[T3] MPS calibration

Tue Jan 4 13:38:58 PST 2011

Is the inner screw the one you should not touch?
I'm not doing this procedure, I was just curious.

 - Bryon

On Sun, Jan 2, 2011 at 3:21 PM, Keith Park <topnotch at nycap.rr.com> wrote:

> Ahh... well, now you have touched that inner stop adjustment your totally
> Boned.
>
> First off, you cant really adjust these with inductance reading except to
> get in the ball park, and you NEVER want to touch that inner stop
> adjustment
> as its made for a particular unit to keep your car from spiking too lean
> under certain light throttle conditions because If you do you can burn up
> the engine on the highway. 1/16 turn makes the difference between right and
> spiking too lean....
>
> You start by prepping the unit for adjustment and that means epoxying the
> inner stop adjustment in place so you can adjust the main mixture without
> touching the inner stop adjustment.  You must also realize that that cap
> screw is actually an outer stop adjustment for full throttle enrichment and
> is CRITICAL for the longevity of the diaphragm and engine.
>
> The only way to truly get it right is mount a wideband O2 sensor in the
> correct location (right side end of muffler)and start the process... get
> the
> main mixture right, then make sure the inner stop doesn't let you lean out
> more than say 15 or so, then the outer adjustment and yes, they all
> interact
> with each other and it's a long process and totally dependant  on
> everything
> else in the system being in PERFECT condition.
>
> I have the adjustment dimensions for a stock 007 miked out, they will get
> you started, but you need the AFR meter to get it right and yes, you can be
> wrong and everything will seem fine till you have a hole in #3 on a hot day
> pulling a long hill.
>
> I went thru all this on setting up my 2056 and when I put the stock motor
> back in I was amazed at how much better I could get it running by tweaking
> out the stock pressure sensor with that AFR in place.
>
> There is a PhD stickey on this on the Samba, read thru it all... its really
> enlightening.
>
> Keith
>
>
> Top Notch Restorations
> topnotch at nycap.rr.com
> http://www.a383ina68.addr.com/radiorest/main.htm
> 71 Squareback "Hothe"
> 65 Notchback "El Baja Rojo"
> 65 Squareback "Eggcrate"
> 87 golf "Winterat"
> 93 RX7 "Redstur"
>
>
> -----Original Message-----
> From: type3-vwtype3.org-bounces at lists.vwtype3.org
> [mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Bryon
> Garvin
> Sent: Sunday, January 02, 2011 4:04 PM
> To: type3 at vwtype3.org
> Subject: Re: [T3] MPS calibration
>
> Hi all -
>
> Well my friend showed up today to take the inductance readings from my PS
> and then attempted to adjust his so that they match.  His '71 Fastback
> MT/FI
> has not been running all that well.  It died on a long trip and a pressure
> sensor from a late 60's model was installed at a shop and got him running
> again....but not great.  He limped home and has been trying to figure it
> all
> out ever since.  Because the "C" sensor would no longer run his car, and
> the
> one the shop put in did allow him to drive, he started by looking at the
> sensor.
>
> He came today and we pulled MY working sensor (we both have 71 Fastbacks
> MT/FI).  First thing we did was use an inductance meter to measure the
> values on both inner and outer pins at zero vacuum.  We then used a hand
> vacuum pump to take readings again at 4 inHg and 15 inHg.  We were
> following
> the instructions on this site:
>
>
> http://members.rennlist.com/pbanders/manifold_pressure_sensor.htm#Adjustment
> s
>
> We then took HIS sensor and removed the screw.  With me holding the
> inductance meter probes on the pins, he turned the inner and outer screws
> and made the values match what my PS readings were.  When we were done, his
> values were exactly like mine.  It took some time as each screw affected
> the
> other and we had to go back and forth.  This brings me to something Jim
> said
> one time and I wanted to ask you, Jim, what you meant:
>
> ".... the 3 adjustments will have to be done in some particular order to
> work.
> The problem is that the adjustments affect each other, so I need a
> proceedure that gets it right in a finite amount of time."
>
> Now that I have tried to do this, why does it all have to happen in a
> finite
> amount of time?  I don't understand that.  Can you elaborate?
>
> We put the sensor in his car, and well....it didn't run the car.  It barely
> started and it sure didn't idle.  So he went home with the newly "tuned"
> sensor in his hand wondering why it all didn't work.  I'm no help!  I was
> just watching and helping take readings.  So, he's kind of back to square
> one.
>
> But I did want to post our procedure and results for anyone that was
> interested.  And Jim I'd love to hear your thoughts on what we did and why
> it didn't seem to work.
>
> One other note of interest....I have 3 "C" sensors that are on my shelf.
>  Since Larry was here with his measuring equipment I figured I'd put them
> thru the tests and see what the values were.  Months ago, they all seemed
> to
> hold vacuum when I sucked on them with a new piece of hose.  One of them
> clearly was worse-off than I thought.  With a hand pump, we applied 15 inHg
> and it slowly dropped in a matter of 8-10 seconds back to zero.  But the
> other two held strong.
>
> Out of the 2 that DID hold vacuum, one had inductance values nearly
> identical to the values of the working sensor in my car.  The 2nd one had
> values that were nearly HALF of what the unit in the car read.  So, what
> does this mean?  I have no idea :)
>
> Anyway, our findings are in this spreadsheet if anyone wants to take a
> look:
>
>
>
> https://spreadsheets.google.com/ccc?key=0AmRobzkiJkYhdGx1aVF3TXpHV2xoaEVFS21
> oZlZpSnc&hl=en&authkey=CJucx48O
>
> Thanks,
>
>  - Bryon, '71 Fastback
>
>
> On Tue, Dec 28, 2010 at 8:01 PM, Bryon Garvin
> <spinningrooves at gmail.com>wrote:
>
> > Hi all -
> >
> > I'm trying to help a friend who wants to attempt calibrating his MPS.  He
> > believes that his needs adjusting even though it holds vacuum.  He is
> > consulting this website:
>
> http://members.rennlist.com/pbanders/manifold_pressure_sensor.htm#Calibratio
> n
> >
> Curves<
> http://members.rennlist.com/pbanders/manifold_pressure_sensor.htm#Cal
> ibration+Curves>
> >
> > He's got a 71 sensor (Bosch 0 280 100 007) which is not listed here and
> I'm
> > asking to see if anyone happens to have the data for this sensor, like is
> > listed below in the table, so that he can do the 0 in.Hg, 4 in.Hg, and 15
> > in.Hg measurements and make calibration adjustments.
> >
> > He lives an hour away and would like to come take the measurements from
> my
> > sensor since I have the same one...but if this data is out there, it
> would
> > be a lot easier to just get him the information.  Additionally, who is to
> > say that my sensor is even going to still be "spec"?
> >
> > Below is the table, I hope that it comes thru the email looking correct.
> >  If not, it's in the link above if you scroll down to "Calibration Values
> > Table".
> >
> > Any help greatly appreciated.  And I believe he is still on this list
> (not
> > totally sure) so he might even see the replies, otherwise I will get the
> > info to him.
> >
> > Thanks very much for any help,
> >
> >  - Bryon, '71 Fastback
> >
> > Calibration Values Table
> >
> > *Bosch p/n*
> > *0 280 100 027**0 280 100 037**0 280 100 043* *0 280 100 049*
> >
> > *Application*
> > Not sure 1973 2.0L 9141974-1976 2.0L 9141970-1973 1.7L 914
> >
> > *Sampling*
> > based on 1 good OEM non-rebuilt unit based on 1 rebuilt unitbased on 2
> > rebuilt and 1 good OEM non-rebuilt unitsbased on 1 NOS unit *Vacuum
> Level*
> >      0 in. Hg1.32 H 1.44 H1.39 H1.34 H4 in. Hg 1.17 H1.26 H1.18 H 1.15
> H15
> > in. Hg0.72 H0.72 H 0.71 H0.71 H
> >
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