Kawi2strokes.com Forum

Seems like everybody so far also believe the mid range with 3:1 is great. And I agree, as I have ridden a stock H2 with this 3:1. It felt very much like a stock exhaust, but as JP said, it faded at 6000 rpm at tacho. And that may be only 5500-5600 as many triple tachos shows more rpm than you actually have.

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

Jorgen, if a 3 into 1 offers scavenging and supercharging, what is the shortcoming? Is it difficult to generate a perfect reversion wave since there is turbulence in the belly of the pipe caused by the cylinder pulses? Would a stinger on such a set up help or hinder the situation by accelerating the exit speed of the exhaust gas? Do modern 2 stroke engines with 3 into 1 pipes overcome the situation with variable exhaust valves?

33
65

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

The theory behind this is, as far as I have understood, they have a scevenging effect, but some of it is wasted varying the pressure in the 2 ex branches that are inactive at the time. And it can have some supercharging effect as the ex pulse of the cyl just opening its ex port raises the pressure in the branch of the cylinder that is about to close its ex port.
And since many sledges use this kind of pipes, the logic would be that the suction is as good as, or even stronger, than a open end almost straight pipe will provide. (like our stock exhaust pipes)

So, I guess the torque is about same as stock exhaust, but since they tend to not rev very well, the peak power is way lower than a 3:3 expansion chamber. My figaroli 3:1 has a stinger, but it's diameter is a lot larger than on a 3:3.

The pipe volume is also quite large, a lot more than one 3:3 pipe, and that may be a part of the reason they scavenge quite well (makes a good suction pulse, or vacuum behind the initial exhaust pulse.

I will assume a variable ex timing will do good, as the blow down then increase significant when fully open, and the pressure in combustion chamber (cylinder) then drops to a value closer to the crankcase pressure when transfers opening. Then less of the hot, spent gases will flow down transfers, and you gain power.

But maybe the most important thing for great mid range power with a 3 into 1 pipes, is that the returning wave (waves, in this case) do not mess up the scavenging process just BEFORE the piston closes transfers, usally at 2/3 rpm of max torque rpm as standard 3:3 does. You gain in the mid range compared to 3:3, but loose big time on peal power as the returning wave(s) is a lot weaker than the standard expansion chambers provide.

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

33 hp at 65 rpm?

I think you loose

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

DITTO..... I'm going with Walms numbers.


this is a bone stock H2 engine I built using 2nd hand used parts (cyls, pistons, crank). Featuring the almighty Strader 3 into 1 pipe.

If I had to guess, I'd say this one is putting out 50rwhp... er, I mean about 35 twin-track horsepower, since there I bet it looses about 15 more horsies due to the twin track drivetrain loss.

Still a riot to ride.

https://www.youtube.com/watch?v=2jB8N6Bj2Zw

Haha, seems like 50 hp was plenty

But is sounds like 500

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

Whatever horsepower it has.... it's still too much.

Fantastic picture that is.

My guess:

85 rwhp at 6800 rpm.

30 rwhp at 4000 rpm.

Hopefully I will be able to make the first run today, and the play with the zeel to observe is that may improve power.

Anyone else?

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison

Then the test is done.

The pipe made a strange curve, but the awsome sound kind of makes up for it.

Don't wanna reveal the results so far, other than NOBODY comes even close to the actual values, exept for the 4000 rpm power.

Peak power rpm was nothing like I had expected, but peak power was not THAT far from some guessings.

1 hint: Peak power is higher than any suggestions, and max torque is WAY lower than with stock pipes.

That means..............

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72 H2, 72 H1B, 74 H2, 74 H2 Cafê Racer, 71 F8 Bison