<VV> Vacuum Advance vs Safeguard turbo application

[Frank DuVal]

As far as  know, Safeguard can only retard timing. It cannot give extra 
when needed. Vacuum advance works by modifying the timing for certain 
driving conditions, and usually advances the timing, not retards it. 
When you are just coasting along, you do not need maximum advance. When 
you accelerate, then you need extra advance for the acceleration duration.

So the safeguard will not increase the timing when accelerating, it will 
only decrease the timing when a knock is detected. This means to get the 
proper timing when accelerating, you would need to have too much advance 
when coasting.

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




On 2/22/2013 6:54 PM, Robert K. Henry wrote:
> Could the SafeGuard Electronic Knock Retard box be substituted for ported
> vacuum advance in an otherwise stock turbo Corvair?
>
> Robert Henry
> '65 Corsa Convertible
> Knoxville, TN
>
> -----Original Message-----
> From: virtualvairs-bounces at corvair.org
> [mailto:virtualvairs-bounces at corvair.org] On Behalf Of FrankCB at aol.com
> Sent: Friday, February 22, 2013 2:22 PM
> To: 62vair at gmail.com; patiomatt at aol.com
> Cc: virtualvairs at corvair.org
> Subject: <VV> Vacuum Advance? Re: custom distributor curve?
>
> Removing the vacuum advance (and plugging the line  connecting it to the
> carb) might make sense to a strictly performance-oriented  Corvair, but IMHO
> is the wrong choice for any car driven in normal street  traffic.  And it's
> not simply a case of fuel consumption.  Vacuum  advance also greatly
> improves part throttle response such as accelerating from a  traffic light
> or even when changing lanes in traffic.
>      Consider the completely stock turbo Corvair that  comes with NO vacuum
> advance and only has pressure ignition  RETARD that works at rpms ABOVE 4000
> (for the 1965 and 66  models).  Driving these cars in traffic means using a
> CONSTANT FIXED  ignition timing (24 degrees BTDC) until you get above 4000
> rpm AND  achieve some boost.  When you compare the STREET driving
> performance  of the turbo Corvairs against the 140 engined cars it's no
> wonder that so  many more 140s were sold than the turbo Corvairs!
>      Adding vacuum advance to a turbo Corvair not only  produces
> significantly better fuel mileage (I got over 20% improvement) but also
> improves the throttle RESPONSE of the engine when driving in  traffic.
>      You can read more about this in my Turbocharging  Chapter 33 in the
> Corvair BASICS manual available from CORSA.
>      Frank Burkhard
>      Boonton, NJ
>