I brought my '74 Super Beetle to the VW shop and had new points installed, valves, timing, idle and mixture adjusted. The mechanic showed me that my distributor was advancing the spark 43 degrees at maximum rpm. He told me that for my dual vacuum 1600 engine the maximum advance should be 34 degrees and that I was overheating the engine. The only thing he could do for me was to plug the advance hose and adjust the timing to get 27 degrees maximum advance at maximum rpm.
I would be driving with a distributor with only centrifugal advance. I drove my car with a 009 but went back to a dual advance distributor. With the 009 the car couldn't go up hills. I notice that he made the timing adjustments with the retard hose still connected. Shouldn't he have removed and plugged the retard hose?
He should have plugged the advance hose before doing the all in mechanical advance test. During cruising conditions on a level surface your total advance(Mech and vacuum) should total some 44 degrees or there abouts..
The engine likes to see 28 to 34 degrees under full load and no vacuum advance..
Seems like your mechanic in charge is not fully into aircooleds..
Cruising at steady speed and very small throttle openings gives you strong vacuum at the throttle plate, where the vacuum signal for the distributor is taken. I.e. max advance.
Accelerating: At first, when you touch the pedal, you get6 a sudden rush of gasoline from the accelerator jet, to accomodate the even bigger rush of air going in. On top of that you get a strong vacuum signal just as you step on the gas pedal. Helps kick things in motion. After that, the more throttle you give, the LESS vacuum there is.
Vacuum is strong ONLY at very small throttle openings. Load or no load. It's a strict effect of air being sucked through a narrow gap between throttle plate and carburator body. Small gap, huge suction, FAST airspeed at the vacuum port. Open the throttle wide open, and the overall volume of air going in grows, but the SPEED at the vacuum port actually drops.
At cruising speeds you have very little load, and small throttle openings, so it's safe to have more ignition advance.
Contradicting terms there: under a load, vacuum indeed goes away. But cruising around at steady speed is not "under load". That's when you get the benefit of vacuum advance.
the sad thing is, you actually believe that. try doing some research, i won't do it for you. the internet is an abundance of information if you seek it out. two minutes on google and you will be back here admitting your mistakes.
I see reading in not high up on your list of things to do today. Not sure where you looked on Google... but here is one of the 1st links I found doing a JimBob oops I mean a simple search:
formatting link
Scroll down to the vacuum advance section.....
"Vacuum advance also adds tim Under a load, i.e. driving down the road, vacuum advance GOES away. and Vacuum advance only comes in when you accelerate or rev the engine in neutral.
Hmmm, let's see..... I said "under a load vacuum advance goes away" and the link said "As the throttle opening increases, load increases and manifold vacuum decreases"
Yep, I guess you're right, BOTH the link and I are wrong. Huh?
Get a long piece of vacuum hose and a vacuum gauge. Tee into your ported hose going to the vacuum advance. You do have one? Or do you still believe a 009 is the greatest thing since sliced bread? Now go drive your vehicle and watch the gauge. You may learn something.
and the link is correct, you are wrong. "under load the vacuum advance goes away" is close to accurate, however "under load, i.e. *driving down the road*, vacuum goes away" is inaccurate. "driving down the road" implies a steady cruise, which is a high vacuum state for your engine, and in turn means higher vacuum advance. do you not understand what you read or just confused on what you wrote? maybe the one crying about comprehension is too ignorant to realize they contradict themselves in their own words.
no ma'am, the link is correct, you are not. you even state that the vacuum advance only works while accellerating or reving in neutral. both are wrong. if you suddenly open the throttle in either neutral or while driving vacuum drops quickly(as stated in your copy/paste from your "reference) as does the advance the vacuum provides. so, you either don't understand the link or are so convinced you are correct that you are blinded. the link you provide to "back" you, is directly contradicting your post. it is evident to everyone. so i again must suggest you take your own advice and take mechanics 101 and to also get a vacuum guage. you may become enlightened by what you see, but you probably won't admit it. i wouldn't expect someone like you to do that.
hose going to the vacuum
thing since sliced bread?
no need, i have a vacuum guage in my Torino GT, and a Mallory Unilite in my vw(009's are for chumps that don't understand how vacuum advance works, so you probably have several) they both work the same, but neither work as you state.
This is true for some distriburtor/carb combinations and not true for others. Most of the people posting on this topic have only seen one of the types and are assuming that what they've seen accurately represents everything out there.
In the end, it depends on where the vacuum pickoff drilling in the carb is located. A few mm will make a lot of difference.
In general, very few, if any, vacuum advances actually run from what is called manifold vacuum. Instead they run from very carefully drilled ports in the side of the throttle body which give a vacuum curve which is taylored to give the response the automaker is after. The vacuum they develop is controlled by Bernoulli's principle, which means that the vacuum is controlled by the air velocity across the face of that port.
The vacuum retards that VW used in some years are similar, but they actually DO use manifold vacuum at idle, but the port is placed so that the vacuum "goes away" as soon as the throttle valve opens a tiny bit, putting the port on the high pressure side of the butterfly.
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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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