Equal Length Manifolds vs. Log Manifolds Explained
02-09-2004, 11:26 PM
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Equal Length Manifolds vs. Log Manifolds Explained
Well, since the new wave of Log vs Equal Length Manifold threads are becoming common again, and since I look like an ******* for not explaining everything once again, it looks like I'll have to waste my time and do it again.
What really is our goal here? To increase volumetric efficiency.
What is Volumetric Efficiency you ask? My buddy Ben Strader simply states it in pretty good terms: It's the actual amount of air the engine ingests compared to that theoretical maximum. There are many factors in which determine how much torque an engine can produce, but the fundamental determinant is the mass of air it can ingest into the cylinders.
Ok lets look at the physical break down of it all. You have the runners and the collector, and also the wastegate placement on the manifold.
We all know heat is energy, and the more energy the more exhaust to spool the turbine. If you have too long of a runner, that can actually cause heat loss; now using a thicker material, such as 8 gauge, will somewhat help aid to keep heat inside. One thing that will cause the gas to slow down is a sudden decrease in temperature. The other thing that can cause a decrease in flow velocity is rapid expansion and turbulence, like going from a small passage (like the exhaust port in the head) to a 6-inch pipe. A smaller-diameter pipe geometry will tend to keep the flow rate up, but it will also lose heat more quickly. However, a large pipe will slow the velocity due to expansion. Worse still, the exhaust is constantly cooling from the moment it leaves the cylinder, meaning it's getting denser and slower. See the problem here? It's all about compromises. The proper pipe size is going to be influenced by the flow rate (volume rate, which is related to RPM and engine displacement), exhaust velocity (again related to RPM), exhaust temperature, and undoubtedly an array of other factors. Just remember flow rate is impacted by a number of different things in addition to raw temperature, including the surface roughness and pipe geometry.
Now, most people will agree, that the most important part of the manifold is the collector.
The log manifold has a poor collector obviously (if you would even call it one). The ideal collector area of the exhaust manifold would be a low angle merge to induce tangential flow. The joining of everything at the same rate, minimizing turbulence will maximize the amount of the exhaust gas energy into the turbine housing.
Basically, its been said that equal length manifolds with proper designed merge collectors optimize heat, pressure, and flow. A log manifold only optimizes heat and pressure, and not flow. With equal length manifolds less energy is wasted which also means a faster spooling turbo and increases in Volumetric Efficiency.
To go on further. We could talk about backpressure, I believe you could correlate it as flow velocities. From what I'm told it is generally accepted by automotive engineers that for every inch of Hg of backpressure approximately 1-2 HP is lost depending on the displacement and efficiency of the engine, the combustion chamber design, etc. So another goal would be to reduce the back pressure from changing the manifold design/wastegate placement.
Now that we've discussed a **** load of theory, how many manifold manufactures actually know all of this? I can only think of one - Full-Race. Only one has done the math and research, they deserve the glory. That's why it pisses me off when someone steals/copies designs. They don't know the slightest bit about fluid dynamics or thermodynamics, but they can certainly copy those who do.
You all can think I'm an *******, but I've done the research too. I wish people would read up on it more instead of cause drama. It wouldn't take long to find this info.
What really is our goal here? To increase volumetric efficiency.
What is Volumetric Efficiency you ask? My buddy Ben Strader simply states it in pretty good terms: It's the actual amount of air the engine ingests compared to that theoretical maximum. There are many factors in which determine how much torque an engine can produce, but the fundamental determinant is the mass of air it can ingest into the cylinders.
Ok lets look at the physical break down of it all. You have the runners and the collector, and also the wastegate placement on the manifold.
We all know heat is energy, and the more energy the more exhaust to spool the turbine. If you have too long of a runner, that can actually cause heat loss; now using a thicker material, such as 8 gauge, will somewhat help aid to keep heat inside. One thing that will cause the gas to slow down is a sudden decrease in temperature. The other thing that can cause a decrease in flow velocity is rapid expansion and turbulence, like going from a small passage (like the exhaust port in the head) to a 6-inch pipe. A smaller-diameter pipe geometry will tend to keep the flow rate up, but it will also lose heat more quickly. However, a large pipe will slow the velocity due to expansion. Worse still, the exhaust is constantly cooling from the moment it leaves the cylinder, meaning it's getting denser and slower. See the problem here? It's all about compromises. The proper pipe size is going to be influenced by the flow rate (volume rate, which is related to RPM and engine displacement), exhaust velocity (again related to RPM), exhaust temperature, and undoubtedly an array of other factors. Just remember flow rate is impacted by a number of different things in addition to raw temperature, including the surface roughness and pipe geometry.
Now, most people will agree, that the most important part of the manifold is the collector.
The log manifold has a poor collector obviously (if you would even call it one). The ideal collector area of the exhaust manifold would be a low angle merge to induce tangential flow. The joining of everything at the same rate, minimizing turbulence will maximize the amount of the exhaust gas energy into the turbine housing.
Basically, its been said that equal length manifolds with proper designed merge collectors optimize heat, pressure, and flow. A log manifold only optimizes heat and pressure, and not flow. With equal length manifolds less energy is wasted which also means a faster spooling turbo and increases in Volumetric Efficiency.
To go on further. We could talk about backpressure, I believe you could correlate it as flow velocities. From what I'm told it is generally accepted by automotive engineers that for every inch of Hg of backpressure approximately 1-2 HP is lost depending on the displacement and efficiency of the engine, the combustion chamber design, etc. So another goal would be to reduce the back pressure from changing the manifold design/wastegate placement.
Now that we've discussed a **** load of theory, how many manifold manufactures actually know all of this? I can only think of one - Full-Race. Only one has done the math and research, they deserve the glory. That's why it pisses me off when someone steals/copies designs. They don't know the slightest bit about fluid dynamics or thermodynamics, but they can certainly copy those who do.
You all can think I'm an *******, but I've done the research too. I wish people would read up on it more instead of cause drama. It wouldn't take long to find this info.
02-09-2004, 11:33 PM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (Mase)
blah.
The runners were created analyzing the essential length to keep the maximum amount of thermal energy into each runner. Each runner is also equal length, transfering each exhaust pulse into a low merge angle collector. The collector allows the exhaust pulsations at high rpm to form from 4 individual finite pulses into one giant pulse giving the maximum amount of thermal and sound energy into the turbine housing. The manifold doesnt per say "flow" better, it transfer the energy more efficiently to the turbine
The runners were created analyzing the essential length to keep the maximum amount of thermal energy into each runner. Each runner is also equal length, transfering each exhaust pulse into a low merge angle collector. The collector allows the exhaust pulsations at high rpm to form from 4 individual finite pulses into one giant pulse giving the maximum amount of thermal and sound energy into the turbine housing. The manifold doesnt per say "flow" better, it transfer the energy more efficiently to the turbine
02-09-2004, 11:36 PM
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good write up. IF you didnt want to type it again, why didnt you just copy and paste what has already been written?
One thing i dont like your logic about is how you are ripping on other manifold makers. Ill give my example and then you can think about it, disagree or agree, whatever you would like. I would just like to show another perspective
Im going to make the assumption that you are on a windows based computer. Well DOS was stolen from MAC basically so bill gates and co. didnt really do the work/research either. basically im saying you are most likely supporting something that you dislike. In closing, this is america. a capitalist nation. If full race or any company decides to price their item at X dollars and someone else does basically the same thing for X-$50 and people buy the cheaper version can they be blamed? Basically i think of it as a buisness. Either you dont mind having other people under sell you b/c you know you "have the better product" or you charge less and become more competitive.
Okay, im done.
One thing i dont like your logic about is how you are ripping on other manifold makers. Ill give my example and then you can think about it, disagree or agree, whatever you would like. I would just like to show another perspective
Im going to make the assumption that you are on a windows based computer. Well DOS was stolen from MAC basically so bill gates and co. didnt really do the work/research either. basically im saying you are most likely supporting something that you dislike. In closing, this is america. a capitalist nation. If full race or any company decides to price their item at X dollars and someone else does basically the same thing for X-$50 and people buy the cheaper version can they be blamed? Basically i think of it as a buisness. Either you dont mind having other people under sell you b/c you know you "have the better product" or you charge less and become more competitive.
Okay, im done.
02-09-2004, 11:39 PM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (PrecisionH23a)
Is there a std dev in which the runners can be *slightly* different lengths but still achieve the same pulse?
Some of the "equal" length turbo manifolds on the market seem to be close to equal, but not completely. How much tolerance (if any) is there for variance in runner length?
Some of the "equal" length turbo manifolds on the market seem to be close to equal, but not completely. How much tolerance (if any) is there for variance in runner length?
02-09-2004, 11:39 PM
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Re: (b18b1hmtlove)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18b1hmtlove »</TD></TR><TR><TD CLASS="quote">good write up. IF you didnt want to type it again, why didnt you just copy and paste what has already been written?
One thing i dont like your logic about is how you are ripping on other manifold makers. Ill give my example and then you can think about it, disagree or agree, whatever you would like. I would just like to show another perspective
Im going to make the assumption that you are on a windows based computer. Well DOS was stolen from MAC basically so bill gates and co. didnt really do the work/research either. basically im saying you are most likely supporting something that you dislike. In closing, this is america. a capitalist nation. If full race or any company decides to price their item at X dollars and someone else does basically the same thing for X-$50 and people buy the cheaper version can they be blamed? Basically i think of it as a buisness. Either you dont mind having other people under sell you b/c you know you "have the better product" or you charge less and become more competitive.
Okay, im done.</TD></TR></TABLE>
i see your point, but lets not go into that ****, discuss the theory behind manifolds please
One thing i dont like your logic about is how you are ripping on other manifold makers. Ill give my example and then you can think about it, disagree or agree, whatever you would like. I would just like to show another perspective
Im going to make the assumption that you are on a windows based computer. Well DOS was stolen from MAC basically so bill gates and co. didnt really do the work/research either. basically im saying you are most likely supporting something that you dislike. In closing, this is america. a capitalist nation. If full race or any company decides to price their item at X dollars and someone else does basically the same thing for X-$50 and people buy the cheaper version can they be blamed? Basically i think of it as a buisness. Either you dont mind having other people under sell you b/c you know you "have the better product" or you charge less and become more competitive.
Okay, im done.</TD></TR></TABLE>
i see your point, but lets not go into that ****, discuss the theory behind manifolds please
02-09-2004, 11:42 PM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (HybridKOOP)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HybridKOOP »</TD></TR><TR><TD CLASS="quote">Is there a std dev in which the runners can be *slightly* different lengths but still achieve the same pulse?
Some of the "equal" length turbo manifolds on the market seem to be close to equal, but not completely. How much tolerance (if any) is there for variance in runner length?</TD></TR></TABLE>
I'll let geoff answer that one, if he chooses, but thats a good question.
Some of the "equal" length turbo manifolds on the market seem to be close to equal, but not completely. How much tolerance (if any) is there for variance in runner length?</TD></TR></TABLE>
I'll let geoff answer that one, if he chooses, but thats a good question.
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02-09-2004, 11:44 PM
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Re: (Mase)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">
i see your point, but lets not go into that ****, discuss the theory behind manifolds please</TD></TR></TABLE>
Agreed.
I'll give my perspective on the manifold design now. I think its all based upon goals. You can have $10,000 to put into your car but if your goals are only to have 250-300whp there is no need to spend $800-1300 on an equal length manifold. Basically i always believe you should buy what is right for your goals. Buying a $800 turbo when a $150 T3 could do the same is silly.
Also, im not sure if it was mentioned, i dont remember but i believe the velocity of the air increases the longer the runner. Im not exactly sure what the physics behind it is, but i believe it has to do with the air expanding or something of that sort.
I have a question now. If you plan on boosting 8 psi will the difference be noticeable, or is it only when you are pushing moderatly high amounts of boost where you will actually see the longer runners come into affect?
i see your point, but lets not go into that ****, discuss the theory behind manifolds please</TD></TR></TABLE>
Agreed.
I'll give my perspective on the manifold design now. I think its all based upon goals. You can have $10,000 to put into your car but if your goals are only to have 250-300whp there is no need to spend $800-1300 on an equal length manifold. Basically i always believe you should buy what is right for your goals. Buying a $800 turbo when a $150 T3 could do the same is silly.
Also, im not sure if it was mentioned, i dont remember but i believe the velocity of the air increases the longer the runner. Im not exactly sure what the physics behind it is, but i believe it has to do with the air expanding or something of that sort.
I have a question now. If you plan on boosting 8 psi will the difference be noticeable, or is it only when you are pushing moderatly high amounts of boost where you will actually see the longer runners come into affect?
02-09-2004, 11:45 PM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (Mase)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">If you have too long of a runner, that can actually cause heat loss; now using a thicker material, such as 8 gauge, will somewhat help aid to keep heat inside.</TD></TR></TABLE>
I've heard an excellent case for thin walled tubing.... once it is heat soaked - which is pretty quickly - it is nearly impossible for the surface area of the thin walled tube manifold to transfer the heat that a thick cast or schedule 40 manifold does.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">To go on further. We could talk about backpressure, I believe you could correlate it as flow velocities. From what I'm told it is generally accepted by automotive engineers that for every inch of Hg of backpressure approximately 1-2 HP is lost depending on the displacement and efficiency of the engine, the combustion chamber design, etc. So another goal would be to reduce the back pressure from changing the manifold design/wastegate placement. </TD></TR></TABLE>
Easiest way to do that is with a bigger turbine housing
I think identifying the manifold as a weak link in your system, ie the need to upgrade from a log to a tubular manifold, is best acheived by comparing turbine inlet pressures to intake manifold pressures across your boost and rpm ranges. As long as you aren't exceeding, as a rule of thumb, 2:1 TIP to MAP, then you're fine. Of course, some people strive for ideals that may or may not add up to anything in the real world. Talking with Mase, I have to agree that around the 400 whp mark in a Honda application a tubular manifold is distinctly superior.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">Now that we've discussed a **** load of theory, how many manifold manufactures actually know all of this? I can only think of one - Full-Race.</TD></TR></TABLE>
Are you speaking exclusively of commercial for-profit entities, or are verbose *** mallets like myself elegible?
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">Only one has done the math and research, they deserve the glory. That's why it pisses me off when someone steals/copies designs. They don't know the slightest bit about fluid dynamics or thermodynamics, but they can certainly copy those who do.</TD></TR></TABLE>
I have told you who designed the first schedule 40 tubular turbo manifold for a Honda, haven't I? AFAIK, it was back in September of 01.
I've heard an excellent case for thin walled tubing.... once it is heat soaked - which is pretty quickly - it is nearly impossible for the surface area of the thin walled tube manifold to transfer the heat that a thick cast or schedule 40 manifold does.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">To go on further. We could talk about backpressure, I believe you could correlate it as flow velocities. From what I'm told it is generally accepted by automotive engineers that for every inch of Hg of backpressure approximately 1-2 HP is lost depending on the displacement and efficiency of the engine, the combustion chamber design, etc. So another goal would be to reduce the back pressure from changing the manifold design/wastegate placement. </TD></TR></TABLE>
Easiest way to do that is with a bigger turbine housing
I think identifying the manifold as a weak link in your system, ie the need to upgrade from a log to a tubular manifold, is best acheived by comparing turbine inlet pressures to intake manifold pressures across your boost and rpm ranges. As long as you aren't exceeding, as a rule of thumb, 2:1 TIP to MAP, then you're fine. Of course, some people strive for ideals that may or may not add up to anything in the real world. Talking with Mase, I have to agree that around the 400 whp mark in a Honda application a tubular manifold is distinctly superior.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">Now that we've discussed a **** load of theory, how many manifold manufactures actually know all of this? I can only think of one - Full-Race.</TD></TR></TABLE>
Are you speaking exclusively of commercial for-profit entities, or are verbose *** mallets like myself elegible?
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">Only one has done the math and research, they deserve the glory. That's why it pisses me off when someone steals/copies designs. They don't know the slightest bit about fluid dynamics or thermodynamics, but they can certainly copy those who do.</TD></TR></TABLE>
I have told you who designed the first schedule 40 tubular turbo manifold for a Honda, haven't I? AFAIK, it was back in September of 01.
02-09-2004, 11:47 PM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (J. Davis)
joey, did i ever tell you, you're one of my favorite people on HT. CHICKEN ******
02-09-2004, 11:47 PM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (PrecisionH23a)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PrecisionH23a »</TD></TR><TR><TD CLASS="quote">blah.
The runners were created analyzing the essential length to keep the maximum amount of thermal energy into each runner. Each runner is also equal length, transfering each exhaust pulse into a low merge angle collector. The collector allows the exhaust pulsations at high rpm to form from 4 individual finite pulses into one giant pulse giving the maximum amount of thermal and sound energy into the turbine housing. The manifold doesnt per say "flow" better, it transfer the energy more efficiently to the turbine</TD></TR></TABLE>I'm probably wrong here but... wouldn't the pulse thats driving the turbine wheel be delivered in a 2 + 2 sequence instead of a pulse thats combined of all 4 cylinders? I say this because I would imagine cylinders 2 and 3 would join forces (in an equal length manifold) as one pulse, driving the wheel when the cylinder 1 & 4 pulse is on the dip inside of the cylinders... ?
The runners were created analyzing the essential length to keep the maximum amount of thermal energy into each runner. Each runner is also equal length, transfering each exhaust pulse into a low merge angle collector. The collector allows the exhaust pulsations at high rpm to form from 4 individual finite pulses into one giant pulse giving the maximum amount of thermal and sound energy into the turbine housing. The manifold doesnt per say "flow" better, it transfer the energy more efficiently to the turbine</TD></TR></TABLE>I'm probably wrong here but... wouldn't the pulse thats driving the turbine wheel be delivered in a 2 + 2 sequence instead of a pulse thats combined of all 4 cylinders? I say this because I would imagine cylinders 2 and 3 would join forces (in an equal length manifold) as one pulse, driving the wheel when the cylinder 1 & 4 pulse is on the dip inside of the cylinders... ?
02-09-2004, 11:49 PM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (Mase)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">joey, did i ever tell you, you're one of my favorite people on HT. CHICKEN ******</TD></TR></TABLE>
rofl
rofl
02-09-2004, 11:56 PM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (HybridKOOP)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HybridKOOP »</TD></TR><TR><TD CLASS="quote">Is there a std dev in which the runners can be *slightly* different lengths but still achieve the same pulse?
Some of the "equal" length turbo manifolds on the market seem to be close to equal, but not completely. How much tolerance (if any) is there for variance in runner length?</TD></TR></TABLE>
Unfortunately I have not taken the heat transfer classes yet to properly answer your question. From thermodynamics I would say that you could not use different size runners and still yield the same pulse.... given that all four cylinders produce the same amount of volumetric flow. The longer runners would have to produce a higher flow rate to compensate for the extra path traveled for the 'pulse'
I would say standard deviation would be a minimal amount though... around a quarter of an inch. To test this, a lot of research and testing would need to take place with several manifolds each using different lengths. I would also think firing order would also come into play I would think with reguards of which runner is longer/shorter. You do not want all 4 pulses arriving to the exhaust manifold at once... that is sort of like a bottleneck.
Some of the "equal" length turbo manifolds on the market seem to be close to equal, but not completely. How much tolerance (if any) is there for variance in runner length?</TD></TR></TABLE>
Unfortunately I have not taken the heat transfer classes yet to properly answer your question. From thermodynamics I would say that you could not use different size runners and still yield the same pulse.... given that all four cylinders produce the same amount of volumetric flow. The longer runners would have to produce a higher flow rate to compensate for the extra path traveled for the 'pulse'
I would say standard deviation would be a minimal amount though... around a quarter of an inch. To test this, a lot of research and testing would need to take place with several manifolds each using different lengths. I would also think firing order would also come into play I would think with reguards of which runner is longer/shorter. You do not want all 4 pulses arriving to the exhaust manifold at once... that is sort of like a bottleneck.
02-10-2004, 05:42 AM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (PrecisionH23a)
Thats a good write up Mase, you did real good up to the the 2nd last paragragh.
quote" Now that we've discussed a **** load of theory, how many manifold manufactures actually know all of this? I can only think of one - Full-Race. Only one has done the math and research, they deserve the glory. That's why it pisses me off when someone steals/copies designs. They don't know the slightest bit about fluid dynamics or thermodynamics, but they can certainly copy those who do."
If you wanted to leave it as theroy then this plug you threw in for FR was not called for IMO. Your theroy is not to be questioned because I can tell your a smart ma *****, but you gotta learn to not open a can of worms when you post (thats where the ******* thing you mentioned comes from). Me personally being a Canadain, That FR mani for me is not 1200 its more like $2000 after I do the conversion and pay my duties and taxes. With that being said I applaud other businesses that make more options for us guys that can't cough up big money for these manis. Whether its log style or equal length, theroy can sound really good when typed out, but in reality people have made over 600whp on log style manis. Efficient or not. It does the job just the same. I difference in most cases is probably 5 to 10 whp, all of which my *** dyno probably wouldn't notice. The thing that brings this into a **** slinging contest is when people try and compare companies and their quailty they have. Everybody has their own opinion, so let them be their own judge. Its not up to you to educate the masses. This is the internet, if people wanted to really find out about fluid dynamics etc. All they have to do is type it under a search engine on their computer and boom, there it is. Just my 2 cents.
quote" Now that we've discussed a **** load of theory, how many manifold manufactures actually know all of this? I can only think of one - Full-Race. Only one has done the math and research, they deserve the glory. That's why it pisses me off when someone steals/copies designs. They don't know the slightest bit about fluid dynamics or thermodynamics, but they can certainly copy those who do."
If you wanted to leave it as theroy then this plug you threw in for FR was not called for IMO. Your theroy is not to be questioned because I can tell your a smart ma *****, but you gotta learn to not open a can of worms when you post (thats where the ******* thing you mentioned comes from). Me personally being a Canadain, That FR mani for me is not 1200 its more like $2000 after I do the conversion and pay my duties and taxes. With that being said I applaud other businesses that make more options for us guys that can't cough up big money for these manis. Whether its log style or equal length, theroy can sound really good when typed out, but in reality people have made over 600whp on log style manis. Efficient or not. It does the job just the same. I difference in most cases is probably 5 to 10 whp, all of which my *** dyno probably wouldn't notice. The thing that brings this into a **** slinging contest is when people try and compare companies and their quailty they have. Everybody has their own opinion, so let them be their own judge. Its not up to you to educate the masses. This is the internet, if people wanted to really find out about fluid dynamics etc. All they have to do is type it under a search engine on their computer and boom, there it is. Just my 2 cents.
02-10-2004, 05:51 AM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (Mase)
I still think you're an ******* mase - but that's for moving my bike 20ft from its original parking spot 
02-10-2004, 06:03 AM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (HybridKOOP)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HybridKOOP »</TD></TR><TR><TD CLASS="quote">I'm probably wrong here but... wouldn't the pulse thats driving the turbine wheel be delivered in a 2 + 2 sequence instead of a pulse thats combined of all 4 cylinders? I say this because I would imagine cylinders 2 and 3 would join forces (in an equal length manifold) as one pulse, driving the wheel when the cylinder 1 & 4 pulse is on the dip inside of the cylinders... ? </TD></TR></TABLE>
No. Just because two pistons are a TDC at the same time doesn't mean that they are firing. One will be on the compression stroke and the other will be on the exhast stroke. The other two at BDC will be Intake and Combustion. So each runner has an exhaust pulse, which should to hit the turbine in an orderly fashion.
</TD></TR></TABLE>No. Just because two pistons are a TDC at the same time doesn't mean that they are firing. One will be on the compression stroke and the other will be on the exhast stroke. The other two at BDC will be Intake and Combustion. So each runner has an exhaust pulse, which should to hit the turbine in an orderly fashion.
02-10-2004, 07:06 AM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (Mase)
Intelligent discussion on h-t...stop the presses! 
Good writeup, Mase. Anyway, one paragraph caught my attention.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">We all know heat is energy, and the more energy the more exhaust to spool the turbine. If you have too long of a runner, that can actually cause heat loss; now using a thicker material, such as 8 gauge, will somewhat help aid to keep heat inside. One thing that will cause the gas to slow down is a sudden decrease in temperature. The other thing that can cause a decrease in flow velocity is rapid expansion and turbulence, like going from a small passage (like the exhaust port in the head) to a 6-inch pipe. A smaller-diameter pipe geometry will tend to keep the flow rate up, but it will also lose heat more quickly. However, a large pipe will slow the velocity due to expansion. Worse still, the exhaust is constantly cooling from the moment it leaves the cylinder, meaning it's getting denser and slower. See the problem here? It's all about compromises. The proper pipe size is going to be influenced by the flow rate (volume rate, which is related to RPM and engine displacement), exhaust velocity (again related to RPM), exhaust temperature, and undoubtedly an array of other factors. Just remember flow rate is impacted by a number of different things in addition to raw temperature, including the surface roughness and pipe geometry.
</TD></TR></TABLE>
At first glance, what you mentioned makes sense. However, this is what Corky Bell has to say (maximum boost page 119):
The wall thickness of a particular material will strongly influence the heat transfer, in that the thicker material, the faster heat will travel through it. This seems contrary to logic at first thought, but consider how fast heat would be drawn out of a high-conductivity, infinitely thick aluminum manifold, as opposed to a very thin piece of stainless surrounded by a nice insulator like air. Heat transfer is directly proportional to surface area. It is therefore reasonable to give considerable thought to keeping the exposed surface area of the exhaust manifold to a minimum.
So based on what Corky says, thin-wall would be ideal. However, the problem with it is that it is weak. I think one of the key reasons that thick-wall has become popular is that it has been shown time and time again that thin-wall manifolds tend to crack. The exception seems to be Hytech, but I don't know if they make it a rule to brace the turbo.
Sonny
Good writeup, Mase.
Anyway, one paragraph caught my attention. <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">We all know heat is energy, and the more energy the more exhaust to spool the turbine. If you have too long of a runner, that can actually cause heat loss; now using a thicker material, such as 8 gauge, will somewhat help aid to keep heat inside. One thing that will cause the gas to slow down is a sudden decrease in temperature. The other thing that can cause a decrease in flow velocity is rapid expansion and turbulence, like going from a small passage (like the exhaust port in the head) to a 6-inch pipe. A smaller-diameter pipe geometry will tend to keep the flow rate up, but it will also lose heat more quickly. However, a large pipe will slow the velocity due to expansion. Worse still, the exhaust is constantly cooling from the moment it leaves the cylinder, meaning it's getting denser and slower. See the problem here? It's all about compromises. The proper pipe size is going to be influenced by the flow rate (volume rate, which is related to RPM and engine displacement), exhaust velocity (again related to RPM), exhaust temperature, and undoubtedly an array of other factors. Just remember flow rate is impacted by a number of different things in addition to raw temperature, including the surface roughness and pipe geometry.
</TD></TR></TABLE>
At first glance, what you mentioned makes sense. However, this is what Corky Bell has to say (maximum boost page 119):
The wall thickness of a particular material will strongly influence the heat transfer, in that the thicker material, the faster heat will travel through it. This seems contrary to logic at first thought, but consider how fast heat would be drawn out of a high-conductivity, infinitely thick aluminum manifold, as opposed to a very thin piece of stainless surrounded by a nice insulator like air. Heat transfer is directly proportional to surface area. It is therefore reasonable to give considerable thought to keeping the exposed surface area of the exhaust manifold to a minimum.
So based on what Corky says, thin-wall would be ideal. However, the problem with it is that it is weak. I think one of the key reasons that thick-wall has become popular is that it has been shown time and time again that thin-wall manifolds tend to crack. The exception seems to be Hytech, but I don't know if they make it a rule to brace the turbo.
Sonny
02-10-2004, 08:02 AM
#19
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Re: Equal Length Manifolds vs. Log Manifolds Explained (Sonny)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sonny »</TD></TR><TR><TD CLASS="quote">
At first glance, what you mentioned makes sense. However, this is what Corky Bell has to say (maximum boost page 119):
The wall thickness of a particular material will strongly influence the heat transfer, in that the thicker material, the faster heat will travel through it. This seems contrary to logic at first thought, but consider how fast heat would be drawn out of a high-conductivity, infinitely thick aluminum manifold, as opposed to a very thin piece of stainless surrounded by a nice insulator like air. Heat transfer is directly proportional to surface area. It is therefore reasonable to give considerable thought to keeping the exposed surface area of the exhaust manifold to a minimum.
So based on what Corky says, thin-wall would be ideal. However, the problem with it is that it is weak. I think one of the key reasons that thick-wall has become popular is that it has been shown time and time again that thin-wall manifolds tend to crack. The exception seems to be Hytech, but I don't know if they make it a rule to brace the turbo.
Sonny</TD></TR></TABLE>
Hrmm, that makes me think.
However, Im not sure why he correlated Surface Area with thickness.
I havent read his book, but I hear its not the best.
However, lets look at this. Thermal Conductivity is the ability of a material to transfer heat, or rather the process by which heat is transported from high to low-temperature regions of the substance.
Now that being said, just because a metal that has high thermal conductivity, doesnt mean it will disapate heat fast. It may only conduct heat to other parts of the material.
But above all, all of this doesnt matter, because it is known that Stainless steels are relatively resistive to heat transport.
At first glance, what you mentioned makes sense. However, this is what Corky Bell has to say (maximum boost page 119):
The wall thickness of a particular material will strongly influence the heat transfer, in that the thicker material, the faster heat will travel through it. This seems contrary to logic at first thought, but consider how fast heat would be drawn out of a high-conductivity, infinitely thick aluminum manifold, as opposed to a very thin piece of stainless surrounded by a nice insulator like air. Heat transfer is directly proportional to surface area. It is therefore reasonable to give considerable thought to keeping the exposed surface area of the exhaust manifold to a minimum.
So based on what Corky says, thin-wall would be ideal. However, the problem with it is that it is weak. I think one of the key reasons that thick-wall has become popular is that it has been shown time and time again that thin-wall manifolds tend to crack. The exception seems to be Hytech, but I don't know if they make it a rule to brace the turbo.
Sonny</TD></TR></TABLE>
Hrmm, that makes me think.
However, Im not sure why he correlated Surface Area with thickness.
I havent read his book, but I hear its not the best.
However, lets look at this. Thermal Conductivity is the ability of a material to transfer heat, or rather the process by which heat is transported from high to low-temperature regions of the substance.
Now that being said, just because a metal that has high thermal conductivity, doesnt mean it will disapate heat fast. It may only conduct heat to other parts of the material.
But above all, all of this doesnt matter, because it is known that Stainless steels are relatively resistive to heat transport.
02-10-2004, 09:13 AM
#21
Honda-Tech Member
Re: Equal Length Manifolds vs. Log Manifolds Explained (Sonny)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sonny »</TD></TR><TR><TD CLASS="quote">
The wall thickness of a particular material will strongly influence the heat transfer, in that the thicker material, the faster heat will travel through it. This seems contrary to logic at first thought, but consider how fast heat would be drawn out of a high-conductivity, infinitely thick aluminum manifold, as opposed to a very thin piece of stainless surrounded by a nice insulator like air. Heat transfer is directly proportional to surface area. It is therefore reasonable to give considerable thought to keeping the exposed surface area of the exhaust manifold to a minimum.
So based on what Corky says, thin-wall would be ideal. However, the problem with it is that it is weak. I think one of the key reasons that thick-wall has become popular is that it has been shown time and time again that thin-wall manifolds tend to crack. The exception seems to be Hytech, but I don't know if they make it a rule to brace the turbo.</TD></TR></TABLE>
It makes perfect sense that an infinitely thick, high-conductivity manifold would rob exhaust heat faster than a thin-walled version of the same manifold. But in the real world, isn't there a point of diminishing return where the rate of metal-to-air dissipation of heat becomes the limiting factor of heat loss, and at some point the manifold becomes more of an insulator than a heat exchanger?
Oh yeah, and the Hytech manifold is not a load bearing member. The weight of the turbo is supported by a brace which is mounted to the transmission, so the only stress it really sees is thermal expansion.
The wall thickness of a particular material will strongly influence the heat transfer, in that the thicker material, the faster heat will travel through it. This seems contrary to logic at first thought, but consider how fast heat would be drawn out of a high-conductivity, infinitely thick aluminum manifold, as opposed to a very thin piece of stainless surrounded by a nice insulator like air. Heat transfer is directly proportional to surface area. It is therefore reasonable to give considerable thought to keeping the exposed surface area of the exhaust manifold to a minimum.
So based on what Corky says, thin-wall would be ideal. However, the problem with it is that it is weak. I think one of the key reasons that thick-wall has become popular is that it has been shown time and time again that thin-wall manifolds tend to crack. The exception seems to be Hytech, but I don't know if they make it a rule to brace the turbo.</TD></TR></TABLE>
It makes perfect sense that an infinitely thick, high-conductivity manifold would rob exhaust heat faster than a thin-walled version of the same manifold. But in the real world, isn't there a point of diminishing return where the rate of metal-to-air dissipation of heat becomes the limiting factor of heat loss, and at some point the manifold becomes more of an insulator than a heat exchanger?
Oh yeah, and the Hytech manifold is not a load bearing member. The weight of the turbo is supported by a brace which is mounted to the transmission, so the only stress it really sees is thermal expansion.
02-10-2004, 09:20 AM
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Re: Equal Length Manifolds vs. Log Manifolds Explained (Sonny)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sonny »</TD></TR><TR><TD CLASS="quote">
So based on what Corky says, thin-wall would be ideal. However, the problem with it is that it is weak. I think one of the key reasons that thick-wall has become popular is that it has been shown time and time again that thin-wall manifolds tend to crack. The exception seems to be Hytech, but I don't know if they make it a rule to brace the turbo.
Sonny</TD></TR></TABLE>
outside of bracement i think if funds were not an issue inconel would be the ideal medium for a thin(relatively) wall manifold
So based on what Corky says, thin-wall would be ideal. However, the problem with it is that it is weak. I think one of the key reasons that thick-wall has become popular is that it has been shown time and time again that thin-wall manifolds tend to crack. The exception seems to be Hytech, but I don't know if they make it a rule to brace the turbo.
Sonny</TD></TR></TABLE>
outside of bracement i think if funds were not an issue inconel would be the ideal medium for a thin(relatively) wall manifold
02-10-2004, 09:26 AM
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Who cares if it is equal length, cast, log manifold if you make the horsepower that you want? People make too big of deal over this. You can make enough HP to please almost everyone on H-T with a log manifold.
02-10-2004, 09:30 AM
#24
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Re: Equal Length Manifolds vs. Log Manifolds Explained (Mase)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase »</TD></TR><TR><TD CLASS="quote">
I havent read his book, but I hear its not the best.
However, lets look at this. Thermal Conductivity is the ability of a material to transfer heat, or rather the process by which heat is transported from high to low-temperature regions of the substance.
Now that being said, just because a metal that has high thermal conductivity, doesnt mean it will disapate heat fast. It may only conduct heat to other parts of the material.
But above all, all of this doesnt matter, because it is known that Stainless steels are relatively resistive to heat transport.
</TD></TR></TABLE>
So, how can it be tested? If you make one manifold out of 1.5" ss sched 40 (.145" wall thickness, 1.61" ID) and another manifold out of 1.5" ss sched 10 (.109" wall thickness, 1.68" ID), you still have a problem. The runners are larger in the the sched 10 manifold, so (assuming an increase in power) does the power difference stem from the differing tubing sizes or from one manifolds ability to keep heat inside the runner better?
Corky does stress that stainless steel is a wonderful choice for manifolds due to the relatively low amount of heat transfer, but it's high coefficient of expansion makes it "unique" to work with.
Sonny
I havent read his book, but I hear its not the best.
However, lets look at this. Thermal Conductivity is the ability of a material to transfer heat, or rather the process by which heat is transported from high to low-temperature regions of the substance.
Now that being said, just because a metal that has high thermal conductivity, doesnt mean it will disapate heat fast. It may only conduct heat to other parts of the material.
But above all, all of this doesnt matter, because it is known that Stainless steels are relatively resistive to heat transport.
</TD></TR></TABLE>
So, how can it be tested? If you make one manifold out of 1.5" ss sched 40 (.145" wall thickness, 1.61" ID) and another manifold out of 1.5" ss sched 10 (.109" wall thickness, 1.68" ID), you still have a problem. The runners are larger in the the sched 10 manifold, so (assuming an increase in power) does the power difference stem from the differing tubing sizes or from one manifolds ability to keep heat inside the runner better?
Corky does stress that stainless steel is a wonderful choice for manifolds due to the relatively low amount of heat transfer, but it's high coefficient of expansion makes it "unique" to work with.
Sonny
02-10-2004, 09:39 AM
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Re: (spooler)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by spooler »</TD></TR><TR><TD CLASS="quote">Who cares if it is equal length, cast, log manifold if you make the horsepower that you want? People make too big of deal over this. You can make enough HP to please almost everyone on H-T with a log manifold. </TD></TR></TABLE>
sorry man, log manifolds are a horrid design
yes they work, but its that whole reversion of exhaust gas back into the cyl (cyl 1 and 4 tubes directly oppose one another) that doesnt sit to well with me, and the fact that exhaust gases are working against eachother and not as one
sorry man, log manifolds are a horrid design
yes they work, but its that whole reversion of exhaust gas back into the cyl (cyl 1 and 4 tubes directly oppose one another) that doesnt sit to well with me, and the fact that exhaust gases are working against eachother and not as one