tuning intake runner lengths

[automotivebreath]

Lately I have been studding the effects of tuning runner lengths to harmonic
pressure pulses. How do you determine an ideal intake runner length that
matches the RPM of the engine? The engine I'm working with (late model LT1)
has a very short runner, I'm considering attempting to tune it to 7000 -8000 RPM

[Cammer]

“Engelman’s Electrical Analogy”

[automotivebreath]

Hi Cammer,
Another familiar name.

I did a little research on Engelman’s Electrical Analogy, it looks like what I have
found so far is over my head.

http://filebox.vt.edu/users/jalee5/F...n%20report.doc

"This method utilizes an accurate mathematical model of a multi-cylinder
intake manifold to predict the resonant frequencies of the manifold. These
frequencies enable the manifold to increase the air flow and air density over
a range of engine speeds. Properly tuning the manifold by designing its
geometry to certain resonant frequencies results in a supercharging effect.
Engelman’s mathematical model is a powerful design tool because it can
accurately predict the engine speed at which the most benefit will occur.
The model, however, is limited in that it cannot define engine performance
or the performance gained by tuning."

[rookie]

Originally Posted by automotivebreath

Lately I have been studding the effects of tuning runner lengths to harmonic
pressure pulses. How do you determine an ideal intake runner length that
matches the RPM of the engine? The engine I'm working with (late model LT1)
has a very short runner, I'm considering attempting to tune it to 7000 -8000 RPM

Automotivebreath

David did a book called, How to build Horsepower Carburetors and Intake Manifolds Amazon.com: How to Build Horsepower, Volume 2 (How to Build Horsepower): Books: David Vizard He goes in to great detail on this and how to figure runner length for the second or third pulse.
This is one of my favorite books.
Although he will probably write about it hear, I still highly recommend the book.

[MaxRaceSoftware]

How do you determine an ideal intake runner length that
matches the RPM of the engine? The engine I'm working with (late model LT1)
has a very short runner, I'm considering attempting to tune it to 7000 -8000 RPM

How do you determine an ideal intake runner length that
matches the RPM of the engine?

That's easy..just use PipeMax (shameless plug)
i Inputed Data from http://filebox.vt.edu/users/jalee5/F...n%20report.doc
at least as much as i could estimate what all the Variables were,
and PipeMax calculated around 12.568" Total Induction Length
for that example in that .DOC File
12.568 minus 3.500 for Cyl Head = 9.068 Intake Manifold Runner

According to that .DOC File using the
Engelman’s Electrical Analogy / Helmholtz formula
resulted in inaccuracies of 1500 RPM or more...
not the most accurate method of calculating Total Induction Tuned Length
for a given RPM Range

The Data appears to show the Stock Intake gave the best Torque Curve,
and all the other Lengths tested had large variation from
the Engelman’s Electrical Analogy Predicted -VS- the Actual Dyno Numbers.

12.500" inches for Total Induction Length gave the best results
between 9000 to 9500 RPM
9.000" = 12.500 minus 3.500" for Cyl_head

*************************************************


the Engelman’s Electrical Analogy rearranged to calculate
Length instead of RPM as in the .DOC file
looks like this equation=>
also in English Units instead of Metric

L = ((77 * S * ((CR - 1) / (CR + 1)) ^ 0.5) / N) ^ 2 * (A / V)

' Helmholtz formula
' where L= length, S=Speed of sound,
' CR= compression ratio, A= intake area,
' V= cylinder volume

S = 1160 'FPS 100.3 deg f = 12.360"
CR = 11 'guesstimated
N = 9167 '= (9000 + 9000 + 9500) / 3 Data Points
A = 1.43 ' OD in inches
V = 9.153 ' Cubic Inches

'Speed_of_Sound_FPS = ((459.67 + TempF) * 2402.625624) ^ 0.5
'1116.319772 fps @ 59 F
'.55 Mach = 613.9758744 fps
'Speed_of_Sound = ((459.67 + TempF) * 1.4 * 32.174 * 53.34) ^ 0.5
'Speed_of_Sound = ((459.67 + TempF) * 1.4 * 1716.567377) ^ 0.5
'and the easiest equation is
'Speed_of_Sound = ((459.67 + TempF) ^ 0.5) * 49.02
'TempF = temperature in degrees Fahrenheit
'459.67 = Rankine degrees

[MaxRaceSoftware]

Forgot to mention,
both PipeMax
and
Engelman’s Electrical Analogy / Helmholtz formula

are using the 2nd Harmonic

the 3rd Harmonic in PipeMax would be = 8.774 minus 3.500 for CylHead
equates to 5.274" Manifold Runner CenterLine Length needed
at 9167 RPM in that example

[automotivebreath]

Thanks for taking the time to put the example together Larry, it will take me a
while to understand what appears very simple to you. I agree it looks like
PipeMax is the answer.

[rookie]

Originally Posted by automotivebreath

Thanks for taking the time to put the example together Larry, it will take me a
while to understand what appears very simple to you. I agree it looks like
PipeMax is the answer.

What is pipemax?
I tried the links above but found nota, I might have went the wrong way.
I get lost on the infomation highwat quite often and i have wwwGPS to tell me where to go.

[MaxRaceSoftware]

Originally Posted by rookie

What is pipemax?
I tried the links above but found nota, I might have went the wrong way.
I get lost on the infomation highwat quite often and i have wwwGPS to tell me where to go.

.PDF Files + a few Pics
PipeMax36xp2

in current version of PipeMax i'm not using
Engelman’s Electrical Analogy / Helmholtz formula,
but in upcoming 4.0 i'll include it as a extra calculation with a footnote .

Sometimes Engelman’s Electrical Analogy / Helmholtz formula
is dead-on accurate, but most times its a mile off.
I'll also try to improve its accuracy with some Fudge Factors
or some kind of Curve Fit as an Input Option.

[Cammer]

Larry,

Why do you put Engelman’s Electrical Analogy and the Helmholtz formula together, as they are two distinctly different concepts?