Progress on the Nomad...

[MGVWfan]

Latest on the continuing saga of my '73 412 wagon. Last night we got the '76 Plymouth Duster (working on for my daughter to drive) rolled out, freeing up the left garage bay for 412 engine and transaxle. The engine is over there, the transaxle will be tonight after getting a bath (it's REALLY filthy ).

Pictures of the Nomad are on the Samba Gallery, I'll post engine/transaxle images as I get them...

http://www.thesamba.com/vw/forum/album_ ... lodeutsch4

Here's the list of remaining things to complete...

>Jack up the front and R&R the entire front suspension using Ray's ideas as much as possible...
>Remove remaining misc. stuff and prep the engine bay and area above the transaxle for repainting with high-temp rattle can paint, then repaint.
>Reinstall the Eber, do a full-up heater test (minus the engine heat exchangers)
>Overhaul the auto transaxle
>clean and relube the CV joints, strip and paint the driveshafts, new boots, reassemble.
>Hang the transaxle back under the car, connect up linkages and driveshafts.
>Strip the engine.
>Pull the heads and jugs, mike out the pistons and cylinders, check the heads.
>Install crankcase vent tubes in the heads for the PCV system.
>Clean, derust, repaint all engine tin, intake tubes, intake plenum, fan housing, etc.
>Since the A/C compressor's a pain to get to with the engine in there, I may overhaul the old compressor just so I can install it with belt on the engine.
>Reassemble the engine with new seals and and gaskets, and anything else needed.
>Install engine, test run
>Have a couple cold ones Maybe a Bitburger Pils or three...
>Replace the windshield seal, maybe the rest too.
>Down the road a bit...repaint

I've already got the rest of the A/C system flushed and inerted, the starter and alternator have been worked over, the floorpans front and rear prepped and repainted, front trunk prepped and repainted, electrical system work and mods done, fuel tank cleaned and inerted, brakes overhauled, new tires, new battery, and Blaupunkt Emden radio repaired and installed (whew)

[ubercrap]

That's awesome man! I feel like a lazy pile of crap now.

[type4org]

How do you plan on doing that without the system fully in place? If nothing else the overheat switch will shut it down after a short time because there won't be any air flowing across the inner heat exchanger to cool it down...

[raygreenwood]

You canmake sure the auxiliary fan is running. It is fine test it without the heat exchangers. Just make sure the auxiliary blower is hooked up and running. Thats all that runs anyway when the heater is on and the engine is off. Ray

[MGVWfan]

Exactly. I've already tested it on the "bench" (the driveway well away from the front of the house!) with the fan ducted up (duct tape is good for lots of uses, including Eber testing ), it worked great (after I got the fuel pump delivery set right). I'll post a photo of the Eber right away on the Samba Gallery.

Well, don't feel too bad Herr Uber, it took me 5 months to get all of the above done...

[MGVWfan]

I've uploaded 5 new images to the Samba Gallery, for your viewing pleasure...

http://www.thesamba.com/vw/forum/album_ ... lodeutsch4

Two of the Eber, three of the engine. Enjoy!

[MGVWfan]

Latest...the AT is out, and de-crudded. Boy, was it FILTHY. The past two days, while waiting for the rain to stop so I could pull the AT, I stripped the engine down, and started wire brushing the stuff that needed it, the coil, brackets, manifold tubes, etc. Now it's on to the front end so I can get Ray the centerlink, then painting the engine bay and the area above the transaxle, or tearing down the engine, whichever works out better at the time.

[raygreenwood]

While the tranny is out....get a seal kit. It will need new seals. Should have had them at 70k miles. They are cheap and only about 45 minutes worth of work. Also, you can identify and get connectors for the ports that you will need for checking the main pressure on the tranny. That way it will be easy to do the driving test once the tranny gets back in, to adjust the modulator. Then it will drive as smooth as glass. Ray

[MGVWfan]

Already done, got the kit from Dallas last month. I've pulsed them for plates and bands, too, I figure I'll do the whole deal while it's out. Only two selective things inside the gear section, endfloat (spacers) and forward clutch (circlip), and no special tools, so why not do it now I figure.

[raygreenwood]

Good deal! I have been there when the seal goes out. Really...really ugly! Ray

[MGVWfan]

OK, I pulled the left head tonight for a look-see (I just COULDN'T wait). No ridge whatsoever, no rust, just some carbon (expected), and the bore measures out to 93mm, so it is a 1.8 L set of P&C's, with 1.8 L heads like the last rebuilder told me (I trust him of course, but it's always good to verify things like that). They appear to be in excellent shape. The heads are in great shape, just some carbon. He did a great job with the previous overhaul, it appears to my Brit car trained eyes.

I could re-seal, re-gasket, clean, reassemble, and probably be OK with my 70 hp engine ...you see, the pistons are dished (low compression).

If the pistons were flat topped, I would just keep on truckin', but since they're dished, I have a decision to make. T4 gurus, advice please, do you recommend...

(a) Do nothing, keep on trucking with a good LC 1.8 L, maybe rebuild for HC later, or
(b) Build a flattop piston 1.8L, or
(c) Build a flattop piston 1.7L, or
(d) Build a domed piston 1.8L (if such things even exist), or
(e) Build a domed piston 1.7L

I'm keeping D-Jet, but adjusting the MPS won't be a major problem for me, and I might even be able to do some Ve compensation by tweaking the waveform generators in the ECU (it helps to be an electronic type guy sometimes), so fuel delivery can get sorted out eventually for any option above. If spending the $$$ for a new set of P&C's makes sense to me, I can do it, but I figure I'll ask first. I definitely don't want to spend the $$$ for a new set of heads, the ones I have now are low mileage (confirmed) and in great shape. I'm looking for a reliable driver with good power and the ability to handle the AT and A/C without becoming a dog on the road (or in town, either). No drag racer, but at least able to keep up with my daughter's /6 Duster.

Thoughts???

[raygreenwood]

I personnally would not mess with the ECU. Yes, you could tweak teh waveform generators, but controling when the enrichment come in..is still up to the MPS...not the ECU. There are several ways just to get across the board enrichment. (1) fuel pressure...quickest and easiest. (2) Ballast the initial rane of the CHT. (3) proper fuel pressure stabilization...right off the bat. (4) A pressure bleed to take fuel pressure away all the time...until certain rpm points are met, wherin you get several more psi.

There are also several mods that can be done to get better part throttle enrichment on the MPS...which is the main problem with D-jet. Control of vacuum and manifold dynamics are the main power robbers.
Seriuosly, get 42 x 36 valves, stabilize fuel pressure, keep the compresion above 8.0:1, get a web # 73 cam. On the 1.7 and 1.8, use the 2.0 vanagon larger TB, use 914 2.0 runners (drill the extra holes)...it is sized better. Get a GOOD ignition system. The car will go MUCH better.
Ray

[MGVWfan]

Not to be a nerdy thang (I have been accused of that )...

The MPS affects the engine-vacuum-vs-injector-duty-cycle curve, the WFM's (3, 4, or 5 depending on application) take in trigger pulses (engine RPM) and change the MPS input injector dwell time (mixture) based on a hard-wired "calibration curve" (compensation for volumetric efficiency). Since changing intake restriction and CR affect pumping losses, these are best tuned with the WFM's, although I'd bet there is enough cross-coupling with the MPS vacuum sensing calibration to allow use of the MPS alone as a way of coping with a CR and intake flow different from that assumed by VW and Bosch (as you're proposing Ray). Since I have 2 ECU's (both for the 1.7L T4), and soon a third (for a '75 914/4), I have some room for error in my playings about with the ECU. I'm definitely keeping the original ECU as a "control" sample and unmolested example, in case Frankenstein and Murphy conspire against me

The other inputs are interesting...some can be done without pulling the engine (intake runners, throttle body), and I could do in stages later...but the real question I guess is, 1.7 or 1.8? Which would make a better daily driver in a 8.0:1 + CR engine? I'm thinking keep the good 1.8L cylinders, hone, and get some domed pistons...but it's dependant on $$$ ($2-300 OK) and availability, then the rest of the mods.

Is a low CR 1.8L really that low on spunk (I just have to ask)?

Good inputs, I appreciate the discussion, more please!

[raygreenwood]

There is a lot ore going on in D-jet...than electronically meets the eye. Yes...the 1.8 is really that different with its low compression. Bear in mind that the 1.8 with low compression, even with D-jet slaved on..still puts out some 12 hP less. The acceleration curve is even worse. Running a carbed 1.7 (low compresson dished) with D-jet...nets about 68hp compared to 82 with the domed pistons. All three have the same cam.

Yes, the MPS primarily affects injection duty cycle. But...even more importantly...it SETS the entire shape of the curve. The duty cycle changes according to the MPS...but the MPS response curve is hugely complex. The triggers do give an rpm reference. What is really important is that they give a finite window of when the injection can happen. The cycle rate rarely encompasses the entire window. The timing of when these happen is critical also. Therefore, ignition timing affects injection timing. Radically altered injection timing affects vacuum. I have found that anything that alters the vacuum signature...GREATLY affects the output of the MPS. Also...radically altering injection timing affects the running of the engine so much...that it radically affects the vaccum on teh MPS....enough that it causes radical swings in fuel pressure...as much as 5 psi...by causing wide usage of the injection "window" at low rpm .

There are 3 primary adjustments to the MPS. It encompasses, in the late model diaphram type...the workings of the full load enrichment switch and a MAP sensor....AND due to the way they designed the system around a specific range of vaccum response...it also approximates the same type of volumetric control of a flap metering unit. Unique and complex device.

Changing the squarewave form patterns is a way to adjust things....love to know more about it...but also.....the main problem with D-jet...is not getting longer injection duration, or more enrichment. Its getting all of these things to happen at the right time ....due to teh repsonses of the MPS. There are areas of poor response in the MPS...due partly to vacuum variances from engine to engine....operating against the factory assembly line, "generalized" state of tune of the MPS's...and also due to compromises that had to be made. If you increase spring pressue to slow the unloading of there aneroids during part throttle peaks....you end up messing up the inner stop position at areas of high vauum (idle) and risk messing up the stroke length of the armature at WOT. Now...there are ways to get around that....if you are willing to tinker ...as I suspect you are. Not saying OT to tinker with the ECU at all....just saying that even if you do....there are things that must be done to the MPS...in order to utilize them. Those things unlock performance in all cofigurations. I would do them first.
In answer to the original question...I would much rather have a high compression 1.7 with domes...than even a low compression 2.0. the throttle response is so much better.

Lastly....and this tells you just how important the entire vacuum signature an MPS relationship is. Low compression ratios on D-jet....run terribly. The MPS's...un modified, do not adjust down with enough sensitivity...to tune them as well as you should be able to, with low compression. it is very very noticable. They run richer, are sensitive to weather changes...and are hard to correct. Some of that is almost a velocity issue. The vacuum signature is lower, so the increase and decrease in vacuum does not happen as quickly or as sharply. It is felt. I have long speculated that on teh 1.8's...with their lower compression....that they kept the same runner size and plenum size as the 1.7...simply to restrict the volume...so the response curve with D-jet would be the same. But...as it immediatly went to L-jet, Its probably just a cost thing...as L-jet is not as sensitive to the problem as D jet.Ray

[raygreenwood]

Needed to add something but the edit feature would not work.
when I noted....the MPS response curve is very complex, I meant to add....that unlike L-jet, whose flap monitors the volume of the air that passes it, D-jets MPS...knows nothing really of the volume that has passed the butterfly, but meters.....its condition...based in vacuum. Anything that alters that makes big changes. Its amazing just how sensitive the MPS unit is. It is actually more sensitive in response, than what the ECU has in its posession....to implement that response. Thats probably one reason why you thought of altering the square wave response. But...a lot of the range of repsonse available to the MPS is wasted...due to adjustability issues.
When you think 3-diemsnionally about this problem...what you would like to create is this: (bear with me now) If while the engine was operating...and if it had a graphing "tool"you could slap a pen into...and it could draw a realtime graph of its needs....and imagine if the MPS had that same graphing "tool".....in a perfect world, the MPS graph should superimpose right on top of the engine graph. It does not. It has spikes in the mod-range. When you adjust for those spikes....it gets spikes in the lower and/or upper range. Tools at the disposal of the system to help it along...are the "zones" of use or enrichment ...afforded it by the ambient air temp sensor (very limited) and the CHT (range is poor...needs to be modified). problem I see right off with altering the square wave response....is how it will mesh with the movements of the armature in the MPS.
One thing I see...in agreement with some others...is that vacuum is actually one of the best response "patterns"..wit which to govern an engine. Hmmm...how better to explain that. Other conversations I have had.....others will tell you flat out, that a modern MAP sensor has a much better range of sensitivity. sensitivity? Yes...maybe so. But thats a diaphram driven strain gauge type device generally. It does not have the same "mechanical" reaction that the MPS does. If you try to slave a MAP to D-jet...it will not respond the same. It may read vacuum....but the MPS was designed to do a bit more than the map sensor. It reacts to both manifold pressure and ambient pressure simultaneously...that means both manifold pressure augmented by ambient pressure...and real time ambient pressure. It woud take two MAPS to do that. Just some things to think about. Ray