One of my goals this year is to come to a better understanding of how tune pipes work and what about them defines their performance.

To help with this, I got two 110” EF Yaks and two motors, a BME 116 and a DA100L, and three sets of pipes. See pics.

The black pipe is the ES Composites 55G.
The middle pipe is the KS 1060.
The outside pipe is the MTW RE2.

ES
Weight 4.35oz
Max diameter 50mm
Length 700mm, 800mm inc stinger

KS
Weight 10.44oz
Max diamiter 59mm
Length 690mm, 742mm inc stinger

Re2
Weight 9.45oz
Max diamiter 55mm
Length 690mm, 750mm inc stinger ( not including the extension shown in the pic )


Looking at the pipes....

The divergent cone sections are quite different.
Where the RE2 has a continuous curve, the KS and ES have single angle cones.
Where the RE2 and ES have short cones, the KS is much longer.

The bellies are also very different.
Where the ES and RE2 have long bellies, the KS is short.

The convergent cone sections are also different.
Where the RE2 and KS have convergent cones, the ES had a flat plate.
Unfortunately I have only been able to “feel” the cones with a stick and I cant feel their specific shapes. Only where they start and stop.

The muffler section in the ES is much larger than the muffler section in the other two.


Some pipe basics.... as I understand it.... which is very iffy....

The Divergent cone is mainly responsible for the shape of the power band before the peak.

The Belly, or area between the Divergent and Convergent cones, is primarily responsible for the shape of the peak itself.

The Convergent cone is responsible for the shape of the power band after the peak.

Can we make any assumptions with this info?
While I don’t know much, I know enough to know its not that simple, but here are some guesses that will be interesting to see if they pan out in the real world.

The KS has a longer shallow angle divergent cone.
This should cause it to take more rpm to go from off pipe to on pipe making the transition zone feel less instant., less light switch.
The RE has a continuous curve cone. The reading I’ve done on pipes suggests that this has the effect of making the cone longer, making the transition less dramatic.
Will be interesting to feel these two pipes in an apples to apples comparison.

The ES has a flat reflector plate instead of a convergent cone. This should kill power fast after peak. If one sets the header length so it peaks on uplines, the drop in power after peak in level flight could help keep air speed more constant and noise down with less throttle management.

The KS has a very short belly compared to the other two, so in theory, its peak should be less wide than the other two, but because of its longggg convergent cone and that it has a divergent cone, it might not be as noticeable as one might think.

From the experimenting I’ve already done with the ES pipe, I can say that header length makes a massive difference to power and engine feel. Given this, getting a good feel of the pipes that is not too colored by the header length’s, which are different for each pipe, and also different for each engine, might be difficult if the differences in the pipes performance is not pretty glaring.

Another pipe I would love to try that gets little mention on the online forums is the Macs Quiet Pipe. Several I've spoken to that use it where very impressed.