Cam timing
01-05-2007, 08:26 AM
#1
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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?
01-05-2007, 01:33 PM
#2
MarineKinetics
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Re: 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?
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
Last edited by rmbuilder; 01-05-2007 at 01:38 PM.
01-05-2007, 01:50 PM
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Re: Cam timing
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
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?
01-05-2007, 02:57 PM
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Re: Cam timing
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
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?
