I did some searching but didn't find a scientific explanation...

I'm not understanding the relationship between aggressive cams (like an s2s2) and higher compression. Why is 11:1+ compression required to run a more aggressive cam?

Thanks.

 

Long duration cams will reduce compression, because the valves are open for a longer period of time.

 

Dynamic compressing is more important than static compression. Lots of overlap usually reduces dynamic compression. More static compression is needed to make up for this.

 

here this may help....

http://www.team-integra.net/se...D=233

or


http://www.team-integra.net/se...D=472

 

I had the same question a few days ago. It was explained to me like above, but was also said that because of the long duration and overlap, you may actually lose power as compared to a less aggressive cam w/ less overlap/duration.

 

It's not required, you car will just run a lil better

 

Great!!! Thanks!!!

That explained it very well. I guess I never realized just how long the intake valves remain open after the piston leaves BDC...

Edit:
With regards to a compression check... It seems like a compression check would yield relatively lower numbers on a motor with an aggressive cam vs. the same motor with a milder cam. The increased duration on the wild cam would result in at least a few psi lower, wouldn't it?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fsp31 &raquo;</TD></TR><TR><TD CLASS="quote">lower numbers on a motor with an aggressive cam vs. the same motor with a milder cam</TD></TR></TABLE>

Bingo. After the piston passes BDC and the valves are still open, it's just pushing air back out of the cylinder instead of compressing it.

 

So what are the most agressive cams u can put in a vtec head without having to upgrade your valvetrain???

 

if you mean ITR valvetrain.. i would be hesitant to put anything bigger than a skunk2 stage 1 or similiar

 

good info

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Oldskool teggy &raquo;</TD></TR><TR><TD CLASS="quote">if you mean ITR valvetrain.. i would be hesitant to put anything bigger than a skunk2 stage 1 or similiar</TD></TR></TABLE>


what about b16a2 and b18c1 heads?