Terry Syd
Addicted to ArboristSite
Stratos
You may want to check out the strato timing versus the intake timing. If you read the 445 strato thread you will see that the two timing figures were quite different. The strato port on the 450 opened for 154 degrees of duration and the intake was at 144 degrees.
I put a bigger carb on the intake (up from 11mm venturi to a 13.5mm) and increased the intake timing. My final figures were 152 on both the strato and intake ports.
My impressions of the Husky 450 strato was that the longer strato timing had a fair bit of influence on how high the saw revved, however it was the intake charge that increased the torque at those revs. I increased the bias of the intake flow (carb and timing) to that of the strato flow and picked up a nice increase in torque at the higher revs.
There is a considerable amount of mixing of the two charges, even though the advertising suggests otherwise. Some of the strato charge is likely to be purged out the exhaust port as the literature states, however the remaining strato charge in the cylinder appears to get mixed in with the intake charge during the squish phase (turbulence) of the compression stroke. A plug check can give you an idea about how the combined mixture is running.
With both strato and intake ports opened, the engine can take big gulps of air. I am already at the edge of my limited coil and won't be extending the intake timing out any further. However, Bitzercreek went to the outer limits on his intake timing and did pick up some nice power up in the revs (he has an unlimited coil on his 455). If a person is running a smaller carb, the increase of intake timing to more than the strato timing could be warranted. I have a larger carb and I can move more air in a shorter period of time - that works for me as I wanted to keep the low end torque of the engine.
I expect that a lot of your power increase came from the increased compression ratio. My clamshell design prevents 'dropping the jug', but I may have a small dome welded on the piston crown in the future. If I can't increase the revs any further, then I might as well increase the torque at the revs I have.
You may want to check out the strato timing versus the intake timing. If you read the 445 strato thread you will see that the two timing figures were quite different. The strato port on the 450 opened for 154 degrees of duration and the intake was at 144 degrees.
I put a bigger carb on the intake (up from 11mm venturi to a 13.5mm) and increased the intake timing. My final figures were 152 on both the strato and intake ports.
My impressions of the Husky 450 strato was that the longer strato timing had a fair bit of influence on how high the saw revved, however it was the intake charge that increased the torque at those revs. I increased the bias of the intake flow (carb and timing) to that of the strato flow and picked up a nice increase in torque at the higher revs.
There is a considerable amount of mixing of the two charges, even though the advertising suggests otherwise. Some of the strato charge is likely to be purged out the exhaust port as the literature states, however the remaining strato charge in the cylinder appears to get mixed in with the intake charge during the squish phase (turbulence) of the compression stroke. A plug check can give you an idea about how the combined mixture is running.
With both strato and intake ports opened, the engine can take big gulps of air. I am already at the edge of my limited coil and won't be extending the intake timing out any further. However, Bitzercreek went to the outer limits on his intake timing and did pick up some nice power up in the revs (he has an unlimited coil on his 455). If a person is running a smaller carb, the increase of intake timing to more than the strato timing could be warranted. I have a larger carb and I can move more air in a shorter period of time - that works for me as I wanted to keep the low end torque of the engine.
I expect that a lot of your power increase came from the increased compression ratio. My clamshell design prevents 'dropping the jug', but I may have a small dome welded on the piston crown in the future. If I can't increase the revs any further, then I might as well increase the torque at the revs I have.
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