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Author Topic: cam degreeing question  (Read 4021 times)

Offline Blitz

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cam degreeing question
« on: November 22, 2003, 10:09:00 PM »
Before I decide on cams for my bike I need to figure out my problem with my bike. But I have a question until then.

I have seen a lot of guys suggest/use these degree #'s on no matter what cams they use. 104/106 105/107 for example. What does this do for power, etc.? I was also told by someone to degree Yoshi Stage cams at 102/100. What would that benefit compared to say 104/106? Please be specific on your answers. Thanks for the help!
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Offline FastKaw

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cam degreeing question
« Reply #1 on: November 23, 2003, 12:15:00 PM »
Simply put,The higher the number the higher the max power comes on in the rpm band/range.The opposite with lower numbers.Cam profiles and the motor's static compression are guide lines to go by on how high a number you would use.The more over lap you have the faster the motor has to spin to out run this pressure loss.It's basically like raising the exhaust port on a 2 stroker.
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Offline DarkFalcon

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cam degreeing question
« Reply #2 on: November 23, 2003, 03:36:00 PM »
quote:
Originally posted by Blitz:


I have seen a lot of guys suggest/use these degree #'s on no matter what cams they use. 104/106 105/107 for example. What does this do for power, etc.? I was also told by someone to degree Yoshi Stage cams at 102/100. What would that benefit compared to say 104/106? Please be specific on your answers. Thanks for the help!
When you adjust cam timing you are doing two different things: changing valve timing and modifying the overlap period. As the intake centerline increases, the intake is being retarded and is closing at a later point to allow cylinder fill at higher RPM's; as the exhaust centerline increases, the exhaust is being advanced and is opening earlier to minimize potential pumping losses. As both centerlines increase, overlap is decreased which some would say delivers a broader torque curve. In the examples, you mention, the following may be said:

      102/100: the intake has been left at the suggested centerline while the exhaust has been retarded five degrees. The lobe center is 101.5 compared to Yoshs' suggestion of 103.5 based upon centers of 102/105. Probably alot of rapid,low-end torque with a loss at the top.
      104/106: the intake has been retarded three degrees and the exhaust has been advanced one degree and the lobe center is 105 versus Yoshs' sugesstion of 103.5. Probably offers a broader torque profile and better mid to high-end performance.
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Offline Blitz

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cam degreeing question
« Reply #3 on: November 23, 2003, 04:54:00 PM »
Interesting. Now the reason I was told to degree the bike for 102/100 was because for anyone that is 250lbs or larger they would benefit more with the low rpm power and a broad mid range w/o sacricficing to much on the top. Would this be a benefit against an exact bike except cam timing difference in a race at 75mph to absolute top end? or any other speeds to whatever?
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Offline 2kidsandabusa

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cam degreeing question
« Reply #4 on: November 25, 2003, 04:49:00 AM »
I went 105 107, and a stock bike wll walk me on a roll on but at the track i picked up 5 mph and 2 tens, happy with the yosh cams
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Offline Blitz

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cam degreeing question
« Reply #5 on: November 26, 2003, 01:34:00 AM »
quote:
Todd Smith
  posted November 25, 2003 05:49 AM                        
 I went 105 107, and a stock bike wll walk me on a roll on but at the track i picked up 5 mph and 2 tens, happy with the yosh cams      
As far as your roll ons, what gear, rpms and/or speeds were you doing these roll ons? It sounds like you lost quite a bit at the lower rev range.
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