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Compression Ratios, what do they mean?

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Milwaukee Midget:

--- Quote from: stay`tee on February 19, 2015, 05:43:41 AM ---. . . i have often wondered what improvement would occure if one was to change their exhaust system in line with exhaust cam timing,,,

--- End quote ---

I can't speak for adjusting exhaust cam timing alone, but I can say that during dyno work over the last two years, we evaluated 5 different headers and 2 different  cam timings.

It's complicated - as Fordboy is fond of saying - and in the case of the 5 port, the predictions and calculations were counter to what actually delivered the best power band.

And notice I didn't say best peak horsepower.

Our final iteration used a header that experience and calculations indicated shouldn't work, but instead, it wound up widening, extending and smoothing the power band right where we needed it.

So yes, I'll say there are improvements to be had in the exhaust system.  None were huge, but the final result gave us a much more drivable and flexible combination.

I would think on a bike at speed, flexibility would be preferable to high hp that was peaky.

Milwaukee Midget:
We also found a horse hiding in the valve adjustment.

tortoise:

--- Quote from: stay`tee on February 17, 2015, 04:41:49 AM ---What are the advantages/disavantages in relation to compression/performance rpm range, of double overhead cams . . .

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Also, a valve drive train without rocker arms allows faster valve opening and closing.

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