Super fun night tonight! Didn't do any riding or anything, but got quite a lot done on analyzing the Eurocylinder 50cc water kit:
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Out of the box, it has 192/130 timing, with a single exhaust port (no aux ports), and 6 really nice transfers/boost ports. This by itself gives it a great starting point against the more popular 50cc water kits, like Doppler, Malossi, Polini, which all are around 175/118 out of the box, if memory serves. It's of course easy to raise an exhaust, but for most of us, probably pretty tough to raise a transfer on a 40mm cylinder and keep the geometry nice.
I recently got a copy of EngMod2T, and used that port mold above to gather data as accurately as possible on port shape, size, direction, etc.
After plugging all of the data in, I am starting to get some results. Mostly what I'm looking for at this stage is the STA data on the exhaust and transfer ports -- these give you a basic idea of how much power you'll be able to achieve if you work some real wizardry - in other words, your upper limit.
Where this kit falls short compared to some others is definitely in its single exhaust port -- not as much blowdown time area and overall exhaust time area compared to say a split port, like the Malossi, or a 3-port (1 main, 2 aux) like the Doppler, or the crazy Polini W-port. Also, there's room to fit bigger transfer windows, and the inlet to the transfers seems big enough to support them, but with 130deg timing I figured it would still be able to flow more than the exhaust port.
So, finally the STA values, and the corresponding theoretical max power from them, at a few engine speeds, 11k, 12k, and 13k:
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So, exhaust port is definitely the limiting factor here. But I'm variated, and aggressively so -- I can keep the engine within 2000rpm from clutch engagement to fully variated, so peaky power won't hurt. Here's the same info, 11k, 12k, and 13k, after raising the port 2mm to get 205deg exhaust port:
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That's a jump from a potential of about 12.5hp to 17hp (just based on exhaust port -- notice that the transfers are always supporting much more power, and the reeds are limiting to about 15hp, but my reed model is definitely not super accurate at the moment).
So for $100, not a bad cylinder... I definitely want to measure up another cylinder for comparison, I've got a Malossi sitting on a shelf...
Out of the box, it has 192/130 timing, with a single exhaust port (no aux ports), and 6 really nice transfers/boost ports. This by itself gives it a great starting point against the more popular 50cc water kits, like Doppler, Malossi, Polini, which all are around 175/118 out of the box, if memory serves. It's of course easy to raise an exhaust, but for most of us, probably pretty tough to raise a transfer on a 40mm cylinder and keep the geometry nice.
I recently got a copy of EngMod2T, and used that port mold above to gather data as accurately as possible on port shape, size, direction, etc.
After plugging all of the data in, I am starting to get some results. Mostly what I'm looking for at this stage is the STA data on the exhaust and transfer ports -- these give you a basic idea of how much power you'll be able to achieve if you work some real wizardry - in other words, your upper limit.
Where this kit falls short compared to some others is definitely in its single exhaust port -- not as much blowdown time area and overall exhaust time area compared to say a split port, like the Malossi, or a 3-port (1 main, 2 aux) like the Doppler, or the crazy Polini W-port. Also, there's room to fit bigger transfer windows, and the inlet to the transfers seems big enough to support them, but with 130deg timing I figured it would still be able to flow more than the exhaust port.
So, finally the STA values, and the corresponding theoretical max power from them, at a few engine speeds, 11k, 12k, and 13k:
So, exhaust port is definitely the limiting factor here. But I'm variated, and aggressively so -- I can keep the engine within 2000rpm from clutch engagement to fully variated, so peaky power won't hurt. Here's the same info, 11k, 12k, and 13k, after raising the port 2mm to get 205deg exhaust port:
That's a jump from a potential of about 12.5hp to 17hp (just based on exhaust port -- notice that the transfers are always supporting much more power, and the reeds are limiting to about 15hp, but my reed model is definitely not super accurate at the moment).
So for $100, not a bad cylinder... I definitely want to measure up another cylinder for comparison, I've got a Malossi sitting on a shelf...