Just in case you don't know....
When the exhaust valve opens the gasses exit at high pressure and speed. As the valve shuts there is a drop in pressure behind the high pressure pulse. This happens every cycle of the exhaust valve.
When the high pressure pulse exits the exhaust it sends a negative pressure wave back down the pipe.
In an ideal world this negative pressure wave will arrive at the exhaust valve just as it is starting to open and thus help suck out the gasses.
The same happens when the negative wave exits except that it sends back a positive wave.
In our rose tinted world, our first negative return wave would also have sucked out some of the fresh mixture and the positive wave would push it back into the cylinder just before the valve shuts.
When this happens will be decided by the length and diameter of the primary pipes and the secondaries (where the two pipes have been joined).
The idea behind the Siamese pipes is to try and take advantage of this effect.
The is one teeny little problem - this 'ideal' effect will happen over a very limited rev range. Bugger!
Back in our rose tinted world, we would have a system that would be able to change the diameter and length of the tubes so that the 'ram' effect could happen throughout the rev range.
So far all we have is the
EXUP valve and the like.
For any (tube) benders out there, you may like to play around with
this calculator and construct your own system.
I have no idea how much you gain or loose with one system or another and if Mark's is better than Kerker, Walker or Fred Bloggs' pipes.
What you gain on the roundabouts with one system will probably be lost on the swings with another.
Bottom line is: would you notice the loss or gain of a few GG's somewhere within the rev range?
No, neither would I.
