Digsy Posted July 26, 2004 Share Posted July 26, 2004 Just re-read your first post. Are you sure its open below 4000RPM and shut above? I would have thought that it would be the other way around. Opening the butterfly would effectively shorten the intake runner, which is better for high engine speeds. Quote Link to comment Share on other sites More sharing options...
Suprash Posted July 26, 2004 Author Share Posted July 26, 2004 Its deffo open below 4k, and then shuts at 4k........ EDITED: Wouldnt having the butterfly open make the runner lengths longer, as there is more room for air to move aorund in, as it can move from one chamber to another, when it closes, it seals off the two chambers, so that air inside woudlnt have another chamber to escape into forcing it into the runners....... Thats my thinking...... Quote Link to comment Share on other sites More sharing options...
lpher Posted July 27, 2004 Share Posted July 27, 2004 I remember this topic about sticking the ACIS/TVIS-flap open was just about discussed to death on the ICOC-list (International Celica Owners Group) a few years ago ...and the conlusion was that it was basicly a pointless mod @lpher Quote Link to comment Share on other sites More sharing options...
Digsy Posted July 27, 2004 Share Posted July 27, 2004 Right - I had a bloody good old chat with one of our performance simulation gurus today about this. Withoug going into details I have direct access to an engine with a multi-mode intake manifold at the moment. First off, opening the butterfly will make the runner lengths shorter. Joining the plenums together effectively short-circuits the runner length. He concured that the butterfly should (following conventional wisdon) be closed at low RPM (it certainly is on the engine I have access to). Long runner = better low range torque. Short runner = better top end power. One thing he expressed surprise at was the size of the butterfly. I was guessing it might be about 30mm across from looking at the outside of the engine? In his experience they usually have to be very large to have a pronounced effect. One possible additional mod for the SZ might be to add an additional long pipe which links the two plenum chambers. By long I mean probably about the whole length of the intake manifold from end to end. Putting a second butterfly inside this would add a futher set of resonant frequencies to the intake tuning. Theroetically what you could do with a lot of time and money and access to a dyno is play with lengthening the primary pipes (the two parallel pipes entering into the plenum) to move the low-end torque peak further down, and then play with the length of the long link pipe to see if you can move its effect into a place where there is a hole in the torque curve. He suggested that the switching might go something like: 0-2000: Short link closed, long link closed. 2000-4000: Short link closed, long link open. 4000-6000: Short link open, long link closed. 6000-max: Short link open, long link opem. What you would have to do would be make up a test intake system with variable length primary pipes and a variable length long link pipe, and run loads of curves to see how changing the effect of each moves the peak torque around. Then you can choose the geometries that give you the best overall effect and plot the curves over each other to establish the switch points in the rev range. Unless you have access to powerful simulation software, like he does, of course. Howvever his final word was that the gains would be 10% at very best, but I wrote it up because it may be an unexplored alley in tuening the NA. Quote Link to comment Share on other sites More sharing options...
Suprash Posted July 28, 2004 Author Share Posted July 28, 2004 Top research though Darren, I now Paul has a virtual dyno, could that be used for something like this...... mmmmm, Paul is going to be busy then......he was talking about making up a new inlet/intake................I'll pass this onto him.... :cool: :cool: :cool: Quote Link to comment Share on other sites More sharing options...
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