I thought I'd make a new thread out of this topic.

LittleRalph asked "so what's the advantage of a 009 distributor?"....

The only answer to that question is "because it's cheap".

That's it - there is NO other advantage of using a 009 on a road car.

They were originally designed for the VW industrial engines which work at relatively constant speeds (generators, pumps, air copressors) and in these applications they work just fine. And they are cheaper than vacuum distributors which helps keep the costs down).

They were also used on the earliest Kombi/buses with the 1200 engine - very low geared, and had to be driven full throttle to get anywhere before Christmas (high rpm, full throttle). But just try getting one of those heavy bodied vehicles away from the lights without the stumbles - lots of revs and clutch slip. High rpm, high power - are you seeing a pattern yet?

They also work well with VW racing engines for the same reason - always at high speed high throttle (there's that pattern again).

But they can't sense the throttle position, which of course is ALWAYS changing in a road car. The vacuum distributors do exactly this (via the changing vacuum signal and the vacuum canister on the distributor).

To get an engine to spin up smoothly, you need both a shot of fuel and a shot of advance. The accelerator pump provides a shot of fuel, and the vacuum canister on the distributor provides the shot of advance. The 009 can't throttle-sense, so you have to compensate by replacing the missing advance with MORE fuel - running the carby richer right through the rev range and having the accelerator pump set for maximum squirt.

And since the 009 doesn't even begin to advance until about 1200-1300rpm - you often get the stumbles off the line anyway.

(A lot of folks who use the 009 say "I can feel the power!" when what they are really feeling is the 009 finally begining to advance as the rpms rise over 1200 and so the power comes up to normal after a slow start - put them in a bug with a well adjusted vacuum distributor and THEN they can tell the difference).

The other advantage of the vacuum distributors is that they can allow up to 40-42 degrees max advance under the right conditions (part throttle cruising for example) and this makes for very good economy, but if you floored the throttle at medium rpm with max 40 degrees advance the engine the engine would ping like crazy. But the vacuum line senses the throttle change, backs off the advance to about 30 degrees and then gradually lets the extra advance back in as the rpm rises to match the "new" throttle position (it senses the change in vacuum as the rpm rises).

So you get economy without pinging. Since the 009 can't throttle sense, you have to set it for "worst case" of 28-32 degrees. And THAT means that for much of the time it's running at LESS the optimal amount of advance for the rpm/throttle position in use.

For all these reasons, it provides less economy than the vacuum distributors, and can cause those "flat spots" on acceleration.

But it's cheap!

Year's ago, a lot of the magazines started the "go fast" craze and recommended 009s because in fact if you are "going fast" all the time (racing) they work quite well.

And since they are a "one size fits all" you can get ANY VW engine to run reasonably well with one - means you don't have to think about different engines /carbies /vacuum signals - right?

So for all the wrong reasons, 009s are popular. But they are NOT best - by a long shot.

But they are cheap!

Have to agree with you on that one, Aussiebug - but I'll admit that it's an opinion from loving driving on the street. They do provide an advantage for full-throttle driving: ie, on the strip - but the quality of modern units (made cheaply in South America,) leaves a lot to be desired and a serious strip runner would be wise to spend the extra on a Mallory. I did successfully run one on a buggy years ago; the power to weight ratio meant the flat spot wasn't obvious and I usually ran flat out anyway (I was young and more than a little mad back then!) I actually gave away another I had bought for the Kombi, after switching back to the original - it offered no advantage (if anyone's wondering, it was the original type, with No3 retard - the guy I gave it to fitted it to another buggy.)

Oops, forgot to mention. The reasons you give for the popularity of 009s is a little cynical. Back in the 70s, almost no-one could afford larger heads, but bigger carbs were cheap (44IDFs and 48IDAs were as common as perms!) This combination meant that, with the engine capacity so easy to enlarge, limiting heads and almost no vacuum available (until the heads ran out) meant that a greater rate of advance, reaching max earlier, had some advantage. Many still use them today for the same reason with dual 2BBL carbs, but improvements in other areas have made them all but redundant for the intelligent (44IDFs can have an extra vacuum hole drilled and use an SVDA or late model dizzy.)

[Edited on 27-3-2003 by 70AutoStik]

009's are good for performance engines, if you have ever tried to run a vacuum advance on a performance / high compression motor you would know what I mean.

The shot of advance that the vacuum gives down low will make a high CR motor ping.

A 009 doesn't give it that shot and doesn't ping down low as bad as a vacuum unit because of that.

Basically, if you want stock smoothness with stock economy, use a stock vacuum dist.

If you want a performance motor you will expect worse than stock economy and the 009 will run the high performance motor better.

Also, a 009 will not cause a flat spot. If you jet your carb too lean like stock carbs are jetted (for emission purposes), you may get a flat spot. So jet it right and you'll be fine. It'll make the motor run cooler too (having jetting that isn't lean).

[Edited on 27-3-2003 by Baja Wes]

i have always used the 009,never had a problem,but i dont drive under 1300rpm very often,most vws seem to be reving most the time.but i like to cruise,i dont like driving the bug in lots of traffic.....
cheers.:beer:beer

Another reason for people using 009s on modified VW engines was that many aftermarket carbs have nowhere to hook a vacuum pipe to. So you couldn't use a stock distributor - you had to use an all-mechanical 009.

Of course you can always engineer any carbs and manifolds for a small vacuum takeoff, but it's easier (and cheaper!) to just bung a 009 on instead.

meh enough with this crap! just go EFI

already have

Rob, with dual carbs " the best choice " is to have the carbs modified to pick up vacuum and run the SVDA.
I dont know if the typical SVDA disy has as quick an advance curve as the Single springed 009's but if that actually did slow down a modified engine then you'd still be better off adjusting the advance curve on a SVDA.
.
Running a 009 is like running half a distributor.

Speaking of distributors and "vacuum advance verses non-vacuum advance" etc, my 2.0l Microbus has two vacuum lines going to the distributor (one from each carb). The engine was originally fitted with an air pump with fixed lines and stuff to pump air into the exhaust ports- anti-pollution gear. I remember there was a sticker in the engine bay (since burnt off in a fire) which said to time it at 0 degrees (i.e. tdc.), so I've always set the timing there at idle. What's the deal with these distributors ? Do they have an advantage over the "ordinary" vacuum advance units ?

Nitram,
I don't have any experience with them, but they were common to on the late US bus's which had all the anti polution gear. From what I've heard they do give slightly better timing curve for the T4 motor running the anti polution gear. They are meant to sense above and below the throttle butterfly. I believe they also work in conjunction with the deceleration valve.
Andy

Has anyone tried both a 009 distributor and a vacuum advance distributor? I have read different peoples opinions about how good each is, but I don't remember reading if anyone has tried both. I want to try the vac type as I want more low down torque to turn the larger rear wheels in my Manx. I tried Micks motors and they didn't seem to think that the vacuum type would give me any differance.

:cry

Steven

The vac gives you more at partial throttle, if you're driving flat out your power (hence torque) will depend a lot more on how well matched your centrifugal advance is matched to your engine.

I probally should have mentioned that my buggy's engine (1600 Twin port), doesn't really start pulling hard below 1600 RPM. Then it's almost like turning on a switch, at 2000 RPM it seems like it's up to full power. This behavior is why I thought that the vacuum distributor might be a good idea.



Steven

hi manxed,

I have tried both on my stock 1500. But first let me say that i am a rank beginner:

It seems there are two opposing camps with regards to vacuum/centrigal advance distributers. One side swears by the 009, the other side says chuck them in the bin....very confusing.....my 1500 had the stock vacuum one, but i bought a spare motor which had a 009 on it. So I swapped them over to see the difference.

I have to say the difference was almost indiscernabe...if anything the 009 seemed to run a bit sweeter, and it seemed to have a little more power around the middle of the rev range, but not much.

That being said the fellows here on the forum point out that with the pict 34 carbies with a 009, you get a flat spot which is very difficult to cure. Not a problem on my 1500 though.

just my very limited experience

cheers
wayne

[Edited on 7-5-2003 by slowbug]

Ive had both if your engine is stock like mine the vacuum advance is better,but theres not much in it unless you need that extra 1hp for the next dyno day.

if your going to try using full throttle at 1000rpm offroading you will find a vacuum advance distributor will make your engine more prone to knocking.

I explained the advantages and disadvantages of both distributors in the last post.

Hi guys
I have a 77, 2ltr, it originally had a air injection pump, but I have removed the pump and all the plumbing, and am now running a single carb with the original vac dizzy with the two vacum ports, there is only one vacum take off on the manifold, witch I have used to connect to the dizzy.
What should I do with the other dizzy port, plug it or just leave it open?
thanks Rob

At Full throttle the vacuum signal to the distributor should be too low to produce advance, so you are left with whatever the centrifugal advance gives you.
The advantage of the vacuum advance is only on part throttle acceleration or cruising.
Full throttle should produce no extra vac advance and hence no extra pinging.
Jeff

Kudos to slowbug: Maybe you're a beginner, but it sounds like you've learnt to listen to your engines and experiment (and, fortunately, your experience lines up with theory.)

Robo: It doesn't matter much what you do with the other port, if it's not seeing any vacuum it won't do anything (but plugging it will prevent corrosion.) Personally, I recommend fitting an earlier, single vacuum dizzy.

Manxed: The port for the vacuum for advance is drawn from the lower part of the carb (just above the butterfly when closed.) The port just below the narrowest part of the venturi is used for retard (on dual vacuum dizzies) or to trigger the valve on an auto.

No, the "pinging" referred to by Wes is due to too much total advance caused by the static advance setting. It sounds a little complicated, but the initial (or static) advance usually ends up a little less with a 009, if used on a less than wild cam; but a properly calibrated dizzy is beyond the scope (and price-range) of most of us.

Ok this is how it works as I understand.
at idle, the vac port is above the throttle butterfly and receives no vacuum and hence produces no advance.
Crack the throttle open and the butterfly moves to above the vac port and exposes it to manifold vacuum. This gives maximum vacuum advance (but not max total advance since this is dependant on revs producing centrifugal advance)
Open the throttle a little more and manifold vacuum decreases because you are providing an opening to the outside atmosphere and vacuum advance decreases corespondingly.
At full throttle manifold and vacuum port vacuum are at their minimum and hence vacuum advance is nil.
So vacuum advance goes from nil at idle, jumps up when you crack the throttle and then reduces to nil as the throttle opens towards full.
Jeff

The vacuum advance port is fairly high up in the solex, well above the bottom, somewhere just below the venturi. I am not sure exactly where it goes inside the carb or if it links to other ports, as I haven’t looked at a solex for some years. I know there is no vacuum at idle, but am not sure whether it is at it’s maximum at full or part throttle.

But it doesn’t really make a difference to the problem I am describing. Before you can get to full throttle you have to use part throttle. Especially if you are going uphill at 1000rpm. Try flattening the throttle and you will find not much happens (you will bog the engine down). So you have to use part throttle first.

When I had a vac advance dizzy on my old engine (with a solex H03/31) it would knock real bad as you squeeze the throttle down (because the vacuum was advancing the timing too much) to try to get up a steep hill (or anytime accelerating really). Sometimes squeezing it past part throttle to full throttle reduced the knocking, sometimes it made it much worse. I was told I could disconnect the vacuum line and run it on the mechanical advance part only, but it didn’t work.

I went to a 009 and found it heaps better. Moving the throttle no longer induced too much low rpm advance and knocking.

That’s my experience anyway. As for will it cause your engine to knock? That depends on a lot of factors, the best way to find out is trial and error.

I would only use a vacuum advance dist if I was interested in trying to get the best economy possible, which I am not so I won’t.

wes,
I do not discount your experiences as you have described.
I do wonder however whether the vac advance dissy you were using may have had other problems such as wear or broken/weak springs. Especially since diconnecting the vacuum did not work.
A new 009 obviously beats a worn or broken original.
my kombi pulls happily uphill in 3rd from 1500rpm with a vacuum advance dissy on either full or partial throttle.(but I did replace the original)
regards
Jeff

Jeff, I am sure a vac advance works great on a standard engine, otherwise VW wouldn't have used it to start with :thumb

I have played with a number if vac dizzy's and I was certain mine was working fine. I even tried changing the number and strength of springs to change the advance curve.

If you have a vac advance dizzy, and you notice it knocking down low, try a 009 and see if the problem goes away (or at least reduces).