<VV> Need Both Re: Vacuum Advance vs Safeguard turbo application

FrankCB at aol.com FrankCB at aol.com
Fri Feb 22 23:06:21 EST 2013

    For your first statement, yes, you could increase  base timing somewhat 
and then use the SafeGuard to automatically decrease it  when necessary to 
prevent knock/pinging.  But running an engine at just a  slight bit less 
than the timing that makes pinging/knock is not necessarily the  timing that 
makes the best TORQUE for those conditions of rpm and load.S
    For your last statement, definitely YES.   Using a standard Corvair 
vacuum advance unit AND a SafeGuard would be MUCH  better than the stock turbo 
pressure retard unit only.  That is almost what  I've been running on my 
1965 Corsa except that I use a Carter EKE (engine knock  eliminator) instead of 
a SafeGuard.  And YES it would have the acceleration  response of the 
normally aspirated Corvair engines (95, 110 and 140) and still  have the safety 
of knock elimination at boosted conditions, whether high or  low.  I think 
the factory should have provided both vacuum advance AND  pressure retard on 
the turbo engines.
    There is one difficulty in adding vacuum advance to  the stock Corvair 
YH carb on the turbo engines.  Unlike the NA Corvair  Rochester carbs, the 
Corvair sidedraft YH carb has NO  open vacuum advance  port in the base of 
the carb.  In the NA carbs this port is  located UPSTREAM of the throttle 
plate when the plate is closed at idle  so the port "sees" atmospheric pressure 
and therefore NO vacuum is sent to  the vacuum advance unit at the side of 
the distributor giving NO vacuum advance  to the engine at idle speed.  Only 
when the throttle plate begins to  OPEN above idle speed does the plate move 
to the other side of the port thereby  exposing it to the intake manifold 
vacuum and thereby "sending" this vacuum to  the vacuum advance and advancing 
the timing.  Since you don't want to  have vacuum advance at idle, one way 
of solving this problem is to put an  normally closed electric solenoid 
valve in the vacuum line between the intake  manifold and the vacuum advance 
unit on the distributor.  Then use a  microswitch set up on the throttle 
linkage so that the solenoid valve stays  closed at idle but opens at speeds ABOVE 
idle to "send" vacuum to the  advance unit.
    What I chose to do was more straightforward but  more difficult to find 
the right part..Remember that the sidedraft Carter YH  carb was also used 
on UN-boosted engines like the early Corvette straight 6  cyl. and the Nash 6 
cyl engines (remember them????)  And if you look  at the YH carb you can 
see that the throttle section is a separate unit from the  rest of the carb so 
I was able to find this separate throttle section that  INCLUDED a vacuum 
advance port INSIDE the carb just upstream of the  throttle plate (this port 
is a slot about 1/8 inch by 1/32 inch).  On  the OUTSIDE of the throttle 
section is a threaded opening  connecting to the inside port.  So I just ran a 
vacuum line from this  outside connection to the vacuum advance unit on the 
side of the  distributor.  This gave me the same function that NA Corvairs  
have - NO vacuum advance at idle but vacuum advance as soon as the throttle 
is  opened above idle speed.
    I definitely recommend adding vacuum advance to the  turbo carb. since 
it not only improves off idle throttle response when driving  in traffic and 
at low/medium UNboosted speeds but also significantly  improves fuel 
mileage (mine went up over 20%).
    Frank "the other one" Burkhard
    Boonton, NJ
P.S.  Another advantage to using the SafeGuard comes if you decide to  add 
water injection to your turbo operation.  You can also get the  SafeGuard 
optional dashboard display that shows the driver WHEN and  HOW MUCH electronic 
retard is being provided at any moment.  Using  this feature can help you 
setup the water flow rate to provide sufficient water  flow for a wide range 
of operating conditions without the danger of  "flooding" the engine.       
In a message dated 2/22/2013 9:11:30 P.M. Eastern Standard Time,  
corvairduval at cox.net writes:

Oh, you  said stock turbo setup, the one without vacuum advance. Again, 
the  Safeguard does not act like a vacuum advance, but it will allow you 
to  increase base timing some and then it will decrease timing to stop 
knock  when necessary. So, no, but it might help overall.

Awaiting Bob Helt or  the other Frank to correct me!

Of course I drove my 64 Spyder  convertible for years with a vacuum 
advance unit and NO pressure retard. I  didn't know it was wrong, the 
used car it was...  If it didn't have  such low compression it might have 
hurt itself.

So my question is,  would using a standard vacuum advance unit and a 
Safeguard be better than  the pressure retard unit only? Would it have 
the acceleration response of  a normally vacuum advance engine and the 
safety of knock elimination at  high boost? Disregard the turbo lag...

Frank  DuVal

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