Plunger Lift vs Timing vs Math?
10-12-2006, 07:27 PM
#1
Registered User
Thread Starter
Plunger Lift vs Timing vs Math?
HTML Code:
215hp BTDC Lift Diviser Difference 9.5 NA 10 NA 10.5 NA 11 NA 11.5 4.70 2.446809 0.053191 12 4.80 2.500000 0.056237 12.5 4.89 2.556237 0.054205 13 4.98 2.610442 0.052280 13.5 5.07 2.662722 0.050456 14 5.16 2.713178 0.048726 14.5 5.25 2.761905 0.041834 15 5.35 2.803738 0.040298 15.5 5.45 2.844037 0.013106 <-- ??? 16 5.60 2.857143 16.5 5.68 2.907143 17 5.75 2.957143 17.5 5.82 3.007143 18 5.89 3.057143 18.5 5.95 3.107143 19 6.02 3.157143 19.5 6.08 3.207143 20 6.14 3.257143 20.5 6.20 3.307143 21 6.26 3.357143 21.5 6.31 3.407143 22 6.36 3.457143 22.5 6.42 3.507143 23 6.47 3.557143
But at 16 degrees, the math stops working. 5.6mm of lift is what I would expect for 16.5 degrees of timing not 16. As you can see above the 'Difference' column is the difference in the diviser between the current timing and the previous one. So if we let the formula handle the timing for 16 degrees and assume the additional .05 for each 1/2 degree of time, we get this:
HTML Code:
215hp BTDC Lift Diviser Difference 9.5 NA 10 NA 10.5 NA 11 NA 11.5 4.70 2.446809 0.053191 12 4.80 2.500000 0.056237 12.5 4.89 2.556237 0.054205 13 4.98 2.610442 0.052280 13.5 5.07 2.662722 0.050456 14 5.16 2.713178 0.048726 14.5 5.25 2.761905 0.041834 15 5.35 2.803738 0.040298 15.5 5.45 2.844037 0.050000 16 5.53 2.894037 16.5 5.60 2.944037 17 5.68 2.994037 17.5 5.75 3.044037 18 5.82 3.094037 18.5 5.88 3.144037 19 5.95 3.194037 19.5 6.01 3.244037 20 6.07 3.294037 20.5 6.13 3.344037 21 6.19 3.394037 21.5 6.24 3.444037 22 6.30 3.494037 22.5 6.35 3.544037 23 6.40 3.594037
10-13-2006, 12:05 PM
#2
Chapter President
A cam lobes profile is not linear. As the cam lobe begins to get closer to TDC the rate of rise is parabolic and slows rapidly. As you advance your timing you are getting closer to TDC earlier in the cycle and less lift is attained for more degrees of crank rotation. Does that help??
10-15-2006, 09:24 PM
#4
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Thread Starter
Well I'll concede and agree with you guys that the cam lobe isn't a perfect circle (or triangle), however by watching the gauge as I roll the engine over and looking at the amount of lift I'm getting, I guess I'm somewhat surprised to start seeing such a distinct change start occurring @ 16 degrees. To me it seems that the rate of lift is still rather uniform all the way up to the .248 inches @ 22 degrees as it is down @ .22 inches. I haven't substantiated it by taking measurements at different rotation degrees to confirm, but the lift "seems" uniform at least between what I see from 13 degrees to what I've blindly said lift should be at 22 degrees.
My question has now changed then, is there an accurate chart that does show lift vs. timing up to 25 degrees?
My question has now changed then, is there an accurate chart that does show lift vs. timing up to 25 degrees?
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