Vacuum Retard
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Thread: Vacuum Retard

  1. #1
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    Default Vacuum Retard

    I do not know much about fuel injection and so I am after an explanation as to why the R17 injection distributor would have a vacuum retard when normal distributors have vacuum advance. As you can see from the photo and the graph the distributor on the left the vacuum unit pulls the plate in the opposite direction (retards the spark). The graph on the right shows the advance would be retarded.



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  2. #2
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    Default

    i thought this thread was going to be about gillard.

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    Default ??

    Hi,
    It's a puzzle to work out what the designers were smoking, er sorry thinking in those days.
    My suggestion would be pollution regs. There were lots of funny advance curves and vacumn mechanisms. Some cars had two diaphram units, both advance and retard together. Usually connected to seperate special ports in the carby or throttle body. Some tubes had temperature dependant switching. All with the aim of getting existing motors through some mandated regulations on exhaust emissions. Tested on the standard dyno test rig.
    Unleaded fuel and Cats made a lot of this sh*t redundant. Plus of course redesign of the combustion end of the engines. Hence we now breath a lot easier.

    jaahn

  4. #4
    1000+ Posts geckoeng's Avatar
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    Default Dizzy !!!

    Check direction of rotation, of each motor !!!!!
    Ray geckoeng

    Think Old, But Run Modern !!

  5. #5
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    Default

    Does it really matter?

    Those dizzys are so corroded...

    Vac retard was used to quell surging and detonation, pinking etc
    as the combination of high engine compression ratio and a crude
    (by todays standards) and slow to react during the transition from idle
    to throttle opening and enrichment of first generation injection system
    would be prone to such problems.

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    Get it?

    Just reading my own post makes me realise how easy it is to
    stuff up your own explanations.

    Bit like Labor policy statements...

    LOOKING TO THE FUTURE.... GARBAGE.....GARBAGE...

    You started it Rob 240...

  7. #7
    bob
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    Default

    G'day,

    objective is to get clean air by stuffing up the motor efficiency.....

    ....The retard was necessary to control Nitrides of Oxygen or NOx. Peak combustion chamber temperatures caused excessive NOx so retarding the timing kept the combustion from completing and getting to hot. Timing on these cars was usually set with the vacuum line disconnected and plugged. You would notice when you hooked it back up that the engine would slow down. This is because the timing was less than optimal for good running. This also caused the engine to put off more heat and consume more fuel.....
    http://georgiajag.com/Documents/Vacu...m%20Retard.htm

    cheers,
    Bob

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    Default

    May be you are right Bob but this started in a 1972 model. And there are no other attempts to save our environment on the cars with injection or the cars with carbys. Not until 1976 when they added a charcoal filter to the cars with a carby and the USA cars got a heap of "save the planet" junk added.

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    bob
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    G'day,

    could be wrong, but as I understand it, your fuel charge takes more or less the same amount of time to burn whether you are idling or cruising. Obviously, when you are cruising the amount of time provided by the mechanics of the thing is far less than when idling, so there is the need for some sort of advance mechanism - initially provided manually by the driver.

    Time moves on and we get the thing all worked out for us with mechanical advance built into the dizzy.

    Also discovered that more complete combustion and better economy could be achieved under light loading conditions by advancing the spark even more, hence vacuum advance was loaded on top of the mechanical advance. When the load was increased at the same speed the vacuum would drop, lessen the advance, and thus prevent "pinking".

    Accordingly, to vacuum retard makes no sense at all unless you are trying to control emissions.

    BTW, 60's cars here had antipollution gear in the form of PCV, no doubt other markets were far more demanding than Oz.

    cheers,
    Bob

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    Default G17

    was it not 1975 on the R17G

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    Default ?

    Quote Originally Posted by Sunroof View Post
    May be you are right Bob but this started in a 1972 model. And there are no other attempts to save our environment on the cars with injection or the cars with carbys. Not until 1976 when they added a charcoal filter to the cars with a carby and the USA cars got a heap of "save the planet" junk added.
    Hi,
    The fact that we did not get "pollution gear" fitted for quite a while after this does not mean the manufacturers were not trying to do something before. The Europeans have always tried to be proactive on lots of issues. They did not always fight the introduction of new technology like the Americans did. They took a public interest stand and looked for ways to improve before they were mandated. That does not always mean it worked out well though.

    However as a motorbike rider I can say that riding behind any old cars is really toxic and I can smell them from a "mile" away. I do not condem the advances of technology that have improved the air in our cities etc even if it means there are some down sides.
    jaahn

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