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RONIN10
Samba Member
Joined: April 30, 2007
Posts: 594
Location: Seattle, WA
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 Posted: Thu Jan 09, 2014 9:20 am Post subject: How to Identify an AFM w/o a Part No. |
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At some point in the past, I picked up this AFM from a salvage yard.
It's a 7 pin connection so I know it's a 76.5 or later, but since it's missing its black plastic cover plate, I don't know the part number. I did some searching around, but couldn't find a way to accurately identify this without cover plate. Anyone have a suggestion?
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Andrew
Oscar: 1976 Westfalia Deluxe Camper, 2.0L FI, Manual Transaxle |
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SGKent 
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Thu Jan 09, 2014 9:29 am Post subject: |
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by the cover plate only or the paper sticker on it which is long gone. It has the hex head idle so my guess, and it is a guess only, it is early like 75 or 76. Generally they will work across the years and unless you are doing a period correct resto no one will know. Use acetic acid free RTV or tape to hold the cover on. Do not use regular RTV.
FIC told me that the parts in the 018 and 020 are identical once the cover is removed. The difference between automatic and manual is in how the unit is tuned when it was built. They suspected that 018 and 020 are identical in tuning. |
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RONIN10
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Joined: April 30, 2007
Posts: 594
Location: Seattle, WA
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| Posted: Thu Jan 09, 2014 9:47 am Post subject: |
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It has a 7-pin connecter (not shown) so that should negate it being pre-76.5, correct?
And maybe more reading is in order, but what really is the difference between an 018 and 020 then, if they are interchangable? Why roll the part number if no change? Inferring from what you said above, the 020 is for automatics?
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Andrew
Oscar: 1976 Westfalia Deluxe Camper, 2.0L FI, Manual Transaxle |
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Wasted youth
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Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Thu Jan 09, 2014 11:14 am Post subject: |
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From my 1977 manual transmission bus, California emissions, chassis No. 227210XXXX with bone-stock set-up....I have two P/N shown on my sealed cover. The first is not VW, but I don't recognize the symbol. That P/N is 0 280 200 020, and below that the VW- Audi P/N is 022 906 3010. These numbers are cast into the plastic, and there is no sticker. It has the seven-pin connector allowing for the Temp. Sensor 1 to have its own terminal.
Hope that helps a little bit. |
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SGKent
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Thu Jan 09, 2014 2:08 pm Post subject: |
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| RONIN10 wrote: |
It has a 7-pin connecter (not shown) so that should negate it being pre-76.5, correct?
And maybe more reading is in order, but what really is the difference between an 018 and 020 then, if they are interchangable? Why roll the part number if no change? Inferring from what you said above, the 020 is for automatics? |
is this a why daddy question or are we going somewhere with it? |
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Wasted youth
Samba Member
Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Thu Jan 09, 2014 2:19 pm Post subject: |
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| SGKent wrote: |
| RONIN10 wrote: |
It has a 7-pin connecter (not shown) so that should negate it being pre-76.5, correct?
And maybe more reading is in order, but what really is the difference between an 018 and 020 then, if they are interchangable? Why roll the part number if no change? Inferring from what you said above, the 020 is for automatics? |
is this a why daddy question or are we going somewhere with it? |
Seems like a fairly legitimate question, Steve. He may be trying to ensure he has the correct part application. Part of this process is trying to understand what and why the differences are. You know that the values change between automatic and manual transmissions, both in stock dual carburetors and fuel injection. |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Thu Jan 09, 2014 4:13 pm Post subject: |
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| Wasted youth/adulthood wrote: |
| Seems like a fairly legitimate question, Steve. He may be trying to ensure he has the correct part application. Part of this process is trying to understand what and why the differences are. You know that the values change between automatic and manual transmissions, both in stock dual carburetors and fuel injection. |
that is what I was thinking. If it is this, Scott at German Supply posted several times on this issue before he noticed no difference in how the units performed when testing the theory of what changed. But if it is why Daddy or I want to sell it with the right label - I can't help anymore than I have already. I had a lengthy conversation with FIC one day while there on these units trying to get my bus to pass smog and the units, at least 018 and 020 are the same unless you can find the engineer(s) who designed them 40+ years ago. Assuming they were in their 40's and 50's they would be in their 80's and 90's now. Good luck with that. |
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RONIN10
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Joined: April 30, 2007
Posts: 594
Location: Seattle, WA
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| Posted: Thu Jan 09, 2014 4:33 pm Post subject: |
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| SGKent wrote: |
| Wasted youth/adulthood wrote: |
| Seems like a fairly legitimate question, Steve. He may be trying to ensure he has the correct part application. Part of this process is trying to understand what and why the differences are. You know that the values change between automatic and manual transmissions, both in stock dual carburetors and fuel injection. |
that is what I was thinking. If it is this, Scott at German Supply posted several times on this issue before he noticed no difference in how the units performed when testing the theory of what changed. But if it is why Daddy or I want to sell it with the right label - I can't help anymore than I have already. I had a lengthy conversation with FIC one day while there on these units trying to get my bus to pass smog and the units, at least 018 and 020 are the same. |
It was a legitimate question. I asked because I'd like to have a full comprehension of the differences, not just a solution to a problem.
I've looked around and seen that people have not been able to detect any performance differences between the 020 and the 018, and treat them as interchangable. I accept that as a proven solution to replacing a bad AFM. But why roll the part number then?
I trust that the part number was rolled for a legitimate reason. Knowing that the 020 and 018 perform the same likely rules out a performance based reason. Maybe the difference is simply cosmetic, a change to improve durability without changing performance, or some other subtle difference which doesn't seem to be documented anywhere I can find. That's why I ask, hoping that it's in someone's head and hasn't been put online yet. Maybe the next person down the line will benefit from this knowledge and not have to ask this question if he/she finds it here.
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Andrew
Oscar: 1976 Westfalia Deluxe Camper, 2.0L FI, Manual Transaxle |
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SGKent
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Thu Jan 09, 2014 5:14 pm Post subject: |
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| RONIN10 wrote: |
It was a legitimate question. I asked because I'd like to have a full comprehension of the differences, not just a solution to a problem.
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Not meaning any disrespect and certainly understanding because I am that way on many things. You have to grasp that these are 40 to 50 year old cars. The people who designed them are gone. There are many threads on AFM's here including one on a NOS 018 unit I tried to document as much as I could since nothing from Bosch on how they made these survives in archives we have access to. What year were you born? Let's say 1970. Imagine your father in 1971 asking why some Rochester carburetors from 1928 had a certain spring length on the idle screw and some had another. The people are gone. Even if they were not, where were you at 6pm on the 4th day of your 3rd grade and why did you choose the words you did in the third paragraph of the sentence you wrote for homework that night? The answer is not coming.
The best place to learn how the AFM works is to read the Bosch FI book by Probst. It explains the theory and evolution of the air to fuel meters Bosch built. This style was the first. |
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Wasted youth
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Joined: July 06, 2012
Posts: 5134
Location: California's Hot and Smoggy Central Valley
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| Posted: Thu Jan 09, 2014 6:18 pm Post subject: |
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| The best place to learn how the AFM works is to read the Bosch FI book by Probst. It explains the theory and evolution of the air to fuel meters Bosch built. |
Totally agree. I was hoping that by reading that section this afternoon, the differences between the two models would be discussed, but it was not mentioned near as I can tell. Nevertheless, while the Bentley has some great information about the system and the components, the Probst book is far superior in its detail, pictures and theory of many more systems than just the L-jet. The Probst book, In my opinion, is a "must have" for anyone dicking around with these ancient systems. |
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