359 days later I could test and learn a few things, that I didn't know any better at the time and that need to be corrected: 0:22 - We didn't. 0:44 - Because one of those internet experts sounded so confident in his statement that: "F1 exhausts are made completely made of titanium" - I've made fun of it and showed that F1 exhausts are made out of inconel, while saying they are made out of titanium... Well.... since reading the Honda Third Era F1 special - the joke is on me. Honda has actually developed Titanium headers to save weight. They were tested and confirmed to last 600km racing distance - although they were never used in a race, but at least they do exist! 3:22 - It sounds obviously not as good as it gets, as demonstrated by the screaming Mustang later in the video. The primary reason for the dramatic difference in exhaust notes between the two is that the Passat header lacks additional inflection points before its collector. 6:40 - "If you put long headers on a high rpm engine it will hurt peak horsepower" - depends on the definition of long. Common knowledge is to keep long tube headers at (roughly) 30 inches in length for a motor with a "normal" rpm range. But this is done to achieve a compromise between power, powerband and packaging. That length aims to capture the 2nd negative reflection of a cylinders pressure pulse at a medium rpm range. Extending the header length drastically to capture the 1st negative pressure wave reflection at high rpm can actually increase power. (There is the possibility of losing pressure wave energy due to shockwave formation and friction, but two additional phase changes won't help to maintain pressure wave energy at maximum either.) Formula One cars do exactly that, but they rev 3-times higher so the pipes can be 3-times as short - so they look normal. By accident I've designed the 12-into-1 header the same way (it wasn't intentional). By making V12 header with way too long primaries (as common knowledge would tell you) we were getting a totally unexpected dyno result in return. Peak torque came in way too late for the common knowledge to make sense - and the torque number wasn't that low either. 6:41 - I saw an interview elsewhere with Darren (the owner and builder of that car) and he seemed a bit disappointed with the sound that the Sprint car V8 made. He expected the 180° degree header would make it sound like a high pitched F1 car. At the time of making this video I thought the reason it doesn't are the collectors. Now one year later I can say - I was totally wrong. If he would have just added a Y-pipe after the collectors - he would have gotten the sound he was looking for (but still changing his collectors to merge collectors would have made it even better.) 10:44 - The explanation is flawed. My understanding of the concept was not as detailed at the time. Thanks to a former F1 engine designer I now understand it even better. The exhaust gas and the pressure wave don't race each other - they race together.. sometimes. Imagine a very long train moving at moderate speed. Its surface is so smooth that a sports car can drive on it. At the train's rear, a sports car begins driving at maximum speed toward the front. Both move in the same direction. Upon reaching the front, the car turns around and races back. From an outside perspective, the car appears much faster when moving with the train (car speed plus train speed) and much slower when moving against it (car speed minus train speed). In an exhaust system, the expelled gases are like the train carrying the pressure wave. The speed difference between a pressure wave moving with versus against the exhaust gas can be as high as 650 ft/second. Therefore, the pressure wave doesn't just influence the gas stream (as shown in the video) - the gas stream also affects the pressure wave's speed (which was not shown in the video). 15:18 - While it's generally true that "pressure wave reflection is strongest when the exhaust pipe ends in a wide open space," there are exceptions. A not so wide open space at high temperature can (in certain circumstances) reflect more wave energy than a wide open space at cold temperature. This principle applies particularly in collectors. 15:30 - Same correction as 10:44 15:45 - The claim: "The baffle collector that still creates quite strong wave reflections, where as the merge collector doesn't" - the way it's worded - it's wrong. Baffle collectors create abrupt, more intense ("shorter") reflections, while merge collectors "stretch" these reflections, making them less intense by comparison. But both collectors can produce strong reflections. 16:50 - Regarding the claim "That (the standing wave) is what's missing for the good sound? No!" - The answer is still no, but resonance, its close relative, is the actual answer. I had suspected that the standing wave was actually responsible and the fat doctor rubber glove should give that away. But I didn't fully understand how or where in the exhaust it was created. The 8-into-1 Mustang header puzzled me until I learned six months later, after speaking with the fabricator, that it was stepped. But it also turns out that standing waves can't be standing when the gas where it's supposed to stand on is constantly moving - so calling it resonance is more accurate. 17:23 - The calculation is overly simplified, not taking into account crucial factors such as pressure wave splitting at multiple inflection points and or even tailpipe reflection. While it was supposed to demonstrate frequency changes with primary pipe length, without accounting for multiple inflection points the results are so inaccurate, that they are worse than guessing. 18:08 - Merge collectors are NOT the cause of the "F1-style" exhaust sound. That sound is created by putting multiple inflection points in series (in addition to getting the more commonly known factors right). However, merge collectors do increase the exhaust note's smoothness and make the sound more refined than "baffle" collectors, as stated in the video - due to the gradual reflection of pressure waves. 18:23 - "The baffle collectors that have the strongest reflection waves..." is poorly worded - see the comment made at 15:45. 18:35 - This statement might have at least one exception - the Lexus LFA. But not only has the LFA the most uncommon collectors of all the cars that have this kind of sound, it was probably the only sports car that prioritized sound over power. There was even a patent made during the LFA development that shows how a coil of coolant is wrapped around one of the secondary pipes - just to change the sound at low rpm! (Side Note: The music branch of the Yamaha company had no involvement in the exhaust sound design of the LFA - as can be read in the book "The Roar of an Angel") As a general rule, though, the "raspiness" of baffle collectors usually makes cars sound far from angelic. But adding a megaphone or bell shaped section can fix this. 19:50 - The "optimal" merge collector angle heavily depends on how high in the RPM range the engine is designed to make power. A much steeper collector angle is preferred when the engine revs to 9,000 RPM and above (for peak power). 20:00 - This angle produces a smooth sound. Steeper angles reduce the reflection length, resulting in a "sharper" sound. 20:18 - The jump up in area size is fine - it actually seems beneficial for power. But as we were only looking for sound, this was the wrong place to look for problems in the first place. The issue came down to a lack of inflection points before the collector. 20:38 - "It seems he did get everything right." - I can now see two problems here. First, the car didn't merge the two 6-into-1 headers into a single pipe (the second inflection point is missing - at least as far as I can see). Second, as Polish UA-camr "Kowalski" has pointed out: these 6-into-1 headers are nowhere near equal length. They really aren't! 24:00 - I didn't have that meeting. No funding was secured. 25:26 - In reality, pulling the engine out, taking the header off, changing the collector, putting it back on, and reinstalling the engine took over six hours each time. 26:12 - While looking for answers, I only found that Ferrari exhaust at the very end of making this video. Its lack of a merge collector made me rethink my theory - see comment about 16:50. 26:42 - "Maybe we have been looking at the wrong section of the pipe." - Yes, exactly that. At the time, I thought the entire length of the exhaust was the solution, believing the wave would resonate back and forth from the exhaust valve to the tailpipe. I even tested this theory with an adjustable-length exhaust - while it would start to resonate at certain distances, it wouldn't create the "high-pitched F1" sound. Instead, only its little annoying brother showed up: exhaust drone. 27:01 - If you've read this far, you should be able to answer these questions for yourself.
These comments capture everything that's needed. Thanks to everyone who brought valuable input.
359 days later I could test and learn a few things, that I didn't know any better at the time and that need to be corrected:
0:22 - We didn't.
0:44 - Because one of those internet experts sounded so confident in his statement that: "F1 exhausts are made completely made of titanium" - I've made fun of it and showed that F1 exhausts are made out of inconel, while saying they are made out of titanium...
Well.... since reading the Honda Third Era F1 special - the joke is on me. Honda has actually developed Titanium headers to save weight. They were tested and confirmed to last 600km racing distance - although they were never used in a race, but at least they do exist!
3:22 - It sounds obviously not as good as it gets, as demonstrated by the screaming Mustang later in the video. The primary reason for the dramatic difference in exhaust notes between the two is that the Passat header lacks additional inflection points before its collector.
6:40 - "If you put long headers on a high rpm engine it will hurt peak horsepower" - depends on the definition of long. Common knowledge is to keep long tube headers at (roughly) 30 inches in length for a motor with a "normal" rpm range. But this is done to achieve a compromise between power, powerband and packaging. That length aims to capture the 2nd negative reflection of a cylinders pressure pulse at a medium rpm range. Extending the header length drastically to capture the 1st negative pressure wave reflection at high rpm can actually increase power. (There is the possibility of losing pressure wave energy due to shockwave formation and friction, but two additional phase changes won't help to maintain pressure wave energy at maximum either.) Formula One cars do exactly that, but they rev 3-times higher so the pipes can be 3-times as short - so they look normal. By accident I've designed the 12-into-1 header the same way (it wasn't intentional). By making V12 header with way too long primaries (as common knowledge would tell you) we were getting a totally unexpected dyno result in return. Peak torque came in way too late for the common knowledge to make sense - and the torque number wasn't that low either.
6:41 - I saw an interview elsewhere with Darren (the owner and builder of that car) and he seemed a bit disappointed with the sound that the Sprint car V8 made. He expected the 180° degree header would make it sound like a high pitched F1 car. At the time of making this video I thought the reason it doesn't are the collectors. Now one year later I can say - I was totally wrong. If he would have just added a Y-pipe after the collectors - he would have gotten the sound he was looking for (but still changing his collectors to merge collectors would have made it even better.)
10:44 - The explanation is flawed. My understanding of the concept was not as detailed at the time. Thanks to a former F1 engine designer I now understand it even better.
The exhaust gas and the pressure wave don't race each other - they race together.. sometimes.
Imagine a very long train moving at moderate speed. Its surface is so smooth that a sports car can drive on it. At the train's rear, a sports car begins driving at maximum speed toward the front. Both move in the same direction. Upon reaching the front, the car turns around and races back. From an outside perspective, the car appears much faster when moving with the train (car speed plus train speed) and much slower when moving against it (car speed minus train speed).
In an exhaust system, the expelled gases are like the train carrying the pressure wave. The speed difference between a pressure wave moving with versus against the exhaust gas can be as high as 650 ft/second.
Therefore, the pressure wave doesn't just influence the gas stream (as shown in the video) - the gas stream also affects the pressure wave's speed (which was not shown in the video).
15:18 - While it's generally true that "pressure wave reflection is strongest when the exhaust pipe ends in a wide open space," there are exceptions. A not so wide open space at high temperature can (in certain circumstances) reflect more wave energy than a wide open space at cold temperature. This principle applies particularly in collectors.
15:30 - Same correction as 10:44
15:45 - The claim: "The baffle collector that still creates quite strong wave reflections, where as the merge collector doesn't" - the way it's worded - it's wrong. Baffle collectors create abrupt, more intense ("shorter") reflections, while merge collectors "stretch" these reflections, making them less intense by comparison. But both collectors can produce strong reflections.
16:50 - Regarding the claim "That (the standing wave) is what's missing for the good sound? No!" - The answer is still no, but resonance, its close relative, is the actual answer. I had suspected that the standing wave was actually responsible and the fat doctor rubber glove should give that away. But I didn't fully understand how or where in the exhaust it was created. The 8-into-1 Mustang header puzzled me until I learned six months later, after speaking with the fabricator, that it was stepped.
But it also turns out that standing waves can't be standing when the gas where it's supposed to stand on is constantly moving - so calling it resonance is more accurate.
17:23 - The calculation is overly simplified, not taking into account crucial factors such as pressure wave splitting at multiple inflection points and or even tailpipe reflection. While it was supposed to demonstrate frequency changes with primary pipe length, without accounting for multiple inflection points the results are so inaccurate, that they are worse than guessing.
18:08 - Merge collectors are NOT the cause of the "F1-style" exhaust sound. That sound is created by putting multiple inflection points in series (in addition to getting the more commonly known factors right). However, merge collectors do increase the exhaust note's smoothness and make the sound more refined than "baffle" collectors, as stated in the video - due to the gradual reflection of pressure waves.
18:23 - "The baffle collectors that have the strongest reflection waves..." is poorly worded - see the comment made at 15:45.
18:35 - This statement might have at least one exception - the Lexus LFA. But not only has the LFA the most uncommon collectors of all the cars that have this kind of sound, it was probably the only sports car that prioritized sound over power. There was even a patent made during the LFA development that shows how a coil of coolant is wrapped around one of the secondary pipes - just to change the sound at low rpm! (Side Note: The music branch of the Yamaha company had no involvement in the exhaust sound design of the LFA - as can be read in the book "The Roar of an Angel")
As a general rule, though, the "raspiness" of baffle collectors usually makes cars sound far from angelic. But adding a megaphone or bell shaped section can fix this.
19:50 - The "optimal" merge collector angle heavily depends on how high in the RPM range the engine is designed to make power. A much steeper collector angle is preferred when the engine revs to 9,000 RPM and above (for peak power).
20:00 - This angle produces a smooth sound. Steeper angles reduce the reflection length, resulting in a "sharper" sound.
20:18 - The jump up in area size is fine - it actually seems beneficial for power. But as we were only looking for sound, this was the wrong place to look for problems in the first place. The issue came down to a lack of inflection points before the collector.
20:38 - "It seems he did get everything right." - I can now see two problems here. First, the car didn't merge the two 6-into-1 headers into a single pipe (the second inflection point is missing - at least as far as I can see). Second, as Polish UA-camr "Kowalski" has pointed out: these 6-into-1 headers are nowhere near equal length. They really aren't!
24:00 - I didn't have that meeting. No funding was secured.
25:26 - In reality, pulling the engine out, taking the header off, changing the collector, putting it back on, and reinstalling the engine took over six hours each time.
26:12 - While looking for answers, I only found that Ferrari exhaust at the very end of making this video. Its lack of a merge collector made me rethink my theory - see comment about 16:50.
26:42 - "Maybe we have been looking at the wrong section of the pipe." - Yes, exactly that. At the time, I thought the entire length of the exhaust was the solution, believing the wave would resonate back and forth from the exhaust valve to the tailpipe. I even tested this theory with an adjustable-length exhaust - while it would start to resonate at certain distances, it wouldn't create the "high-pitched F1" sound. Instead, only its little annoying brother showed up: exhaust drone.
27:01 - If you've read this far, you should be able to answer these questions for yourself.
Looking for amazing engine performance? Checkout David Vizard's channel - www.youtube.com/@DavidVizard
New video: ua-cam.com/video/mQlUH5gyyag/v-deo.html