D jet questions

perception 1979 · Post by **perception 1979** » Mon May 21, 2001 1:09 am

Hey there,
Do any of you guys now if the pressure sensor on D jet motors is universal? I've been looking around the forums and have learned that a 1.7 can be adjusted to a 2.0 by adjusting the factory setting which had been set in epoxy. Other companies used this injection, including volvo. Would a p1800 or even a VW 311 unit work? I have a D jet 311 unit with the epoxy setting. It has four wire terminals. Looking for a usable unit. Any help would be appreciated..

Bleyseng · Post by **Bleyseng** » Mon May 21, 2001 7:57 pm

As I understand it, each Pressure sensor was set up for that model/year car, that's why there is so many model numbers. You can use a 914 MPS and tune it using Kjell's article but... The way I hear it now is the way to go is to get a rebuilt unit. It is difficult to "Set it up" to factory specs' due to the internals of the MPS. If your car doesn't run, then get one from a junkyard and tune it using Kjell's article to get you back on the road. To do it right, order one and pay the money. I don't think using a Type 3 MPS is going to work very well if at all.
Geoff

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76 914 2.0L

Roland Kunz · Post by **Roland Kunz** » Wed Jul 04, 2001 9:59 pm

Hello

The MB 280 SE euro 185 HP with the yellow point will work on a 73on euro 2,0 100 HP engine.

I didn´t find a other good working combo and I testet some 30 units from Opel, Volvo, Jaguar, Mercedes.

This unit goes direct into the ecu and controls the inection lenght.

They age and get cracks. Also they are hard to messure as the ecu reads conductivity.

Grüsse

ned_glenn · Post by **ned_glenn** » Tue Jul 10, 2001 8:55 pm

Now what year was that Benz that had the same sensor?

Ned

pbanders · Post by **pbanders** » Wed Jul 11, 2001 8:11 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Bleyseng:
As I understand it, each Pressure sensor was set up for that model/year car, that's why there is so many model numbers. You can use a 914 MPS and tune it using Kjell's article but... The way I hear it now is the way to go is to get a rebuilt unit. It is difficult to "Set it up" to factory specs' due to the internals of the MPS. If your car doesn't run, then get one from a junkyard and tune it using Kjell's article to get you back on the road. To do it right, order one and pay the money. I don't think using a Type 3 MPS is going to work very well if at all.
Geoff

<HR></BLOCKQUOTE>

Geoff is correct, all of the MPS's used on the 914's are basically the same, they've all been adjusted differently for the specifc year and engine application. See my MPS article for more information:
http://members.rennlist.com/pbanders/ma ... sensor.htm

I also agree with Geoff, that adjusting the MPS is not for the faint of heart, and to do it really correctly, you need specialized equipment that isn't available any more. I give a procedure in my article that is more comprehensive than what Kjell's article covers, but I suggest it as a "last resort" process. Getting a rebuilt unit from Performance or some other source is the cheapest/best way to go.

Brad Anders

pbanders · Post by **pbanders** » Wed Jul 11, 2001 8:18 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Roland Kunz:
Hello

The MB 280 SE euro 185 HP with the yellow point will work on a 73on euro 2,0 100 HP engine.

I didn´t find a other good working combo and I testet some 30 units from Opel, Volvo, Jaguar, Mercedes.

This unit goes direct into the ecu and controls the inection lenght.

They age and get cracks. Also they are hard to messure as the ecu reads conductivity.

Grüsse<HR></BLOCKQUOTE>

I believe the part number on the sensor that Roland describes is 0 280 100 012. Looking at the tables I have, he's right, this sensor's adjustment values are fairly close to the 2.0L 914's, but are fairly rich.

The cracks that Roland refers to form at the flange edge of the adjuster in the full-load diaphragm. Every time you floor the accelerator, this metal diaphragm flexes. Over time, metal fatigue at the sharp edge joint causes cracks to form and a vacuum leak results. The sensor will then gradually get richer and richer, eventually totally failing. Replacement parts for the diaphragm are not commercially available - replacement with a rebuilt or new unit is the only cure.

For more information on the MPS, see my web page at:
http://members.rennlist.com/pbanders/ma ... sensor.htm

Brad Anders

pbanders · Post by **pbanders** » Wed Jul 11, 2001 8:20 pm

<BLOCKQUOTE>quote:<HR>Originally posted by perception 1979:
Hey there,
Do any of you guys now if the pressure sensor on D jet motors is universal? I've been looking around the forums and have learned that a 1.7 can be adjusted to a 2.0 by adjusting the factory setting which had been set in epoxy. Other companies used this injection, including volvo. Would a p1800 or even a VW 311 unit work? I have a D jet 311 unit with the epoxy setting. It has four wire terminals. Looking for a usable unit. Any help would be appreciated..<HR></BLOCKQUOTE>

One more thing - I noticed you said you have a "VW 311" unit - is this a Type 3 sensor? If so, if it is from a 1968 or 1969 car, it's not possible to use this sensor with a 914 ECU and throttle switch. Can you post the part number printed on the sensor so I can check it?

thanks,

Brad Anders

Roland Kunz · Post by **Roland Kunz** » Thu Jul 12, 2001 11:52 pm

Hello

The 280 D-Jetronic engines where used in the 107, 108 ( absolute rare ), 115, 116 and 123 Mercedes Types. In 1981 they shiftet to CIS ( KE jetronic ).

Now if you look at some cars you will find the units have different Bosch numbers for the same engine. But they also have little paper dots sticked on. Mostly to find are blue, yellow, orange. Some have red, black, white or two color codes.

I never finded out the real background as I don´t beleive MB made mathings on that subjects. Also they are mostly interchancable inside the MB series.

The sensor did not have the same Bosch# but worked very well on the later 2,0 ECU ( with bufferd sensor reading ).

Back when I was young I allways salvaged the injectors and most other D-Jet components ( A failed injector killed the engine ) and so I had a basket full of stuff to experimentate.

Back then I had a 2,0 euro with a sharper cam and other nice goodies and I wantet to get 115+ HP with the D-Jetronic.

Grüsse

perception 1979 · Post by **perception 1979** » Sun Jul 22, 2001 5:57 pm

Here is the part number for you guys. Sorry it took so long to reply. Been away for a while..

311 906 051C

There is also a number above this without a VW symbol before it. It is as follows..
0 280 100 007
I will no be using this part so if any of you are interested drop me a line at [email protected]

Bleyseng · Post by **Bleyseng** » Mon Jul 23, 2001 7:22 pm

So Roland did you suceed in your quest for 115 hp?? What other goodies did you have on the motor?
Geoff

------------------
76 914 2.0L

ray greenwood · Post by **ray greenwood** » Tue Aug 07, 2001 1:49 pm

Hey guys,jumping into this conversation about 10 days late...so I hope you read this. All of the D-type pressure sensors were basically the same, but fall into a couple of categories. (1) the early ones..they has no copper diaphram in the back. That function..which was for acceleration enrichment and was done by the pressure switch. Different brain..different wires. So if your pressure sensor does not have the little oblong air-holes in the back...its an early model, and you must have a good pressure switch. You can take over this function with a variable fuel pressure regulator...but its a lot of tuning. (2) late model with the copper diaphram in back. (3) the long nose and short nose version of both of the above. I believe this was a design change to allow more center pin throw and the use of the later model ceramic brushes/bearings inside. They seem to be a little more sensitive to delicate vacume changes but will work either way. There is no special equipment for tuning these parts...Never was. They were dynamically tuned with the standard VW test apperatus on a test bed motor. Some of these pressure sensors were set for different climate rates in different countries. IE the altitude sensing version with the open chamber in the back...very rare...not very necessary unless you live in the alps. The reason special test equipment is not necesary, is that all of the pressure sensors had the same resistance on the primary and secondary coils. This resistance was altered moment to moment by the rate at which the iron rod passed between them...in effect the sensitivity to vacume load. This is set by you, with a scew driver while tuning the engine. Every engine being different...simply setting these to factory specs is useless. Also the screw under the expoxy is only one of three adjustments. It is the outer depth stop for the flex of the diaphram when you open throttle. Do not move it unless the car is running and the diaphram has sucked in and tension is is off of it...so you can find out how far it has been set from the diaphram for a baseline setting. The second is the screw in the center underneath. This applys spring tension or load to the chambers inside and is your basic fuel mixture setting. It also, through adding load to the barometric chambers...sets the sensitivity to vacume of the entire unit...so watch it!.The third is the center ring surrounding the mixture screw just described and requires a hollow hex key to adjust. This sets the depth that the diaphram can be drawn down. The outer cover screw and this screw set the... range... of acceleration enrichment in which the diaphram may flex. The last part which no one seems to be aware of...is the flap seal in the vacume inlet pipe. This seal pops closed so that the vacume release when you pop the throttle open is not so instantaneous that you dont get a good length of time on your enrichment pulse. I hope this helps. My 412 has a basically stock D-jet 1.7 w/ 8.2:1 comp, web cam #73, good port job, 42x39 valves , solid lifters and spacers...and a whole lot of F.I. tuning. It is turning 102 hp on the dyno at 4100 rpm....It has taken me years to figure out how to get good tuning out of stock injection...but it is very possible. Ray

pbanders · Post by **pbanders** » Fri Aug 10, 2001 4:25 pm

Ray,

Good info there on the MPS, I have a few things to add:

1. You mention the long and short-nose versions of the MPS. It's unclear to me if these were specific applications of the sensor or was a basic design modification. Most of the MPS's I've seen are the short-nose versions. Long-nose versions lacked a physical stop for the armature when fully in the core, and had a different coil spring, which gave a slightly slope to the linear part-load region.

2. There are no bearings or brushes inside of the MPS. The armature is suspended in the core of the linear variable transformer using two flat springs and has no bearing. There are no brushes as the device is a basically a transformer.

3. There are some minor differences in the diaphragm parts in some MPS's. The inner screw is identical on all the units. The outer screw height is either 8.3 mm or 9.15 mm, permitting more full-load adjustability for the shorter screw. The mounting flange thickness on the diaphragm also is found in two thicknesses. Rebuilt units often have a completely different diaphragm than OEM units, as the rebuilder has a supplier and a process for replacing worn-out diaphragms.

4. The original calibration of the MPS was most likely done by starting with a system model, deriving a starting point for the adjustments, then refining the measurements on a dyno. Nobody I'm aware of knows how Bosch then characterized these units to provide a calibration standard for new units. It could be as simple as doing a series of mechanical measurements of the screw positions, or it could have been an electronic process. The rebuilder (Bret Instruments) uses a set of "gold standard" MPS's (new units from Bosch) that he matches the calibration of rebuilt units to through the use of a bench setup of the D-Jetronic system. He matches the injector pulse widths under different conditions for calibration. I have developed a simpler electronic calibration method that requires only a fairly inexpensive meter (as little as $30) to accomplish. I currently have my MPS web page off-line while I'm updating it with this new info, it should be back on line next week.

5. The resistance of the coils does not vary as the armature moves in and out of the core. The parameter that varies is the inductance of the primary and secondary windings, and the coupling or mutual inductance. The ECU sends a pulse to the primary that is synchronized to the trigger contact point closure. This pulse induces a voltage on the secondary that holds a transistor in the loop circuit off until the voltage decays to a certain voltage level. The rate of this voltage decay is directly related to the inductance of the secondary, and is therefore directly related to the intake manifold pressure, which moves the armature in the core of the LVT.

6. I agree with your explanations of the action of the MPS adjustment screws. Here is how I put it:

A: The central screw adjusts the basic part-load mixture. The slope, or rate of change of the mixture at part-load is not adjustable and is a function of the design of the aneroid cells.

B: The outer screw, which has the inner screw in the middle of it, and screws into the diaphragm flange, pre-tensions the diaphragm at part-load, and controls the vacuum level where the transition to full-load behavior begins (typically around 6 in. Hg). The transition takes about 3 to 4 in. Hg before the upper shoulder of the outer screw comes in contact with the full-load stop (see below).

C: The full-load stop (the "plug" in the end of the MPS) sets the maximum position of the armature under full-load conditions.

I've got a ton of new stuff that I'm putting into my MPS page:

- electronic characterization
- calibration curves
- electromechanical model

I'll put up a posting when it's ready.

Brad Anders