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| equal length exhaust ? (Page 2/2) |
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Yellow-88
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JUN 06, 03:05 PM
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| quote | Originally posted by ericjon262:
your ideas are way oversimplified, and I'm not sure I understand what you mean by a "Tri-Y", that's typically a style reserved for V8's and 4 cylinders. the only thing I've seen done on a V6 that could be called mistakenly called a "Tri-Y" would be a system where companion cylinders merge, then the 3 pipes from those merges, merge into one. A few guys have attempted to replicate this on a Fiero after a guy in Taiwan did it to his car. in theory, this would produce a strong scavenging signal in the pipes, and offer some level of increased performance, how much over a typical header isn't clear, as it requires longer primary tubes than a typical header that would bring each bank's 3 cylinders together.
Primary diameter and length have different effects on performance, and while they comprise the volume of the tube, the tube volume isn't really a recognized factor for most exhaust builders, you could install a pipe 1" long with the same volume as a pipe 100" long, and they would have massively different performance.
as far as equal length is concerned, it can have an affect on performance, both positive and negative, but it really comes down to what you can package in the vehicle. I have a Suburban that I'm putting a 454 in, the same header ideas I can apply to that, I would have a much more difficult time applying to a Fiero with a V8, just based on space, and those headers will be built with unequal length headers in a Tri-Y configuration, to hopefully produce a very large gain in low to mid range torque. as someone who has built more than one header, it's not easy, it's not cheap, and it's not a fast process. |
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Yellow-88
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JUN 06, 03:07 PM
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During my multiple careers as a designer I’ve learned that the best designs start with “over simplification” and end somewhere near where they started.
The subject of header design can get very complicated, very quickly given the many variables involved. Fortunately the laws of physics don’t break and that removes at least one of those variables.
I think the term “Tri-Y” was originally a marketing term from a header manufacturer in the sixties. “Tri” suggests three. Neither 4 nor 8 divide by 3 so the term shouldn’t apply to 4 or 8 cylinder engines. But it does work nicely with 6 cylinders. 3 into 1 X 2 then 2 into 1.
To over simplify, a multi cylinder engine is multiple single cylinder engines working together. So starting with 1 cylinder is a logical approach. At the exhaust stroke, a high pressure pulse of gas is forced into a pipe open at one end. Because an area of high pressure always moves to one of lower pressure, the gas will exit the open end of the pipe. The ideal design would be to constantly reduce the pressure as it moves toward the open end. The length of the pipe depends on the RPM and displacement of the cylinder. Ideally, when the pulse of gas reaches the open end of the pipe, the next one is entering. Mass in motion tends to stay in motion so the hot gas “wants” to keep going. Yes, simplified but not overly at this point.
Back to the tri-y concept and the 2.8L V6. One can think of the V6 as two 3 cylinder engines running 120 degrees out of phase. One bank of cylinders firing order is 1, 3, 5 and the other is 2, 4, 6. If you merge 1, 3, 5 into a “collector” and 2, 4, 6 into another, you now have 2 exhaust ports instead of 6. From an exhaust point of view, this “looks” like a 2 cylinder engine running at 3 times the RPM of the 6 cylinder engine. Similarly you could merge 1 and 2 into one collector, 2 and 3 into another and 5 and 6 into a third collector. From the exhaust view point, looking at the 3 collectors, you now have a 3 cylinder engine running at twice the RPM of the 6 cylinder engine. 2 into 1 X 3 than 3 into 1. “Tri-Y”.
The physics of it can get deep into fluid dynamics and thermal dynamics but in reality it’s about reducing the resistance of gas movement in an open-ended tube system. There are lots of calculators and formulas published on the subject, but in the end header design is a compromise between the engine and how it will be used. Big engine high RPM needs bigger diameter shorter tubes and small engine low RPM needs smaller diameter longer tubes. “Equal length” is really the most important and by far the most difficult.
Yellow-88
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ericjon262
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JUN 13, 01:20 PM
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| quote | Originally posted by Yellow-88:
During my multiple careers as a designer I’ve learned that the best designs start with “over simplification” and end somewhere near where they started.
The subject of header design can get very complicated, very quickly given the many variables involved. Fortunately the laws of physics don’t break and that removes at least one of those variables.
I think the term “Tri-Y” was originally a marketing term from a header manufacturer in the sixties. “Tri” suggests three. Neither 4 nor 8 divide by 3 so the term shouldn’t apply to 4 or 8 cylinder engines. But it does work nicely with 6 cylinders. 3 into 1 X 2 then 2 into 1.
To over simplify, a multi cylinder engine is multiple single cylinder engines working together. So starting with 1 cylinder is a logical approach. At the exhaust stroke, a high pressure pulse of gas is forced into a pipe open at one end. Because an area of high pressure always moves to one of lower pressure, the gas will exit the open end of the pipe. The ideal design would be to constantly reduce the pressure as it moves toward the open end. The length of the pipe depends on the RPM and displacement of the cylinder. Ideally, when the pulse of gas reaches the open end of the pipe, the next one is entering. Mass in motion tends to stay in motion so the hot gas “wants” to keep going. Yes, simplified but not overly at this point.
Back to the tri-y concept and the 2.8L V6. One can think of the V6 as two 3 cylinder engines running 120 degrees out of phase. One bank of cylinders firing order is 1, 3, 5 and the other is 2, 4, 6. If you merge 1, 3, 5 into a “collector” and 2, 4, 6 into another, you now have 2 exhaust ports instead of 6. From an exhaust point of view, this “looks” like a 2 cylinder engine running at 3 times the RPM of the 6 cylinder engine. Similarly you could merge 1 and 2 into one collector, 2 and 3 into another and 5 and 6 into a third collector. From the exhaust view point, looking at the 3 collectors, you now have a 3 cylinder engine running at twice the RPM of the 6 cylinder engine. 2 into 1 X 3 than 3 into 1. “Tri-Y”.
The physics of it can get deep into fluid dynamics and thermal dynamics but in reality it’s about reducing the resistance of gas movement in an open-ended tube system. There are lots of calculators and formulas published on the subject, but in the end header design is a compromise between the engine and how it will be used. Big engine high RPM needs bigger diameter shorter tubes and small engine low RPM needs smaller diameter longer tubes. “Equal length” is really the most important and by far the most difficult.
Yellow-88 |
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it has nothing to do with being divisible by 3, it has to do with there being 3 "Y" pipes in the header. there's alot more going on here than I think you realize.
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"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
I invited Lou Dias to trash me in my own thread, he refused. sorry. if he trashes your thread going after me. I tried.
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Neils88
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JUN 15, 08:49 AM
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One thing not mentioned here is weight. When designing a complex exhaust, the weight increase from the added pipe can render the performance increase irrelevant. Just one more factor to consider in the design.
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Yellow-88
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JUN 15, 10:12 AM
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| quote | Originally posted by ericjon262:
it has nothing to do with being divisible by 3, it has to do with there being 3 "Y" pipes in the header. there's alot more going on here than I think you realize.
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I stand corrected on "divisible by 3". Add 2 more cylinders to your drawing and it's still "Tri-Y". That's the design I've been working on.
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Yellow-88
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JUN 15, 10:25 AM
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| quote | Originally posted by Neils88:
One thing not mentioned here is weight. When designing a complex exhaust, the weight increase from the added pipe can render the performance increase irrelevant. Just one more factor to consider in the design. |
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I'm not sure just how much a header system would weigh. Yes less weight equals more useable HP. For me, performance isn't so much about HP, it's about response and engine "feel".
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ericjon262
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JUN 19, 08:56 PM
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| quote | Originally posted by Yellow-88:
Add 2 more cylinders to your drawing and it's still "Tri-Y". That's the design I've been working on. |
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not by commonly accepted nomenclature. ------------------
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
I invited Lou Dias to trash me in my own thread, he refused. sorry. if he trashes your thread going after me. I tried.
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Yellow-88
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JUN 22, 11:56 AM
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| quote | Originally posted by ericjon262:
not by commonly accepted nomenclature.
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3 into 1 collectors are readily available from "exhaust parts" vendors. There must be a reason for that.
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ericjon262
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JUN 23, 09:36 AM
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a 3-1 collector is not commonly referred to as a "Y", but as a 3-1 collector. Typically a "Y" or wye refers to the junction of two pipes into one pipe. again, by conventional nomenclature, you have not described a "Tri-Y" you have described an exhaust system that would most likely be described as a 6-2-1, 6 pipes merge into two banks of 3, the two banks of three then merge into 1 pipe. As far as performance goes, the system you're describing isn't really much more than a V6 with headers and a Y pipe, pretty standard stuff. ------------------
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
I invited Lou Dias to trash me in my own thread, he refused. sorry. if he trashes your thread going after me. I tried.
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Yellow-88
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JUN 24, 08:52 AM
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| quote | Originally posted by ericjon262:
a 3-1 collector is not commonly referred to as a "Y", but as a 3-1 collector. Typically a "Y" or wye refers to the junction of two pipes into one pipe. again, by conventional nomenclature, you have not described a "Tri-Y" you have described an exhaust system that would most likely be described as a 6-2-1, 6 pipes merge into two banks of 3, the two banks of three then merge into 1 pipe. As far as performance goes, the system you're describing isn't really much more than a V6 with headers and a Y pipe, pretty standard stuff.
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OK. Whatever one calls it, "standard stuff" or otherwise, why hasn't anyone done it yet? Meaning actual equal length headers.
(" Tri-Y" ) headers are 2 stage systems. In my design the Y pipe is the "secondary" part of the "header", it's not just a Y pipe. Its diameter and length are as important as the primary tubes. The idea is to reduce the amount of tube in the system. The 2.8 optimized for mid range RPM requires 36" X 1 1/4" for each cylinder. 36 feet of tube is both heavy and extremely complicated to stuff into the sideways engine bay. My system splits the 6 cylinder engine into two 3 cylinder engines. Just like all "Tri-Y" systems.
Carefully read my description and forget the" nomenclature".
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