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Roland goes back to 'Y' manifold engine for Sturgis
Mike used the dual carb heads on a race engine so he didn't have an engine for the S2 for Sturgis week.
He decided to port the stock heads and put them on the bike for a 'rider'.
He left the cams and pistons just as they were for the dual-carb engine (slightly different cam timing) and plopped the ported stock heads on the S2 with an S&S 'G' carb and manifold and a Buell 'race' pipe.
89 horse is fine, but the torque seemed quite low. Mike remembered that the engine liked the end-cap on the Super-Trapp instead of the open end that he was running, so we changed to the closed end-cap and dropped 1 size on the main jet and the results can be seen below.
After some ignition timing changes (which helped the low end most) the results were pretty good. OK torque and great HP (for a 'Y' manifold engine.)
So, how much power did he give up by going back to the 'Y' manifold configuration?
Take a look at the chart below.
That would be a loss of 27 HP at 6175 RPM and 25 HP at 6750 RPM.
At the torque peak of the 'Y' manifold engine (5200 RPM) the difference is only 12 lb-ft, but at the torque peak of the dual carb engine (6100 RPM) the difference is 21 lb-ft.
Some of the difference is from compression loss (although Mike hasn't oiled the 'Y' manifold engine to see just were it is) but basically, we're convinced that the dual carb has a lot of potential.
Finally, I have to note that the torque of the separate inlet configuration is better everywhere. And don't try to tell me that torque below 3500 RPM even matters.