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      02-01-2014, 04:35 AM   #290
Boss330
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Quote:
Originally Posted by swamp2 View Post
Sure I can but it is more prominent at idle and I simply contend that the state of tune and exhaust have more to do with the sound than the crank arrangement. Round and round we go...

Have and eat: You claim that cross plane vs. flat plane is so radically different in sound but then at the same time a twin turbo inline 6 can sound very similar to a NA flat plane V8. I agree on the latter (at least during cold start and definitely not under load). Why can this happen - again the importance on the exhaust and state of tune.

The lengthy lesson on all of the other details wasn't necessary at all. Your statement read to me that the crank angle between firings was non uniform which is isn't.
Swamp2, really??? That is disappointing coming from you. Your last post tells me you have a lack of elementary understanding of this subject (to paraphrase on how you described me recently)...

It seems that you think I believe the V8 warble comes from an uneven firing sequence per crank rotation/angle... And since it doesn't I'm wrong.

No, the V8 warble doesn't come from a uneven firing sequence per crank rotation, it comes from two cylinders on each bank firing consecutively, and with less crank rotation separating those two sequences than the other sequences per bank. That is because of the design/layout of the crankshaft. Yes, all crank pins are evenly distributed with equal placement on a 360 degree rotation. But when you place the pistons in each cylinder bank, one piston in each bank reaches TDC "out of sync" with the 3 other pistons on that bank. In a flat plane crank V8 all 4 pistons on the same bank are in sync. They are grouped 2 and 2 together with 180 degree of crank rotation separating TDC for the two groups. So piston 1 and 4 is at TDC at the same time and 2 and 3 are at TDC at the same time. So if it was a 4 cyl you would have one ignition per 180 degree crank rotation (remember that one of the 2 pistons at TDC at the same time is on the exhaust stroke and only one is on the combustion stroke). Since we are talking about a V8, we have two cylinder banks and there is a combustion stroke every 90 degree of crank rotation. Just as there is on a cross plane V8, but where the flat plane separates each combustion stroke 180 degree per cylinder bank, the cross plane has 3 combustion strokes with 180 degree separation per bank and 1 combustion stroke that is just 90 degrees after the previous one on that bank.

THAT creates the unmistakeable warble and also creates a backpressure problem in the exhaust manifold/headers.

There is NO way that the "state of tune" can eliminate the 2 cylinders firing out of sequence, neither can a exhaust system after the collectors on the headers. It has to be done before the collectors, just as BMW does on the S63tu and Ford did on the GT40. Just Google 180 degree headers if you don't believe me!

The main reason we have cross plane V8 is that they are in balance as regards second order harmonics, the flat plane is not. The flat plane is in balance in first order harmonics though, meaning the crank don't need heavy counterweights like a cross plane does. This makes the flat plane preferrable for a high performance, small displacement, application as the only downside that configuration has is vibrations. The cross plane is compromised in it's heavy crank and less than ideal exhaust scavenging, but is ideal in large engines and passenger cars because of it's second order balance.

As I don't expect you to believe what I say, here is just one article that might help: http://craig.backfire.ca/pages/autos/v8-engines

And since you obviously didn't understand that a cross plane V8 has that unmistakeable sound because of it's unique distribution of firing sequences per cylinder bank, that NO other engine has then it isn't hard to understand why you don't get how engines that has the same even distribution of firing sequences per cylinder bank can sound more similar to each other either... The I4, I6 and flat plane crank V8 all have a even distribution of exhaust pulses entering the collector(s), creating a more similar sound (not the same as the number of cylinders and thereby exhaust pulses differ over a 720 degree crank rotation). The cross plane V8 is the elephant in the room as that has that unique (and undesirable) adjacent cylinders firing consecutively on the same bank and entering the same exhaust manifold and the same collector. On the other hand, that exact firing sequence per cylinder bank is what most people love about the cross plane V8 sound It's more "musical" and sonorous than a Ferrari at idle (which can sound harsh and atonal). That is how it seems the S55 sounds, harsh, metallic and "racy". It's TOTALLY different from the S65 and I have NO problem understanding that the V8 brigade would be disappointed by that sound. But if you, like me, rather prefer the hard, metallic, "racy" sound then it sounds good...

I don't expect you to agree though, as I have found out you are never wrong or mistaken... But please at least come up with some sources that back up your views and shows that what I have written is wrong!

My postulation:
Unless you have a 180 degree header or a flat plane crank, a V8 will have the unmistakeable cross plane warble and exhaust sound. You can have a quiet exhaust and you can have a loud exhaust, but it WILL have to work with the exhaust pulses coming from the collectors on each bank. FACT!!! You cannot eliminate the consecutively firing cylinders on the same bank with the "state of tune", that is just wishful thinking! What you claim is basically implying that instead of using 180 degree headers (like BMW and Ford) you can get the same effect with the engines "state of tune" and exhaust system after the collectors...

Care to explain how the "state of tune" can eradicate the consecutively firing cylinders on the same bank? To me, that makes just as much sense as saying that beating on a different drum, but in the same beat will create a different rythm... No it won't, it will sound different, but it will still be with the same rythm! If you have two guys beating on a drum, one on the right hand side and one on the left hand and both beating at the same rythm as a cross plane V8 firing sequence per bank. Then, surely just changing the drums they beat on or how hard they beat (state of tune or exhaust) will NOT change the rythm, will it? NO it won't. It will sound more muffled or louder etc, but the unmistakeable rythm will still be there. And you can change the frequency they beat in (increasing or decreasing the revs), they still beat in the same sequence with a "double beat" constantly present.



Some videos to illustrate how a 180 degree header changes the sound:

Here you get a good glimpse of the 180 degree manifold, and listen to it rev and run on the track! This car has a small block Ford V8, but listen to how the exhaust sounds more like a Ferrari.



Now, listen to these Pantera's running on the same track (same mid engine layout, but doesn't have the 180 degree headers):



And the E92 M3 on a track, which of the above exhaust sounds are most similar to the M3??? (induction sound is awesome on the E9x though )







And finally this CSL. Now which of the E9x M3 the E46 CSL or the GT40 has a exhaust sound that is more similar to a Ferrari V8 exhaust? To me, the GT40 and CSL comes way closer than the E9x M3.



Now if you put on a 180 degree header like this on your M3, we are getting there on sound:



or, the more common GT40 "bundle of snakes manifold":



Here is a good illustration of what an aftermarket cross plane (180 degree) header for the S63Tu looks like:

http://www.europeanautosource.com/in...13-f06-m6.html



And let me finish off by quoting BMW M Head of engineering:

http://f10.m5post.com/forums/showthread.php?t=588858

Quote:
And on the exhaust side? We’re constantly hearing about “cross bank exhaust manifold” and “twin scroll twin turbo technology” without actually understanding the advantages.

(Laughs.) The cross bank exhaust manifold is an optimised collector of exhaust gases for the turbocharger from each of the cylinders. The V8 engine runs with a stutter anyway, giving rise to the typical V8 bubbling. A twelve cylinder always ignites the cylinders in the bank in crosswise fashion, one left, one right, nice and regular. For reasons of comfort, the V8 is fitted with a crankshaft that ignites twice in succession on the one bank and then jumps to the other. You can hear this highly irregular ignition sequence as the typical V8 bubbling in the exhaust tract, a sound you cannot hear from the engine of the new BMW M5.


Quote:
The cross bank exhaust manifold is made up of pipes that are joined to both banks in a rigid structure. The exhaust gases are therefore transferred optimally to the turbochargers. Every cylinder can therefore “expirate” under the optimal conditions. When I open the exhaust valve, a very hot, high energy jet of exhaust gases is released under a high pressure that hits an exhaust gas duct and then the charger turbine with virtually undiminished force. I therefore utilise the energy not only in the exhaust gas flow, but also in its momentum. As an analogy, imagine blowing on a pinwheel with a single breath: you’ll see that not only the volume, but also the momentum of the air has an effect.
You might disagree with me all you want, but I'd rather be in agreement with every other engine experts and engineers on the causes of exhaust sound from a V8 Please continue with your wishful thinking that the "state of tune" and exhaust system can eradicate the cross plane V8 sound

For me, and it seems Head of engineering at BMW as well as EVERY source I have found, agree with my view that you either need a flat plane crank or 180 degree headers to eradicate the cross plane V8 burble or "bubbling". How your "state of tune" magically can change the effect of that cross plane V8 firing sequence is beyond my understanding... (perhaps by cylinder deactivation on the cylinder that is "out of sync" )

Last edited by Boss330; 02-01-2014 at 06:24 AM..
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