Intake manifold runner length.
09-01-2009, 03:48 PM
#21
not everyone takes the time and study to understand how engines work and how to successfully design systems for them.
Making a beautiful looking intake manifold which has the wrong dimensions for making power is a lot like polishing a turd. It may look good, but in the end it's still a turd.
Jon[/QUOTE]
So true, or they do and then they dont use it all the time and forget.
Making a beautiful looking intake manifold which has the wrong dimensions for making power is a lot like polishing a turd. It may look good, but in the end it's still a turd.
Jon[/QUOTE]
So true, or they do and then they dont use it all the time and forget.
09-01-2009, 10:16 PM
#22
FormerVendor
iTrader: (3)
Join Date: Jun 2007
Location: Virginia Beach,Virginia
Posts: 2,991
Likes: 0
Received 2 Likes
on
2 Posts
while i agree that an intake needs to be designed by "professionals" to be correct for the application,most "professionally" built sheetmetal intakes have nothing to do with being correct for the engine-but more to do with what looks good and fits under the hood.
09-02-2009, 04:08 AM
#23
A very basic formula is:
L = 72C/N, +/- 3 inches
Where L = intake tract length, N = RPM of max ram effect, and C = speed of sound. This formula is accurate though if and only if speed of sound in the runner is 1166 ft/sec.
As for the valve events, the intake and exhaust tuning formulas are based off that in relation to camshaft degrees. That's where the cam comes in.. last, as Jon said. The exhaust side (header primary diameter and length) is imo just as important as what you want to do on the intake side. There are formulas to calculate that too. But, you only get the first formula,
Side note: Jon, do you happen to have "Hot Rod Magazine" July and August 1964 issues laying around? I'd pay to have Gordon Blair's article Xerox'd and mailed to me.
L = 72C/N, +/- 3 inches
Where L = intake tract length, N = RPM of max ram effect, and C = speed of sound. This formula is accurate though if and only if speed of sound in the runner is 1166 ft/sec.
As for the valve events, the intake and exhaust tuning formulas are based off that in relation to camshaft degrees. That's where the cam comes in.. last, as Jon said. The exhaust side (header primary diameter and length) is imo just as important as what you want to do on the intake side. There are formulas to calculate that too. But, you only get the first formula,
Side note: Jon, do you happen to have "Hot Rod Magazine" July and August 1964 issues laying around? I'd pay to have Gordon Blair's article Xerox'd and mailed to me.
09-02-2009, 01:42 PM
#24
TECH Fanatic
A very basic formula is:
L = 72C/N, +/- 3 inches
Where L = intake tract length, N = RPM of max ram effect, and C = speed of sound. This formula is accurate though if and only if speed of sound in the runner is 1166 ft/sec.
As for the valve events, the intake and exhaust tuning formulas are based off that in relation to camshaft degrees. That's where the cam comes in.. last, as Jon said. The exhaust side (header primary diameter and length) is imo just as important as what you want to do on the intake side. There are formulas to calculate that too. But, you only get the first formula,
Side note: Jon, do you happen to have "Hot Rod Magazine" July and August 1964 issues laying around? I'd pay to have Gordon Blair's article Xerox'd and mailed to me.
L = 72C/N, +/- 3 inches
Where L = intake tract length, N = RPM of max ram effect, and C = speed of sound. This formula is accurate though if and only if speed of sound in the runner is 1166 ft/sec.
As for the valve events, the intake and exhaust tuning formulas are based off that in relation to camshaft degrees. That's where the cam comes in.. last, as Jon said. The exhaust side (header primary diameter and length) is imo just as important as what you want to do on the intake side. There are formulas to calculate that too. But, you only get the first formula,
Side note: Jon, do you happen to have "Hot Rod Magazine" July and August 1964 issues laying around? I'd pay to have Gordon Blair's article Xerox'd and mailed to me.
1964? Damn, I had just turned 21 and got my first GTO. Prof. Blair is a little older than I but he was still a youngster back then.
Perhaps you meant 2004?
You can get most of his info in here:
http://www.amazon.com/Design-Simulat...e=UTF8&s=books
FWIW this in in the sticky Books 101 in this forum. Too bad people don't study it.
Jon
09-02-2009, 02:21 PM
#25
On The Tree
Join Date: Jan 2008
Location: Where you least expect me
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
After a physics degree and John Dixon's "Tires, Suspension and Handling", I'm no stranger to heavy reading or doing my own research. When the time comes I'll be getting some of those books. I think I already have Scientific Design of Exhaust and Intake Systems on the shelf... just haven't built the first headers or manifold yet.
I am continually amazed at how unwilling people are to explain advanced topics in a forum called "advanced engineering tech". I moderate tech forums elsewhere on the internet and I get *tired* of answering the simple questions. It makes my day when someone wants to dig down into the deep magic and really understand something.
Oh well...
I am continually amazed at how unwilling people are to explain advanced topics in a forum called "advanced engineering tech". I moderate tech forums elsewhere on the internet and I get *tired* of answering the simple questions. It makes my day when someone wants to dig down into the deep magic and really understand something.
Oh well...
09-02-2009, 02:24 PM
#26
On The Tree
Join Date: Jan 2008
Location: Where you least expect me
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
While this is a nice formula, I'm looking for the *derivation* of this and similar math (*math*, not arithmetic; there aren't any numbers in math). I guess it just isn't on the internet anywhere.
09-02-2009, 03:18 PM
#27
TECH Fanatic
I am continually amazed at how unwilling people are to explain advanced topics in a forum called "advanced engineering tech". I moderate tech forums elsewhere on the internet and I get *tired* of answering the simple questions. It makes my day when someone wants to dig down into the deep magic and really understand something.
Oh well...
A few years ago I tried explaining things in detail on this forum, but most of it fell on deaf ears and the typical response was, "So what is the answer I need. I don't have time to figure it out." I decided to stop explaining (give the man a fish) and rather suggest avenues where they could find the information for themselves (teach a man to fish). Those that "learn to fish" are better for it and those who just want to be given a fish....well I don't care to oblige.
There are times when you can lead someone toward understanding, but they just don't get it. Either their mind is already made up (often on an erroneous notion) or they don't have the ability to understand. Either way it is frustrating to deal with such people.
"There are some people who, if they don't already know, you can't tell 'em."....Yogi Berra
God love you, Yogi!
A few other folks I know also stopped explaining stuff they learned the hard way to those who are too lazy to work for the information.
Jon
09-12-2009, 10:44 AM
#29
On The Tree
Join Date: Jan 2008
Location: Where you least expect me
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
My take is that the average Joe can buy a cookbook and find the good enough answer more easily than even the apt pupil can sift through hundreds of pages and hundreds of dollars (the advanced engine analysis books in the recommended reading thread total over $800) of advanced reading, do all the derivations, etc.
I realized a long time ago that I can't fix all the ignorance on the internet. These days I usually just toss out a casual question to get someone to doubt his fundamental assumption. If the light bulb comes on, great. If not, oh well.
http://xkcd.com/386/
09-13-2009, 12:04 PM
#30
I am continually amazed at the peple who want to be spoon fed the answers without expending any effort to try to understand what it is all about. That's why I don't give out the math. It is available and if one studies the "why" and gets an understanding then the formulae are useful.
A few years ago I tried explaining things in detail on this forum, but most of it fell on deaf ears and the typical response was, "So what is the answer I need. I don't have time to figure it out." I decided to stop explaining (give the man a fish) and rather suggest avenues where they could find the information for themselves (teach a man to fish). Those that "learn to fish" are better for it and those who just want to be given a fish....well I don't care to oblige.
There are times when you can lead someone toward understanding, but they just don't get it. Either their mind is already made up (often on an erroneous notion) or they don't have the ability to understand. Either way it is frustrating to deal with such people.
"There are some people who, if they don't already know, you can't tell 'em."....Yogi Berra
God love you, Yogi!
A few other folks I know also stopped explaining stuff they learned the hard way to those who are too lazy to work for the information.
Jon
A few years ago I tried explaining things in detail on this forum, but most of it fell on deaf ears and the typical response was, "So what is the answer I need. I don't have time to figure it out." I decided to stop explaining (give the man a fish) and rather suggest avenues where they could find the information for themselves (teach a man to fish). Those that "learn to fish" are better for it and those who just want to be given a fish....well I don't care to oblige.
There are times when you can lead someone toward understanding, but they just don't get it. Either their mind is already made up (often on an erroneous notion) or they don't have the ability to understand. Either way it is frustrating to deal with such people.
"There are some people who, if they don't already know, you can't tell 'em."....Yogi Berra
God love you, Yogi!
A few other folks I know also stopped explaining stuff they learned the hard way to those who are too lazy to work for the information.
Jon
07-20-2010, 12:08 AM
#31
Teching In
Join Date: Mar 2009
Location: Mid- MO
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
intake design basic?? I know this thread is nearing a year old. I'm posting this for 2 reasons.
1. Its more avaliable for someone researching seeking info in the future.
2. Hopes to get a little verification on what I think to be right.
The math I believe for runner length is
L=((EVCD x 0.25 x V x 2) \ (RPM x RV)) -1/2D
Where as
EVCD=effective valve closed duration
RV= Reflective Value
V= Pressure wave speed
D= runner Diameter
EVCD?
Evcd =720degrees - (ad-30)
25degrees-30 degrees off the advertised duration of cam = (ad-30)
30 degrees works well for a higher reving solid drag motor.
720 degrees being the full stroke cycle in degrees.
RV= the pressure wave your attempting to tune at.
V= pressure wave speed ( a hot intake 1250-1300)
D runner diameter
Taper on the runner...you want to increase velocity when possible but don't wanna compromise yourself going too far a 1.5% to 2% increase is typical I'm pretty sure.
Factor this by figuren' the area just in front of the valve(seat side) add the 2% and construct
Say you had a area of 2.56 a 10 inch runner 2% increase your area where the port meets the plenum should be about 3.12 sq inch.
A lot of this info I got from other sources on the net...kinda jangled it all in my own terms best I could.
I've met nothing but mountains and hills trying to do my own intake everyone wants to hide the magic and tell you to buy that 3k intake......no one understands teach me to fish and ill eat for a lifetime.
I'm intending to do my first couple in steel and do my last one in proper intake material and should come well with in the 3grand they want for these high dollar intakes...and when its all said and done I get the satisfaction of being done by me.
Sorry to pull a old thread up.....but anyone feel free to pm me with corrections or alterations or hell just flat tell me I'm wrong.......I'm no pro.
Thanks guys
Cody
1. Its more avaliable for someone researching seeking info in the future.
2. Hopes to get a little verification on what I think to be right.
The math I believe for runner length is
L=((EVCD x 0.25 x V x 2) \ (RPM x RV)) -1/2D
Where as
EVCD=effective valve closed duration
RV= Reflective Value
V= Pressure wave speed
D= runner Diameter
EVCD?
Evcd =720degrees - (ad-30)
25degrees-30 degrees off the advertised duration of cam = (ad-30)
30 degrees works well for a higher reving solid drag motor.
720 degrees being the full stroke cycle in degrees.
RV= the pressure wave your attempting to tune at.
V= pressure wave speed ( a hot intake 1250-1300)
D runner diameter
Taper on the runner...you want to increase velocity when possible but don't wanna compromise yourself going too far a 1.5% to 2% increase is typical I'm pretty sure.
Factor this by figuren' the area just in front of the valve(seat side) add the 2% and construct
Say you had a area of 2.56 a 10 inch runner 2% increase your area where the port meets the plenum should be about 3.12 sq inch.
A lot of this info I got from other sources on the net...kinda jangled it all in my own terms best I could.
I've met nothing but mountains and hills trying to do my own intake everyone wants to hide the magic and tell you to buy that 3k intake......no one understands teach me to fish and ill eat for a lifetime.
I'm intending to do my first couple in steel and do my last one in proper intake material and should come well with in the 3grand they want for these high dollar intakes...and when its all said and done I get the satisfaction of being done by me.
Sorry to pull a old thread up.....but anyone feel free to pm me with corrections or alterations or hell just flat tell me I'm wrong.......I'm no pro.
Thanks guys
Cody
