Vacuum advance questions
Re: Vacuum advance questions
Matt, et all,
Here is what I have found on my spider:
11° stamped on the dizzy advance plate. (I also measured the mechanical advance using a protractor);
10° BTDC initial timing (on the crank pulley);
My vacuum advance is currently broken (new one to be ordered), but I wanted to see how much advance could be input so I measured it using a protractor centered on the dizzy shaft, and a straight pin taped to the magnetic pickup:
14° maximum possible from the vacuum advance. http://www.glocktech.net/fiat/b1.jpg
Does this mean that I will have to adjust the ball connector on the new vacuum advance rod to limit the travel to 4°
(11° * 2) + 10° + 4° = 36°
Thanks
Here is what I have found on my spider:
11° stamped on the dizzy advance plate. (I also measured the mechanical advance using a protractor);
10° BTDC initial timing (on the crank pulley);
My vacuum advance is currently broken (new one to be ordered), but I wanted to see how much advance could be input so I measured it using a protractor centered on the dizzy shaft, and a straight pin taped to the magnetic pickup:
14° maximum possible from the vacuum advance. http://www.glocktech.net/fiat/b1.jpg
Does this mean that I will have to adjust the ball connector on the new vacuum advance rod to limit the travel to 4°
(11° * 2) + 10° + 4° = 36°
Thanks
- manoa matt
- Posts: 3442
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- Your car is a: 1978 Fiat 124 Spider 1800
- Location: Honolulu, Hawaii
Re: Vacuum advance questions
Tulsa, 16 deg? are you sure? pictures?
Bill, It's good measure to adjust the white plastic connector back so there is plenty of room for the plate to advance via the linkage rod, however even though the pickup plate is capable of 14 deg of movement, and the vac advance modules available are stated as 10 and 14 deg units.
I've not done testing (but could do so, see below) to find out how much advance the vacume advance module actually gives. However just by sucking on the vacume advance module port in order to make the linkage rod move, you have to suck pretty hard to get the full travel. I doubt the engine produces enough vacume to make the vacume advance modules give the full 10/14 deg of advance.
Take a vacume gauge, hook it up to the ported vacume port on the carb and take readings of the engine vacume at idle, part throttle and wide open throttle. Now put a vacume bleeder on the vac module, simulate the vacume conditions and use the protractor to read how much advance the vacume advance module will give for the various engine conditions.
Bill, It's good measure to adjust the white plastic connector back so there is plenty of room for the plate to advance via the linkage rod, however even though the pickup plate is capable of 14 deg of movement, and the vac advance modules available are stated as 10 and 14 deg units.
I've not done testing (but could do so, see below) to find out how much advance the vacume advance module actually gives. However just by sucking on the vacume advance module port in order to make the linkage rod move, you have to suck pretty hard to get the full travel. I doubt the engine produces enough vacume to make the vacume advance modules give the full 10/14 deg of advance.
Take a vacume gauge, hook it up to the ported vacume port on the carb and take readings of the engine vacume at idle, part throttle and wide open throttle. Now put a vacume bleeder on the vac module, simulate the vacume conditions and use the protractor to read how much advance the vacume advance module will give for the various engine conditions.
-
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- Location: Carthage, MO
Re: Vacuum advance questions
With the help of matt I just completely removed my vacuum advance . I secured the pickup plate so it won't move and adjusted timing to 14* since mine is 11* dizzy.....also I think it looks a lot cleaner under the hood
By the way thanks Matt for the help
By the way thanks Matt for the help
- manoa matt
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Re: Vacuum advance questions
I am by no means a distributor/timing expert, so while doing some research for this post regarding vacume advance modules, I've come to the same conclusion the Fiat engineers did. They are there for a reason. While you can "get by" without them, your performance and fuel economy will suffer.
As an example: I'm currently running a Marelli Plex style distributor that was designed without a provision for the vac advance, its a purely mechanical advance distributor. I installed this distributor because like most owners got fed up with the high cost and frequent replacement of the vac advance module. However I find that I need to blip/feather the throttle coming off a stop in order to get the RPMs up for the weights to kick in. With a vacume advance module I would not have this problem. If I get a chance this weekend I'm going to re-install my spare dizzy with the vac advance to gauge the difference between the two setups.
I think this article sums it up nicely: http://www.type2.com/library/electrip/advance.htm
BTW Kolls, how is it working?
I've tried wrapping the vac module with header wrap and then a custom heat shield...but it only cooked it faster. Just leave it alone, have a heat shield on the exhaust manifold, and the module will last over two years of daily use.
As an example: I'm currently running a Marelli Plex style distributor that was designed without a provision for the vac advance, its a purely mechanical advance distributor. I installed this distributor because like most owners got fed up with the high cost and frequent replacement of the vac advance module. However I find that I need to blip/feather the throttle coming off a stop in order to get the RPMs up for the weights to kick in. With a vacume advance module I would not have this problem. If I get a chance this weekend I'm going to re-install my spare dizzy with the vac advance to gauge the difference between the two setups.
I think this article sums it up nicely: http://www.type2.com/library/electrip/advance.htm
BTW Kolls, how is it working?
I've tried wrapping the vac module with header wrap and then a custom heat shield...but it only cooked it faster. Just leave it alone, have a heat shield on the exhaust manifold, and the module will last over two years of daily use.
Re: Vacuum advance questions
Kolls, Do you need to blip the throttle when you pull away from a complete stop in order not to stumble or stall the engine?
Matt: yes I will try the suggested vacuum test once I get a new vacuum advance (Vick's is currently out of stock). I hope I can get the 14° one.
Matt: yes I will try the suggested vacuum test once I get a new vacuum advance (Vick's is currently out of stock). I hope I can get the 14° one.
Re: Vacuum advance questions
When checking the engine vacuum hook to a MANIFOLD vacuum port not a ported port. And the vacuum advance itself does not aid in off-idle accel, the vacuum drops when opening the throttle and thus the vacuum advance does not advance.
- bradartigue
- Posts: 2183
- Joined: Thu Sep 20, 2007 2:35 pm
- Your car is a: 1970 Sport Spider
- Location: Atlanta, GA
Re: Vacuum advance questions
It was a factory approved replacement for years and sold as a kit so people who ran cars prior to 1979 could enjoy an electronic distributor. Expensive, even then, but nice to have especially when compared to points.I installed this distributor because like most owners got fed up with the high cost and frequent replacement of the vac advance module.
Some misconceptions about the vacuum advance persist. I suggest anyone curious as to how this thing work get in a fuel injected Spider 2000 that has everything set to stock (timing, etc.) and the vacuum advance is known to be working. From a dead stop drive the car. Then, open the hood and disconnect the advance from the manifold. Now drive the car. Note your 0-30 MPH time goes down by about 1/4. Same "operation" can be tested on any car with the vac advance but the FI is most noticable because L-Jet is (a) so smooth and (b) the most potent of the stock fuel delivery systems.
I've found it to be a reliable device that results in smooth acceleration on every TC motor I've installed it on. Any of the ADF carbs and most of the DMS/DHS/DFE series have or can be easily drilled to have the correct port to drive it. Some of the IDFs even have them, I think the 70 series but it's been too long to really remember.
As far as the unreliable comments, yes, a 30+ year old paper and rubber diaphragm is likely a failure by now. Replace it and remember that exhaust manifold heat shield you threw away or your car never had? It helps protect the diaphragm.
1970 124 Spider
http://www.artigue.com/fiat
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- TulsaSpider
- Posts: 1547
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- Location: Tulsa, Ok
Re: Vacuum advance questions
Brad, Yup I am sure. the stamping is so small I doubt I could take pics. I'll try this weekend The stamping is located just north of of where the spring attaches, near the pivot point for the weights. The other thing is that from what I have learned on here only that the current diaphragms an the market are of very poor quality and fail quickly so what you are saying is you recommend doing what exactly?
1978 Spyder 1800 make that 2L! Finally making real progress!
Re: Vacuum advance questions
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
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
- maytag
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- Location: Rocky Mountains....UTAH! (Not Colorado)
Re: Vacuum advance questions
Keith:majicwrench wrote: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
Is your assumption that we're always either ON THE GAS (WOT) or ON THE BRAKE (fully-closed)?
'cuz if so: I though I was the only one who drives that way!
But I guess the point is that under normal driving, we spend a lot of time at hi-vacuum conditions, and this is when the vacuum advance helps smooth part-throttle acceleration and gas mileage.
I'm no Boy-Racer..... but if I can't take every on-ramp at TWICE the posted limit.... I'm a total failure!
Re: Vacuum advance questions
Maytag,
You are correct, that is when the vacuum advance comes into play. An early post had made mention of vacuum advance influencing 0-30mph times, and that is what I was refering too.
Full throttle......had to think for a second. Ya know, I almost NEVER full-throttle my car
Keith
You are correct, that is when the vacuum advance comes into play. An early post had made mention of vacuum advance influencing 0-30mph times, and that is what I was refering too.
Full throttle......had to think for a second. Ya know, I almost NEVER full-throttle my car
Keith
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Re: Vacuum advance questions
Matt,
My vaccum advance has not worked in awhile i just plugged the vaccum line for a temp fix. And was going to try and fix the vaccum advance by opening it up and fixing the rubber diaphram.. I am cheap i just could not bring myself to spending from 75 dollars to 90 dollars including shipping to buy a new one. no offense to the vendors..so when i took it off the plastic tab broke. so that is the real reason i did it the way i did it. But back to your question.. I have not seen any perfomance issues with taking off from a dead stop ,, no stalling or pedalling to get it to go.. gas mileage i really have not really measured it with out the vaccum advance or with it since it has not worked since i got the car. now if someone had a nonworking vaccum advance they want to get rid of i sure would like to try and first see if i could actually repair it and 2 see if it actually makes that much of a difference..
Kevin
My vaccum advance has not worked in awhile i just plugged the vaccum line for a temp fix. And was going to try and fix the vaccum advance by opening it up and fixing the rubber diaphram.. I am cheap i just could not bring myself to spending from 75 dollars to 90 dollars including shipping to buy a new one. no offense to the vendors..so when i took it off the plastic tab broke. so that is the real reason i did it the way i did it. But back to your question.. I have not seen any perfomance issues with taking off from a dead stop ,, no stalling or pedalling to get it to go.. gas mileage i really have not really measured it with out the vaccum advance or with it since it has not worked since i got the car. now if someone had a nonworking vaccum advance they want to get rid of i sure would like to try and first see if i could actually repair it and 2 see if it actually makes that much of a difference..
Kevin
- TulsaSpider
- Posts: 1547
- Joined: Tue Apr 29, 2008 7:33 pm
- Your car is a: 1978 Spyder 124 2L
- Location: Tulsa, Ok
Re: Vacuum advance questions
So who knows what my 16 degree stamp means?manoa matt wrote:If you turn it upside down and look at the plate the advance weights are mounted on you will see a post that drops down into a slot. You either need to file the slot so the post can advance more, or file down the post.
In order to do so, you need to remove the central shaft from the distributor = complete disassembly.
FYI you are not modifying the weights or springs themselves. Modifying the weights and springs controls the advance curve. You are modifying the advance limit of the distributor.
The vac module advances the plate the electronic pickup is mounted on and only works during periods of high intake vacume, ie. idle and part throttle. At wide open throttle there is not much vacume and hence not much vac advance.
It also depends on the distributor you are working on. There are two versions of the 79-85 electronic distributor. One had 22 deg of centrifugal advance and one had 28 deg. You can verify if you remove the rotor and move the weighs out of the way. the 22deg version will have 11 stamped and the 28 deg version will have 14 stamped into the advance plate.
I would not modify the 28 deg version. If you set your initial timing to 10 deg and add 28 you end up with 38 deg total advance which is plenty. If you modify the 22 deg version you only need about 4 deg more advance so your total advance is 36. Or just you set your initial advance to 14.
The Marelli Plex distributors are the same basic unit minus the vac advance. They are purely mechanical advance and 28 deg. units.
1978 Spyder 1800 make that 2L! Finally making real progress!
- TulsaSpider
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- manoa matt
- Posts: 3442
- Joined: Thu Oct 26, 2006 4:28 pm
- Your car is a: 1978 Fiat 124 Spider 1800
- Location: Honolulu, Hawaii
Re: Vacuum advance questions
Tulsa, Pictures?? Sure its not an 11 with the deg mark (o) stamped near one of the 1's?