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Cam timing
If you advance the cam timing you get more low end torque at the expense of high end hp and the hp/rpm curve shifts down the rpm. Retard cam timing and the reverse occurs. What happens if you just add duration to the intake and exhaust closing as if the cam was retarded on that end of the cycle only?
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Re: Cam timing
1 Attachment(s)
Originally Posted by Rage
(Post 1983174)
If you advance the cam timing you get more low end torque at the expense of high end hp and the hp/rpm curve shifts down the rpm. Retard cam timing and the reverse occurs. What happens if you just add duration to the intake and exhaust closing as if the cam was retarded on that end of the cycle only?
By adding duration only to the closing sides of the lobes you will, in effect, be retarding the cam relative to the centerlines even though the IVO and EVO placement remains unchanged. The attached sheet illustrates this numerically. I have used seat durations and centerlines that will facilitate the reading of the valve events. Because the centerlines of the lobes are a byproduct of valve events they must change as a result of the unequal distribution of duration. Cam 1 is baseline Cam 2 is the addition of 10* to the exhaust closing side Cam 3 is the addition of 10* to the intake & exhaust closing All cams retain the same IVO/EVO events. Notice the relationship of the ICL/ECL/LSA angles and overlap. Bob |
Re: Cam timing
Originally Posted by rmbuilder
(Post 1983468)
Rage,
By adding duration only to the closing sides of the lobes you will, in effect, be retarding the cam relative to the centerlines even though the IVO and EVO placement remains unchanged. The attached sheet illustrates this numerically. I have used seat durations and centerlines that will facilitate the reading of the valve events. Because the centerlines of the lobes are a byproduct of valve events they must change as a result of the unequal distribution of duration. Cam 1 is baseline Cam 2 is the addition of 10* to the exhaust closing side Cam 3 is the addition of 10* to the intake & exhaust closing All cams retain the same IVO/EVO events. Notice the relationship of the ICL/ECL/LSA angles and overlap. Bob Crystal clear explanation of the change in cam geometry. Do we know what the relative difference will be in the max hp of 1 versus 2 as apposed to 1 versus 3? |
Re: Cam timing
1 Attachment(s)
Originally Posted by rmbuilder
(Post 1983468)
Rage,
By adding duration only to the closing sides of the lobes you will, in effect, be retarding the cam relative to the centerlines even though the IVO and EVO placement remains unchanged. The attached sheet illustrates this numerically. I have used seat durations and centerlines that will facilitate the reading of the valve events. Because the centerlines of the lobes are a byproduct of valve events they must change as a result of the unequal distribution of duration. Cam 1 is baseline Cam 2 is the addition of 10* to the exhaust closing side Cam 3 is the addition of 10* to the intake & exhaust closing All cams retain the same IVO/EVO events. Notice the relationship of the ICL/ECL/LSA angles and overlap. Bob Cam 1 is baseline Cam 2 is the addition of 10* to the exhaust & intake closing side Cam 3 is the retardation of 10* to Cam 1 The question is if Cam 3 versus Cam 1 reportedly shifts the Hp/rpm curve, reduces low end torque and increases high end/max hp then what does Cam 2 do to Cam 1 relative to those same parameters? |
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