ITB and adj runner lengths
Moderators: The Dark Side of Will, Series8217
ITB and adj runner lengths
Since the butterfly valve is "non existant" when at WOT, it makes sense that you could swap different length velocity stacks on after the throttle bodies and find the perfect length for your engine....
Tuned runners if you will.
You could probably go to a dyno with a handfull of exhaust bits and have a good idea on what works best on a particular engine.
Now would this translate over to a conventional manifold if you added a plenum?
Tuned runners if you will.
You could probably go to a dyno with a handfull of exhaust bits and have a good idea on what works best on a particular engine.
Now would this translate over to a conventional manifold if you added a plenum?
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Are your trying to design an intake (Plenum and runners), based on data collected from an ITB test session with different length runners?
There should be some correlation, depending on the plenum volume. Obviously the bigger the plenum the more similar to no plenum it is. also the larger the TB opening and closer to each runner the more similar it will be.
Draw it out on paper, and estimate your pressures at any given time with a runner intake and plenum setup. Use the Ideal gass law to determine the conditions of the air in the plenum. Now do the same with the Runners only and see how much of a difference there is with out the plenum. You should be negligable at or near WOT because the velocity pressure of the incoming air, overcomes the resistance of the single TB.
There should be some correlation, depending on the plenum volume. Obviously the bigger the plenum the more similar to no plenum it is. also the larger the TB opening and closer to each runner the more similar it will be.
Draw it out on paper, and estimate your pressures at any given time with a runner intake and plenum setup. Use the Ideal gass law to determine the conditions of the air in the plenum. Now do the same with the Runners only and see how much of a difference there is with out the plenum. You should be negligable at or near WOT because the velocity pressure of the incoming air, overcomes the resistance of the single TB.
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Take a cue from Yamaha:
http://www.motorcycle-usa.com/Article_P ... 819&Page=1
There's even an animated picture halfway down to show how it works.
http://www.motorcycle-usa.com/Article_P ... 819&Page=1
There's even an animated picture halfway down to show how it works.
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- Series8217
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The chinesse finger trap idea is the ideal solution, Think of the Boxing glove that comes out of the wall and reaches across the room. The arm gets thinner and longer. Now take that square peg and make it a round one. The solution (variable length) is easy enough, the ideal solution (variable length and diameter) is very complex.
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specificly expandable braided sleeving - there is a lot of braided sleeving that is not expandable.Blue Shift wrote:That braided wire tube they use to cover cables or hose works just like those chinese finger traps if the weave is right. The stuff I played with was. If you could impregnate it with some sorta elastomer to seal it, you could probably make VGI runner out of it?
http://cableorganizer.com/braided-sleeving/
or $$$$ for the high temp stuff good to 200C
http://cableorganizer.com/Bentley-Harri ... -686dm.htm
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Well, I understand why would would want a variable length trumpet but its just not needed.
With a good exhaust, cams and ITBs you are looking to make 400+hp and 330+ torque. Why does a fiero need any more power down low to begin with? 1st gear is going to be traction limited and everything after that is going to be in the power band anyways.
Why not make a good set of trumpets that are tuned for upper rpm power and leave it at that.
I agree you will need a variety of trumpet lengths for tuning purposes to see how much power they make but a variable length trumpet would be hell to tune.
With a good exhaust, cams and ITBs you are looking to make 400+hp and 330+ torque. Why does a fiero need any more power down low to begin with? 1st gear is going to be traction limited and everything after that is going to be in the power band anyways.
Why not make a good set of trumpets that are tuned for upper rpm power and leave it at that.
I agree you will need a variety of trumpet lengths for tuning purposes to see how much power they make but a variable length trumpet would be hell to tune.
If I were to go to the dyno, I would want to test everything from 0" to 20" of runner length.crzyone wrote:Why not make a good set of trumpets that are tuned for upper rpm power and leave it at that.
I agree you will need a variety of trumpet lengths for tuning purposes to see how much power they make but a variable length trumpet would be hell to tune.
I forget the kind of dyno, I think it's a mustang, but one of them lets you set the load speed. Imagine being able to hold the RPM @ 3000 and varying the intake runner length for the best torque. Hold it at 3500, etc etc.... Now I don't think they'll let you stand behind a car on a dyno (nor would you want to) so some kind of automatic dial-a-matic deal would be necessary.
But I can settle for random lengths of exhaust tubing and an hour of dyno runs... *shrug*