Re: dumping q's

[QSHIPQ@aol.com]

In a message dated 97-02-14 23:40:40 EST, you write:

<< >UrQ intercoolers which are
 >all aluminum are not adaptable to the third inlet needed for a
 >proper dump valve installation? 
 even if the intercooler is made out of alum. there is no reason why you
 can't add a third opening, look at my post from yesterday,
  >the dump valves
 >but I don't like the fact they dump into the atmosphere.
 I am not sure about the UR. Q but you can not dump to atmosphere on a 5K,
 the fuel injection is a sealed system and when the dump valve is engaged
 (vacuum pres.) the system is open, the 5K will not run...
 Avi Meron 
  >>
Avi:
You can run a dump valve in a 5kt, either to atmosphere or to closed loop...
 The valve opens on vaccuum, that is correct, but at idle it is closed, there
is a spring in there....  The reason the valve needs to be closed loop is for
the avoidance of a rich fuel spike when the valve opens....  Here's what
happens>

*  valve is closed at idle
*  Boost is added to spring pressure keeping valve closed on boost
*  Throttle shuts, valve opens, dumping air pressure to inlet side of turbo
or atmos

Dumping to atmosphere:

Valve is closed, opens to atmosphere when throttle closed, turbo is still
spinning, demanding more air (exponentially with a CIS system, theory is the
same in a MAS) keeping the flap open for more fuel, when indeed the demand is
idle-sized....  So raw fuel is dumped into motor....  DANGER DAN:  That can
cause a backfire either on the intake side, stalling out the turbo, blowing
the IC end caps, or worse yet, back pressuring the air flap...  Or  the
backfire occurs at the turbo (raw fuel in 1600degree exhaust man), sending a
flame out the exhaust, cooking O2 sensors, and clogging Cats......  Kinda
kills the whole idea of the valve.....

Dumping back into turbo inlet:
The misnomer here is that it helps "spin" the turbine, that has never been
confirmed.  in fact, it prolly upsets the airflow more than helping (which
accounts for minor increases in Talon list quarter mile times).  What it does
do is allow the turbo to freewheel, increasing turbo response when back on
boost.....  Closed loop means, that since the air is "measured" it should
stay that way, eliminating the "demand" for more air as the turbo
freewheels...  This should be done on anything but the all out racer.  A .3
increase in the 1/4 mile times on a 16 sec quarter is really silly.  And
increased O2 life, Catalytic converter life, both make a lot of sense to
me....

Hope this clears up the two theories, for all out racing, the atmosphere dump
is prolly valid.  For those just trying to increase turbo life, IC life, and
make a more dependable mod, put the measured air closed loop...

Scott