Blower Cams and Overlap
03-23-2005, 03:24 PM
#31
Originally Posted by Mort
Yup the overlap is still 18.5 degrees but the Intake Duration, Exhaust Duration and Intake and Exhaust Installed Centerlines are not correct unless you enter the IVO and EVC as negative numbers for Nakid's cam profile.
are you agreeing with 18.5deg overlap or -18.5deg overlap?
sorry for the 20 questions fellas, I'm just trying to nail this down to a nats ***, I'm compelled to figure this Cam **** out
03-23-2005, 03:36 PM
#32
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Originally Posted by moregrip
ohhhhh
are you agreeing with 18.5deg overlap or -18.5deg overlap?
sorry for the 20 questions fellas, I'm just trying to nail this down to a nats ***, I'm compelled to figure this Cam **** out
are you agreeing with 18.5deg overlap or -18.5deg overlap?
sorry for the 20 questions fellas, I'm just trying to nail this down to a nats ***, I'm compelled to figure this Cam **** out
The overlap is -18.5 degrees not positive 18.5 degrees. The IVO is 8.1 degrees ATDC and the EVC is 10.4 degrees BTDC so then the overlap has to be - 18.5 degrees @ .050 lift. The EVCloses 18.5 degrees before the IVOpens therefore the overlap is -18.5 degrees. I also presume those figures are @ .050 lift and not .006 lift.
03-23-2005, 04:01 PM
#33
Originally Posted by Mort
The overlap is -18.5 degrees not positive 18.5 degrees. The IVO is 8.1 degrees ATDC and the EVC is 10.4 degrees BTDC so then the overlap has to be - 18.5 degrees @ .050 lift. The EVCloses 18.5 degrees before the IVOpens therefore the overlap is -18.5 degrees. I also presume those figures are @ .050 lift and not .006 lift.
What I'm confused about is which point should we be calculating, .050 or .006?
03-23-2005, 04:26 PM
#34
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Originally Posted by moregrip
that makes more sense @ .050
What I'm confused about is which point should we be calculating, .050 or .006?
What I'm confused about is which point should we be calculating, .050 or .006?
Go get excel and open that table I posted. It'll really help.
03-23-2005, 04:35 PM
#35
Originally Posted by SportSide 5.3
All of them. You do one at a time to find the valve events of that given lift. And because duration is different at different lift values, the valve events are not the same. Nor overlap. That's why there is .006 overlap, .050 overlap
Go get excel and open that table I posted. It'll really help.
Go get excel and open that table I posted. It'll really help.
03-23-2005, 04:48 PM
#36
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I am not a cam expert but .006 would seem to be enough lift to measure the total durations of the cam profile. At .050 lift maybe there is enough lift to start measuring meaningful movement into and out of the cylinder and to calculate figures to compare to other camshafts and to calculate overlap, centerlines and durations. I know it doesn't really answer your question but what happens from .006 to .050 lift may not be too significant it terms of measureable performance. I don't really know so hopefully someone who does will post up for you. 
03-23-2005, 05:02 PM
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Oops, must of misunderstood your question. Thought we were talking about ve's.
Be sure to look at both (.050 & .006). Only looking at one can be deceiving.
#3720 lobe
269* @ .006
220* @ .050
143* @ .200
.581'' lift
#3713 lobe
273* @ .006
220* @ .050
138* @ .200
.564'' lift
The #3720 uses a more aggressive lobe. Spends less time @ seat duration. A more aggressive lobe is helpful because the valve spends its time open enough where the heads flow well.
Be sure to look at both (.050 & .006). Only looking at one can be deceiving.
#3720 lobe
269* @ .006
220* @ .050
143* @ .200
.581'' lift
#3713 lobe
273* @ .006
220* @ .050
138* @ .200
.564'' lift
The #3720 uses a more aggressive lobe. Spends less time @ seat duration. A more aggressive lobe is helpful because the valve spends its time open enough where the heads flow well.
N/A you want to get the intake valve open as fast as possible to get it flowing. Ideally you want as much .200 lobe duration as you can get. (.150 on great flowing heads like the LS1). With boost behind the intake valve there is not a "need" to have such an aggressive intake lobe. As soon as the valve cracks open (.006 duration) the pressure difference will make the heads flow. With a boosted setup .006 duration is MUCH more important then with an N/A setup. Sure, you'll still gain from an aggressive intake lobe on a boosted setup, but it's nothing 1 more psi of boost won't overcome if you had a weaker intake lobe profile.
Same goes for overlap....it's definately a benefit, but not "needed". More boost will always equal things out.
Same goes for overlap....it's definately a benefit, but not "needed". More boost will always equal things out.
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