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Generally, a smaller LSA means a "peakier" cam - a narrower power band. Idle roughness is a function of the duration and the LSA. In fact, all of these numbers interact, its very hard to change just one and get a predictable result.
so to make sure I have this correctly. Smaller LSA numbers make more power higher in the RPM range and larger LSA numbers make power lower in the rpm range?
so to make sure I have this correctly. Smaller LSA numbers make more power higher in the RPM range and larger LSA numbers make power lower in the rpm range?
Generalization: The larger LSA cam will have a flatter torque and hp curve with a slightly lower peak number, the lower LSA cam will have a steeper curve before and after peak is reached. Smaller LSA cams usually have a tighter intake centerline (earlier intake valve closing). This offers very good low rpm torque.
Having said that, LSA is not what you want to look at in choosing the valve events for a cam. Intake valve closing point, durations for the particular engine size and objective considering overlap, head flow at various lifts, the ratio between intake and exhaust flow are all much more important. LSA is just a number after getting these other events correct for your application.
From: When all is said and done... there is a hell of a lot more said than done. Riverside,Texas
St. Jude Donor '05 thru '26
Originally Posted by gtovan
LSA is not what you want to look at in choosing the valve events for a cam. Intake valve closing point, durations for the particular engine size and objective considering overlap, head flow at various lifts, the ratio between intake and exhaust flow are all much more important. LSA is just a number after getting these other events correct for your application.
Good point - The key is in moving air in and out most efficiently.
I'm not going to get into an argument here, but some of what gtovan says above is correct but tighter lsa gives more overlap which produces rough idle which hurts low end torque. It is true that less angle closes the intake sooner which will give more torque, if you were comparing to alike cams. This can get real technical and I could get into a real argument here but I won't. I have built hundreds of racing engines and degreed hundreds of cams. I have built my own flow bench and have done extensive testing on single cylinder race kart engines. The principles are the same in multi cylinder engines. To quote Smokey Yunick, "A larger separation angle generally produces more low-end torque and a loss of top end power."
Later, Ron
Last edited by Speed7; Jan 13, 2007 at 01:43 PM.
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