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Vacuum advance\retard ??
72 911, MFI. Has anyone dissconectied the vacuum advance unit by plugging the vacuum hoses. If so, what does this do. Does it cause the timing not to retard at higher rpm? And visa versa at idle? Any benefits?
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72 911 Although it is done at the moment, it will never be finished. |
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07-24-2002, 11:45 AM
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Join Date: Jan 2002
Location: Glyndon MD
Posts: 327
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My '72 T arrived with the vacuum line disconnected and plugged. I'm not sure what the goal was, since I am told this is a vacuum retard unit that works only at idle.
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David Porter Glyndon MD '72 911T Targa |
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07-24-2002, 12:16 PM
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Location: Washington
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It is a vacuum retard at idle. If you disconnect and plug the line you advance the idle timing ~5 degrees(5 degrees ATDC to TDC). That is ok and it may even idle better, although your idle rpm will increase. Best to reduce idle speed with air screws since, if you compensate by retarding the timing (turning the distributor) at idle, you also reduce the top end timing that amount.
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07-24-2002, 12:32 PM
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Location: Woodbine, Maryland USA
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Leave the line connected. It doesn't affect performance, but rather affects idle emissions. As soon as the throttles open and you move off idle, the unit stops retarding timing.
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John 1972 911T Coupe PCA- Potomac Region |
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07-24-2002, 01:03 PM
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T-Bird, my Jack Russell looks just like the picture of yours, all white with a brown head. Nickname "the white streak" at 12 yrs old he's still fast. Nice dogs!
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07-24-2002, 01:21 PM
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Location: Woodbine, Maryland USA
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Pferg
Mine's a blast. He's 4 and never runs out of energy. Jacks are not for everyone, though!
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John 1972 911T Coupe PCA- Potomac Region |
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07-24-2002, 01:48 PM
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Location: TX USA
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blu,
I doubt there is much to be gained ... and there would be a need to go thru all of the fuel injection basic settings and calibration checks and adjustments from the effect of a 10° timing change to additional advance at idle! And, bear in mind that the 911/83 RS 2.7 engine used the very same vacuum retard module ... and it didn't seem to suffer any performance penalties!
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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07-24-2002, 02:31 PM
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Thanks all. Will leave well enough alone. Car runs great as is. The only reason I ask is because I have modified the vacumm retard in my turbo saab which added amazing amounts of low end torque and less boost bounce at higher psi.
Apples and oranges... Thanks again
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72 911 Although it is done at the moment, it will never be finished. |
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07-24-2002, 03:37 PM
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Tobluforu
