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 Post subject: intake manifold length
 Post Posted: Thu Nov 15, 2012 9:08 pm 
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sbc 23*- when optimizing runner length for the 4th harmonic <typical single plane > what benefits more from tuned length ivo or inc, is the peak aimed at max ve torque or max ve hp, when trying to maximize runner differences long vs short, is it worth it to increase long runner csa only to try and raise rpm timing point to match short runners or just juggle rocker ratios with equal runner porting, sorry for the long post, thanks-tom


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 Post Posted: Thu Nov 15, 2012 10:42 pm 
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I suggests your better off going to runner length for maximum HP, the max torque point really doesnt need much help, its the top that need it. Changing the CSA wont change the tuned length, it will only change the fill rate of the cylinder and where it finally fills etc, creating cam issues. The biggest problem is working out when to shut the intake valve, its the main factor that stuff engines up.


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 Post Posted: Sat Nov 17, 2012 8:10 pm 
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I agree that the peak HP is where I'd target runner length tuning.

The ivc (or just before) would benefit from the tuned runner. I don't think a wave timed at ivo would have any benefit.

Rick


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 Post Posted: Sat Nov 17, 2012 9:09 pm 
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i thought the overlap period would benefit the most from pulse tuning, in and ex, but most formulas arent clear where the in pulse is tuned for, i asked this on pipemax site where his harmonic is tuned for and didnt get an answer


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 Post Posted: Sat Nov 17, 2012 9:51 pm 
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The exhaust tuning would benefit at overlap and ivc. You want a low pressure in the exhaust port and chamber at ivo to help clear the chamber of residual exhaust gas.

Rick


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 Post Posted: Sat Nov 17, 2012 10:57 pm 
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thanks rick, dose your program predict optimal in runner length @ inc for max hp rpm


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 Post Posted: Sun Nov 18, 2012 2:45 pm 
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I did some reading in "Engine Pro-The Book" that Patrick Hale wrote in 2007 that explains and shows calculations for how his Engine Pro software does it's stuff.

His formula for intake tract length doesn't target peak TQ rpm or peak HP rpm, it uses a modified average of the two weighted more toward peak TQ rpm. He also addresses the waves and he mentions both a wave at ivc and a different wave at ivo. The wave at ivc is caused by the piston max velocity and is a 2nd harmonic and the wave at ivo is caused by ivc and is a 4th harmonic.

He calculates both and does another modified average of them with the weighting going more toward the ivc wave.

I'll take a pic of the relevant pages and email it to you. It's too much to type.

Rick
PS: if your email has changed, PM your new email.


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 Post Posted: Sun Nov 18, 2012 6:53 pm 
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got it, great , thanks rick, it strange how you hear alot of people talk about intake tuning then you ask them what harmonis and where ino or inc and you never get a clear answer, makes you wonder if they even know,,thanks again- tom


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 Post Posted: Sun Nov 18, 2012 8:01 pm 
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zums wrote:
it strange how you hear alot of people talk about intake tuning then you ask them what harmonis and where ino or inc and you never get a clear answer, makes you wonder if they even know,,thanks again- tom


Yep, I know what you mean. I wonder so much that I think many don't know that act like they do. I have a lot of opinions about engines but I don't KNOW very much about them.

Rick


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