Further to my recent response to Tracy’s posting, I wanted to clarify that I was not disagreeing that there benefits to be gained from tuned induction. Clearly there are.  I would just like to see some hard data to support that the way it is being done with the “wrap-over” tubes is really giving significant benefits.  Is anybody really getting more than about 85 hp/rotor at 6000 rpm in their NA engine.

 

I question it based of theory; not on fact.  There is a reason why pipe organ pipes are straight, and why Mazda used straight-in tubes on their 4-rotor that won at Lemans.  In that manner there is the least amount of spreading of the pulse generated by the sudden closing of the intake port. The pressure wave front travels at the same speed at all points in the cross-section of the tube.  Of course there is some mixing, and wall friction distorting and flattening (extending) the pulse.  When the tube makes 180 degree turn, the different distances traveled by the different parts of the pulse spread and flatten it further. Do this a couple of times, out and back, with the mixing and wall friction, and how much pressure increase is left?  It may still help -  a couple of hp?

 

I’ve seen the argument about various automotive tuned induction systems being curved.  True; but looking closely at those that are curved more than about 90 degrees show that there are some added features to make some compensation – reverse curves, dual reflected waves traveling in different directions and reinforcing or whatever. 

 

So, I don’t know.  We need some data.  Tracy is guessing that his engine puts out 180hp. Could be; but I’m guessing we don’t know what it is, and it could just as likely be 165.

 

Al