David Redszus wrote: ↑Tue Sep 27, 2022 1:33 am
juuhanaa wrote: ↑Mon Sep 26, 2022 2:01 pm
People think 4 valves are hard to improve and yet the same group of people are more than willing to change their cams.
Comparing camshafts can be a bit more complicated than often assumed.
Let's compare two camshaft angle area; that is to say the areas under their lift curves.
Assume both are 3-4-5-6 polynomial lobe designs.
Cam 1
Lift.....0.429"
Dur.....280 deg
Valve..2.0"
Cam 2
Lift......0.448"
Dur......260 deg
Valve...2 1/16"
Which cam has the greater angle area?
Which has the higher velocity?
Which has the greater acceleration?
Which requires a larger flat tappet?
In a given engine, which cam will produce more air flow?
David,
Using 3456 and a lobe designed for a rocker arm ratio of 1:1
Cam2 has a peak velocity of just under 0.006
Cam1 has a peak velocity just about 0.0052
The greater velocity of cam2 will require a tappet with a larger diameter that cam1.
Cam2 has a peak acceleration around 0.000127
Cam1 has a peak acceleration around 0.000105
VALVE_____Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area
_________0.00000____30.00_|__70.00_|_280.00_|__27.46
_________0.00600____11.98_|__51.98_|_243.95_|__27.42
_________0.01000_____8.33_|__48.33_|_236.67_|__27.40
_________0.02000_____2.01_|__42.01_|_224.02_|__27.32
_________0.04000____-6.50_|__33.50_|_207.01_|__27.06
_________0.05000____-9.87_|__30.13_|_200.26_|__26.92
_________0.10000___-23.18_|__16.82_|_173.64_|__25.89
_________0.15000___-33.90_|___6.10_|_152.21_|__24.65
_________0.20000___-43.65_|__-3.65_|_132.70_|__22.92
_________0.25000___-53.18_|_-13.18_|_113.64_|__20.66
_________0.30000___-63.07_|_-23.07_|__93.87_|__17.89
_________0.35000___-74.15_|_-34.15_|__71.71_|__14.29
_________0.40000___-88.74_|_-48.74_|__42.51_|___9.01
_________0.42500__-102.19_|_-62.19_|__15.61_|___3.21
VALVE_____Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area
_________0.00000____20.00_|__60.00_|_260.00_|__26.62
_________0.00600_____3.53_|__43.53_|_227.06_|__26.60
_________0.01000_____0.20_|__40.20_|_220.39_|__26.58
_________0.02000____-5.57_|__34.43_|_208.87_|__26.49
_________0.04000___-13.32_|__26.68_|_193.36_|__26.25
_________0.05000___-16.38_|__23.62_|_187.23_|__26.12
_________0.10000___-28.46_|__11.54_|_163.08_|__25.23
_________0.15000___-38.13_|___1.87_|_143.73_|__23.97
_________0.20000___-46.88_|__-6.88_|_126.23_|__22.58
_________0.25000___-55.35_|_-15.35_|_109.29_|__20.56
_________0.30000___-64.02_|_-24.02_|__91.97_|__18.07
_________0.35000___-73.47_|_-33.47_|__73.07_|__15.12
_________0.40000___-84.97_|_-44.97_|__50.06_|__10.99
_________0.42500___-92.85_|_-52.85_|__34.30_|___7.70
Stan