Even with a perfectly functioning MPS...that means no vacuum leaks and all resistance readings correct....it will still have to be adjusted to whatever engine it mates with.
That was the original failing of VW.....the thought that all MPS's are calibrated the same. No two engines are alike...and no two vacuum signatures are alike.
The factory engines when new....were alike enough that just installing an MPS and turning the key would result in a decent running engine. Mark that as "decent" running....not perfect.
Some did run perfect...others had quirks in various weather and driving conditions. As engines aged....thevacuum characteristics changed and the marginal engiens ran worse.
This is partly how D-jet got such a bad reputation. I have found many people who bought new type 3 or 4 and found them to run superbly. I have also found just as many people who bough new type 3 and 4's and after a very short time they ran terribly and were problematic. There were no other apperent cross correlations. Many excellent drivers who treated their cars like gold had horribly unreliable D-jet....while others who treated their cars liek sh*t had extreme reliability.
In later years....late 412 and 914...Istarted seeing colored paint or grade marking on MPS's. I surmise that VW got smart and started out with a range of MPS calibrations...instead of just one....and started further tuning the vehicles before they left the factory....or could retune vehicles that had aged by swapping in a differnt calibration of MPS at a dealer.
Either way...the state of tune of D-jet even at its best...was marginal in my opinion.
If you have a bunch of little things off like slopping weights in the dizzy, minor vacuum leaks, slop in the TPS or slop in the valve adjustment or weak ignition, maxed out head temp sensors etc......you end up adjusting the MPS in teh midst of tehse things and it may run well....but will never be able to be tuned to its maximum potential. Ray
411 is gassy
-
SureFit Travis
- Posts: 168
- Joined: Thu Mar 23, 2006 10:23 pm
Sorry, guys, I was away for about five days on a bit of a family holiday, and didn't dare mention trying to check e-mails or VW stuff.
Yeah, while we were at the car show a couple of weeks back, we had a few people come up to us to say that hey had bought a 411/412 or type-3 brand new, and the stories were either one extreme or the other: great performance/reliablility/fuel economy, or horrible performance/reliablilty/economy. Some people loved them, and the others could barely stand looking at our cars. Quite funny!
As far as the PCV valve, I did measure the orifice, which was about 3.6mm. I figured that was a bit big, so I ended up removing the threaded center of a Marrett, and drilling a 2.3mm hole in the end, and stuffing it into the hose......wasn't a bad fit; it kind of looks like a snake that has swallowed something a little large. RPM's have come down a bit; it still affects idle RPM when the hose is pinched, just not as extreme.
I have an old MPS with a cracked diaphram that I took apart about 2 years ago, so at least I have something to play with to make a tool to hold the outer adjuster. I'm thinking that I will end up buying an el-cheapo 3/8-drive #45 torx bit, filing a bit off of each point, and drilling out the center for a jewelers' screwdriver to slide through for the center adjuster. Until I have an appropriate tool made, my adjusting plans are on hold.
Just to eliminate this question, I have checked the o-ring in the base of the oil filler, as well as replaced the cork gasket in the base of the breather box.
vwbill: I'm pretty sure that the MPS on this car is the one that you sent to Jen. It seems to hold 15" of vacuum quite well. I did buy another one off eBay a while back, but for some reason I can't seem to find it. I bought it as a spare. Speaking of Jen, she came out to the car show while I was away getting my truck from the hotel (I had bought bulky parts at the swap area, including a front clip for a type-3), and she sent me a picture of herself standing beside the car. That was cool.
I'm going to re-check fuel pressure and timing (hopefully) this weekend. I have doubts about the accuracy of my timing light, and am going to borrow a Snap-On unit from a friend.
I'll check back in after I have completed these steps.
Travis
Yeah, while we were at the car show a couple of weeks back, we had a few people come up to us to say that hey had bought a 411/412 or type-3 brand new, and the stories were either one extreme or the other: great performance/reliablility/fuel economy, or horrible performance/reliablilty/economy. Some people loved them, and the others could barely stand looking at our cars. Quite funny!
As far as the PCV valve, I did measure the orifice, which was about 3.6mm. I figured that was a bit big, so I ended up removing the threaded center of a Marrett, and drilling a 2.3mm hole in the end, and stuffing it into the hose......wasn't a bad fit; it kind of looks like a snake that has swallowed something a little large. RPM's have come down a bit; it still affects idle RPM when the hose is pinched, just not as extreme.
I have an old MPS with a cracked diaphram that I took apart about 2 years ago, so at least I have something to play with to make a tool to hold the outer adjuster. I'm thinking that I will end up buying an el-cheapo 3/8-drive #45 torx bit, filing a bit off of each point, and drilling out the center for a jewelers' screwdriver to slide through for the center adjuster. Until I have an appropriate tool made, my adjusting plans are on hold.
Just to eliminate this question, I have checked the o-ring in the base of the oil filler, as well as replaced the cork gasket in the base of the breather box.
vwbill: I'm pretty sure that the MPS on this car is the one that you sent to Jen. It seems to hold 15" of vacuum quite well. I did buy another one off eBay a while back, but for some reason I can't seem to find it. I bought it as a spare. Speaking of Jen, she came out to the car show while I was away getting my truck from the hotel (I had bought bulky parts at the swap area, including a front clip for a type-3), and she sent me a picture of herself standing beside the car. That was cool.
I'm going to re-check fuel pressure and timing (hopefully) this weekend. I have doubts about the accuracy of my timing light, and am going to borrow a Snap-On unit from a friend.
I'll check back in after I have completed these steps.
Travis
-
Lars S
- Posts: 321
- Joined: Sat Jul 07, 2007 12:25 pm
Travis,
this is wery much the same expeeience I have when parking my car; Previous 411/412 or type-3 owners smiling tells about the good, but mostly about the bad experiences: a lot of trouble with the D-jet.
My personal experiences after driving these cars since mid 70's are the opposite, the D-jet is wery reliable.
I believe the bad experiences comes from a not wery well prepared service organisation, and some early D-jet control boxes weakness.
MPS calibration is also fundamental something the VW workshops over here certainly did not handle (besides changing the MPS to a new one).
For me its natural to keep the D-jet as long as I want a relaible an fuel economic drive.
Lars S
this is wery much the same expeeience I have when parking my car; Previous 411/412 or type-3 owners smiling tells about the good, but mostly about the bad experiences: a lot of trouble with the D-jet.
My personal experiences after driving these cars since mid 70's are the opposite, the D-jet is wery reliable.
I believe the bad experiences comes from a not wery well prepared service organisation, and some early D-jet control boxes weakness.
MPS calibration is also fundamental something the VW workshops over here certainly did not handle (besides changing the MPS to a new one).
For me its natural to keep the D-jet as long as I want a relaible an fuel economic drive.
Lars S
-914/4 -72 daily driver
-Husqvarna 120cc rat bike -48
-Husqvarna 120cc -52
-BMW 600 Road Scrambler -69
-Suzuki T500 Cobra -69
-VW411LE 2-door sedan -70
-Porsche 914/4 -72
-VW412LE 4-door sedan -73
-Suzuki K50 -77
-Husqvarna 120cc rat bike -48
-Husqvarna 120cc -52
-BMW 600 Road Scrambler -69
-Suzuki T500 Cobra -69
-VW411LE 2-door sedan -70
-Porsche 914/4 -72
-VW412LE 4-door sedan -73
-Suzuki K50 -77
-
raygreenwood
- Posts: 11906
- Joined: Wed Jan 22, 2003 12:01 am
This is my finding as well. Though many will complain that D-jet is way obsolete and does not have any tuning parameters.....I find that not true. Yes it is obsolete, but when several things are taken into account it is very reliable and excellent performance and throttle response.
The key that many people who only work with aftermarket programmable injection can't wrap their heads around...is that like any othe rinjection....D-jet IS infinitely expandable to use on larger engines...as long as they stay within certain parameters. Most notably...parameters that may affect a stable vacuum signature.
There were even a few V-8's built that used D-jet. The difference is...that just like with an aftermarket system sooner or later you wil need larger intakes, injectors and more channels for more cylinders. All else stays the same.
The MPS is simply a complicated adjustable MAP sensor. Within reason...its response can be adjusted for most any engine size so long as the vacuum signatures do not radically stray.
The biggest issues facing D-jet were a poor harness connector design (just build your own) and no real specific tuning for MPS's (we know that now) poor resolution on the few sensors it had (just ballast them or replace them), lots of slop in the resistance of the of the trigger points and TPS (easy to fix when you know its there) and lastly....too much variance in fuel pressure (easy to fix with a feeder pump and a good regulator).
Add to this....things we know now. (1) better cam. Even a web #73...is a large improvment...especially if you do all these other tuning tehcniques just mentioned) (2) slightly larger valves (42 x 36, 41 x 35, 42 x 35 or 34)...get rid of the PCV....all of these make a large difference.
All of this makes tuning makes the tuning of the MpS and the repsonse...a lot more sensitive. Put in a better ignition and even with the stock exhaust....the performance and reliability of D-jet is worlds away better than how it came from the factory.
On a 1.7 or 1.8 with good high compression....23-25 mpg should be no problem in the city. Mid-30's on the highway is average. At 65-70 mph....36-38 was not uncommon. I also suspct that lowering the front end slightly on my 412 helped this.
In the right application (stock, near stock, hot modified stock)...I still think D-jet has few equals.
My 1.7 ran sub 10 seconds 0-60 with the factory 4-speed. Before it was about 13 seconds 0-60. And...it got better gas milage than most people get with aftermarket programming.
I just think that unless you have made all of the perfect and necessary changes to the design of the manifolds and airflow and exhaust....you just cannot use all of the rogramming capacity of aftermarket to do much better than D-jet is alreday doing on engines of the above configuration.
It really is in the limitations of the manifold and plenum. If the stock manifolds on D-jet cars were more highly developed ...we would indeed need the tuning capacity of aftermarket systems for it.
I see people tuning, piddling and swapping maps with each other for months....all working around cobbled together intake systems on engiens that are possibly too large or wrongly configured for them...cause its all they have. In the end....the HP may be larger (and the engine as well)...but in general the fuel milage and throttle response...doen't greatly exceed what D-jet started with.
If you are staying stockish....just stick with teheD-jet and perfect its tuning. Ray
The key that many people who only work with aftermarket programmable injection can't wrap their heads around...is that like any othe rinjection....D-jet IS infinitely expandable to use on larger engines...as long as they stay within certain parameters. Most notably...parameters that may affect a stable vacuum signature.
There were even a few V-8's built that used D-jet. The difference is...that just like with an aftermarket system sooner or later you wil need larger intakes, injectors and more channels for more cylinders. All else stays the same.
The MPS is simply a complicated adjustable MAP sensor. Within reason...its response can be adjusted for most any engine size so long as the vacuum signatures do not radically stray.
The biggest issues facing D-jet were a poor harness connector design (just build your own) and no real specific tuning for MPS's (we know that now) poor resolution on the few sensors it had (just ballast them or replace them), lots of slop in the resistance of the of the trigger points and TPS (easy to fix when you know its there) and lastly....too much variance in fuel pressure (easy to fix with a feeder pump and a good regulator).
Add to this....things we know now. (1) better cam. Even a web #73...is a large improvment...especially if you do all these other tuning tehcniques just mentioned) (2) slightly larger valves (42 x 36, 41 x 35, 42 x 35 or 34)...get rid of the PCV....all of these make a large difference.
All of this makes tuning makes the tuning of the MpS and the repsonse...a lot more sensitive. Put in a better ignition and even with the stock exhaust....the performance and reliability of D-jet is worlds away better than how it came from the factory.
On a 1.7 or 1.8 with good high compression....23-25 mpg should be no problem in the city. Mid-30's on the highway is average. At 65-70 mph....36-38 was not uncommon. I also suspct that lowering the front end slightly on my 412 helped this.
In the right application (stock, near stock, hot modified stock)...I still think D-jet has few equals.
My 1.7 ran sub 10 seconds 0-60 with the factory 4-speed. Before it was about 13 seconds 0-60. And...it got better gas milage than most people get with aftermarket programming.
I just think that unless you have made all of the perfect and necessary changes to the design of the manifolds and airflow and exhaust....you just cannot use all of the rogramming capacity of aftermarket to do much better than D-jet is alreday doing on engines of the above configuration.
It really is in the limitations of the manifold and plenum. If the stock manifolds on D-jet cars were more highly developed ...we would indeed need the tuning capacity of aftermarket systems for it.
I see people tuning, piddling and swapping maps with each other for months....all working around cobbled together intake systems on engiens that are possibly too large or wrongly configured for them...cause its all they have. In the end....the HP may be larger (and the engine as well)...but in general the fuel milage and throttle response...doen't greatly exceed what D-jet started with.
If you are staying stockish....just stick with teheD-jet and perfect its tuning. Ray
-
Lars S
- Posts: 321
- Joined: Sat Jul 07, 2007 12:25 pm
This may be out of this thread, but I plan to do a project when times calm down...namely to convert a MPS sensor into modern technology. This is partly to ensure availability of the MPS in the future but mostly of pure intrest.
Shortly the MPS body and inductive feedback coil and axle but not the diaphragms will be re-used. The axle movement will be actuated by a precision step motor which is controlled by a programable miniature PLC. The PLC is also connected to an electronic differetial pressure sensor at the manifold. This opens for a lot easier tuning of the MPS, and also other sensors could be connected to the PLC and have their pre set influenses.
Dont know about the lifetime of the step-motor but this is as said mostly a project of pure intrest.
Lars S
Shortly the MPS body and inductive feedback coil and axle but not the diaphragms will be re-used. The axle movement will be actuated by a precision step motor which is controlled by a programable miniature PLC. The PLC is also connected to an electronic differetial pressure sensor at the manifold. This opens for a lot easier tuning of the MPS, and also other sensors could be connected to the PLC and have their pre set influenses.
Dont know about the lifetime of the step-motor but this is as said mostly a project of pure intrest.
Lars S
-914/4 -72 daily driver
-Husqvarna 120cc rat bike -48
-Husqvarna 120cc -52
-BMW 600 Road Scrambler -69
-Suzuki T500 Cobra -69
-VW411LE 2-door sedan -70
-Porsche 914/4 -72
-VW412LE 4-door sedan -73
-Suzuki K50 -77
-Husqvarna 120cc rat bike -48
-Husqvarna 120cc -52
-BMW 600 Road Scrambler -69
-Suzuki T500 Cobra -69
-VW411LE 2-door sedan -70
-Porsche 914/4 -72
-VW412LE 4-door sedan -73
-Suzuki K50 -77
-
Lars S
- Posts: 321
- Joined: Sat Jul 07, 2007 12:25 pm
There is wery little air movement in the line. The MPS diaphragms are 100% tight and the only air movement is the small volume that represents the change of air volume in the MPS chamber caused by the diaphragms being flexed. A valve could therefore not cause any useful pressure drop.
You could of course shut the line by a valve but not adjust the pressure sensed by the MPS to anything adequate.
Lars S
You could of course shut the line by a valve but not adjust the pressure sensed by the MPS to anything adequate.
Lars S
-914/4 -72 daily driver
-Husqvarna 120cc rat bike -48
-Husqvarna 120cc -52
-BMW 600 Road Scrambler -69
-Suzuki T500 Cobra -69
-VW411LE 2-door sedan -70
-Porsche 914/4 -72
-VW412LE 4-door sedan -73
-Suzuki K50 -77
-Husqvarna 120cc rat bike -48
-Husqvarna 120cc -52
-BMW 600 Road Scrambler -69
-Suzuki T500 Cobra -69
-VW411LE 2-door sedan -70
-Porsche 914/4 -72
-VW412LE 4-door sedan -73
-Suzuki K50 -77
-
raygreenwood
- Posts: 11906
- Joined: Wed Jan 22, 2003 12:01 am
Long ago, I valved the inlet line for the MPS. It can help to extend part throttle enrighment of the orifice in small enough...but it so retards throttle response elsewhere that it was not worthwhile. Just an experiment.
It sounds interesting on the MPS. But....though I agrtee wholeheartedly with getting rid of the vacuum (actually pressure not vacuum)..cans/aneroids.....going to a stepping motor to move the armature/axle...will actually be a step in reverse.
As it is, right now, the response of the MPS is "infinite" within the range of its available response. A stepping motor is not. Also, the stepping motor will be slower...as it is about three points electrically removed from the actual vacuum source.
I do agree that using a modern map could benefit....though it would have to accomplish more than one thing at a time. You would have to possible have two maps of differenet range and then somehow translate their signal.
I know thats what you are trying to do with the stepping motor....move the rod...translating the signal from the modern map through the coils of the MPS.
Admirable...but I'm not sure where it would leave you.
That being said.....as we have noted, the adjusment and tuning of teh MPS's as they came from the factory is not ideal.
I think a large portion of the reposne issues could most probably be the vacuum/pressure cans.
In hindsight....why would it be correct that every D-jet car on every corner of the planet would use the same reference pressure in these "cans" for response to.
I have also found that not every car will require teh same mainspring balance pressure as the two main styles the factory built into the MPS's. As your vaccum signature changes....the spring loading "should" change. If teh spring loading changes....the pressure in teh cans should also change to match the response curve. When these two things happen........the stroke of the main armature/axle will change slightly.
Since the sensing response to the armature rod by the coils....is fixed.....as the stroke or the rod changes...its length must be adjustable if the previous two adjustments ...tension on the pressure cans....and mainspring tension....are to be maintained.
When my engine gets off the ground this year....there are three main changes to the elctronic part of the D-jet system in the works already:
(1) The injection is now sequential. We'll see if it works
(2) Aside from new vacuum cans (that may be next year) the mainspring is now fully adjustable on my MPS as is the armature rod length to compensate for changes...like mentioned above.
(3) The CHT no longer resides in the head. It is now a 7 stage timed stepped resistor.
This is all aside from changes in the intake tract.
D-jet is fun!
Ray
It sounds interesting on the MPS. But....though I agrtee wholeheartedly with getting rid of the vacuum (actually pressure not vacuum)..cans/aneroids.....going to a stepping motor to move the armature/axle...will actually be a step in reverse.
As it is, right now, the response of the MPS is "infinite" within the range of its available response. A stepping motor is not. Also, the stepping motor will be slower...as it is about three points electrically removed from the actual vacuum source.
I do agree that using a modern map could benefit....though it would have to accomplish more than one thing at a time. You would have to possible have two maps of differenet range and then somehow translate their signal.
I know thats what you are trying to do with the stepping motor....move the rod...translating the signal from the modern map through the coils of the MPS.
Admirable...but I'm not sure where it would leave you.
That being said.....as we have noted, the adjusment and tuning of teh MPS's as they came from the factory is not ideal.
I think a large portion of the reposne issues could most probably be the vacuum/pressure cans.
In hindsight....why would it be correct that every D-jet car on every corner of the planet would use the same reference pressure in these "cans" for response to.
I have also found that not every car will require teh same mainspring balance pressure as the two main styles the factory built into the MPS's. As your vaccum signature changes....the spring loading "should" change. If teh spring loading changes....the pressure in teh cans should also change to match the response curve. When these two things happen........the stroke of the main armature/axle will change slightly.
Since the sensing response to the armature rod by the coils....is fixed.....as the stroke or the rod changes...its length must be adjustable if the previous two adjustments ...tension on the pressure cans....and mainspring tension....are to be maintained.
When my engine gets off the ground this year....there are three main changes to the elctronic part of the D-jet system in the works already:
(1) The injection is now sequential. We'll see if it works
(2) Aside from new vacuum cans (that may be next year) the mainspring is now fully adjustable on my MPS as is the armature rod length to compensate for changes...like mentioned above.
(3) The CHT no longer resides in the head. It is now a 7 stage timed stepped resistor.
This is all aside from changes in the intake tract.
D-jet is fun!
Ray-
Lars S
- Posts: 321
- Joined: Sat Jul 07, 2007 12:25 pm
Yes Ray, D-Jet is fun!
I also agree that adding a stepper motor to the MPS is in a way a step backwards, it adds a lot more components to the system just to mention.
My try with this is mostly because my interest for expereiments.
The inductive feedback from the MPS is hard to exactely emulate without using a MPS components themself.
The resulotion of the relatively cheap linear stepper motor I aim for is abuot 200 positions in the total stroke needed (~2,5mm) which should be more than enough. It will repeat its positions within 0,01mm each time. I have not found out the max speed but assume it can go the full stroke some times per sec which also sounds enough. But still there are a lot of known and unknown problems to solve...but if succeded the mapping will be interesting...
Keep on D-jetting!
Lars S
I also agree that adding a stepper motor to the MPS is in a way a step backwards, it adds a lot more components to the system just to mention.
My try with this is mostly because my interest for expereiments.
The inductive feedback from the MPS is hard to exactely emulate without using a MPS components themself.
The resulotion of the relatively cheap linear stepper motor I aim for is abuot 200 positions in the total stroke needed (~2,5mm) which should be more than enough. It will repeat its positions within 0,01mm each time. I have not found out the max speed but assume it can go the full stroke some times per sec which also sounds enough. But still there are a lot of known and unknown problems to solve...but if succeded the mapping will be interesting...
Keep on D-jetting!
Lars S
-914/4 -72 daily driver
-Husqvarna 120cc rat bike -48
-Husqvarna 120cc -52
-BMW 600 Road Scrambler -69
-Suzuki T500 Cobra -69
-VW411LE 2-door sedan -70
-Porsche 914/4 -72
-VW412LE 4-door sedan -73
-Suzuki K50 -77
-Husqvarna 120cc rat bike -48
-Husqvarna 120cc -52
-BMW 600 Road Scrambler -69
-Suzuki T500 Cobra -69
-VW411LE 2-door sedan -70
-Porsche 914/4 -72
-VW412LE 4-door sedan -73
-Suzuki K50 -77
-
raygreenwood
- Posts: 11906
- Joined: Wed Jan 22, 2003 12:01 am
Cool! Its the same kind of experimentation that I had to do for years. I still to this day.....recimmend for anyone who wants to learn the very fundamentals of tuning EFI....to learn to work on D-jet. Between the the wicked injection timing issues and the very critical tuning of the MAP on this system...you learn more about injection in its base form than almost any system. That and CIS. Ray