means, bends, pipe size variations to keep exhaust velocity and resistance as close to equal as possible?

Or is the difference in back pressure not big enough to cause a difference in appropriate cam timing/lift/duration for bank 1 and 2?
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      10-28-2020, 03:23 PM   #43
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Originally Posted by DKX4///M View Post
I'm no engineer, but learned as much about the science of tuning as I could when I was younger and have always been into physics and chem and spent a few years 15 years ago building some pretty wild cars...

I mean it seems like common sense, maybe I'm wrong but wouldn't you really need equal back pressure for bank 1 and bank 2, as cam phasing for peak HP would vary slightly on back pressure? And as far as I know VANOS doesn't allow different phasing or varied lift/duration for each individual cylinder?

Maybe they engineered it to be as close to equal as possible and use other means, bends, pipe size variations to keep exhaust velocity and resistance as close to equal as possible?

Or is the difference in back pressure not big enough to cause a difference in appropriate cam timing/lift/duration for bank 1 and 2?
Tuned exhaust length manifolds are critical for efficient scavenging on NA engines. This is not the case on turbocharged engines, first because since the intake is pressurized, there’s no need for exhaust scavenging, second, the turbine of the turbo in the exhaust stream disrupts the pressure waves that would be used for scavenging. So short answer, there’s no performance benefit to equal length exhausts on a turbo engine.
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      11-04-2020, 12:27 PM   #44
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Who said the downpipes will be easy access 😥
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