<VV> Vacuum Advance vs Safeguard turbo application

[kevin nash]

> 
> 
> ------------------------------
> 
> Message: 4
> Date: Fri, 22 Feb 2013 21:11:09 -0500
> From: Frank DuVal <corvairduval at cox.net>
> Subject: Re: <VV> Vacuum Advance vs Safeguard turbo application
> To: virtualvairs at corvair.org
> Message-ID: <5128253D.2010504 at cox.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 

> 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
> 
  Frank- Yes, having vacuum advance and boost retard on a turbo is extremely helpful all the way around, however, a big "trick" to getting all there is to get performance  wise with that strategy is to get the vacuum advance to "decay" properly- I would have to look at my timing map on my car to give specifics (I have a completely programable distributorless set-up), but I remember it definitely not being a straight line drop in advance- like what would happen if a standard advance unit was used coupled with a safeguard. Using the safegard for boost retard in place of the stock boost retard is an excellent idea, and when I was running a distributor on my turbo, I disabled the stock boost retard and let the safegard handle the boost retard. I did that because theres complete control over when the boost retard starts and the boost retard rate, versus the stock unit. Now, as far as using a standard advance can coupled with a safegard for boost retard goes- I believe that it could work quite nicely, and yes your throttle and acceleration responce will be much improved, but no, its not going to be like an n/a car when out of boost- it will be like a turbo car with vacuum advance, and again, for best results, the vacuum advance needs to decay much differently than it would in a n/a car, so as to get the exhaust temps somewhat correct for boost.   Kevin Nash