Air Flow / CFM's

[FMP]

Think of it as an acoustics wave. Like what you see ahead of blast on a testing range. Or if you have ever walked on a floating dock when a fresh inch of ice is on the bay. The first wave of energy is fast and moves out in all direction way ahead of the disturbed wave. You see and hear it ripping under the ice and crashing into any solid. That pulse hits the next cylinder according to spacing distance and pin angle and it's effect is dependent on when it arrives. Higher ports mean the pulse is at the next cyl sooner because it let out earlier with respect to degrees all things being equal. So it hits as the next port is closing stuffing the short circuit charge back in raising cylinder pressure as it closes. Tuning pairs within the l and r triple. The bottom 5,6 looking like heck is a lack of scavenging time resulting from port to tuner length difference compared to top cylinders. Spent charge is left hanging and the pulse pushes it in again. Not so bad in a stock motor but with extra heat and volumes? I m shoveling snow as I type this so I may miss something.

[AZMIDLYF]

But having all the cylinders throwing waves into a common area would have positive and negative waves bouncing all over wouldn't it?

[FMP]

The pulse is out and gone with the scavenging effect right behind it. Hits the walls and out the tuner and it's over, scavenging slows ,next one coming ....

[AZMIDLYF]

The new BRP G2 is stepping up with individual bank exhaust...

[BarryStrawn]

This timing diagram from the original OMC patents explains the three cylinder effect as well as I have seen. Anyone can debate how effective this really is in practice but it appears the V6 and triples have an edge over the twins, fours and eights that do not benefit from the 120 degree timing.

edit - I think that was from an SAE paper, not a patent.

[Chaz]

Some of that makes sense , some of it is really reaching for the moon . And some statements contradict each other.
I'll just have to roll one over by hand to see the backside of the event for myself .
I have never questioned the fact that having more than one cylinder share the same conduit would have one effect the other. I have just seen it as hindering the next one in line , never an asset .

However if I ever saw an inch of ice on the bay , I would miss the show because I would have to race to the store ... cuz shorts and a Tee shirt would be runnin just a little too lean ...

[H2OPERF]

I ran 2 G2 engines on a friends boat and they are torque monsters.

[FMP]

What's reaching and contradictory?

[AZMIDLYF]

I ran 2 G2 engines on a friends boat and they are torque monsters.

Pictured is the Water Valve Assembly found on the Gen2 250HO and the 300. Upon water valve activation water is injected into the exhaust runners directly into the exhaust pulse wave path. By changing the exhaust wave path the engine is able to produce more torque. It activates at 600 RPM if the ignition process has switched to homogenous and remains active depending on RPM demand (utilized to plane boat quickly) At 2500 rpm there is a difference of 15hp when injecting water vs without. This simple valve re-tunes exhaust wave for increased low end torque.

[RBT]

Cool, didn't know they used water injection on the G2. MSD makes a kit for sea doo's that is adaptable to outboards. Tricky though, as the 3 into 1 that we are dealing with does have the potential for reversion. Notching the tuner upstream can help alleviate some of this.
Chaz, finest example I can think of is the Polaris ultra 680 snowmobile. It came factory as a 3 into 1 package, super smooth, reliable and lame. Add three tuned pipes and it added something like 40% power. But the package was much more complex and cumbersome, while retaining reliability and loosing the lame.

[W2F a V-King]

Pictured is the Water Valve Assembly found on the Gen2 250HO and the 300. Upon water valve activation water is injected into the exhaust runners directly into the exhaust pulse wave path. By changing the exhaust wave path the engine is able to produce more torque. It activates at 600 RPM if the ignition process has switched to homogenous and remains active depending on RPM demand (utilized to plane boat quickly) At 2500 rpm there is a difference of 15hp when injecting water vs without. This simple valve re-tunes exhaust wave for increased low end torque.

Does this work because it adds back pressure to the system?

Or by decreasing the back pressure by cooling the exhaust gasses which would reduce it's volume because it is condensing due to the cooling?

[RBT]

Does this work because it adds back pressure to the system?

Or by decreasing the back pressure by cooling the exhaust gasses which would reduce it's volume because it is condensing due to the cooling?

In a round about way, yes

[AZMIDLYF]

by injecting water into the tuned pipe, the exhaust gases are cooled, the speed of sound is lowered, and the pipe shortened. Furthermore, it has also been found that the lower the rpm of the motor, the cooler the exhaust gases should be to maximize efficiency. Thus, when more water is injected into the tuned pipe, efficiency at lower rpms can be increased.

[FMP]

Looks like the result is to prolong the high pressure low rpm pulse at the closing port to mimic a later arrival pulse to compensate for high ports and high rpm tuning.

[H2OPERF]

The first pic is a power valve block, they haven't put that into the production motor yet. The g2 looks to have real potential, crank / rods are basically same as early bullet proof omc and cyls are not canted so intakes are even with the rod slots along with crank rotation towards the intakes on both banks. Dave