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B20Paul,
Your point is well taken. I've got to rely on this car as a commuter for the winter. I thought that I'd maximize what I've got now because I'm going to be living with the results for at least 60K miles. I've got other stuff going on too. (Know anyone who wants an Atkins built 13B street ported rotary? Cheap.)
In an earlier post about the B230 buildup, you indicated a maximum of 120HP using twin HS6 carbs. That is a contradiction to the only tuning manual I've got which has a graph like the one on the SWEM website showing twin 1.75 inch carbs capable of 160HP. I know you are an experienced builder and racer so I reckon you've bumped into an horsepower wall on a twin HS6 setup. I got to wondering why that would be; the carbs will move at least 250CFM each.
I think I've reasoned out why. Tell me if I'm right or wrong. The firing order separates the pulses so we get an uneven pull on the carbs. To overcome this, Volvo (and several others) utilize a log style manifold, and that is the source of problem. The very design that smooths the vacuum signal also destroys any ram effect. There are pressure waves bouncing from one end of that log to the other completely out-of-sync with the incoming charge. Besides ruining any potential ram effect, at certain RPMs there will be negative pressure waves at the entrance to the opening intake valve, pulling energy out of the incoming charge at the very moment you want to push the charge in.
Am I close or have I missed something entirely?
--
Mr. Shannon DeWolfe -- (I've taken to using Mr. because my name tends to mislead folks on the WWW. I am a 51 year old fat man ;-) -- KD5QBL
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