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Registered:
June 2003
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Ignition timing on 18RGU
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Wed, 18 June 2003 15:13
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Hi, I've got an 18RGU with Weber carbies,
and the previous owner has removed the
vacuum advance. The timing at idle speed
is still correct, but I'm not sure whether
the timing is correct at higher speeds.
So my question is; is it common or useful
to remove the vacuum advance when using
aftermarket carbies? The previous owner
has done some foolish things with the electrics
so I'm not assuming there is a good reason
for this alteration, but on the other hand it
might just serve some purpose. Advice
would be appreciated,
the Plow King
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Location:
Gold Coast
Registered:
January 2003
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Re: Ignition timing on 18RGU
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Wed, 18 June 2003 21:18
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vacume advance is there for economy while cruising. It will not effect wide open throttle from any rpm because as soon as you crack the throttle the vac drops. Therefore the advance(from vac advance) will retard.
Unless you want a bit more economy and power with no load them you don't need it. I would suggest you hook it up thou(if its just a vac hose)
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Location:
Adelaide
Registered:
June 2003
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Re: Ignition timing on 18RGU
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Thu, 19 June 2003 04:58
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If the vacuum advance for dizzy is meant to be connected infront of the butterfly valve, wouldn't the vacuum become greater once the throttle has opened.
Please correct me if I'm wrong.
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Location:
Gold Coast
Registered:
January 2003
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Re: Ignition timing on 18RGU
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Thu, 19 June 2003 09:14
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vacumm is a term used regarding the air pressure between the butterfly and the valves. When the butterfly is wide open the pressure will return to almost atmospheric.
If the vacumm line for the dizzy is connected to the air filter side of the butterfly it will do nothing.
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Location:
Adelaide
Registered:
June 2003
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Re: Ignition timing on 18RGU
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Fri, 20 June 2003 03:21
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I stand corrected.
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Location:
Brisbane
Registered:
May 2002
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Re: Ignition timing on 18RGU
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Fri, 20 June 2003 03:37
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| BansheeBuzz wrote on Thu, 19 June 2003 19:14 |
vacumm is a term used regarding the air pressure between the butterfly and the valves. When the butterfly is wide open the pressure will return to almost atmospheric.
If the vacumm line for the dizzy is connected to the air filter side of the butterfly it will do nothing.
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This isn't strictly true. On many carby engines, the vac advance is hooked up before the butteryfly. Vacuum increases in proportion to engine load largely because of the venturi effect.
I'm not sure if the same applies to EFI engines, but vacuum certainly can exist before the butterfly, especially if the engine uses a flapper-type AFM.
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Location:
Nor Calif USA
Registered:
June 2002
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Re: Ignition timing on 18RGU
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Fri, 20 June 2003 03:41
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It's true on both engines
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