Increasing Cams Overlap
07-29-2007, 12:11 AM
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Increasing Cams Overlap
Guys...
Since our place don't have any dyno facility...
I want to know what will happen if i increase overlap by retarding exhaust and advancing intake... I've tried several combination, in-0 ex-retard and in-retard ex-retard but my new combination seem more power at top-end if i do compare with in-retard ex-retard combination...
what i know in-advance ex-retard will waste AF caused AF will flow out through exhaust due to more overlap... did i missed something...?
I'm doing on stock b16b block, 11.5 cr, 82mm tb, port and polish head and spoon cams...
thanks
Since our place don't have any dyno facility...
I want to know what will happen if i increase overlap by retarding exhaust and advancing intake... I've tried several combination, in-0 ex-retard and in-retard ex-retard but my new combination seem more power at top-end if i do compare with in-retard ex-retard combination...
what i know in-advance ex-retard will waste AF caused AF will flow out through exhaust due to more overlap... did i missed something...?
I'm doing on stock b16b block, 11.5 cr, 82mm tb, port and polish head and spoon cams...
thanks
07-30-2007, 07:14 AM
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Re: Increasing Cams Overlap (DC2jdmIntegra)
im pretty sure he means 82mm bore....
anyway i cant say one way or the other because each cam is different but usually retarding the exhaust cam will help mid/high end power by increasing exhaust scavenging but will sacrafice idle/low end quality. keep in mind you should change your fuel curve to match after you set your cam gears.
course the only way to tell is to dyno it (or maybe your a really consistant bracket racer i dunno)
anyway i cant say one way or the other because each cam is different but usually retarding the exhaust cam will help mid/high end power by increasing exhaust scavenging but will sacrafice idle/low end quality. keep in mind you should change your fuel curve to match after you set your cam gears.
course the only way to tell is to dyno it (or maybe your a really consistant bracket racer i dunno)
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08-01-2007, 02:45 AM
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Re: Increasing Cams Overlap (zamrioo2)
well then genius why dont you go actually try this out yourself and tell us since your so smart? or maybe you could actually read a book or two on engine theory.
the problem is you didnt give us any information to work with so the best i could do was a generalazation, im sorry it wasnt up to your spoonfeeding expectations.
the problem is you didnt give us any information to work with so the best i could do was a generalazation, im sorry it wasnt up to your spoonfeeding expectations.
08-01-2007, 05:31 AM
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Re: Increasing Cams Overlap (zamrioo2)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zamrioo2 »</TD></TR><TR><TD CLASS="quote">is that only the explaination...? pity, if so then i don't have to post here... 
</TD></TR></TABLE>
You are right you don't have to post here go away.
</TD></TR></TABLE>You are right you don't have to post here go away.
08-01-2007, 08:41 AM
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Re: Increasing Cams Overlap (zamrioo2)
Every motor is different. Some will want more overlap, some will want less. Without a dyno to measure gains/losses you are just fumbling around in the dark. If a dyno is unavailable to you, you should degree the cams to the manufacturers specs.
If you dial in too much overlap you can get valve to valve contact and say goodbye to your motor.
If you dial in too much overlap you can get valve to valve contact and say goodbye to your motor.
08-01-2007, 06:10 PM
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Re: Increasing Cams Overlap (JCushing)
u are prof-X am i right...? or jeane or something... maybe wolverine...
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JCushing »</TD></TR><TR><TD CLASS="quote">im pretty sure he means 82mm bore....</TD></TR></TABLE>i'm not that smart as u to read other think... 
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JCushing »</TD></TR><TR><TD CLASS="quote">im pretty sure he means 82mm bore....</TD></TR></TABLE>i'm not that smart as u to read other think...
08-01-2007, 06:24 PM
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Re: Increasing Cams Overlap (JCushing)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JCushing »</TD></TR><TR><TD CLASS="quote">well then genius why dont you go actually try this out yourself and tell us since your so smart? or maybe you could actually read a book or two on engine theory.</TD></TR></TABLE>understanding the theory is not just reading thousand of books... or being a monkey wearing glass... 
08-01-2007, 09:23 PM
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Re: Increasing Cams Overlap (zamrioo2)
Increasing duration - Increases HP and TQ, also moves peak HP and peak TQ to a higher RPM.
Increasing lift - Increases HP and TQ, but does not move the point of peak HP and peak TQ up or down the RPM range.
Increasing overlap - Increases peak HP at the sacrifice of low end TQ.
Increasing lift - Increases HP and TQ, but does not move the point of peak HP and peak TQ up or down the RPM range.
Increasing overlap - Increases peak HP at the sacrifice of low end TQ.
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