Re: 89.5 10vt [200]

[STEADIRIC@aol.com]

>>>>>  Good explanation of overlap.  However, a turbo motor has two demands
>on the cam profile, lift and duration.  Given the reduction in overlap of
the
>"newer" cam, this can be overcome, in fact improved on, by addressing lift
>instead of duration.  Yes the valves are open at the same time for a time
>(increasing HC output), the opposing factor to that is that increasing lift
>at the same time creates a valve float problem.  So the trade off is a
>slightly revised exhaust ramp for increased lift, or decreased lift for a
>decrease in overlap.  My homework indicates that for mamimizing turbo
>efficiency, lift is more important than a slight reduction in overlap.  As
>you change the sizing of the valves this theory moves some, but lift still
>prevails.

Bzzzzzzzzzzttttttttttt,  Wrong.

Having raced for too many teams that have turbo cars I know a thing or 
two about what a turbo engine wants cam wise.

Lift just really does'nt matter, after all your Shoving that charge air 
into each cyl under pressure.  Duration and lack of overlap are the 
important things when it comes to turbo cams.   Reasonable lift that's 
all it takes, which makes for nice ramp profiles abd long duration. If 
lift was important IMSA tech inspectors would have been able to bust the 
turbo guys when they had cams that "Bent" the rules.  Audi BTW had a 
really, really nice one for the firehawk car.....



Later!


Eric Fletcher S.O.C.
'87 5KCSTQIA2RSR2B
St. Louis, MO

STEADIRIC@aol.com