Is overlap effectiveness rpm dependant?
02-18-2007, 04:49 PM
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Is overlap effectiveness rpm dependant? Does small duration (under 214@50)and big overlap work and where in the rpm range? Can the amount of overlap hurt low end power, with a lesser duration and greater DCR?
02-18-2007, 05:51 PM
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A samll duration cam like that will not be able to have much overlap at all unless you have like a under a 105 LSA. A cam like that on a 110LSA even has negative overlap.
02-18-2007, 06:54 PM
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Originally Posted by brad8266
A samll duration cam like that will not be able to have much overlap at all unless you have like a under a 105 LSA. A cam like that on a 110LSA even has negative overlap.
214 108
But back to the question is overlap effectiveness Dependant on rpm?
02-18-2007, 07:30 PM
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Originally Posted by 02sierraz71_5.3
negative -2 overlap @ 50 will still work out to +52 degrees at .01 which is a considerable amount
214 108
But back to the question is overlap effectiveness Dependant on rpm?
214 108
But back to the question is overlap effectiveness Dependant on rpm?
ok whatever, lol, a cam like that has no considerable amount of overlap but think what you want.More overlap is better for higher rpm operation, it aids in filling the chambers with fresh air. The overlap causes the leaving exhaust gases to suck in fresh air.
02-18-2007, 07:34 PM
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Not only RPM, but also exhaust tuning and restriction. Same applies for the
intake side.
Everything roots down to pressures in the cylinder and ports. More overlap will
work at lower RPM on larger displacement engines with longer strokes.
Generally (< I love that word):
Piston speeds and the pressures created by a longer stroke/higher displacement engines within a
range of RPM can accept more overlap than a shorter stroke/ smaller displacement
engine at the same RPM.
intake side.
Everything roots down to pressures in the cylinder and ports. More overlap will
work at lower RPM on larger displacement engines with longer strokes.
Generally (< I love that word):
Piston speeds and the pressures created by a longer stroke/higher displacement engines within a
range of RPM can accept more overlap than a shorter stroke/ smaller displacement
engine at the same RPM.
02-18-2007, 09:53 PM
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Originally Posted by Adrenaline_Z
Not only RPM, but also exhaust tuning and restriction. Same applies for the
intake side.
Everything roots down to pressures in the cylinder and ports. More overlap will
work at lower RPM on larger displacement engines with longer strokes.
Generally (< I love that word):
Piston speeds and the pressures created by a longer stroke/higher displacement engines within a
range of RPM can accept more overlap than a shorter stroke/ smaller displacement
engine at the same RPM.
intake side.
Everything roots down to pressures in the cylinder and ports. More overlap will
work at lower RPM on larger displacement engines with longer strokes.
Generally (< I love that word):
Piston speeds and the pressures created by a longer stroke/higher displacement engines within a
range of RPM can accept more overlap than a shorter stroke/ smaller displacement
engine at the same RPM.
What do you consider a smaller stroke/bore?
Is there a range of compression for a range of overlap?
When does overlap hurt power under 2krpms?
Last edited by 02sierraz71_5.3; 02-18-2007 at 10:06 PM.
02-18-2007, 10:17 PM
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Higher compression really wont do anything for overlap. Since both valves
are open at this time, rasing SCR isn't going to help.
That depends on how much valve overlap you plan to use.
No. Think of RPM and displacement when you tune a specific overlap duration.
When the exhaust pressure is higher than the cylinder pressure and intake
pressure.
This prevents the gasses from exiting the chamber.
are open at this time, rasing SCR isn't going to help.
What do you consider a smaller stroke/bore?
Is there a range of compression for a range of overlap?
When does overlap hurt power under 2krpms?
pressure.
This prevents the gasses from exiting the chamber.
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02-18-2007, 10:54 PM
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Originally Posted by Adrenaline_Z
Higher compression really wont do anything for overlap. Since both valves
are open at this time, rasing SCR isn't going to help.
That depends on how much valve overlap you plan to use.
No. Think of RPM and displacement when you tune a specific overlap duration.
When the exhaust pressure is higher than the cylinder pressure and intake
pressure.
This prevents the gasses from exiting the chamber.
are open at this time, rasing SCR isn't going to help.
That depends on how much valve overlap you plan to use.
No. Think of RPM and displacement when you tune a specific overlap duration.
When the exhaust pressure is higher than the cylinder pressure and intake
pressure.
This prevents the gasses from exiting the chamber.
02-18-2007, 11:11 PM
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I'm not going to stick my neck out and say a stock LS1 will hit low 13's on that
cam.
There's much more going on aside from the cam specs that will determine how
the engine performs.
Based on the numbers however, it would seem the low and mid range performance
would be strong. It's not an overly aggressive camshaft by any stretch.
Even on a 108 LCA, the valve timing and overlap dictate a well behaved
street motor with a nice ilde (and idle vacuum).
cam.
There's much more going on aside from the cam specs that will determine how
the engine performs.
Based on the numbers however, it would seem the low and mid range performance
would be strong. It's not an overly aggressive camshaft by any stretch.
Even on a 108 LCA, the valve timing and overlap dictate a well behaved
street motor with a nice ilde (and idle vacuum).
02-19-2007, 07:50 AM
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Originally Posted by Adrenaline_Z
I'm not going to stick my neck out and say a stock LS1 will hit low 13's on that
cam.
There's much more going on aside from the cam specs that will determine how
the engine performs.
Based on the numbers however, it would seem the low and mid range performance
would be strong. It's not an overly aggressive camshaft by any stretch.
Even on a 108 LCA, the valve timing and overlap dictate a well behaved
street motor with a nice ilde (and idle vacuum).
cam.
There's much more going on aside from the cam specs that will determine how
the engine performs.
Based on the numbers however, it would seem the low and mid range performance
would be strong. It's not an overly aggressive camshaft by any stretch.
Even on a 108 LCA, the valve timing and overlap dictate a well behaved
street motor with a nice ilde (and idle vacuum).
02-19-2007, 09:56 PM
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Originally Posted by Adrenaline_Z
Sorry, my oversight. Same characteristics will apply however.
Im wondering about how far I can push this thing before I run into problems with too much overlap or piston to valve. The heads already have 50 off and Im running a 2" intake valve with stock gaskets.
If I could drop down to the 108/106 range it would give me more leeway with the duration and keep the IVC where I want it. But at some point I guess I just need to realize the motor isnt optimally setup for this type of cam, with my last cam this thing ran great I just dont want to redo the top half.
