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| - | Vacuum advance is a spark timing mechanism. It advances the timing under light load, thereby making more power and better fuel economy. It lets the timing go back to normal under heavy loads, thereby preventing [[detonation]] (pinking/pinging). | + | Vacuum advance is a spark timing mechanism. It advances the timing under light load, thereby making more power and better fuel economy. It lets the timing go back to normal under heavy loads, thereby preventing detonation (pinking/pinging). |
| = Overview = | = Overview = | ||
| This is a good system that adds both extra performance, better fuel economy, and smoothness to the driving experience. | This is a good system that adds both extra performance, better fuel economy, and smoothness to the driving experience. | ||
| - | The only downside is for high-RPM A-series racing engines, where the advance mechanism adds some mechanical instability to the spark timing of the [[Distributor]]. | + | The only downside is for high-RPM A-series racing engines, where the advance mechanism adds some mechanical instability to the spark timing of the [[Distributor]] over 8000 rpm. |
| = Connection = | = Connection = | ||
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| <br><img size=400>http://datsun1200.com/uploads/photos/245.jpg</img> | <br><img size=400>http://datsun1200.com/uploads/photos/245.jpg</img> | ||
| + | = Manifold Vacuum = | ||
| + | The stock setup is distributor connected to the carburetors ported- | ||
| + | Spark which works OK. | ||
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| [[Category:Distributor]] | [[Category:Distributor]] | ||
Revision as of 02:36, 6 May 2014
Vacuum advance is a spark timing mechanism. It advances the timing under light load, thereby making more power and better fuel economy. It lets the timing go back to normal under heavy loads, thereby preventing detonation (pinking/pinging).
Contents |
Overview
This is a good system that adds both extra performance, better fuel economy, and smoothness to the driving experience.
The only downside is for high-RPM A-series racing engines, where the advance mechanism adds some mechanical instability to the spark timing of the Distributor over 8000 rpm.
Connection
The rubber hose on the Distributor goes straight over the 'vacuum advance port' on the Carburetor. That's it.
Emission controlled vehicles have a Tee in this line for the TCVAS system. This system cuts vacuum under some conditions, lessening performance but improving pollution (less pollution).
Degrees
For a factory stock engine, including 1.5" exhaust this a typical factory advance curve:
Vacuum Advance - part D412-80 for manual transmission
For more details, see Spark Curve
Maintenance
The only maintenance is to periodically make sure the diaphragm is not leaking.
See: Vacuum Leaks
Vacuum Retard
Some newer USA engines (e.g. 1981 B310) are fitted with a vacuum retard diaphragm. This is for emission control reasons, it actually retards the spark timing. This results in improved emissions (less pollution).
Note that this does not hurt performance. It is activated via the Throttle Opener vacuum control line, so only works when Decelerating.
Vacuum Advance - To use or Not?
Yes, use it. It is good. It advances your engine. More spark = more power.
Manifold Vacuum
The stock setup is distributor connected to the carburetors ported- Spark which works OK.