Jeremiah's 73 412 restoration project

[Jeremiah Berger]

Looking at the price of a used MPS vacuum tested at an average of $300- $450 and refurbished ones at $1200 ! makes me wish I just got some flipping carbs or a new efi to start. This thing is making me broke.

[Pepperbilly]

Well, that is a bummer. We are type 4 people so we know that we can’t give up!

I would get ahold of Jim Adney. He rebuilt my original fuel pump and it works flawlessly. I understand he also rebuilds the MPS.

I can also send you the instructions I have for dealing with the MPS. I will mail it to you. I have your address.

Bill

[raygreenwood]

What is the part # on your MPS? I will check my stock of parts. really, all the diaphrams are the same....just the setting varies. Ray

[Jeremiah Berger]

There are two numbers not sure which is part # you need

0280100049
022906051E

[Pepperbilly]

I like my mityvac vacuum tester. Also shown are the 2 adjustment tools if you remove the epoxy and unscrew the plug. If you are just replacing the diaphragm and set up the adjustment fitting as it was originally, you won’t need the tools. Shown here is a good MPS holding vacuum at 10 in. Hg for at least 5 minutes. If I remember correctly the test is good if it holds for 3 minutes.

Here are the tools if you remove the epoxied plug. They fit into the MPS and the tools slide into one another to make the dual adjustment.

Bill

[raygreenwood]

[Pepperbilly]

Wow Ray, you certainly have my attention! Good for you. Yeah, for those of us that want to keep our D-Jets in business we’re certainly in need of these diaphragms.

Bill

[Jeremiah Berger]

Funny that's exactly where my mind went when I started thinking about it. Seams like such a simple thing that could be replicated with some time and patience...but more importantly the right material.

That's all way to much for me as someone who is just getting a grasp on how the thing works though.

Hopefully you are successful or Tangerine starts making them again.

I have been reading and trying to understand the DJet in further depth and found these right ups very informative.

This guy is a Jaguar guy I think but especially knowledged with the DJet.Wich most of it is obviously applicable across model differences especially with parts like the MPS.

https://members.rennlist.com/pbanders/manifold_pressure_sensor.htm

I tried my local connections and don't think I have any available. Daniels says he possibly has some hidden in the attic of parts but think it's not a part he thinks he ended up with a lot of because he was rarely taking anything that wasn't already removed from vehicles and the fact this is mounted to the vehicle and not the engine in most situations he didn't end up with many.

Gonna try the other tomorrow when he returns from his summer break but that's a hit or miss for sure.

I'll keep my fingers crossed.

[Jeremiah Berger]

Funny that's exactly where my mind went when I started thinking about it. Seams like such a simple thing that could be replicated with some time and patience...but more importantly the right material.

That's all way to much for me as someone who is just getting a grasp on how the thing works though.

Hopefully you are successful or Tangerine starts making them again.

I have been reading and trying to understand the DJet in further depth and found these right ups very informative.

This guy is a Jaguar guy I think but especially knowledged with the DJet.Wich most of it is obviously applicable across model differences especially with parts like the MPS.

https://members.rennlist.com/pbanders/manifold_pressure_sensor.htm

I tried my local connections and don't think I have any available. Daniels says he possibly has some hidden in the attic of parts but think it's not a part he thinks he ended up with a lot of because he was rarely taking anything that wasn't already removed from vehicles and the fact this is mounted to the vehicle and not the engine in most situations he didn't end up with many.

Gonna try the other tomorrow when he returns from his summer break but that's a hit or miss for sure.

I'll keep my fingers crossed.

[raygreenwood]

Many years ago, around 1999 to 2001, I spoke to Brad Anders once or twice. At that point in time we were both searching for ECU connectors and trying to get around the IP lock that Amp had on the 25,000-ish connectors they had in stock.

We spoke about MPS details at one point. Brad Anders is the most knowledgeable person regarding D-jet electronic function and original design specification. If anyone at all is close to him regarding knowledge of inside the ECU and how each component works, it would be the guy that runs the Dr. D-jet site. He is mostly Mercedes oriented.

However, I do have some fundamental disagreements with Brad. And that does not mean he is incorrect in any way.
Brad approaches D-jet from an nearly strict engineers point of view. He knows what is going on in the ECU and what it can and cannot do. I have always known, even though I work in the industry that makes printed electronics and circuit boards....that I will never have the knowledge to be able to tweak or adjust or repair a system from the ECU function direction. So I worked from the outside (the engine) toward the inside (the ecu)

BUT..... having put probably 700,000 + hard miles on D-jet cars and worked and tweaked on them all along the way, ....I learned and have proven to myself (again if no one else) that just like the thousands of semi-analog equipment I have worked on in factories around the world.....one can do an awful lot of adjusting by tweaking with the mechanical parts of the engine that changes what the electronic part sees. I can change vacuum signature (and therefore what the MPS sees)....and/or tweaking with TS-1, TS-2, trigger points timing (not duration), vacuum leaks by design, mix and match of any of those sensors from other cars....and adjusting the MPS.

Keep in mind....like Brad Anders states, you cannot go beyond the parameters that the ECU is capable of but you can go a long way toward lying to the ECU about timing, temperature and vacuum. It only sees what the sensors show it. You can modify what these sensors do if you get creative. Because the ECU has ranges of voltage, amperage and induction that are set....all you can do is modify the what and when data is sent within those allowable ranges.

I actually learned a lot early on when I was tweaking parts in my very first 411....years before I actually KNEW how the system worked. I remember when I found out by accident....in high school no less....that when I accidentally knocked the hose off the MPS ....while driving at highway speed....and it greatly increased enrichment and output. I was already running lean because I had a fuel pressure problem I was working with. I knew I needed a new FPR but did not have the money that week.
But when at 65 mph I suddenly found the engine just wanted to climb in rpm and speed....at a very low throttle crack.....I was very quickly at 80 mph.

I slowed down and pulled over and it stalled a minute later. Opened the hood and saw that hose off and the lightbulb went off in my head. "Oh....so that's how that thing works!".

I went to a pet shop and bought a fish tank air valve and installed it in inline with the MPS to make an "engineered" adjustable vacuum leak. I found it amazing how much drivability could be adjusted in by simply changing an orifice to tweak the MPS response. I tried it with a Tee bleeding in outside air to the MPS vacuum and in-line to slow down onset of vacuum and release or vacuum. Two very different effects and very enlightening.

One of many calculated shade tree tweaks over the years.

But back to the diaphragm. This is one of those parts that in later years when I knew a lot more about machines, physics, chemistry and manufacturing...I thought would be super critical in tolerances and virtually impossible to produce differently than the factory to get a response that I could adjust to near factory tolerances.

Years later, I realized that there was actually quite a lot of variation in the diaphragm. As long as it's flexibility, tension/temper and range of motion were within what was required....most of the rest could simply be adjusted into the stack up in the MPS.

If it's too stiff like the stainless one....it does not have the range of movement and has poor response.

If it's too soft....like the couple of rubber ones I made just to see what could be done.....it moved too much and oscillation and was not stiff enough to drive the armature stack up even with very high vacuum.

But....there is a lot in between those two choices....that I knew could be worked with. I KNEW that because across many MPS that I have taken apart over the years....and measured the thickness of the copper diaphragm and counted the corrugations/rings....and noted the variations in the stamping and rudely tested flexibility with stacks of gram weights and a dial indicator....later I actually used vacuum and a dial indicatoron some....(there are variations in all of these).....many times in the same part # MPS......I realized that the copper diaphragm was NOT all that super precise.

It accuracy/precision....falls within a range. The rest is adjustment to spec.

In terms of adjustment....again from long experience when I had nothing else. There were no books but I had to do something.....so I locked down parameters, measured, tested while driving, adjusted, made notes....repeat, repeat, repeat.

This is another area where I KNOW what I have proven to work....and I diverge from what Brad Anders does (and again he is not wrong). Brad approaches adjustment of D-jet from the whats possible from the design point of view. He likes to adjust MPS to the known factory numbers he has discovered over the decades by bench setting with an induction meter and vacuum source. Then any extra tweaks while running are done with a wide band 02 sensor.

The problem with this method....if you read a lot of threads across a lot of forums.....is that while many have emulated this method....the success rate with good running....is about 50/50 to 60/40 successful.

Why is that?

It's because the rest of the engine is no longer similar enough to original factory to produce an exact enough vacuum signature. And/or.....there are some age related variances in the MPS, ECU, TS-1, TS-2 and TVS....and especially wear in the distributor and ignition.....not to mention changes in the fuel.

If you approach from the other direction.....the mechanical end.....make your engine, fuel supply and voltage as sound and uniform as you can (same for TS-1 and TS-2)....but get some variable resistors to have on hand in case you need to ballast/tweak......you get left with adjusting the MPS for drivability....by hand....by effect. Then you can check the 02.

The gist is that the function of the copper diaphragm is narrow and specific. It has to flex a limited amount at certain vacuum points.....but does not provide constant adjustment through the whole driving range. It is as some people say....a wide open throttle function. Yes it does that. But it also moves about the same distance for a very short amount of time (a second or less) when you crack the throttle off the line and when you have a shift point. It moves between the inner and outer stop...from one to the other...and does not float around in between.

It is not that precise of a part. It's adjustment is fairly precise.

When I finally realized it was beryllium copper and not copper....I also realized that making one of these is more subtle than making one of copper. Copper is a bit more...soft and elastic.
When pressing copper into a mold....more force and energy can and should be used. But where you press a rib or groove in with copper....it compacts the metal. It's partially work hardens it. If you do to much....it needs to be annealed to remain flexible and and not crack. That's not hard to do.

With beryllium copper.....it already comes "solution annealed". Its ready to go. But when pressing it to shape.....IF....you can avoid pressing too hard and deep and compacting the cross section (work hardening it).....then you do not have to anneal it. But if you do press it too hard.....the baseline annealed process is a lot more involved. Not what you want to do.

I believe....due to the very limited flex that this diaphragm needs to do....maybe 0.090" at the most.....that a straight up flat beryllium copper plate at the thinnest thickness I have found in these plates....about 0.003".....could work just fine. Ray

[Jeremiah Berger]

Definitely really in depth right ups on the djet and really helps someone like me get an initial understanding of the system.Ive also checked out Dr. D-jet jet as well .I truthfully until recently had no idea it was used in so many other models. Pretty cool to have some collective information from all over the world.

But your approach makes a lot of sense and I was considering that aspect when reading about tuning it to the exact stock specifications.

We all know that a 50 year old engine is no longer operating on all those same parameters, and a newly built engine is certainly not either.

In my case I have introduced a new cam better flowing exhaust slightly different compression etc. and to my understanding may have ended up needing to make an adjustment to the mps to obtain an optimal AFR.

And more on that later after I get the initial tuning all dialed in I plan on getting an AFR gauge and really dialing in the tuning.

I did get a vintage speed exhaust and I am very happy so far. It's has a bung on either side of exhaust for o2 sensor not sure which is better place to put it? but it is very nice quality and sounds good. pretty classic air-cooled sound not to throaty or crazy but sounds good.

So I'll have more questions on that later. One thing at a time though.

[raygreenwood]

So...how is that exhaust working? Which model/part # is it?

Ah!...wait...I found it on their site:

UPC: 155-208-R3500

I have been agonizing for years about what to do when I finally get to my exhaust when I get back up off the ground. With all of the tuning and build changes I made over the years that really helped my 1.7L run much better than stock:

42 x 36 valves with unshrouding work
8.5:1 compression
Web #73 cam
40Kv coil, triple electrode plugs and points replacement module..much better grounding and voltage all around
Adjusted timing of trigger points
Too slack out of distributor and set up adjustable advance unit
Lots of little tweaks to TS-2, TS-1 and MPS adjustment
Much better fuel pressure stability...big difference

And....the final piece (but it did not really go far enough) was an Ernst muffler which was about 12% higher internal volume and made enough difference in tuning that it required a fuel mixture adjustment.

All in all this made about a 10hp difference and a LOT of throttle resonse difference.

But....the Ernst exhaust, as much better as it was than the other stock mufflers....was only enough better due to a slight internal volume icrease and bigger and more well distributed perforations inside.

It was still the same design as any other stock muffler inside. It still had unequal lengths left to right and still had some restrictions.

I have been designing a slip together and tack-weld 4 into 1 for years for my car.

I ahve also long ago taken note about what jake Raby said about the basic Thunderbird 4 into 1 header. That it was a pretty good improvement over stock (even though build quality is still shit). And...EMPI makes a stainless verion of it....but then you still have to find a muffler and it still has a length imbalance.

Or....from what Alstrup states, the Vintage speed exhausts are pretty good for smaller displacement engines. If it works well it could be so much simpler to just buy one of those. Ray

[Jeremiah Berger]

Gonna try to post in sections for some reason this post won't go through...

So far I haven't got to a really gotten much time behind the wheel since I've got these tuning issues I only took it out a couple times and stopped driving and running it since I figured out my mps was bad. But I definitely have gained power and it is overall happy and seems to be breathing well.

Like I said it has that classic sound but a little tad louder. The Quality is top notch and the welds are very nice. Quality hardware & installation. Looks wise, what you would expect for how much you are paying.I got mine from Heritage parts. They have it listed as so ..

Vintage Speed Sports Exhaust, Std Tailpipe, Bay Type 4 87089235

They also carry a type 4 sports dual tip one that is rated for 150hp...

Thanks for the feedback on the fine-tuning. Ive already been thinking about and looking into some of those things.

[Jeremiah Berger]

(I figured it out .. apparently I can't use the degree symbol?)

1 Many things I've read about the 9590 cam and the djet working well and according to Jake I want to get about 14* at idle and limited to 28-32* total which is obviously not gonna happen without modification. So I'm definitely interested in hearing more about the adjustable advance...

2 I've been realizing that I probably want to consider a better coil. I actually have a crane cams fireball xr700 but Ive misplaced the coil over this whole thing and I set it up with a new German coil. But running into problems getting it started my spark seamed week so I put points a and condenser on, didn't turn out to be my problem but I just kept the points in after reading and being confused on which coil I needed to run with the fireball...

Not sure if that is a good points replacement to go with but if it is it always worked good before I took it off.. maybe you could help me figure out what coil I need to get? Online it says I need a 1.5 ohm coil or a 3 0hm coil with a ballast resistor. Electrical is not my thing... It didn't have a ballast resistor before. Looking online I can get a 1.5 ohm 40,000w flamethrower like I have on my bug for my petronix. Seams like this is what I want but I just wanna be sure

3 Fuel pressure. What do I want my start fuel pressure to be? Increasing the fuel pressure also enriches the AFR correct? A combination of the MPS band width the timing of the injectors and the fuel pressure correct? So is this something I wait for my AFR gauge and then dial in or do I want to check it and adjust it to start to a certain point as a first step? And then go on to other extents for enrichment if needed?

[raygreenwood]

[Jeremiah Berger]

Well I have not had any luck locating any MPS units locally. I scoured eBay and found a few that might be decent options.

There is a sealed one epoxy and rivets. Same part # looks good .$140..but not vacuum tested ( says in the add that they don't have any way of testing it but they are a Porsche parts supplier selling multiple MPS's so that's kinda red flag)

https://www.ebay.com/itm/152965860924

Then there is an equivalent that is vacuum tested $295!

https://www.ebay.com/itm/267055175039

Then there is one that is remanufactured for $645!!!

https://www.ebay.com/itm/355599208833

I could put a whole new efi on the car for the price of a new OEM unit .. Really wish I could get one of those kits somewhere...

[raygreenwood]

[Jeremiah Berger]

Thank you Ray, I would be very thankful for either option. If it happens to have a bad diaphragm Bill has offered to let me have the extra diaphragm that he has if I can't find anything. He has also sent me a copy of the Tangerine racing instructions Incase I end up going the route of rebuilding...I think I could easily make the tool. If I need to make adjustments to it then that is something I'm sure I can figure out.

I did mention that I messed with the screws and noticed the outer screw moved, but wasn't sure if I had moved it already...I may have slightly moved it, i think it is very close to where it was but I may end up needing to adjust my full load stop( outer screw). I know exactly how many turns on the inner one ....

[raygreenwood]

[Jeremiah Berger]

Awesome, that would certainly be a great help to keeping these cars on the road.

I will continue to wait patiently, I appreciate your help tremendously. Take your time. I'm taking a breather and enjoying summer a bit anyway.