I'm new to the site and don't know alot about Hondas but I do know quite a bit of machanic information in general. In my history, I've always heard of people having issues picking the best cams for boost. Here's a bit of info on the subject. For boost, you want cams with high lift but short duration. Overlap is one of the biggest killer of hp and tq on a boosted motor.
What is Camshaft Duration and why is it important?
Duration is the period of time, measured in degrees of crankshaft rotation, that a valve is open. Duration (at .050" lifter rise) is the deciding factor to what the engine's basic RPM range will be. Lower duration cams produce the power in the lower RPM range. Larger duration cams operate at higher RPM, but you will lose bottom end power to gain top end power as the duration is increased. (For each ten degree change in the duration at .050", the power band moves up or down in RPM range by approximately 500 RPM.)
What is the difference in Advertised Duration and Duration at .050" Lifter Rise (Tappet Lift)?
In order for duration to have any merit as a measurement for comparing camshaft size, the method for determining the duration must be the same. There are two key components for measuring duration-- the degrees of crankshaft rotation and at what point of lifter rise the measurements were taken. Advertised durations are not taken at any consistent point of lifter rise, so these numbers can vary greatly. For this reason, advertised duration figures are not good for comparing cams. Duration values expressed at .050" lifter rise state the exact point the measurement was taken. These are the only duration figures that are consistent and can accurately be used to compare camshafts.
-With turbo cams, you want as little overlap as possible. Also, you would usually want a little more intake duration than exhaust. This is to help with exhaust gas reversion due to higher exhaust pressure due to the turbo. Since we are looking at duration at .050", you want the overlap to be definitely in the negatives because below .050" it will have more overlap. Like I said, you want as little overlap as possible.
-You also want as high a lift as possible. Basically with f/i motors you want the valve to lift 20-25% past its peak flow point (something you calculate based on the cylinder head). You don't want it to open only to its peak flow point because that would only happen one time per cycle. If it opens past, then there is time where it is open to its peak flow point while the valve is still going up and then starting back down. Basically it allows you to have the valve open at its peak flow point longer. I would think that the higher, the better. Keep in mind with some profiles, you may need valve relieft in your pistons.
Now to compute OVERLAP you:
-Add the intake and exhaust durations
-Divide the results by 4
-Subtract the lobe separation
-Multiply the results by 2
I hope this information will be good for someone.
What is Camshaft Duration and why is it important?
Duration is the period of time, measured in degrees of crankshaft rotation, that a valve is open. Duration (at .050" lifter rise) is the deciding factor to what the engine's basic RPM range will be. Lower duration cams produce the power in the lower RPM range. Larger duration cams operate at higher RPM, but you will lose bottom end power to gain top end power as the duration is increased. (For each ten degree change in the duration at .050", the power band moves up or down in RPM range by approximately 500 RPM.)
What is the difference in Advertised Duration and Duration at .050" Lifter Rise (Tappet Lift)?
In order for duration to have any merit as a measurement for comparing camshaft size, the method for determining the duration must be the same. There are two key components for measuring duration-- the degrees of crankshaft rotation and at what point of lifter rise the measurements were taken. Advertised durations are not taken at any consistent point of lifter rise, so these numbers can vary greatly. For this reason, advertised duration figures are not good for comparing cams. Duration values expressed at .050" lifter rise state the exact point the measurement was taken. These are the only duration figures that are consistent and can accurately be used to compare camshafts.
-With turbo cams, you want as little overlap as possible. Also, you would usually want a little more intake duration than exhaust. This is to help with exhaust gas reversion due to higher exhaust pressure due to the turbo. Since we are looking at duration at .050", you want the overlap to be definitely in the negatives because below .050" it will have more overlap. Like I said, you want as little overlap as possible.
-You also want as high a lift as possible. Basically with f/i motors you want the valve to lift 20-25% past its peak flow point (something you calculate based on the cylinder head). You don't want it to open only to its peak flow point because that would only happen one time per cycle. If it opens past, then there is time where it is open to its peak flow point while the valve is still going up and then starting back down. Basically it allows you to have the valve open at its peak flow point longer. I would think that the higher, the better. Keep in mind with some profiles, you may need valve relieft in your pistons.
Now to compute OVERLAP you:
-Add the intake and exhaust durations
-Divide the results by 4
-Subtract the lobe separation
-Multiply the results by 2
I hope this information will be good for someone.
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