Re: Turbo cam in NA I5

[Ken <kkeith@qnet.com>]

"Bruce Bell" <bbell@bbell.com> wrote:

> Turbo motors because of the back pressure from the turbo
> (help me Scott, anyone) gain little or nothing from
> increased overlap that is there is no meaningful exhaust
> scavenging effect..  

I've venturing into schtuff I don't know fer sure about, 
but I thought it was _also_ because you don't want the pressurized 
intake charge blowing through the cylinders which are still 
basically at the end of their on their exhaust strokes, as you 
are trying to fill the other cylinders during their intake 
strokes.  The pressure is needed to fill the relevant cylinders 
at that point in time, and shouldn't be wasted blowing through 
the one with the overlapping valves.

Is that anywhere near the idea?

BTW, if I'm wrong, that's OK.  I don't mind it so much, and 
I don't really have the time lately to be reading any books 
on supercharging! ;-)
 
> One last note. It is true that too much cam (overlap) will
> create harmonic disturbances that disrupt the flow through
> the air sensor plate on CIS motors. However, the Schrick
> cam above idles smoothly and pulls strong through 6000 rpm
> on a 4Kq. To cause these problems you will need a lot more
> cam than that! If you happen to have carbs or a MAF then
> the sky is the limit if you can handle the driveability.

Aha, I'm not crazy!  Not exactly right regarding the cam 
we're discussing, but not totally <bzzzzt!> wrong. :-)

Yep, that Schrick cam idles pretty good, unless you idle is 
turned down pretty low.
(or your damn computer fuse is popped!)

Ken