Jeremiah's 73 412 restoration project

[Jeremiah Berger]

I got everything figured out with to the ignition and got the tune dialed in pretty good for a starting point.The new ballast resistor is working great and giving me 8.9 v to the coil. I also had to add a diode to my starter circuit to coil so that it would only flow one way to the coil and not back to the starter.

I got the timing down to just a about 12 degrees at idle and 28 @ 3k rpm. It runs great. Idle is decent, started wandering and chugging a bit when I let it sit and idle a long period once but otherwise it is running pretty good for a baseline.

I am gonna get afr gauge an cht sensors setup before I really spend alot of time fine tuning it.But really happy at this point with how its all going.

[Jeremiah Berger]

Finally getting back to doing work on the car again over the last week or so. I have been chasing brake issues and needed new tires. Things that where making it difficult to get much time behind the wheel, but finally got all of those issues figured out

It's always the little simple things that end up haunting me. Like the spec of rust in the rear brake cylinder causing uneven braking and pulsing. I also had tires on it from a previous build that where worn because it was out of alignment so it was pulling one way. luckily I put new tires on it and it rights nice and straight.

I am liking the air ride, definitely a lot softer then stock though and needs the airbags full and stiff to help keep it stiff and safe.Overall.it rides pretty great though. And it is really low. I definitely didn't do it to improve the ride quality and realize it may be a strain on other components of the suspension and may not be as safe as stock. But that being said it is mostly for fun and to take to shows and enjoy so I'm not to worried about being able to put a ton of miles on it or use it for any type of regular commuter. All in all it turned out pretty great and what I was going for!.

Now I'm able to drive it and tune it. I have a new AFR gauge installed and it so far seams to work great. I installed it on the driver's side bung on my VS exhaust, there is one on either side but I've read that people have had better success with the driver's side. It is very responsive and seams to be high quality.

Upon cold start the gauge reads 11/1 -12/1 range and as it heats up it comes up to 14.5/1 range where I have it adjusted to with the nob on the top of the ECU. This adjustment seams to effect the idle and the initial afr reading as you first accelerate. So adjusting it to a somewhat ideal ratio at idle(after everything is all warmed up) and going from there I currently get about 12.5/1-13/1 range upon acceleration and leaning out more as rpm increase putting it in the 14 range at top speed. Take off gas and coast and it's about 12/1 . Cruise at low speeds barely any gas pedal and it's in the 14 range ...for the most part it's majority of the time it's in the 12.5 - 13.5 range. So from what I understand I'm not to far off right?

So my questions are
1. I know that 14.7/1 is the ideal number for fuel economy but I'm more concerned with peak performance Or balance between the two. What is an ideal AFR for this fuel injection?

2. From what I've earlier gathered I will be able to fine tune my vacuum unit to adjust certain aspects of the fuel ratio, wether it be turning both screws or one or the other either way. Is the goal to get a consistent reading throughout acceleration and different points of acceleration and load by making these adjustments?

3. The switch on the ECU, when and how should that come into play in the tuning process? Should I start with it at a certain point and then try to adjust everything else first and then worry about my idle afr later?

[raygreenwood]

Lets see....

[Jeremiah Berger]

So the "fuel shut off" are you talking the idle cut off circuit in the TPS? If so that's is probably where my issue is with the overrun, I had been messing with the TPS when I was trying to originally get it idling right before I had figured out my main issue. I was confused and had been messing with that adjustment. I will go back and check and reset that with multimeter and make sure it didn't end up out of adjustment.There is no deceleration valve...and it does do a kind of grumbling on fast deceleration.

Other then that I guess I'm off to a pretty good start because the switch on the ECU after messing with it a bunch it ended up being right dead in the middle(11 clicks to either side, total of 22 clicks)

I will check the TPS and do some more driving and really get an idea of what I think it really needs and maybe ill try and lean the idle a couple clicks with the switch and see if I can get it down with one or two clicks maybe see where everything is at there.

I also have a CHT on the way from the UK so when I get that in I can get a better idea of the temps and dial the timing first.It definitely seams to run super cool if anything based on what it did before and now the ambient temp is low. But outside temps are getting low too.

Like always thanks for the feedback.

[raygreenwood]

[Jeremiah Berger]

I'm not sure how to tell what TPS I have vs. others? I got it set back to where it always was and checked it with the multimeter. It seams to be if anything it was still working but not letting throttle close all the way where I had it set.

It has a idle cut off I believe, but like I said I'm not sure if that is the same to what you are referring too. Is the fuel cut off you are referring to the same idle shutt off? Wich is the lower circuit in the TPS I believe 12 or 17? The circuit that you test when setting with the multimeter....

I'm not sure if i have a deceleration valve or not? It's Automatic. I use to call this a deceleration valve but then at some point I thought I was wrong and it was not a deceleration valve and was called something else and main purpose was to compensate the load from transmission tc at idle when put in gear

Is this a deceleration valve for automatic?

[Pepperbilly]

I have always known it as an idle speed regulator on automatics only. I can’t imagine it as a decel valve. The adjustment is detailed in the VW factory “Troubleshooting Guide” which I do use. If you need that I can take a photo and shoot it to you.

Also, what I am reading about the TVS there are early and late types. The early types used terminal #17 for cutting off fuel on deceleration. Later styles (after 1971) donot use terminal #17, so no fuel cutoff.

Bill

[Jeremiah Berger]

[quote="Pepperbilly"]I have always known it as an idle speed regulator on automatics only. I can’t imagine it as a decel valve. The adjustment is detailed in the VW factory “Troubleshooting Guide” which I do use. If you need that I can take a photo and shoot it to you.

Also, what I am reading about the TVS there are early and late types. The early types used terminal #17 for cutting off fuel on deceleration. Later styles (after 1971) donot use terminal #17, so no fuel cutoff.

Ok that's what I thought...so yeah I do have a fuel cut off but not a deceleration valve...

I drove the car after resetting the TPS and it seemed to help lean the runout down a bit but still not super lean . In the range of everything else though so probably not an issue going forward.

I think I know the procedure for the idle speed regulator pretty good but it is definitely finicky to setup right. I usually have to run my initial idle speed a.touch high to get it to work just right without pulsing...

[raygreenwood]

Yes, terminal 17 on earlier models is fuel shuttle off. How it works is that when you are off the gas....meaning throttle totally closed (if the TPS is adjusted correctly)....that little forked floating switch will deflect toward closed and come out of contact with the contact that is connected to the wiper arm.

But, in order for that fuel cut off function to work, the secondary wiper arm must be on the little comtact pad on the circuit board that I call the "parking area".

When those two items have been accomplished....meaning your foot off the gas and the throttle totally closed....the ECU will shut off fuel when you are above something like 1500 rpm (going off memory so don't quote that rpm).

The problems this function can cause which are more severe on the automatic....are that if your TVS is not perfectly adjusted and/or has some wear to the floating bushing a d is not perfectly adjusted....then you can get excessive lag when reestablishing your foot on the pedal.

Like..... you are at 50 mph going around a cloverleaf getting on or off the interstate. Rpm is maybe 2500 to 2800. You lift off the gas and it goes into fuel shut off and engine is decelerating. You get halfway through the curve and touch the gas to give it a bit of sustainment....and you get either a slight bucking or a hesitation.

On one hand....this can go away if you have MUCH better/finer adjustment to the TVS. But, you will not get that level of adjustment using the adjusting method I virtually all of the books. Those do not ac out for the float/slop in that floating switch.

Add to this on the automatic....with that dash pot attached to the TB....when you let off the gas and your rpm is spooning down toward idle....vacuum triggers that dash pot and pops the throttle open a millimeter or so for a second or two. It's designed to keep the idle just so for a second to allow the torque converter to disengage and not stall the car. But if you are not really planning on coming to a stop but are close to it and reengage the gas pedal....that throttle pusher and fight with the TVS a little and give you a stumble.

Then add into this the deceleration valve which is electric on the automatic and has its own adjustment issues. It should not be triggering down in the low rpms like I just described above....but it can fight with TVS adjustment up in the upper rpms.

So on an automatic you really need the throttle pusher if you drive a lot of city light to light. In that case like when I lived in Atlanta I disconnected #17 on my 411 and worked hard to adjust the pusher better.
I found the electric deceleration valve to be a pain in the ass in a hilly city with a throttle pusher so I disconnected it and adjusted my tvs better.

The fuel shut off is just an emissions thing. If I had an auto I would disconnect it.

To know what you have, the part number is on the back side of the TVS and let us know how many wires it has. Ray

[Jeremiah Berger]

Ok good to know, I got the TVS right and then fought the dashpot so maybe I'll just disconnect the idle fuel shut off.

"Add to this on the automatic....with that dash pot attached to the TB....when you let off the gas and your rpm is spooning down toward idle....vacuum triggers that dash pot and pops the throttle open a millimeter or so for a second or two. It's designed to keep the idle just so for a second to allow the torque converter to disengage and not stall the car. But if you are not really planning on coming to a stop but are close to it and reengage the gas pedal....that throttle pusher and fight with the TVS a little and give you a stumble."

I think this is happening at times too.

Thanks for all the clarification. I will see what TPS I have and make sure again that it is set right. I just reread the thread on adjusting the TPS and will do it according to your instructions this time.

[Pepperbilly]

Jeremiah,

Now I am really curious about this “electric decel valve”. My wagon does not have one and don’t believe it ever had one. Our wagons are the same year and transmission and you have it? Now maybe it was taken off during it’s first 20,000 miles before our family purchased it as a used car, but doubtful.

Bill

[Pepperbilly]

The manual I use alot. Sometimes other tricks are needed because we are talking about old, altered cars.

Bill

[raygreenwood]

[Jeremiah Berger]

I took the TVS off again and double checked it using your method and I am confident that it is set up correctly at this point. I had used the Dr. D- jet method before and it was essentially no change in the position from them to now. I also have a little mark I put on the unit when I first took it apart years ago and it is exactly on that mark, which is essentially where it was set from factory as this car was very unmolested.

Here are some pics and include part number.It has four wires on harness and five pins on the TVS. Lacking full load enrichment circuit 2/14.

I drove the car around a bit and it still doesn't run lean when I coast and take foot off gas pedal. I'm not sure if it is the idle.cut off or not or wether I really need to worry about that very much. If you are saying I should just disconnect it anyway then I probably don't need to chase that.

I'm also still kinda confused. If the fuel cut off doesn't kick in until below 1500 rpm wouldn't the RPM in an Auto at coast still be pretty high?

I turned the knob on ECU two clicks and richened the idle up just a bit. I've driven it around a few times and the AFR seams to be right where it should be most of the time except when I under load.

When under load it runs very lean. 15/1- 16.5/1 range....like when taking off from still. Through the first two gears getting up to speed very lean. Then when it drops into third it comes down substantially. At speed it generally stays at ideal range wether I floor it or take it easy on the pedal.Cruising slow or putting around with lite acceleration it stays in good range.On a hill it also runs very lean. Anytime the engine is under excessive load it runs very lean. In neutral with no load the AFR stays in range through all RPMs

Not sure how much it was doing this before if I wasn't noticing it as much or I changed something? Probably just wasn't noticing or pinpointing exactly when it was happening before, I definitely had some high readings at points but hadn't pinned down when or why it was happening yet.

Does this have to do with the full load enrichment? Since this is on the MPS on my model is that something I can adjust? Is that the outer screw adjustment?

I'm still a little unclear on how many adjustments can be made on the MPS or in short What the outer screw adjustment changes?

[KTPhil]

I think the fuel cutoff speed is about 1800 rpm.

It helps emissions, but also might avoid some backfiring on overrun.

If it is lean when accelerating, I wonder if the enrichment circuit (the 10 or so extra injections triggered by the TPS) aren't working.
_________________
Current Fleet:
- '71 Fastback
- '69 Westfalia
Retired:
- '67 Beetle
- '65 Beetle (x2)
- '65 Bus
- '71 Squareback

[Pepperbilly]

I think if it were me I would break in the engine fully before getting too precise with the settings. Not sure how many miles you have on the engine since the rebuild. Get it good enough or close to where it runs nicely for now and after say 800 to a 1,000 miles revisit the setup.

Bill

[Jeremiah Berger]

[Jeremiah Berger]

[raygreenwood]

[Jeremiah Berger]

The TPS is working and does all 20 clicks.

I believe compression ratio ended being 8.5/1.

The main reason I am questioning the outer screw adjustment is when I rebuilt mine with new diaphragm I was able to make sure and get the center screw set exactly to where the original was but the outer screw had turned before I realized exactly what was happening and I messed with that outer screw adjustment. Only return in it to where I thought it visually by memory was originally.