Vacuum advance questions

[TulsaSpider]

Try as I might I could not get a clear pic. I am positive is says 16 (degree mark) 30'. best pic I could get..

[TulsaSpider]

So did I stump everyone?

[manoa matt]

Yes

[TulsaSpider]

Bahahaha so if it has 16 degrees it should prolly have enough advance already? Maybe I should put it up for sale? One of a kind! only $499.99!

[manoa matt]

"so if it has 16 degrees it should prolly have enough advance already?"

Prolly so. I'd set it for 4-6 deg initial advance, which would give 36-38 deg total advance.

[bradartigue]

Brad,
No misconception on my part....
Again respectfully, the vacuum advance does NOTHING under accelleration, there is NO vacuum under acceleration...thus NO advance. Plugged or unplugged, it is not going to make a diff on accel.
Keith

FIAT vacuum advance is ported; there is no vacuum at idle (closed throttle) or WOT (full open throttle). When the throttle is open vacuum increases steadily to a point then goes to nil at WOT. I don't know how to interpret your "there is no vacuum under acceleration" unless you are trying to say "there is no vacuum at WOT" - because a gauge will tell you something completely different regarding vacuum from that port under rotation of the throttle plate (which is what I call acceleration).

Plugged or unplugged makes a significant difference, too many years of cars behaving well with it and kind of sluggish without.

Same with the carburetors BTW, the position of the port is such that no vacuum exists at idle or WOT but is progressive in between.

[majicwrench]

Yes, "No vacuum under full-throttle accelleration" would have been a more accurate statement. And I was refering to your earlier statement about 0-30mph times, plugged or unplugged, it shouldn't make any difference, as there is no vaccum under full-throttle accel.
But YES, cars certainly behave better WITH a vacuum advance! They cruise better, get better mileage etc. It just doen't make any diff on accel.

[maytag]

But YES, cars certainly behave better WITH a vacuum advance! They cruise better, get better mileage etc. It just doen't make any diff on accel.

I'm still going to pick at the statement above :
LOTS of acceleration happens at hi-vacuum conditions. MOST of the acceleration we do in daily driving WILL use the vacuum advance. it is true that the wider-open the throttle, the less vacuum will exist, to the point of zero vacuum under WOT load. However, if you are accelerating under part-throttle..... you have vacuum, and ignition advance based on that.

[bradartigue]

Yes, "No vacuum under full-throttle accelleration" would have been a more accurate statement. And I was refering to your earlier statement about 0-30mph times, plugged or unplugged, it shouldn't make any difference, as there is no vaccum under full-throttle accel.
But YES, cars certainly behave better WITH a vacuum advance! They cruise better, get better mileage etc. It just doen't make any diff on accel.

But you're assuming that to get from 0-30 you'll be at WOT, why? And the vehicle absolutely generates vacuum, even at WOT, at lower speeds. There isn't a sudden binary ON or OFF to how it works. You can simply watch the advance working if you care to verify, or hook a gauge to it.

[TulsaSpider]

So Brad... What would you do? But a vacuum advance that may fail quickly or no?

[maytag]

So Brad... What would you do? But a vacuum advance that may fail quickly or no?

How about one of Mark's electronic distributors?

[bradartigue]

So Brad... What would you do? But a vacuum advance that may fail quickly or no?

I assume you meant "buy a vacuum advance..."

I'm a bit out of the loop here on the quality of these things; the last bunch I bought were all Marelli brand and worked fine. This may correlate to the last time I owned a Spider 2000 - 2002. Since then I've only owned block-mounted distributors on older cars.

So being out of the loop I'm making the assumption that the part actually works; if not, that's a different story. I'm not sure what I'd do. The electronic distributor with vacuum advance doesn't work well without the advance. I'd get it modified to all mechanical or I'd buy a Marelliplex. Barring those options doesn't someone make a decent, modern replacement (distributorless or otherwise) these days?

And another point I'll make, I'm not very interested in the later cars any more. I enjoy the very early Spiders far more - and I like to keep them relatively stock, which means a points distributor on the block in most cases.

If the part has gotten so bad it can't be used then shame on the vendors and manufacturers. If the part is available and people don't want to buy it (which contributes to cheaper parts being made) then shame on the owners. I've found the latter to be true a lot of the time!

[TulsaSpider]

Well I am finishing up a 2L motor build 4mm domed pistons, mild cam and over budget (broke)and still have more parts to buy. The word is that the replacement parts that are available fail quickly. So it appears I'll leave the distributor I have as I have been running it before the build (no vacuum can) and then go ahead and pony up the $$ for the vacuum can when I get the chance.

[majicwrench]

Brad
"... WOT, Why?" In one of your earlier posts in this thread you wrote "Note your 0-30MPH time goes down by 1/4" and yes, I assumed from that statement that you were WOT, or how would you time it with any consistancy??

Vacuum, there is no vacuum in the intake at WOT. Hook up a gauge and try it. At very very high RPM, esp if carb is undersized, you will start to get some vacuum back. I'll hook a gauge to my Subaru and report back. My Fiat still snowed into the garage. Am planning on digging it out any day, spring is coming!!! Can't wait. I did start it the other day....aahhhh.

Binary switch, nope, but pretty close. Hook up a vacuum gauge, go WOT. Gauge will slam to 0. Release throttle back to idle, gauge will slam back up.

Now I just got to figure out how to quote people with those cool yellowish boxes......
Good discussion all.
Keith

[majicwrench]

Hooked a gauge to trusty Subara. Go WOT sitting still, vacuum drops instantly to 0. On road, anything near WOT accel, vacuum 0. There is no vacuum in intake at WOT accell. Hook a gauge up and see for yourself. Even moderate, part throttle accell drops vacuum to almost nothing. Ported vacuum or not makes no diff. Vacuum does not "increase steadily to a point then goes to nil at WOT".
The only way to accel under high vacuum conditions is to be going down hill with throttle closed.
Keith