MPS Mapping, How and what info do you want? Options

[FlacaProductions]

Many of you may remember my 123 Distributor install that finally worked out.
(here: http://www.914world.com/bbs2/index.php?sho...370332&hl=)

I now have a vacuum pump and multi meter - TELL ME WHAT YOU WANT TO SEE.

Unit is an 041 and has obviously been cracked open - before my time.
It's marked with a Sharpie "74-76 2.0" which I believe is incorrect and should be for a 71-72 1.7. Maybe this accounts for the opening and potential adjustment.

Currently holds 15in pretty much indefinitely and I get 93ohms between pins 7 and 15, and 344ohms between pins 8 and 10.

All that seems pretty much right on - but it would NOT start after putting in the 123. Prior to the 123, it ran "fine" but then started running warm due to a distributor vacuum issue (more in another thread) Distributor was an 011 with a Pertronix Igniter II. Installed a "correct" 043 MPS and it fired right up and works great with the 123.

Honestly - I'm just looking to acquire some database info for the World and then move this on, so if someone wants it, just yell. I have no idea what it's worth.

[emerygt350]

I would like to see a pressure vs inductance curve. Just start at 0 and record the inductance every 2 inhg up to 25inhg.

[FlacaProductions]

Across what pins?
EDIT - ah - I found the procedure here:
https://members.rennlist.com/pbanders/manif...sure_sensor.htm

But...my meter ain't gonna cut it, is it....

[rjames]

Edited- replied before you updated your post. You need an LCR meter.

There's probably someone else closer to you, but if you feel like shipping it out to me (98133) I can measure it using the same LCR meter that Anders used and then ship it back. Probably cheaper than buying an LCR meter that you'll never use again.

[emerygt350]

True, but I don't mind a non-anders lcr, I am just interested in the shape of the curve...

[FlacaProductions]

Hey Robert @rjames - I can do that.
I'm in Los Angeles so it's not that bad.
Sending you a PM

[windforfun]

Across what pins?
EDIT - ah - I found the procedure here:
https://members.rennlist.com/pbanders/manif...sure_sensor.htm

But...my meter ain't gonna cut it, is it....

This might work. It might also be a piece of junk.

https://www.amazon.com/Proster-Multimeter-C...383068&th=1

[JamesM]

Honestly - I'm just looking to acquire some database info for the World and then move this on, so if someone wants it, just yell. I have no idea what it's worth.

Given that one has been cracked open any data gathered from it wouldn't be of much benefit as its unknown what material diaphragm was used and how it was calibrated/adjusted. Also any inductance readings are only of value at the place and time they are initially read as due to the nature of the device they will read differently in a different location and even a different day.

Ive said this before but its worth repeating. Having someone send you the numbers from their MPS will at best get you in the ballpark. The only way to get a factory adjustment on one is to have a good reference sensor on hand to clone as you are doing it.

[rjames]

Honestly - I'm just looking to acquire some database info for the World and then move this on, so if someone wants it, just yell. I have no idea what it's worth.

Given that one has been cracked open any data gathered from it wouldn't be of much benefit as its unknown what material diaphragm was used and how it was calibrated/adjusted. Also any inductance readings are only of value at the place and time they are initially read as due to the nature of the device they will read differently in a different location and even a different day.

Ive said this before but its worth repeating. Having someone send you the numbers from their MPS will at best get you in the ballpark. The only way to get a factory adjustment on one is to have a good reference sensor on hand to clone as you are doing it.

I agree that just tuning by inductance numbers doesn’t usually work, especially since one will get different numbers from different LCR meters, but different numbers on different days? I don’t think so. Numbers will vary by location, but that’s due to altitude.

I’m offering to take readings just to provide the curve because there was interest. I’m not calibrating it for his car. If Brian wants me to open it up to see what material the diaphragm is made out of I’m happy to do so, but that’s his call. I have rebuilt 2 MPS’s and calibrated 3 of them, including one that had been rebuilt by someone else and set to spec using an LCR meter which made my car run extremely rich. You really need a wideband O2 sensor to tune them correctly (which I also have installed in my car).

[JamesM]

I agree that just tuning by inductance numbers doesn’t usually work, especially since one will get different numbers from different LCR meters, but different numbers on different days? I don’t think so. Numbers will vary by location, but that’s due to altitude.

They are impacted by altitude because of the change in atmospheric pressure which can vary by location and day even at the same altitude.

[emerygt350]

I am just interested in the curve and the fact it didn't work. I don't believe the inductance numbers are really of any value.

[Superhawk996]

I am just interested in the curve and the fact it didn't work. I don't believe the inductance numbers are really of any value.

(IMG:style_emoticons/default/agree.gif)

I think the curiosity is the rough shape of the curve and whether there is some sort of characteristic that would account for the rapid change between runs and doesn’t run.

[rjames]

I agree that just tuning by inductance numbers doesn’t usually work, especially since one will get different numbers from different LCR meters, but different numbers on different days? I don’t think so. Numbers will vary by location, but that’s due to altitude.

They are impacted by altitude because of the change in atmospheric pressure which can vary by location and day even at the same altitude.

You're right- I thought about that later after I posted. Nice catch.

[FlacaProductions]

Headed north to @rjames

[Olympic 914]

I would like to see a pressure vs inductance curve. Just start at 0 and record the inductance every 2 inhg up to 25inhg.

running a decel valve set to open at 17 inhg So I didn't chart past 15

You should not be seeing 25 inhg it will shorten the life of your MPS diaphragm

But his will give you an idea of the settings that work on my engine

[emerygt350]

I pull 21 at idle. That decel, stock, should protect against anything over 24. I have a vacuum gauge in my cluster, I used it for tuning the MPS.

I will track down the curve I posted last year.

I use 25 as the max as around 24 there is no more change occuring in the mechanism. At least not in mine...

Here is what I posted last year.

I have been to the Dyno for tuning since and leaned it out with the inner screw and also leaned the WOT with the stop so this probably doesn't reflect where I am at now.

http://www.914world.com/bbs2/index.php?showtopic=367529

[rjames]

The results are in. I took readings using the same model Meterman LCR55 that Anders documented that he used for his measurements. I've adjusted Anders' measurements to reflect the altitude at my house.

As Flaca noted, his MPS has the following part #s stamped on it:
Bosch 0 280 100 041
VW 022 906 051 E

Anders' web site doesn't show an entry for x041, but does show 022 906 051 E, which on Anders' site is associated with Bosch 0 280 100 049 (designed for a '70-'73 1.7 liter).
I haven't opened up the MPS (which has been opened before) but I'm guessing that it doesn't have the spacer that's in the 2.0 liter MPS.

Flaca's MPS


Compared with Anders' readings for a 2 liter x043 MPS and a 1.7 x049 mps which matches the same VW part # on Flaca's MPS (The chart uses only the 3 inHg data points that Anders provides.)

[brant]

The diaphragm is berriliym-copper alloy
As replicated by Chris at CFR

An AFR is the only way to tune
The gasoline formulas are different than the gasoline available when the cars were built

[rjames]

The diaphragm is berriliym-copper alloy
As replicated by Chris at CFR

An AFR is the only way to tune
The gasoline formulas are different than the gasoline available when the cars were built

I fully agree that an AFR is needed to tune. An LCR meter is not needed at all if you know how to set the inner screw properly.

What I don't think we know in this case is who rebuilt this particular MPS, if the diaphragm was ever replaced, and if so, what was used? My understanding is that before Chris made the beryllium ones people had tried using other materials, or even 'patching' the original diaphragms. We also don't know if the 2.0 spacer is in it.

[brant]

The diaphragm is berriliym-copper alloy
As replicated by Chris at CFR

An AFR is the only way to tune
The gasoline formulas are different than the gasoline available when the cars were built

I fully agree that an AFR is needed to tune. An LCR meter is not needed at all if you know how to set the inner screw properly.

What I don't think we know in this case is who rebuilt this particular MPS, if the diaphragm was ever replaced, and if so, what was used? My understanding is that before Chris made the beryllium ones people had tried using other materials, or even 'patching' the original diaphragms. We also don't know if the 2.0 spacer is in it.

good points..
and I also had heard that "fuel injection corp" was using a tin or not original diaphram with different characteristics than original back in the day