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Lars S
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Joined: October 04, 2007
Posts: 787
Location: Sweden
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 Posted: Tue Jun 14, 2022 10:11 pm Post subject: Re: Wagon progress update…getting closer! |
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| Pepperbilly wrote: |
......
My original sensor that I had stored away held vacuum for a 5 minute test but did slowly bleed down to 7 Hg. So it has a slow leak.
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The MPS rarely holds vacuum over longer time, they can still be OK, PBAnders says:
"....pull a vacuum of 10 in. Hg on the sensing port of the MPS. If a vacuum cannot be pulled or it leaks down (< 5 in. Hg in one minute), then the sensor is leaky and must be repaired....."
Since the MPS is continiously fed by vacuum (underpressure) from the plenum tiny leaks dont have any impact but they can be a sign of a minor crack in the diaphragm which by time get worse. Also the o-ring can cause a leak but over time not nessecary getting worse.
To adjust the MPS i have found that a wideband AFR sensor/meter is the most accurate way.
/Lars S
_________________
Porsche 914 -72, Bahia Red daily driver 
VW411 2-d -70, White, sold 
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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Pepperbilly
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Joined: April 08, 2017
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| Posted: Wed Jun 15, 2022 9:38 am Post subject: Re: Wagon progress update…getting closer! |
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Lars S,
I was wondering about that also. If the diaphram has only a very small leak then it should not make any difference because the vacuum from the intake plenum is constantly being produced and pressurizing the MPS while the engine is running. So, the original spare I have tested with a very small leak should be ok to use for now. But I guess it also means in the future it’s diaphram could completely fail and not hold vacuum at all.
The test I used from the PB Anders Pages was this one:
Using a hand vacuum pump, pull 20 in. HG and watch for 5 minutes. Results should not drop below 15 in. HG. Where did you read the testing procedure for 1 min?
Bill |
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Lars S
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Joined: October 04, 2007
Posts: 787
Location: Sweden
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| Posted: Wed Jun 15, 2022 10:01 am Post subject: Re: Wagon progress update…getting closer! |
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| Pepperbilly wrote: |
Lars S,
....
The test I used from the PB Anders Pages was this one:
Using a hand vacuum pump, pull 20 in. HG and watch for 5 minutes. Results should not drop below 15 in. HG. Where did you read the testing procedure for 1 min?
Bill |
I copied the text directely from PBs website...he may have written the procedure in more then one page with some differences.
Link here, look under "MPS diagnostics."
https://members.rennlist.com/pbanders/manifold_pressure_sensor.htm#MPS%20Diagnostics
We are talking about really small leaks here, far from the size where idle or running is affected.
Here is another good D-jet site, it also has a test procedure written in it.
https://jetronic.org/en/d-jetronic/55-mapsensor
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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raygreenwood
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Joined: November 24, 2008
Posts: 21533
Location: Oklahoma City
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| Posted: Wed Jun 15, 2022 12:33 pm Post subject: Re: Wagon progress update…getting closer! |
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Before this next post I need to state a couple of items up front:
First, I must state that Brad Anders is the absolute master of D-jet in most ways. He knows the inside and outside of the circuits and ECU of these systems better than anyone and his site is fantastic. I have learned much from his work and still do.
However....I disagree with a handful of items he has written about over the years...not because they are not correct by factory standards and what the diagnostics say....but because they do are not entirely supported by the reality I have seen of tuning and driving....the drivability aspect.....I have seen in D-jet engined VW's and Porsche since 1978 and over a total of close to 1 million miles.
And while I was learning and driving for numerous years I had to tune and drive almost weekly on some engines...across every weather and terrain. I have LOTS of tuning experience and probably more on the road tuning experience than most because D-jet cars have been my ONLY daily driver vehicles from 1978 to 2001 and then even more since then but not as a daily driver....and I used mine as a business car.
One period of five years with my 411 wagon and 412 covering 13 states and averaging over 1000 miles per week....I did a LOT of tuning, measuring and note taking. I learned a lot of things.
One of the first things I learned is that what is in the books for D-jet...what little there is really compared to all other EFI systems....is adequate on the "what is the function and how does it function" aspect of the system....but is extremely poor to non-existent on the tuning the system and its components for changes in the engine, ambient conditions or even general NORMAL ageing and wearing and changes in the engine and system. There just is no factory information.
The system DOES NOT...function...exactly like the engineering texts say it should in the real world. Its close....but there are too many variables to just tune it on the bench or by the book.
Too many people offer up the Probst book. Great book! I have it. Its 100% worthless for D-jet for ACTUALLY tuning the system and has no alternatives for mild wear in components other than replacing them.
Lars Said:
| Quote: |
The MPS rarely holds vacuum over longer time, they can still be OK, PBAnders says:
"....pull a vacuum of 10 in. Hg on the sensing port of the MPS. If a vacuum cannot be pulled or it leaks down (< 5 in. Hg in one minute), then the sensor is leaky and must be repaired....."
Since the MPS is continiously fed by vacuum (underpressure) from the plenum tiny leaks dont have any impact but they can be a sign of a minor crack in the diaphragm which by time get worse. Also the o-ring can cause a leak but over time not nessecary getting worse. |
This is both correct and incorrect. The testing method is excellent. But all that tells you is that the MPS is "usable"..."functional".
The problem with that statements assessment that TINY leaks have no impact is that it assumes you have no ther tiny leaks. Not very long after a 411/412 or type 3 is new..... typically by 50k miles.......you have enough wear in just the throttle body butterfly plate to qualify as a TINY leak that causes no "impact". However it slowly causes the effect that you have to tweak the idle air screw very slightly to hit exact idle. The MPS can adjust around that.
Then we have the known issue with the PCV valve. That is another not so TINY leak ...but can qualify as a TINY leak. I have found that even NOS PCV valves leak slightly when new.
Thene there is the AAR. I HAVE NOS AAR and they rarely close absolutely 100% in cold weather.
Vacuum is a stacked tolerance in these systems.
But back to my point.
This is whats important:
While a small crack in the copper diaphragm or a small leak in the MPS body o-ring does not let in enough air to cause a readable fuel mixture change...at idle.........what it DOES change is the actual RESPONSE SENSITIVITY of the MPS unit.
This changes its "tunability" AND....it changes the SPEED of response from a standing start and at throttle transitions.
This is because the copper diaphragm in these units is actually more sensitive to RATE/SPEED change than the aneroid chambers. That is actually its total function in these units as compared to the earlier A and B type units of type 3 engines.
I did enough extensive driving and testing over several years ...yes at several points with the aid of the emissions test station next to my apartment in Atlanta (and the persuasion of a $20 bill)....by testing MPS's I was driving on that had the classic small hairline crack in one sector of the copper plate at the edge.
I tuned the engine and adjusted the outer stop and main laod of my MPS and then tweaked it for best drivability I could get. It was pretty good.
That MPS leaked down slowly but passed the same test quoted here.
Then I sealed up the fine hairline crack with a needle and syringe filled with catalyzed silicone (I liberated that from work).
The MPS now passed the vacuum test. The at idle fuel mixture on the exhaust sniffer did not change.
BUT....and this is key....the off the line from a standing start performance RADICALLY improved....and I had to adjust the outer full load stop INWARD about 1/4 turn.
Why?...because the RATE of enrichment from a standing start and at throttle transitions had INCREASED because that TINY vacuum leak had been sealed.[/b][/color]
Was this point from you Lars or Brad Anders?
| Quote: |
| To adjust the MPS i have found that a wideband AFR sensor/meter is the most accurate way. |
Yes I agree...to a point. The biggest problem with using a wideband for tuning is this:
1. Its too sensitive (more on that in a minute) The numbers that the factory and dealer quote...were done at idle and with a narrow band.
They also used the classic long armored probe to get very deep into the muffler. That last part is REQUIRED if you are using a stock muffler.
2. Because of what I listed above, with a stock muffler you are troubed by the fact that oxygen gets to the probe unless you can get it very deep inside.
Even then, the wideband type of sensor typically presents you with a rapidly "oscillating" reading or target. You will chase that reading...especially if the system is very far off of normal either lean or rich...because the rich or lean condition oscillates inside of the multi-chamber muffler system. It has delays in presenting the exhaust from one bank of cylinders and the other at idle speed.
A wideband is actually more accurate on our cars with stock muffler...above about 1500-1800 rpm...where the exhaust gas replenishment rate is fast to enough to somehwat "homogenize" what the wideband is reading
Also the fact that the injectors are paired and the stock muffler system does not inject the exhaust plumes into the stock muffler in their exact pairings...and the system is not equal length....you get a "muddy-ing" of the reading with any system.
Let me tie this together:
This means that when tuning with EITHER a wide band or narrow band...at idle....you can only get so good of a tuning and reading resolution.
And...virtually all D-jet systems are known to typically be set up either slightly lean in order to prevent being overly rich in the midrange or set slightly rich to avoid being slightly lean in the midrange and at WOT (most are this way).
This means that...and I have been syaing this far a couple of decades now.....the general tuning of most D-jet systems is sloppy from the factory. This does not mean that they do not run well. Its just not ideal....AND...tuning them with the AFR meter.....typically sets your mixture to correct numbers but sacrfices "DRIVEABILITY".
My point is to FIRST adjust to just a stable baseline and then disconnect the AFR sensor and drive it and adjust it until you get rid of flat spots and transitional issues and THEN go back to check with the AFR to make sure you are not grossly lean or rich.
Pepperbilly said:
| Quote: |
| I was wondering about that also. If the diaphram has only a very small leak then it should not make any difference because the vacuum from the intake plenum is constantly being produced and pressurizing the MPS while the engine is running. So, the original spare I have tested with a very small leak should be ok to use for now. But I guess it also means in the future it’s diaphram could completely fail and not hold vacuum at all. |
Its OK to use....but as you noted...it could fail rapidly at some point. Also as I noted....it DOES change the response of the unit.
Ray |
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Lars S
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| Posted: Sun Jun 19, 2022 12:38 am Post subject: Re: Wagon progress update…getting closer! |
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Ray, agree to (most) of what you write, its hard to find a good place to put the lamda sond with a stock muffler. In the car where I have an Bursch exhaust (914) I have put the probe at the and oft the 4 to 1 collector pipe just before it enters the muffler.
When I tune a "new" MPS I first adjust it in bench with a vacuum pump and set it to my "default" curve. Then i put it in the car and run it a lot, always with a AFR-meter and also a vaccum meter in the cockpit. If there is a flat spot (often at low load steady flat road cruising) I can usually see that the AFR gets high in this (narrow) interval and also read at exactly what manifold pressure it occurs. Bench adjusting it to a richer running in that interval is the next step followed by more test running in car.
| raygreenwood wrote: |
.....
That MPS leaked down slowly but passed the same test quoted here.
Then I sealed up the fine hairline crack with a needle and syringe filled with catalyzed silicone (I liberated that from work).
The MPS now passed the vacuum test. The at idle fuel mixture on the exhaust sniffer did not change.
BUT....and this is key....the off the line from a standing start performance RADICALLY improved....and I had to adjust the outer full load stop INWARD about 1/4 turn.
Why?...because the RATE of enrichment from a standing start and at throttle transitions had INCREASED because that TINY vacuum leak had been sealed.
Ray |
Im not sure what you mean here Ray, if the manifold pressure is affected by a vacuum leak the pressure should drop (otherwise the MPS is not affected since it only reads pressure) and the engine should then run richer since low pressure represents big load = richer running required. So fixing the leak made your engine run leaner... but Im sure Im missing something here...
/Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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raygreenwood
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Joined: November 24, 2008
Posts: 21533
Location: Oklahoma City
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| Posted: Sun Jun 19, 2022 9:49 am Post subject: Re: Wagon progress update…getting closer! |
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| Lars S wrote: |
Ray, agree to (most) of what you write, its hard to find a good place to put the lamda sond with a stock muffler. In the car where I have an Bursch exhaust (914) I have put the probe at the and oft the 4 to 1 collector pipe just before it enters the muffler.
When I tune a "new" MPS I first adjust it in bench with a vacuum pump and set it to my "default" curve. Then i put it in the car and run it a lot, always with a AFR-meter and also a vaccum meter in the cockpit. If there is a flat spot (often at low load steady flat road cruising) I can usually see that the AFR gets high in this (narrow) interval and also read at exactly what manifold pressure it occurs. Bench adjusting it to a richer running in that interval is the next step followed by more test running in car.
| raygreenwood wrote: |
.....
That MPS leaked down slowly but passed the same test quoted here.
Then I sealed up the fine hairline crack with a needle and syringe filled with catalyzed silicone (I liberated that from work).
The MPS now passed the vacuum test. The at idle fuel mixture on the exhaust sniffer did not change.
BUT....and this is key....the off the line from a standing start performance RADICALLY improved....and I had to adjust the outer full load stop INWARD about 1/4 turn.
Why?...because the RATE of enrichment from a standing start and at throttle transitions had INCREASED because that TINY vacuum leak had been sealed.
Ray |
Im not sure what you mean here Ray, if the manifold pressure is affected by a vacuum leak the pressure should drop (otherwise the MPS is not affected since it only reads pressure) and the engine should then run richer since low pressure represents big load = richer running required. So fixing the leak made your engine run leaner... but Im sure Im missing something here...
/Lars S |
NOOOOOOOL....NO!  ......just so I get your attention.
The MPS does Not....not....not.....read pressure......as in POSITIVE pressure.
It is a vacuum reading unit STRICTLY. This is also true of almost all modern sensors that are called or named "MAP"....or "manifold absolute pressure" sensors. The vast majority read VACUUM.
Yes.....modern MAP sensors that range from simple diaphragm (quite rare now) to strain gauge and chip based.....ARE capable of reading "PRESSURE"....meaning positive pressure like atmospheric pressure......but most do not. Why would the engine care? Modern cars figure out external atmospheric pressure as a function of air density change....and benchmarked by vacuum pressure loss....at the MAP sensor.
Calling the MPS a pressure sensor is a little deceiving ......unless one thinks of the definition of "PRESSURE".....as the possible full range of pressure......and that is not JUST positive pressure like say...."0 to 250 psi".
Naming the MPS a "pressure sensor"....thinks of pressure across a complete range of say....30" hg of mercury drop....vacuum....up to 0 and then upwards in positive pressure.
Except.....that the MPS is not EQUIPPED to read positive pressure at any high level or in super great accuracy. This is why Porsche, some Mercedes and BMW has a seperate barometric unit that plugged in to the ECU.....that compensated for high altitude mountain driving.
The MPS does NOT read vacuum AND pressure. It reads VACUUM and the LACK OF vacuum....up to 0 and a maximum 14.696 psi....which is "one atmosphere". More on this in a minute.
The MPS adjustment and spring pressure and aneroid chamber is ONLY barely calibrated to react to basic atmospheric pressure.
This is why....it's virtually impossible without serious tweaking inside of the MPS units...
to the mainspring and initial factory armature adjustment (not the part we normallyadjust with) .....to use D-jet with a turbocharged or supercharged manifold.
They do not read pressure. They read vacuum. This is why....any vacuum leak in a D-jet system....causes ENRICHMENT and not LEAN like a carburetor or even like L-Jet injection.
This is precisely why I am working on a "how to" for adjusting the MPS.....about 75% of which is simply about how exactly the MPS works.
Back to ONE ATMOSPHERE of pressure. This is very important to understand. It's the heart of how the MPS works.
Understand.....that inside of the MPS.....the unit works in REVERSE of how many people thinks it does in their minds eye!
At standard atmospheric pressure....14.696 psi....at sea level (lets say you are at the beach doing this!)......if you remove the aneroid chamber from inside of the MPS.....and measure its thickness.....let's say it reads 13mm or about one half inch.
That is as THIN as the aneroid chamber ever going to get. Let's call that "0".
The only time this aneroid chamber is ever going to be exposed to the normal 14.696 psi of atmospheric pressure ....when the engine is running.......is when the throttle is opened all the way allowing atmospheric pressure to come inside.
At WOT.....Because this aneroid is as THIN as its ever going to be.....it has allowed the metal rod....to EXIT or slide out of the induction coil. This signals ENRICHMENT. Maximum enfichment.
But.....once the engine is running and the throttle plate is closed.....that same aneroid chamber that was 13mm thick....now swells up to about 19mm thick (not really that much....just for concept)......which drives the iron rod deeper into the induction coil....signaling LEAN.
The problem with thinking that the MPS actually measures POSITIVE pressure is that the aneroid chamber is not really capable of getting any thinner with added pressure unless it s really high added pressure.....because the atmosphere sealed up inside of the aneroid chambers.....is nearly at 1 atmosphere already.
Back to your question....fixing the copper diaphragm leak allowed my car to run leaner.....because VACUUM is what creates the lean signal.
Lack of vacuum....is what creates enrichment. A vacuum leak does not create "lower pressure,".....it creates less VACUUM.
There is no "PRESSURE" in the manifold. It is VACUUM or negative pressure. That signals LEAN. Throttle closed.
A big vacuum leak vents this vacuum pressure to "0"....which is normal atmospheric pressure....which signals maximum richness.
A small vacuum leak.....signals somewhere in between the factory maximum enrichment setting and factory maximum lean setting.
Most important to understand.....is that all of the pieces in the MPS that are capable of reacting to vacuum....are literally ONLY applying SPRING FORCE in reaction to vacuum or atmospheric pressure......against the iron rod or armature.....whose magnetic mass is being measured by the induction coil....as it slides in and out of the coil.
So the MPS as set up by the factory.....bench set.....at "0" vacuum....has a certain amount of spring pressure which holds the iron rod/armature at a certain position or certain amount of penetration of the induction coil.
The iron rod is held between two springs.
That spring pressure is generated at one end by the main coil spring in the horn shaped casting of the vacuum inlet end......and at the other end....by a combination of the aneroid chamber and the copper plate.
You will notice....that the copper plate creates virtually "0" actual spring pressure......when the engine is off and no vacuum is applied to the unit. In the "0" vacuum load condition, the copper diaphragm is pushed outward and is up against the outer full load stop.
The copper diaphragm......is only capable of creating spring load when it is being acted on by VACUUM.
The important part to remember.....is that.....the function of the copper diaphragm is NOT to crush the aneroid chamber down thinner....causing higher enrichment. It's not really capable of that. But it can lend enough force to shove the aneroid chamber harder against the iron rod....pushing it farther into the induction coil (making it leaner).....which is why there is an inner stop plate to prevent this.
The purpose of the copper diaphragm is to increase the SPEED of reaction.....the speed of movement...of the entire stack up of springs....the aneroid chamber and the iron rod. It's purpose is to get it to start moving out of the induction coil FASTER to start enrichment faster.
So.....because the copper diaphragm was leaking very slightly.....it caused it to stay flexed outward just slightly......which allows the entire spring stack up to flex outward.....which signals ENRICHMENT.
Fixing that leak did two things:
1. It allowed the copper diaphragm to fully vacuum inward at idle under maximum vacuum. Inward movement....pushes the iron rod/armature....further into the induction coil. This signals LEAN.
2. Because the copper diaphragm ....now fixed and leak free.....is pulled inward to its maximum......it now has a larger GAP between it and the outer full load stop that it can traverse .....when you open the throttle....and it rapidly flexes outward.....which increases the SPEED RATE of movement outward of the aneroid chamber and iron rod/armature......which signals enrichment.
This larger available gap to traverse....caused an initial rich spot of the line from a standing start that had to be adjusted for.
So.....just having that small vacuum leak at the copper diaphragm.....caused two points of unwanted enrichment.....one at idle (maximum vacuum) and one when leaving from a standing start.
Fixing the leak made higher vacuum which is leaner.....and allowed me to adjust the unit more accurately.
Those who say the minor copper diaphragm leak does not really affect the unit because of constant vacuum from the engine are correct in one respect.
A very small vacuum leak in the MPS at the copper diaphragm or at the main body o-ring.....are too small to affect MANFIOLD vacuum.....and are too small to affect the expansion and contraction of the aneroid/barometric chamber........but they DO/WILL affect the copper diaphragm which is MUCH more sensitive than the aneroid/barometric chamber.
This does not affect the expansion or contraction of the chambers.....it affects the POSITION of the chambers.....which because the are connected in the spring stack up to the iron rod.....affects the position of the iron rod and therefore the fuel mixture.
One last point.........sorry for the long length.and...
The MPS is not a "MAP" sensor. I wish people would quit calling it that. It does NOT read "absolute" pressure of the manifold.
It reads manifold pressure.....AND.......it reads RATE OF CHANGE....relative to atmospheric pressure.
It is a "differential" pressure sensor.
It is also NOT electronic.....per-se. It uses an electrical coil and magnetic field. It is electromechanical.....using Faradays theories.
Ray |
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Lars S
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| Posted: Sun Jun 19, 2022 10:29 am Post subject: Re: Wagon progress update…getting closer! |
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Thank you for answering Ray!
Yes, to me pressure can be both positive and negative (compared to atmosphere) and in this case, in the manifold iof a D-jet car, the pressure is of course always negative (to atmospere), no problem at all with that.
In fact the MPS is told to be quite sensitive to positive pressure, people say they have spun around with their D-jet cars on racetrack, stalled and reversed in forward gear and blown the diaphragm in the MPS....I dont know.
I did not know that the ECU reads the SPEED of the iron rod and used it for enrichment but that explains your better response after fixing the leak, thank you for explaining that!
//Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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Pepperbilly
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| Posted: Sun Jun 19, 2022 12:51 pm Post subject: Re: Wagon progress update…getting closer! |
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Hey Guys,
All this info is very important to me right now! As we speak I am trying to sort out running problems and it looks like everything is pointing to the MPS sensor. More on this later as I keep testing and tuning.
Just curious... what is the intake plenum vacuum supposed to be when at idle and the AAR closed when warmed up? I am asking this because of the vacuum bench tests done on the vacuum port of the MPS. Anders suggests to draw vacuum to 20 in HG. What can the MPS handle before stressing it too much?
Bill |
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raygreenwood
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| Posted: Sun Jun 19, 2022 1:12 pm Post subject: Re: Wagon progress update…getting closer! |
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| Lars S wrote: |
Thank you for answering Ray!
Yes, to me pressure can be both positive and negative (compared to atmosphere) and in this case, in the manifold iof a D-jet car, the pressure is of course always negative (to atmospere), no problem at all with that.
In fact the MPS is told to be quite sensitive to positive pressure, people say they have spun around with their D-jet cars on racetrack, stalled and reversed in forward gear and blown the diaphragm in the MPS....I dont know.
I did not know that the ECU reads the SPEED of the iron rod and used it for enrichment but that explains your better response after fixing the leak, thank you for explaining that!
//Lars S |
To be clear...the ECU...does not actually read the SPEED of the rod movement. The ECU is pretty quick in its decision making....once it gets the signal it needs.
What the copper diaphragm does is it causes the rod to literally move faster than the aneroid can cause it to move.
It simply gets the part that creates the signal...the iron rod....to start the process of moving...quicker than the aneroid chamber alone can.
It does not allow the iron rod to move farther than normal....it just starts the process quicker.
The copper diaphragm is an impulse movement generator.
From my experience......there are two primary ways that people blow out or crack the diaphragm in their MPS especially in sporting events on the track. Well...really three ways....two ways and a root cause condition.
1. From discussions many years ago on the STF and some on the Porsche forum, Dave Darling brought up the point that on the track...a lot of the 914 guys had issues with the iron rod rattling and causing changes to fuel mixture........keeping in mind that a lot of the tracked 914's have very stiff suspension...and are flat low cars. Going over washboard or chicanes at high speed....yes...I can see the armature rod ...even suspended in its front and rear leaf springs...suffering from inertia related movement.
That means that the same type of inertia movement could happen in the fore and aft direction...with the rod slamming rearward against the copper diaphragm....when someone goes into a violent spin on the track. Its centrifugal force.
Bearing in mind...that the diaphragm has an outer limiter stop and an inner limiter stop.....BUT...in a violent spin....the speed of movement of the iron rod could easily exceed the elasticity of the copper plate and just rip the center out of it. More on why that is very possible in a minute.
2. So...in the same conditions on the track....a violent spin.....one must look at what else is happening during that spin. The drive wheels will have obviously lost traction. The engine may over-rev.....the throttle gets dropped closed ate very high rpm....the very quick re-establishment of vacuum "could" do the same thing....ripping the center out of the vacuum diaphragm.
Conversely.....if during this "over-rev"...way over rev....you get a lot of piston blow-by that enters into the manifold through the PCV circuit at the oil breather...and it would have to be a LOT of pressure (probably more than this problem is capable of making)...sure...it could POP the diaphragm.
And conversely again....Part of this same condition...is the leaf spring valve inside of the MPS at the vacuum inlet. It is designed to modulate severe vacuum on and off and to prevent rapid oscillation of the internal vacuum components. There are a range of different strength springs and vacuum venting on this part. Its a pretty good bet that the amount of venting to this part as can be seen in the different slot and groove sizes on various MPS.....that they may not have been designed with track usage in mind....higher HP, tighter tuning, higher vacuum and more radical vacuum signature oscillation at quick throttle transitions.
That last problem is probably the most "probable" cause of when the copper plate gets blown out...which usually means it shears off all around the perimeter.
Again, more on why this is possible in a minute.
Ok....here is why a lot of this is possible. Now...I have to say this first.....I have not yet read or heard about any of the new replacement diaphragms having this issue. If that is the case....then what I am about to say,,,would fit.
The biggest problem with the copper diaphragms in these MPS...and the reason why they fail with age in the first place.....is fatigue and work hardening.
They are made of a beryllium copper alloy from what I have heard. With age and flexing, the perimeter joint where the vast majority of flex happens... work hardens and gets brittle. While its far better and long lasting than unannealed copper....it does eventually happen.
If the diaphragms are old and work hardened....any of the above could "pop" one.
BY the way...when I finish the adjusting how to....I will excerpt all of the last few posts from everyone to put them into the proper thread. Ray |
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Lars S
Samba Member
Joined: October 04, 2007
Posts: 787
Location: Sweden
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| Posted: Sun Jun 19, 2022 10:11 pm Post subject: Re: Wagon progress update…getting closer! |
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Thanks again Ray!
Agree, most of the diaphragms fail with age!
I think what the race guys means when they (sometimes) blow a MPS-diagram at a violent spin is that when the car is thrown backwards in a forward gear, the engine is forced to rotate in the wrong direction, sucking in air through the exhaust and building up a (positive) pressure in the intake system enough to crack the diaphragm.
/Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21533
Location: Oklahoma City
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| Posted: Mon Jun 20, 2022 8:02 am Post subject: Re: Wagon progress update…getting closer! |
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| Lars S wrote: |
Thanks again Ray!
Agree, most of the diaphragms fail with age!
I think what the race guys means when they (sometimes) blow a MPS-diagram at a violent spin is that when the car is thrown backwards in a forward gear, the engine is forced to rotate in the wrong direction, sucking in air through the exhaust and building up a (positive) pressure in the intake system enough to crack the diaphragm.
/Lars S |
Ooooooooh......that would be a bad day. More than just a cracked diaphragm.
Pepperbilly said:
Hey Guys,
All this info is very important to me right now! As we speak I am trying to sort out running problems and it looks like everything is pointing to the MPS sensor. More on this later as I keep testing and tuning.
Just curious... what is the intake plenum vacuum supposed to be when at idle and the AAR closed when warmed up? I am asking this because of the vacuum bench tests done on the vacuum port of the MPS. Anders suggests to draw vacuum to 20 in HG. What can the MPS handle before stressing it too much?
Good question!.......and the answer is actually part of the whole tuning issue and why the MPS ....NEEDS....tuning on most engines.
Ok.....first......in general, excessive vacuum (on the ranges an engine is capable of generating) cannot stress or damage the MPS.
Keep in mind....the copper diaphragm has an inner plate and an outer stop screw. These limit the throw or flex of the plate to not only prevent it from over enriching or over leaning of the fuel mixture....but to prevent it from breaking or buckling.
So damaging the plate by applying vacuum......can only really happen if either the inner or outer stop screw position is way out of whack or the outer stop screw is missing and it's run or driven that way for a considerable amount if time.
I should probably add that yes.....if maybe you could generate upwards to 30" hg or more...sure....you might suck the middle areas of the diaphragm far enough in to shear the inner crimping loose or the outer perimeter.
But....I can guarantee you that if you drive without the outer stop screw installed.....it will drive very badly and stall alot when you are in light to light traffic where you have a lot of shifting and starting off from lights at a standing stop.
I discovered that fact by accident....and it was a small revelation into how exactly the outer full load stop worked.
I already had pretty good knowledge and tuning under my belt....car had just been serviced abd tuned and was running great. I left on a business trip from Atlanta Georgia to a small town North of Gadsden Alabama via a stopover in Birmingham....about 300 miles each direction. Got through in-town traffic....car running super well.....got onto I-20.....drove about 2 hours to Birmingham at about 65mph steady state. Car ran super well.
Pulled off the interstate and stopped at a light. Light turns green and I feather the gas and clutch....and it stalls dead!  ......restarts easy.....feather the gas and it coughs and gets moving but I can smell the rich spot.
It drives well as long as the throttle is at steady state.
My brain is instantly thinking....problem with the TVS?....right?
So I pull over in a gas station with engine running....and pop the hood and look inside to survey.........and.....  .....the damn outer full load stop screw had literally rattled out during the two hour 65 mph+ highway drive!
Luckily it was laying in the crevice down by the engine compartment sheet metal seal.
See.....I already knew what the outer full load stop did for off the line mixture enrichment.....and I knew the importance of adjusting it and knew how many turns outward my MPS required at idle to run properly......but I had never tried to drive with it REMOVED.
I had polished the threads well so it turned very smoothly so it was easier to do the delicate adjustment. They turned TOO SMOOTHLY! The engine vibration had rattled it out.
I re-installed it....went inside the convenience store and bought a tue of super glue and put a small drop on the outside at one point and then colored it red with a sharp so I could see it.
It drove perfect again. So.....the moral of the story is that the outer full load stop adjustment is critical to off the line and shift transition.....and if it's too far turned out or missing.....it allows the copper diaphragm to extend outward too far. Too much fuel....and....that "COULD" also cause excessive fatigue and cracking.
Yes.....Brad Anders choice of 20" of vacuum is a wise choice. I am not sure if he found this was a spec somewhere or came about it through experience......but it's a pretty good maximum number....for tuning.
I will also say.....that probably a daily vacuum check with a good gauge by each owner in this forum....will show that idle vacuum is all over the place.
Because.....
1. Your engine condition and age. If your compression is low from age and wear....your vacuum will be a lower number. Like....instead of 15"hg....it might be 10-12" hg. That would make a big tuning difference. A number like that is common with a 1700 with 100k+ miles on it.
2. Your altitude may be quite different. Some altitudes above sea level of places where I have tuned my MPS.
Kansas city- +909
Atlanta- +738
Dallas- +430
Oklahoma city- +1200
Amarillo Tx- +3600
Dahlonega Ga- +1450
I can tell you that for example that the differences between Atlanta GA and Dahlonega Ga....and Oklahoma city and Dallas Tx.....both were common business trip to visit clients about every other month when I lived in both Atlanta and Dallas......were just about the limit of altitude difference (when you tuned the MPS in one city and drove to the other) where you could barely tell the difference....but you COULD tell the difference.
Going to Okc from Dallas.....the vacuum produced by the engine is slightly lower in OKC. In itself not a big deal. But with the extremes of weather in the region.....a rapid barometer drop in OKC on a business trip....meant slightly sluggish off the line and less gas mileage.
But....I spent a couple if days at textile mills in Dahlonega Ga. Got there in good weather....and a storm blew in. Barometer dropped. Car was running super rich.
So I tweaked the MPS a little to clean that up....  ...stupid! A big barometer drop is like a big artificial change in altitude. It was about the equivalent in the short term of adding an extra 1000 feet. By the time I got back to Atlanta....I was running hot and lean.
I have never seen manifold vacuum on any of my 411 or 412 or any of my type 3 or other ACVW I have worked on....at any of those places where I lived and did a lot of tuning (Atlanta, Dallas and Okc).....higher than 20" hg. Most average 15"-18" hg.
Then again I have never tuned an MPS at sea level in a beach town or above 3600 feet like the time I had to re-tweak my mps in Amarillo on a 4 day trip...because it was just annoyingly rich enough to cause off the line issues. Vacuum had been about 16-18" in Dallas and was about 11"- 13" in Amarillo.....but the altitude difference was about 2200 feet.
Ray |
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Pepperbilly
Samba Member
Joined: April 08, 2017
Posts: 978
Location: Seattle, Wa
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| Posted: Mon Jun 20, 2022 2:46 pm Post subject: Re: Wagon progress update…getting closer! |
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Thanks for your detailed response Ray!
All I can say is thank the lord I am retired now. This is all very time consuming.
Since last time I went through checking all my FI wiring at the pins with the computer disconnected. It all checked out and I have good continuity. I used Anders instructions for checking the harness. All ok here.
I finally located a proper Head Temp Sensor from an independant Porsche shop. The tests I made on it look good. I also got an original spark plug set…Bosch W175T2. They are still out there!
Now on to the diagnostics…. Remember that original backup MPS unit I checked for a good bill of health? The engine did not run well at all with this one. Well, ok WTF! So I plugged in my other one that had failed all my vacuum tests. The engine ran really well with this one. Ok now, getting somewhere.
All my basics are spot on with timing and dwell. The proper spark plugs now in. New CHTS in. The TVS properly adjusted and passes ohm meter tests. I even had the trigger points back out to reclean and inspect. They did get a bit oily from previously oiling the distirbutor shaft…my mistake.
This morning…
11:14 60 degrees F. Engine started immediately and AAR fully open. Very good and sharp throttle response. High idle at about 1600 rpms. Idle acts as it is misfiring or missing occasionally
11:18. Idle uneven but drops to about 1400 rpms.
11:23. Engine stalls, I restart it but stalls again. AAR is fully closed now. Restart engine with some throttle and it remains running at about 1000 rpms now. Throttle response is again excellent and very responsive! Idle still is somewhat uneven though. On hard acceleration black puffs of exhaust out tail pipe. Its running rich. Idle climbs to 1200 rpms.
11:32. Idle creeps up to 1400 rpms.
11:40. I readjust the idle air screw to 1000 rpms. The air screw is very adjustable and sensitive. I feel that is a really good thing!
11:45. Clearly engine is running pretty rich. I shut it down.
12:00. I restart the engine and starts quickly as before. Lumpy idle though at around 800 rpms. Again excellent throttle response willing to rev to redline. Still black rich smoke when accelerating. Shut down engine.
12:05. I go ahead and plug in the other MPS which tested good. Engine starts but terrible idle. Bad throttle response and engine will not rev to over 2500 rpms. Clearly, this MPS is not working…interesting
I went ahead and pulled the plugs. Yep, she’s running rich. Take a look at the photos
All this testing has been done with the car on the lift. It’s not ready to be driven yet. What makes things even more interesting is I have run out of gas twice now  My sender ain’t in the tank yet.
Bill
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21533
Location: Oklahoma City
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| Posted: Mon Jun 20, 2022 4:39 pm Post subject: Re: Wagon progress update…getting closer! |
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Pepperbilly said:
| Quote: |
I finally located a proper Head Temp Sensor from an independent Porsche shop. The tests I made on it look good. I also got an original spark plug set…Bosch W175T2. They are still out there! |
While that is the stock plug and is ok with the stock coil, I have always had issues with getting that plug...which is the W7C....to run perfectly clean. There are better plugs out there. Its not the problem right now...but just thought I should mention it.
| Quote: |
Now on to the diagnostics…. Remember that original backup MPS unit I checked for a good bill of health? The engine did not run well at all with this one. Well, ok WTF! So I plugged in my other one that had failed all my vacuum tests. The engine ran really well with this one. Ok now, getting somewhere.
All my basics are spot on with timing and dwell. The proper spark plugs now in. New CHTS in. The TVS properly adjusted and passes ohm meter tests. I even had the trigger points back out to reclean and inspect. They did get a bit oily from previously oiling the distirbutor shaft…my mistake. |
This all sounds good....just a note for clarity. When adjusting the TVS...be sure you understand that the only setting you need to use on your VOM is continuity right?
I say this because there are a couple of books out there that instruct you to read ohms....which has no bearing in the operation. All that is looking for is if you have a TVS that is very dirty and has corrosion.
WE have had long conversations in the STF and in the Samba where people got hung up testing for ohms and missed getting spot on adjustment and even others who have discarded parts because their ohm readings were slightly high.
| Quote: |
This morning…
11:14 60 degrees F. Engine started immediately and AAR fully open. Very good and sharp throttle response. High idle at about 1600 rpms. Idle acts as it is misfiring or missing occasionally
11:18. Idle uneven but drops to about 1400 rpms. |
So.... when the AAR is open, you really should not get HIGH rpms. You should get slightly elevated rpms. If your idle is supposed to be at 800 rpm, you should maybe get 1000 rpm or 1100 tops. What this is indicating (as you already know) is that you have excessive fuel in the BASELINE fuel mixture.
The added air from the open AAR is not only causing the MPS to enrich....its adding the missing air that is needed to create what is essentially and "open throttle" response...which is high rpm.
In proper operation...if fuel pressure is correct...and the baseline fuel mixture setting of the MPS is correct...you should be getting just a little bit of extra enrichment for cold starting. That means that when the AAR is open...it should be giving just that little bit of extra air to use with that extra fuel.
| Quote: |
11:23. Engine stalls, I restart it but stalls again. AAR is fully closed now. Restart engine with some throttle and it remains running at about 1000 rpms now. Throttle response is again excellent and very responsive! Idle still is somewhat uneven though. On hard acceleration black puffs of exhaust out tail pipe. Its running rich. Idle climbs to 1200 rpms.
11:32. Idle creeps up to 1400 rpms.
11:40. I readjust the idle air screw to 1000 rpms. The air screw is very adjustable and sensitive. I feel that is a really good thing! |
The uneven idle, the stalling and then the subsequent higher rpm/acceleration are...yes...its rich and also because by this time the ports are wet and its scavenging fuel.
The fact that the idle screw is still responsive is another confirmation of being rich...but not hideously rich. Any extra air you can add in to mix with the excessive fuel gives a response.
When the mixture is very excessively lean...turning the idle screw outward does nothing because it already has more air than it can use. Turning it inward does nothing either because its other sources of air are already larger than what the idle screw can supply.
Likewise if its very excessively rich....the idle screw can become unresponsive because turning it outward cannot add a significant enough amount of air to lean out the excessive fuel. Turning it in will be unresponsive because there is so much fuel that the small amount of air the idle screw bypasses is insignificant. Usually in that last case...it does not remain running long before it floods.
You have neither of these conditions yet.....which probably means that the overall...main load mixture of the MPS is fairly close to where it should be.
This is the MPS with a leaking diaphragm right? A very small leak right? Even if its the o-ring leaking...or is leaking vacuum around the pins of the plug....it can cause what I am about to describe.
The conversation we were having last week....Brad Anders and others have noted that a small SLOW leak does not cause an issue in the face of constant high level vacuum. I noted that this ONLY means that the unit is "functional" and will generally operate. Yes you can use it....but it DOES have this issue.
A small, slow vacuum leak...I agree...is not large enough to affect the "MAIN" fuel mixture at the MPS. By this I mean....it is not enough of a vacuum leak (in the face of constant manifold vacuum)....to cause the aneroid barometric chambers to expand or contract...which is what moves the armature rod and causes the MPS to enrich or lean out the mixture.
BUT.....it is enough of a vacuum change.....especially at relatively low rpms...to cause the copper diaphragm to slowly flex outward as vacuum drops. When this happens and rpm rises....you get higher constant vacuum. This sucks the copper diaphragm back inward.
Understand that the copper diaphragm is a SPRING...that is operated/driven by vacuum. When its sucked in...it applies SOME spring force to the aneroid chambers...pushing them inward a very minute amount...which pushes teh armature into the coil a very minute amount....causing it to lean out.
When it flexes outward as vacuum leaks away through a crack or a bad seal around the edge...or even from a leaky o-ring on one of the adjusting screws or the main o-ring on the MPS body.... this takes the spring load off of the aneroid chambers...causing the armature rod to move outward minutely...causing it to enrich the mixture.
While this spring pressure is ONE of the functions of the copper diaphragm....its main function as I noted to Lars....is as a SPEED of enrichment multiplier. Right now...its slowly oscillating in and from a small vacuum leak. When you open the throttle and cause a LARGE vacuum leak....this plate flexes outward (again releasing the spring force its creating)....at a very high rate of speed.....allowing QUICK enrichment for getting away from a standing stop or shift points.
| Quote: |
11:45. Clearly engine is running pretty rich. I shut it down.
12:00. I restart the engine and starts quickly as before. Lumpy idle though at around 800 rpms. Again excellent throttle response willing to rev to redline. Still black rich smoke when accelerating. Shut down engine.
12:05. I go ahead and plug in the other MPS which tested good. Engine starts but terrible idle. Bad throttle response and engine will not rev to over 2500 rpms. Clearly, this MPS is not working…interesting |
That puff of black smoke when you rev it....is the off the line enrichment function from two parts....the copper diaphragm causing quick enrichment...and the contacts in the TVS. As the wiper arm pass over each line in the two tracks in the TVS...it causes the pair of injectors on that channel which are already not injecting at that particular millisecond...to inject out of time. Extra enrichment.
Now...plugging in the MPS that does not have a vacuum leak....and it will not rev. You note it has bad idle and will not rev....but can you tell if its rich or lean?
And....has the outer 13mm round plug had its epoxy removed? That question goes for both MPS.
Also.....does the tested good MPS have rivets holding it together or screws? That question goes for both MPS.
What you describe on the second MPS...sounds like one of two things. Either the main load mixture screw is improperly adjusted...its running excessively rich or lean.....or....and this is an even more likely cause.....if the epoxy on the outer full load stop screw has been removed.....this "effect" happens when the outer full load stop screw has been turned in too far. It does not allow the copper plate to flex outward....which does not allow both releasing the spring pressure on the aneroid chambers to allow them to move toward "enrich".... and...just as importantly it does not allow it to flex outward to accelerate the start of enrichment.
And...even if the epoxy is undisturbed...there are a fair portion of Porsche and Mercedes people...who prefer to open the unit at the four screws and make adjustments from the inside with a small 6mm wrench. Its adjustment can still be off.
Take a couple of pictures...one of each MPS from teh back side opposite the vacuum line.
Ray |
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Pepperbilly
Samba Member
Joined: April 08, 2017
Posts: 978
Location: Seattle, Wa
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| Posted: Mon Jun 20, 2022 5:18 pm Post subject: Re: Wagon progress update…getting closer! |
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Ray,
You have misunderstood my descriptions. The first series of tests running the engine UNTIL 12:05 were all done with the MPS that failed to hold any vacuum at all, although the resistance readings on the terminals were in range. This is the crazy thing. The MPS that held vacuum with only a tiny leak down and also checked out ok resistance wise that I plugged in at 12:05 did not work at all...no way could I adjust engine basics to make it run right. Both these MAS units are still original with rivets and epoxy as they came from the factory. I will post their photos later.
The TVS was cleaned on the bench and passed the continuity test a while ago. Testing gave the 10 deflections on the meter when rotating the shaft.
So to sum it up...the MPS that I lastly plugged in which was supposedly OK did not work at all. I know this is telling us something...but what?
Bill |
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Pepperbilly
Samba Member
Joined: April 08, 2017
Posts: 978
Location: Seattle, Wa
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| Posted: Mon Jun 20, 2022 5:55 pm Post subject: Re: Wagon progress update…getting closer! |
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Here are the photos comparing the two. The one with the darker epoxy is the original that came with the car. The lighter epoxy is the replacement installed in the early 1990’s. I noticed it has fewer numbers stamped on it. Neither one of these have ever been tampered with, although the 2nd one may have been a refurbished unit…not sure.
Bill
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21533
Location: Oklahoma City
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| Posted: Mon Jun 20, 2022 7:43 pm Post subject: Re: Wagon progress update…getting closer! |
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| Pepperbilly wrote: |
Ray,
You have misunderstood my descriptions. The first series of tests running the engine UNTIL 12:05 were all done with the MPS that failed to hold any vacuum at all, although the resistance readings on the terminals were in range. This is the crazy thing. The MPS that held vacuum with only a tiny leak down and also checked out ok resistance wise that I plugged in at 12:05 did not work at all...no way could I adjust engine basics to make it run right. Both these MAS units are still original with rivets and epoxy as they came from the factory. I will post their photos later.
The TVS was cleaned on the bench and passed the continuity test a while ago. Testing gave the 10 deflections on the meter when rotating the shaft.
So to sum it up...the MPS that I lastly plugged in which was supposedly OK did not work at all. I know this is telling us something...but what?
Bill |
Ok....got it. And your TVS testing sounds good but be sure its adjusted right. Look at my MPS adjusting how to....but that should not be the big issue right now.
As for your excellent pictures....
On one hand they "look" to be untampered with. Note that in your 5th picture down, the MPS on the right...the newer looking one...has an inspectors number stamped on the rivet. The other one should have one too. Its not anything special but definitely denotes they are not rebuilds.
Ok....the one with the tiny vacuum leak that you say "does not operate at all"....which I will suggest that it probably does....just not fully or correctly.
The location of that tiny vacuum leak will/could be significant.
So...with your hand pump connected to it....draw a vacuum and plug the two holes near the epoxy plug in the back end with something like Silly putty. If it stops the leak, then you have a cracked copper diaphragm at worst or a leaking outer diaphragm gasket at best.
Either way...a good candidate for a diaphragm kit.
If that does not fix the slow leak down....wrap the seam between the two halves with electrical tape after you clean it well. If that stops it...its a simple fix.
If thats not the leak, take some motor oil on a pin or needle and drip a little around the plastic plug and down into the plug socket. Check again. If this is the leak...its a little harder to fix but very fixable. It also rare.
Do not use silicone oil. Its a dielectric and will be hell to get off of the pins.
All three of these repairs mean you need to take the unit apart but its not a big deal.
Test both units this way.
So of the two main possible leakage points (copper diaphragm or case gasket)...which one would be most likely to cause teh issue you found with your "small leak" MPS?
Well....the copper diaphragm leak would cause the most havoc to the mixture on revving it up. But, usually it does not completely cause lack of being able to rev all the way up. It does not control that function. The aneroid chambers do.
So....a badly leaking gasket on the main body can cause this problem with the aneroid chambers. So its possible that the leak is bigger than the hand pump can demonstrate.
Bear in mind that the MPS does not see "constant" smooth vacuum. It sees oscillating vacuum. Tee a GOOG vacuum gauge at the MPS vacuum hose and you will see that the vacuum reading ...the gauge needle...is not steady at idle. It rattles. There are impulses.
I have seen numerous MPS that had "slight" leaks when tested....but when connected to the rougher vacuum of the engine...they leaked alot...most especially once they got hot.
But a couple of other things to check. Having opened a lot of MPS over the years.....any of them that have driven serious miles with an oil bath air cleaner....have oil puddled inside them from oil and fuel vapor condensation. When it gets deep enough it can make them sticky
Also...take a 3-4mm Allen key and slowly push it into the vacuum nipple until you contact something. Then push it about 2mm more and see if it moves and then returns under spring pressure. You are checking that the flap valve is moveable and not stuck down by sludge or rust.
Also on the one with only a small leak...connect it to the engine, start the engine...and with a flashlight look through one of the two vent holes in the back cap. When you crack the throttle open ...if you do not see the copper plate move outward....thats the issue. Thats where your leak is.
Also make sure those vent holes are open. Ray |
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Pepperbilly
Samba Member
Joined: April 08, 2017
Posts: 978
Location: Seattle, Wa
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| Posted: Mon Jun 20, 2022 9:26 pm Post subject: Re: Wagon progress update…getting closer! |
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Ray,
Thanks for all the tips... will be checking this stuff during the week.
Yeah, I was wondering why one sensor had both VW and Bosch part numbers and the other only a Bosch number. I remember buying the 2nd one from a VW dealer back in the '90s. Also, can't imagine any oil build up in the suction port because this wagon had the paper air filter.
Bill |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21533
Location: Oklahoma City
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| Posted: Mon Jun 20, 2022 10:29 pm Post subject: Re: Wagon progress update…getting closer! |
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| Pepperbilly wrote: |
Ray,
Thanks for all the tips... will be checking this stuff during the week.
Yeah, I was wondering why one sensor had both VW and Bosch part numbers and the other only a Bosch number. I remember buying the 2nd one from a VW dealer back in the '90s. Also, can't imagine any oil build up in the suction port because this wagon had the paper air filter.
Bill |
THAT...is interesting....the paper filter part. I have seen very few. I have one for mine. It came with an oil bath.
Good. That takes that issue out of the equation. It can still get a little fuel condensation or water....which can cause rust. Typically though the internal anti-rust build quality is good.
Ray |
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Lars S
Samba Member
Joined: October 04, 2007
Posts: 787
Location: Sweden
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| Posted: Mon Jun 20, 2022 10:40 pm Post subject: Re: Wagon progress update…getting closer! |
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| Pepperbilly wrote: |
Ray,
....Also, can't imagine any oil build up in the suction port because this wagon had the paper air filter.
Bill |
From model year 73 and on all 412 had paper filter (did they not... )
Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21533
Location: Oklahoma City
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| Posted: Tue Jun 21, 2022 7:24 am Post subject: Re: Wagon progress update…getting closer! |
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| Lars S wrote: |
| Pepperbilly wrote: |
Ray,
....Also, can't imagine any oil build up in the suction port because this wagon had the paper air filter.
Bill |
From model year 73 and on all 412 had paper filter (did they not... )
Lars S |
Thats what the "book" says. In the USA I think the reality was a little fuzzy depending on actual model.
This is the reason why I am interested.
Reality seems to follow what the books say...a little loosely in the USA sometimes. The ROUND paper element air cleaner is kind of a hard part to find here.
The two doors with 004 four speed transmission.... here.... were direct imports....not a US model...Gray market only. Of the handful of two doors I have seen all but two had oil bath filters. Thats to be expected kind of because the two doors at least those that came here were all D-jet even through 1974.
One of the two doors was a 1974 model...still with D-jet...and it had a round paper filter. The other was a very late 1973 with a paper filter.
On the rest of the 1973 I have seen...all US models with automatic...four-doors and wagons.....it seems like the early 1973 within the first few months of model change date (like September and October)....could have easily came with oil bath. Most of the 412 I have seen that were not 1974 specific with L-jet and aluminum bumpers...have had oil bath air filters.
Of course all of the 1974 with L-jet had the square paper filter.
I "think" its "possible"......some of this "bleed over" in equipment.....may have been caused by a kind of obscure import rule I read about years ago regarding the policy that the date/model of imported cars at specific port(s) was changed to reflect not so much when it was built but when it was shipped or arrived in port.
There was also some blurry-ness to some of the super beetle equipment around this point in time in the US with regard to a newer model year having some equipment from an earlier model year ...like some standard beetle equipment bleeding over into the "super" era.
The parts book Copy I have is dated August of 1972 and earlier. It shows silhouettes of both the 411 and 412 cars in the front so it "should" cover early 1973 at least.
There are four air cleaner part numbers. The newest part # showing "FROM" engine W/EA August of 1972....is 022 129 607 H....and it iS the round paper filter...here is mine:
....but it did not come with the car.
Again my car was originally delivered and picked up in Frankfurt Germany and a couple years later was shipped out of Oslo Norway.
That leads me to two more "possible' reasons why I "THINK" the round paper filter is kind of rare here.
1. This was basically an emissions filter. The oil bath filters already gave issues with emissions testing in the US. This may go back to the port of delivery as for sure the California vehicles would be the first to demand paper filters.
2. As I came across plastic round air filter bodies over the years in salvage yards and in parts stashes at repair shops...and they were rare to come by.....a good portion of them were either warped to the point where they could not function on the lower half or were outright cracked.
This happens due to a combination of heat...but mainly from overtightening the screw WITH added heat.
Its possible that a great many of the plastic round ones just did not survive and the owners of the 1973 cars simply went back to the oil bath filters which are readily available at salvage yards.
Ray |
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