Different runner lengths...looking for some good tech.
Different runner lengths...looking for some good tech. Okay, I posed this question on Speedtalk and got some good info to start from. I am a beginner when it comes to wave harmonics in the intake runner system. So I figured I would attack the question from different perspectives to help me out.
So onto the question...
I notice that there are the lt1 intakes which are in the 3.5" range for the intake runner length, while the ls1 runner lengths are near the 10" range. They cylinder head runner lengths are virtually the same, so I keep them out of the argument.
They both have comparable RPM ranges.
Take another example, from my side of things (Mustangs).
I see many carb runners in the 6 inch range, while some EFI runners are in the 14-16 inch runner range.
They are both ranked at the same powerband, for example, Idle-5500 on the same cubic inch engine, a 302.
What allows the different intake runner lengths to act the same when the total runner length is much different?
How can a "short" carb act the same as a "long" EFI manifold runner?
What factors are we looking at:
- Cross sectional differences
- Taper
- Wave Tuning
I am just looking for more feedback
So onto the question...
I notice that there are the lt1 intakes which are in the 3.5" range for the intake runner length, while the ls1 runner lengths are near the 10" range. They cylinder head runner lengths are virtually the same, so I keep them out of the argument.
They both have comparable RPM ranges.
Take another example, from my side of things (Mustangs).
I see many carb runners in the 6 inch range, while some EFI runners are in the 14-16 inch runner range.
They are both ranked at the same powerband, for example, Idle-5500 on the same cubic inch engine, a 302.
What allows the different intake runner lengths to act the same when the total runner length is much different?
How can a "short" carb act the same as a "long" EFI manifold runner?
What factors are we looking at:
- Cross sectional differences
- Taper
- Wave Tuning
I am just looking for more feedback
I am not positive, but can it be that the efi manifolds that you are referencing are all dry flow manifolds, where as the shorter carb style manifolds are wet flow? I would think that the fuel and air would have more of a chance to seperate in the longer runners of the ls1/ls2 style manifolds. Just an idea..
Anthony
Anthony
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
Okay, I posed this question on Speedtalk and got some good info to start from. I am a beginner when it comes to wave harmonics in the intake runner system. So I figured I would attack the question from different perspectives to help me out.
So onto the question...
I notice that there are the lt1 intakes which are in the 3.5" range for the intake runner length, while the ls1 runner lengths are near the 10" range. They cylinder head runner lengths are virtually the same, so I keep them out of the argument.
They both have comparable RPM ranges.
Take another example, from my side of things (Mustangs).
I see many carb runners in the 6 inch range, while some EFI runners are in the 14-16 inch runner range.
They are both ranked at the same powerband, for example, Idle-5500 on the same cubic inch engine, a 302.
What allows the different intake runner lengths to act the same when the total runner length is much different?
How can a "short" carb act the same as a "long" EFI manifold runner?
What factors are we looking at:
- Cross sectional differences
- Taper
- Wave Tuning
I am just looking for more feedback
So onto the question...
I notice that there are the lt1 intakes which are in the 3.5" range for the intake runner length, while the ls1 runner lengths are near the 10" range. They cylinder head runner lengths are virtually the same, so I keep them out of the argument.
They both have comparable RPM ranges.
Take another example, from my side of things (Mustangs).
I see many carb runners in the 6 inch range, while some EFI runners are in the 14-16 inch runner range.
They are both ranked at the same powerband, for example, Idle-5500 on the same cubic inch engine, a 302.
What allows the different intake runner lengths to act the same when the total runner length is much different?
How can a "short" carb act the same as a "long" EFI manifold runner?
What factors are we looking at:
- Cross sectional differences
- Taper
- Wave Tuning
I am just looking for more feedback
Most of your questions were answered on that other forum, especailly the referenced thread you said you didn't have time to read.
The short answer is different runner lengths for similar rpm peaks are using different harmonics. For example, using certain formulae for tuning lengths, a 6000 rpm peak may use these lengths from the valve seat to the plenum:
20.2"
15.0"
11.7"
9.4"
Each shorter length uses the next higher (and weaker) harmonic. If you subtract the port length in the head, you will get runner length.
If you really want to learn, read Prof. Gordon Blair's stuff. Studying it yourself beats asking for simple answers to be spoon fed to you. Understanding it takes some work. I see too many folks who don't really want to work to learn something. Heck, they are posting all over the internet. Their likes, who also don't know much, have trouble sorting out the real stuff from the bovine scat.
No, I won't tell you how i got those numbers. Dig into the books. Hint: see the sticky on Books 101. Look in the advanced area for Blair's book. It is NOT 101 level, but it has most of the answers to all the questions you have ever asked about engines, and a TON of questions you have not yet thought to ask.
Jon
Thanks for the responses so far; very helpful. Just an FYI. I am not going into the automotive business. I am soon to graduate with another degree of my choosing. I simply ask questions that get me curious, and ask it where I believe I can get some answers. I am not trying to get so far "in-depth", because that is just not practical for me. It is not going to be my life, but just some general info is nice
I purchased John Heywood's book a while back to help learn, and much of that stuff is way over my head. Blair's is even more so. Being a college student, I buy enough books ($$$$) as is. If I had lots of time to actual learn this aside from my full-time schooling, I would.
Anyways...
So if a carb intake uses the higher (weaker) harmonics, and you put one of those 6" carbs on an EFI set-up, would you not go slower based on that alone? Weaker signal = weaker power?
I purchased John Heywood's book a while back to help learn, and much of that stuff is way over my head. Blair's is even more so. Being a college student, I buy enough books ($$$$) as is. If I had lots of time to actual learn this aside from my full-time schooling, I would.
Anyways...
So if a carb intake uses the higher (weaker) harmonics, and you put one of those 6" carbs on an EFI set-up, would you not go slower based on that alone? Weaker signal = weaker power?
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
Thanks for the responses so far; very helpful. Just an FYI. I am not going into the automotive business. I am soon to graduate with another degree of my choosing. I simply ask questions that get me curious, and ask it where I believe I can get some answers. I am not trying to get so far "in-depth", because that is just not practical for me. It is not going to be my life, but just some general info is nice
I purchased John Heywood's book a while back to help learn, and much of that stuff is way over my head. Blair's is even more so. Being a college student, I buy enough books ($$$$) as is. If I had lots of time to actual learn this aside from my full-time schooling, I would.
Anyways...
So if a carb intake uses the higher (weaker) harmonics, and you put one of those 6" carbs on an EFI set-up, would you not go slower based on that alone? Weaker signal = weaker power?
I purchased John Heywood's book a while back to help learn, and much of that stuff is way over my head. Blair's is even more so. Being a college student, I buy enough books ($$$$) as is. If I had lots of time to actual learn this aside from my full-time schooling, I would.
Anyways...
So if a carb intake uses the higher (weaker) harmonics, and you put one of those 6" carbs on an EFI set-up, would you not go slower based on that alone? Weaker signal = weaker power?
If college has taught you not to get in-depth with complex subjects and to ask others for simple answers to those complex problems with no effort expended on your part, I hope you are not majoring in the physical sciences and especially not in medicine. Perhaps you will be the new Dr. Phil.
Good luck...
Jon
If college has taught you not to get in-depth with complex subjects and to ask others for simple answers to those complex problems with no effort expended on your part, I hope you are not majoring in the physical sciences and especially not in medicine. Perhaps you will be the new Dr. Phil.
Good luck...
Jon
Good luck...
Jon
I had an easy "A" in Physical Science. Cookie cutter class...
You just missed my point, that is all.
I have a thought, then I put it in the form of a question to those that may know. This helps me figure out more of an answer to the question, instead of just remaining a question.
Thanks Jon.
You obviously took the wrong Physical Science. There's more calculus in physics 2 than there is in cal 1. Ohh well, business majors always get easier classes, I heard its because they can't hack it with all the engineering kids....
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My brother is in his junior year of mechanical engineering. I like reading the books here and there. Dynamics, Thermodynamics, Calc. 3, et al. He is doing VERY well. He is going for his Masters afterwards. I enjoy talking with him about it.
Please do not make this personal. Do not act better than someone.
Remember...
"Everybody is ignorant, only on different subjects." - Will Rogers
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Verdad Gallardo TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
I'm not so sure I missed your point. You continue to show me that you missed mine. I am not communicating it well enough.
OK, one more try. Pipemax is excellent, BUT....you really need to get into what makes an engine move air. That's the "forest". Calculating or even thinking about what inlet length to run is just one limb on one "tree", and it may not be the correct tree!
My answer is that "camshaft intake valve timing" is important but not necessarily "pretty critical" unless/until everything else is correct or at least working together. I can't stress how important it is to understand how an engine moves air.
Ask your ME-to-be brother for a two-word answer to this question: "What causes air to move into and out of an operating internal combustion engine?" I can think of a couple of two-word answers which mean the same thing. No cheating. If you get a response here, don't tell your bro. Let's see what he says. He has already had enough classes to know the answer.
Jon
5.0,
I'm not so sure I missed your point. You continue to show me that you missed mine. I am not communicating it well enough.
OK, one more try. Pipemax is excellent, BUT....you really need to get into what makes an engine move air. That's the "forest". Calculating or even thinking about what inlet length to run is just one limb on one "tree", and it may not be the correct tree!
My answer is that "camshaft intake valve timing" is important but not necessarily "pretty critical" unless/until everything else is correct or at least working together. I can't stress how important it is to understand how an engine moves air.
Ask your ME-to-be brother for a two-word answer to this question: "What causes air to move into and out of an operating internal combustion engine?" I can think of a couple of two-word answers which mean the same thing. No cheating. If you get a response here, don't tell your bro. Let's see what he says. He has already had enough classes to know the answer.
Jon
I'm not so sure I missed your point. You continue to show me that you missed mine. I am not communicating it well enough.
OK, one more try. Pipemax is excellent, BUT....you really need to get into what makes an engine move air. That's the "forest". Calculating or even thinking about what inlet length to run is just one limb on one "tree", and it may not be the correct tree!
My answer is that "camshaft intake valve timing" is important but not necessarily "pretty critical" unless/until everything else is correct or at least working together. I can't stress how important it is to understand how an engine moves air.
Ask your ME-to-be brother for a two-word answer to this question: "What causes air to move into and out of an operating internal combustion engine?" I can think of a couple of two-word answers which mean the same thing. No cheating. If you get a response here, don't tell your bro. Let's see what he says. He has already had enough classes to know the answer.
Jon
The piston pulling away from TDC causes a pressure differential.
Those are my two stabs at the "two words."
Edit: Thanks for keeping this atleast somewhat objective, unlike Drew.
BTW. cam timing has nothing to do with Helmholz resonance.
Why are you getting all butt hurt about this? I could provide you with an answer to this but OldSStroker has already taught you how to fish. What you're realling wanting is an answer to all your questions without doing any real research yourself. If you have Heywood's book or Dr. Blair's you wouldn't be asking these questions. I realize its hard to be a full time student but instead of playing video games for an hour or whatever you could be researching your questions in material you already have. I'm only a junior in my degree plan, I can't say I know everything but I know I have done more research today on my ultimate goals than you have in a week. I know this is OT and almost getting on a personal level, but there's already been multiple topics about this, your search button would have found the answers you were looking for.
BTW. cam timing has nothing to do with Helmholz resonance.
BTW. cam timing has nothing to do with Helmholz resonance.
Ok, I'll quit being an ***. There's some good info in this thread, would suggest reading though some of it.
https://ls1tech.com/forums/advanced-engineering-tech/829948-taking-advantage-helmholtz-theory-custom-intake-manifold.html
https://ls1tech.com/forums/advanced-engineering-tech/829948-taking-advantage-helmholtz-theory-custom-intake-manifold.html
So I am guessing that my two word estimate was off.
I am looking at getting Gordon Blair's Design and Simulations of 4-Stroke Engines. I believe that is the book many are referring too.
I am looking at getting Gordon Blair's Design and Simulations of 4-Stroke Engines. I believe that is the book many are referring too.
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
You are correct on the book. I believe it will be extremely intimidating to a non-science major. The first time or two through it was intimidating to me. Try to borrow a copy before you spend $100 on it.
Good luck.
Jon
