Discussion
Something to do with unbalanced exhaust soundwaves I think.
The reason why the M5 V8 is so muted is because its got an X Pipe to balance out the rumble. Remove it, and you get the NASCAR effect.
That's how I understand it anyway.
Same thing goes for the Sccoby's and 5 cylinder engines - they're unbalanced.
The reason why the M5 V8 is so muted is because its got an X Pipe to balance out the rumble. Remove it, and you get the NASCAR effect.
That's how I understand it anyway.
Same thing goes for the Sccoby's and 5 cylinder engines - they're unbalanced.
neil_bolton said:
Something to do with unbalanced exhaust soundwaves I think.
The reason why the M5 V8 is so muted is because its got an X Pipe to balance out the rumble. Remove it, and you get the NASCAR effect.
That's how I understand it anyway.
Same thing goes for the Sccoby's and 5 cylinder engines - they're unbalanced.
Ooo, never knew that!The reason why the M5 V8 is so muted is because its got an X Pipe to balance out the rumble. Remove it, and you get the NASCAR effect.
That's how I understand it anyway.
Same thing goes for the Sccoby's and 5 cylinder engines - they're unbalanced.
It has a lot to do with the angle of the V, whether it has a crossplane crank (or not), and whether it has equal length exhaust manifolds.
Rover V8s, and traditional Amereican V8s burble because they have the crossplane crank which dictates that each bank taken in isolation doesn't have even firing timings. Even if you fit a X-pipe it barely evens it out. The X pipe is intended that one bank's exhaust output assists with the scavenging of the other bank.
A flat-plane-crank V8 like the Cerbera sounds completely different. Very "hard". These have even firing per bank and usually can't make any effective use of an X pipe. Having said that the Cerbera is different again because it has very unusual 75 degree angle which effectively means cylinder firing is like a heartbeat - 1, 2... 1, 2... 1,2. Unusually for a flat plane crank, people have reported postive gains from fitting an X pipe even though the layout of the car dictates you cannot get the X close-enough to the collector to gain full benefits.
4-cyl Subarus sound rumbly because they have uneven manifold lengths. ScoobySport offers equal length manifolds which improve power output and remove that burble sound. Boxer engines like those used by Subaru are the most naturally balanced engines. You can add a pair of cylinders to the basic design to make 2, 4, 6, 8, 10, 12 cylinder engines with equally low (absent?) harmonic vibrations.
Rover V8s, and traditional Amereican V8s burble because they have the crossplane crank which dictates that each bank taken in isolation doesn't have even firing timings. Even if you fit a X-pipe it barely evens it out. The X pipe is intended that one bank's exhaust output assists with the scavenging of the other bank.
A flat-plane-crank V8 like the Cerbera sounds completely different. Very "hard". These have even firing per bank and usually can't make any effective use of an X pipe. Having said that the Cerbera is different again because it has very unusual 75 degree angle which effectively means cylinder firing is like a heartbeat - 1, 2... 1, 2... 1,2. Unusually for a flat plane crank, people have reported postive gains from fitting an X pipe even though the layout of the car dictates you cannot get the X close-enough to the collector to gain full benefits.
4-cyl Subarus sound rumbly because they have uneven manifold lengths. ScoobySport offers equal length manifolds which improve power output and remove that burble sound. Boxer engines like those used by Subaru are the most naturally balanced engines. You can add a pair of cylinders to the basic design to make 2, 4, 6, 8, 10, 12 cylinder engines with equally low (absent?) harmonic vibrations.
Edited by Mars on Friday 3rd December 13:42
Efbe said:
neil_bolton said:
Something to do with unbalanced exhaust soundwaves I think.
The reason why the M5 V8 is so muted is because its got an X Pipe to balance out the rumble. Remove it, and you get the NASCAR effect.
That's how I understand it anyway.
Same thing goes for the Sccoby's and 5 cylinder engines - they're unbalanced.
Ooo, never knew that!The reason why the M5 V8 is so muted is because its got an X Pipe to balance out the rumble. Remove it, and you get the NASCAR effect.
That's how I understand it anyway.
Same thing goes for the Sccoby's and 5 cylinder engines - they're unbalanced.
The noise isn' so different because of an X-pipe as opposed to an H-pipe although I understand the best sound comes from an H-pipe with something like a 1 7/8" bore. Of course the crux of any sound is how much blockage and slowing of trhe pulse there is along the way in terms of catalysts, silencers and tortured routing.
X-pipes simply speed up the scavenging of each bank but the only difference it made to my Mustang is it possibly makes a higher-pitched roar at the top end but I doubt anyone could tell just by listening.
X-pipes simply speed up the scavenging of each bank but the only difference it made to my Mustang is it possibly makes a higher-pitched roar at the top end but I doubt anyone could tell just by listening.
Efbe said:
neil_bolton said:
Something to do with unbalanced exhaust soundwaves I think.
The reason why the M5 V8 is so muted is because its got an X Pipe to balance out the rumble. Remove it, and you get the NASCAR effect.
That's how I understand it anyway.
Same thing goes for the Sccoby's and 5 cylinder engines - they're unbalanced.
Ooo, never knew that!The reason why the M5 V8 is so muted is because its got an X Pipe to balance out the rumble. Remove it, and you get the NASCAR effect.
That's how I understand it anyway.
Same thing goes for the Sccoby's and 5 cylinder engines - they're unbalanced.
They have an uneven sound because they have an uneven firing order. Most V8's are more akin to two V4's joined with a common crank rather than two inline 4's.
The exception to this is flat plane crank as found in the TVR AJPV8 and most Ferrari V8's, these are far more akin to two inline 4 engines and have a very different sound.
The mid pipe on the exhaust exists to promote exhaust scavenging from each cylinder bank. H pipes then to give a different sound to X pipes admittedly, but both can still sound rumbly and uneven.
LuS1fer said:
The noise isn' so different because of an X-pipe as opposed to an H-pipe although I understand the best sound comes from an H-pipe with something like a 1 7/8" bore. Of course the crux of any sound is how much blockage and slowing of trhe pulse there is along the way in terms of catalysts, silencers and tortured routing.
X-pipes simply speed up the scavenging of each bank but the only difference it made to my Mustang is it possibly makes a higher-pitched roar at the top end but I doubt anyone could tell just by listening.
X pipe or H pipe... the requirement for one over the other is usually dictated by packaging. The Cerbera tends to use an H pipe. One of the Cerbera lads has a very high powered LS in his, and he has basically bent both exuahst together, cut a hole and welded them up to create a very soft X pipe... more of a "merged" pipe really.X-pipes simply speed up the scavenging of each bank but the only difference it made to my Mustang is it possibly makes a higher-pitched roar at the top end but I doubt anyone could tell just by listening.
My 6-cyl Scooby has a single pipe running the length of the car, before it splits again under the boot area and feeds into 2 backboxes. I would imagine the single centre section was a packaging requirement whereas the twin backboxes are probably cosmetic.
Mars said:
One of the Cerbera lads has a very high powered LS in his, and he has basically bent both exuahst together, cut a hole and welded them up to create a very soft X pipe... more of a "merged" pipe really.
Most aftermarket X pipes are made this way as it's far easier - mine is and that's from a top end US manufacturer (Corsa). The noise is important but has to be allied to cost. My last Z28 had dual cats but they led into a single pipe which was actually flattened under the driver's floor. This ran to a big restrictive back box. I replaced the pipe with full bore and took out the back box altogether but put in a small bullet box before the rear axle to reduce the drone you get with long runs.
Ford actually spent a lot of time tuning the 2005 Mustang exhaust to get the right noise. the previous Mustang had a fairly tortured exhaust system. The 2005 had fairly free-flowing cats and a true dual system to the rear where two boxes hung. Even when you replace the rear boxes for greater volume, you don't get any increase in power in these though I fitted the X-pipe to try as it can't do any harm.
Mars said:
Stuff
Absolutely correct, and to expand a little more, a small block chevy [like what powers the humble tvrolet] fires 1-8-4-3-6-5-7-2. Looking at the front of the car, 1 is front-right, so if you then look at the firing order split by bank you get:__________Right Bang (1)
Left Bang (8)
Left Bang (4)
__________Right Bang (3)
Left Bang (6)
__________Right Bang (5)
__________Right Bang (7)
Left Bang (2)
So each bank is going Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent, Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent, Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent...
Unlike a flat-plane (Cerb) where there's a bang equally from each bank every 180 degrees (and then another set of offset bangs from the other bank, also equally spaced).
tvrolet said:
Mars said:
Stuff
Absolutely correct, and to expand a little more, a small block chevy [like what powers the humble tvrolet] fires 1-8-4-3-6-5-7-2. Looking at the front of the car, 1 is front-right, so if you then look at the firing order split by bank you get:__________Right Bang (1)
Left Bang (8)
Left Bang (4)
__________Right Bang (3)
Left Bang (6)
__________Right Bang (5)
__________Right Bang (7)
Left Bang (2)
So each bank is going Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent, Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent, Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent...
Unlike a flat-plane (Cerb) where there's a bang equally from each bank every 180 degrees (and then another set of offset bangs from the other bank, also equally spaced).
tvrolet said:
So each bank is going Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent, Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent, Bang, Silent, Silent, Bang, Silent, Bang, Bang, Silent...
That's quite a good visual way of viewing this. 
tvrolet said:
Unlike a flat-plane (Cerb) where there's a bang equally from each bank every 180 degrees (and then another set of offset bangs from the other bank, also equally spaced).
Yes. Other flat plane cranks, like those from Ferrari, have 90 degree angles between the V, so even the firing pulses *between* banks is as evenly spaced as those *within* a bank. The Cerb's 75 degree angle gives it that unique sound.Mars said:
4-cyl Subarus sound rumbly because they have uneven manifold lengths. ScoobySport offers equal length manifolds which improve power output and remove that burble sound. Boxer engines like those used by Subaru are the most naturally balanced engines. You can add a pair of cylinders to the basic design to make 2, 4, 6, 8, 10, 12 cylinder engines with equally low (absent?) harmonic vibrations.
Surely the straight six is the most naturally balanced? Often described as having perfect primary and secondary balance.Edited by Mars on Friday 3rd December 13:42
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