No Subject

[PDQSHIP@aol.com]

sage dated 96-02-26 20:50:31 EST, you write:

>
>      Well, actually, if I remember correctly, the Rally cars used a back
off
>v
>alve (also called a "pop-off valve" I think), whick releases the pressure
>from
>when the intake is clsed and all that pressure from the turbo needs a place
>to
>go....this if high enough pressure, is what will blow hoses.  This also
>prevent
>s some of the lag.

Slam shut throttle pressure spike......
S4 uses this, so do many production cars, it feeds to the intake side of the
turbo, hence your following surge valve (same thing)
>
>      Also, many of the Rally cars also had surge valves.  The Audi S4 has
>one
>of these two I believe.  It works like the above, but channels that back off
>ai
>r back into the turbo to keep it spinning while changing gears, etc.  Then
>when
>you hit the accelerator again, you are not starting from ground zero and
have
>s
>ome boost there when you need it.  This greatly reduces turbo lag, which is
>ver
>y noticable on the S4.  

That's more a function of the turbo, NJTH
>If I remember correnctly someone last year put the S4
>s
>urge valve on a 5KTQ, and they work great.  I think it is a rather
>inexpensive
>mod as well....something to look into anyways.

30.00 or so cost-wise
Did that bleeding the Sport quattro valve to atmosphere no less, IC still
went POP!!  Maybe two for me......  Now the valve collects dust again in the
garage.....
>
>     Of courese, the Rally drivers best ways of keeping boost up while
>cornerin
>g was to hit all three pedals at the same time, thatway they were braking,
>yet
>the boost was still up and they'd slide through the corner and off the gas
>and.
>....whaaaaaaa!!!  They'd wail right on by!
Hmmmm......  Ok
>                                       

there are no differences in the valves....  The Rally guys didn't care to
feed air back into the intake of the turbo, so the farts you heard were pop
off/surges bleating to atmosphere.....  The noise is "cool" but hardly
appropriate for a  first date.....  The feedback back into the intake is for
closed loop system of measured air and noise control, not really any pressure
spool of the turbo.  I does allow less Pressure Braking of the cold pressure
side, so basically the valve allows the turbo to free spin....

Scott