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camshaft selection? Why is this asked when selecting a camshaft for a performance application?
 

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camshaft selection? Why is this asked when selecting a camshaft for a performance application?
Because to little duration and too much static compression can create too much Dynamic compression depending on the application, or vise versa, too little static compression and too much duration will let all the compression out and make a pig. i'm sure thats just the tip
 

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The camshafts "work week" is during 2 cycles. . .the intake cycle and the exhaust cycle. What does it do during the compression cycle?
 

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The camshafts "work week" is during 2 cycles. . .the intake cycle and the exhaust cycle. What does it do during the compression cycle?
Just re-read this, Is this a trick question? If the question is pointed at a given cylinder i'd say its resting, but on and engine with multiple cylinders the camshaft as a whole should always be moving something, no?
 

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If you did your job right;) at the bottom while the piston is in a dwell state and part way back up, slowly gaining momentum, it is still in an intake mode (in a given RPM range). Below that range, some of the intake charge get pushed back up the intake track. The further below the range, the more so, there by lowering the effective compression of the motor. If I win, please send my free roller to 288/298 @ .050 Drive, BBCalif.:D



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Discussion Starter #9
If you did your job right;) at the bottom while the piston is in a dwell state and part way back up, slowly gaining momentum, it is still in an intake mode (in a given RPM range). Below that range, some of the intake charge get pushed back up the intake track. The further below the range, the more so, there by lowering the effective compression of the motor. If I win, please send my free roller to 288/298 @ .050 Drive, BBCalif.:D
Bob, Let's not get into Ram effect just yet. Let's keep this simple. I promised Mike F I would go into Ram effect and we have this as another "winter discussion".
 

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Why is this asked when selecting a camshaft for a performance application?
When it comes to camshaft selection, I spend a lot less time considering compression ratio than I do other far more important factors such as the in/exh port designs and their performance, engine displacement, intended rpm range, other engine combination factors, etc. I don't feel compression is as big a factor as many seem to think, when it comes to planning a camshaft. Power making, YES compression plays a big role, but compression's influence on cam profile is not to me as significant as others seem to take it.

And that's all I'm saying about that...

LO

P.s.: Hi Chris, been slammed, hope all's well. :)
 

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camshafts 101

Is this a quiz or something? ;)
i don't know , but it's sure beats call me and i'll sell you a cam when someone asks a cam tech question . i agree with lakes to a point and then with Josh that too much duration without increasing port flow and compression will kill the cylinder pressure and not increase power or extend the powerband .
 

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When it comes to camshaft selection, I spend a lot less time considering compression ratio than I do other far more important factors such as the in/exh port designs and their performance, engine displacement, intended rpm range, other engine combination factors, etc. I don't feel compression is as big a factor as many seem to think, when it comes to planning a camshaft. Power making, YES compression plays a big role, but compression's influence on cam profile is not to me as significant as others seem to take it.

And that's all I'm saying about that...

LO

P.s.: Hi Chris, been slammed, hope all's well. :)
Thank You. You said that so well.
 

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Discussion Starter #16
Sorry, I go sidetracked on an FE project. When a cam company ask you how much compression in the engine why do they need to know? The cam deals with 2 cycles and neither is the compression cycle, so why do they need to know this? How does compression play into the "cam tech's" ability to recommend a camshaft?

I'll be back tomorrow.
 

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more compression, more heat/work effeciency, cooler exhaust. Less exhaust pressure and volume, cylinder purges quicker. Bigger changes at lower static compressions. Much more of this from 8:1 to 10:1 than from 11:1 to 13:1.

i hope
 

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Spiral out
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It dictates the IC of the valve.

The short version.

W/ a higher compression ratio......closing the valve later is desired as to not have too great a compression psi at "low" rpm....likely leading to a detonation type concern.

Chris, I've been waiting the ram effect thread for as long as I and everyone else has been waiting for me to put my boat on the water.:)hand
 

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If you did your job right;) at the bottom while the piston is in a dwell state and part way back up, slowly gaining momentum, it is still in an intake mode (in a given RPM range). Below that range, some of the intake charge get pushed back up the intake track. The further below the range, the more so, there by lowering the effective compression of the motor. If I win, please send my free roller to 288/298 @ .050 Drive, BBCalif.:D

Oh Boy!!! .... Somebody got a new DART board :D
 

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When a cam company ask you how much compression in the engine why do they need to know? The cam deals with 2 cycles and neither is the compression cycle, so why do they need to know this?


This is not true.

The cam greatly effects all cycles (Intake/Exhaust/Compression/Power) and the phases in between each cycle.

You know that as long as the intake valve is open the compression can't really happen. IVC occurs (ABDC) when the piston is going towards top dead center of the compression stroke. And exhaust ,and the changes made for compression, well, that's maybe a post for later.
 
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