TDI Timing Revisited

[aslspiderman]

Trying to understand

So I just purchased VCDS and did a IP reseal. Doing some research on what proper IQ and timing should be, I ran across this thread. Prior to finding this thread, I found info that told me to run IQ at 3mg/st and set timing above center on the timing scale.

I have read through this thread and everything is still very fuzzy. So I took some shots of current settings, in the hopes that I can increase my knowledge with the help of those with more knowledge here.

The car is my 02 Jetta. The motor is bone stock, with 203K miles on it. Everything is original (other than TB and associated parts).
IQ is set at 3

So here are some current readings:

Honestly I don't have enough knowledge to ask relevant questions. Looking at aNut's readings:

1. Should start of injection be .4 or is it relative, as long as requested and actual are the same?

2. Will adjusting my timing down, reduce start of injection?

I have thick skin so you can flame/chide/laugh-at. My goal is to increase knowledge and hopefully be able to pass on my gained knowledge.

Thanks in advance for any help.

 

[aslspiderman]

No thoughts or suggestions?

 

[Jesse_Boyer]

I'm no expert, but here's how I interpret your information. No flame or laughing necessary, we're all here to learn.

At that exact moment, your car is trying to achieve 1.3°BTDC (requested,) but its actually starting at 1.8°BTDC. Note the cold start valve is at its minimum value of 2.8%. The car cannot retard timing enough to achieve 1.3°BTDC as 2.8% is the minimum value if I'm not mistaken.

So, having understood the above, there are two paths forward:
One, if you want it to start at 1.3°BTDC, you need to retard the mechanical timing VERY slightly (moving the 22mm nut counter clockwise with the three bolts loose,) to allow the car to achieve 1.3°BTDC requested and 1.3°BTDC actual. Note, its a very small amount of adjustment and you'll know if you go to far as the value shown for the cold start valve will rocket above 2.8%.

Or...
Run a little more advance timing by adaptation via VCDS. Your advance would equal requested, cold start value would remain at/near 2.8%, and everyone would be happy. I tend to like a little 'advance' timing and I would change the value in the adaptation slightly via VCDS. (Lots of people run advanced timing well above the stock level (32768 value, IIRC) and love the way the engine performs. Better mileage is the goal for most.)

 

[aslspiderman]

At that exact moment, your car is trying to achieve 1.3°BTDC (requested,) but its actually starting at 1.8°BTDC. Note the cold start valve is at its minimum value of 2.8%. The car cannot retard timing enough to achieve 1.3°BTDC as 2.8% is the minimum value if I'm not mistaken.

So, having understood the above, there are two paths forward:
One, if you want it to start at 1.3°BTDC, you need to retard the mechanical timing VERY slightly (moving the 22mm nut counter clockwise with the three bolts loose,) to allow the car to achieve 1.3°BTDC requested and 1.3°BTDC actual. Note, its a very small amount of adjustment and you'll know if you go to far as the value shown for the cold start valve will rocket above 2.8%.

Or...
Run a little more advance timing by adaptation via VCDS. Your advance would equal requested, cold start value would remain at/near 2.8%, and everyone would be happy. I tend to like a little 'advance' timing and I would change the value in the adaptation slightly via VCDS. (Lots of people run advanced timing well above the stock level (32768 value, IIRC) and love the way the engine performs. Better mileage is the goal for most.)

Thanks for your input Jesse. Your explanation brings up more questions.

1. Where do I find the specs and tolerances for timing values and cold start values? Are they based on hard numbers or do they depend on other factors such as ambient temperature and fuel temperature? I have a Bentley manual but have not yet found them.

2. I think I would like to try to change timing mechanically rather than adaptation at this point. Also, you mentioned "if" I want my timing at 1.3* BTDC. I don't know what I want it set to, at this point. I want to experiment and see what different setting do to performance/mpg's

3. Where does the magic IQ number of 3mg/st come from?

4. If I mechanically retard the timing, will that change the cold start value?

 

[mrrhtuner]

Great thread, thanks!

 

[Jesse_Boyer]

Thanks for your input Jesse. Your explanation brings up more questions.
1. Where do I find the specs and tolerances for timing values and cold start values? Are they based on hard numbers or do they depend on other factors such as ambient temperature and fuel temperature? I have a Bentley manual but have not yet found them.
2. I think I would like to try to change timing mechanically rather than adaptation at this point. Also, you mentioned "if" I want my timing at 1.3* BTDC. I don't know what I want it set to, at this point. I want to experiment and see what different setting do to performance/mpg's
3. Where does the magic IQ number of 3mg/st come from?
4. If I mechanically retard the timing, will that change the cold start value?

I'm no expert, but here's my take. I'll gladly accept help from aNut and the other more knowledgeable people on the forum.
.
1. I recall seeing anywhere from 1.x°BTDC to 0.4°BTDC for the requested value. If you haven't changed the requested timing via logging-in and adaptation, group 4 and the value remains at 32768, your requested timing is stock and would be in this 0.4-1.x range (could be as high as 2.0BTDC from what I read.)
The 'cold start value' generated from VDCS is a reading of the cold start's signal while trying to achieve said value. This value will change depending on where you have the mechanical timing (at/near the bottom line, middle of the graph, at/near the top line or anywhere in between.) The common thought at this time is to have the value as low as possible so at the upper RPM, when timing IS further advanced, even on the factory tune, the pump can adjust timing enough to achieve said advance.
.
2. If you want to experiment, read here:
http://forums.tdiclub.com/showthread.php?t=53139
Note, don't stop reading after you see the first page of 'the sky is falling' posts. This thread is 11 years old and I'm not aware of one failure due to this advancement of timing. Personally, it lowered EGT's, increased my MPG's, and causes a more appealing sounding ALH. I've done this on five of my personal cars and not one hiccup, not one issue. 130k+ miles on one car, 45k+ miles on another, 10k on my latest. Not one issue. I'm at 4.8BTDC with my current ALH and that's with a large nozzle. Still playing with it to see where the combo wants to be regarding power and efficiency.
.
3. 3mg/st just seems to be a happy place where stock nozzles seem to perform. If they're considerably lower, you'll get slow-down shudder. Considerably higher and you'll be under-fueled. Most people only adjust IQ on stock nozzles/tunes if they have a smoke issue or more commonly a 'slow down shudder' issue.
.
4. The cold start value will stay at 2.8% to a certain point as requested doesn't yet meet actual, but will increase if you retard timing too far. Note, you're not likely to hurt anything if the value increases, it just means the cold start injector is opening/closing to maintain the requested injection. Common thought lately is to have the mechanical timing advanced enough to lower the value to 10% or lower (or so I read at one point. This genuinely changes depending who's post you read, what time of day its posted, etc, etc.) I KNOW my first ALH had to have the value in the mid-40-50%. I ran 5°BTDC advanced and had the mechanical timing in the upper half of the graph. With that much advance, the cold start injector almost HAD TO BE working hard to achieve this value. Result? Best mileage I ever achieved, zero issues.

 

[aslspiderman]

Thanks for the reply and further explanation Jesse. The mental fog is beginning to clear I'm gonna look at the thread you referenced as soon as I get a minute--just spent two hours reading, guess its gonna take more than "a minute"

 

[aslspiderman]

So I reset my timing today to dead center and got my specified and actual start of injection the same. Then I went into adaption and this is what I got??? From what I've read, the factory setting number should be 32768--is that correct?

So the number in my adaptation (32858), does that mean that someone has changed it before I owned the car? And is that the reason my start of injection is at 1.3 and not .4?

 

[SFHGolfTDI]

That would explain it. Put the number back to stock and see where your specified and actual end up and whether they still match.

 

[aslspiderman]

That would explain it. Put the number back to stock and see where your specified and actual end up and whether they still match.

Mystery solve--thanks SFH

Need to install windows through bootcamp first. Running VCDS through VMware is too glitchy. Can't get adaptation module to stay connected.

 

[SFHGolfTDI]

Mystery solve--thanks SFH

Need to install windows through bootcamp first. Running VCDS through VMware is too glitchy. Can't get adaptation module to stay connected.

I moved from VMWare to Parallels and it works great. (I also have a bootcamp installation but rarely use it for VCDS; Parallels is sufficient.)

 

[Wankel7]

So is it better for efficiency to set the timing at the blue line instead of the yellow line?

 

[UhOh]

My head is still spinning from reading this entire thread! I'm SLOWLY starting to get "there," but am wanting to try and apply things to a known problem with one of my cars. I am fairly certain that VCDS can tell me why there's a difference between my two cars.

My 2000 Golf starts hot or cold with just a flick of the key (less than a second!): might be the best starting vehicle I've ever had. I have not changed a thing with this car since I did the TB about 7k miles ago. Fuel mileage is pushing over 50mpg (though nearly all highway- I'm thinking that it should still be better). Performance is smooth and strong. In light of this thread I'll have to take a look at the "numbers" for my car: as of now I only know that the timing is around 62 or so (fuel temp 120). Now on to the car in question...

My wife's 2000 Golf needs to be cranked at least for a couple/three of seconds before it starts. It's a bit better when warm. It's fairly smoky at startup too. I'd adjusted the IQ up from about 2 to around 3.6 in the hope of helping with cold starts: I'm not really finding this to be doing anything. Her car is a bit noisier than mine. Fuel mileage has hit upwards of 50mpg, but it doesn't seem to do so with the ease that mine does. Can't recall of the top of my head what the timing number is, other than it shows up about the mid way between the blue and green lines: same as my car. Battery is good: I see the same draws with both cars. Performance is good: it might be a bit crisper than mine. So, the question...

What would one expect to find for the requested and actual SOIs and the cold start valve that would suggest these actual conditions expressed by my wife's car?

Engines in both cars are stone stock: her car has about 30k more miles than mine; its TB was changed about 25k miles ago (by PO). I have cleaned the intakes on both cars: wife's car I cleaned the ports in the head, in which case it should be even better than mine. No CELs. Engine temps both reach and hold in the 190 - 195 range.

I just recently got VCDS, and am not proficient with it yet.

 

[UhOh]

I'll add that my wife's car's TB was done by a dealer, in which case I'd figure that they actually timed it. I haven't made any changes to my car (had been waiting to get VCDS), and, frankly, given that it's performing exceedingly well all across the board I don't think there's a need to make any changes.

 

[Rembrant]

What would one expect to find for the requested and actual SOIs and the cold start valve that would suggest these actual conditions expressed by my wife's car?

Are you referring to the slower starting and smoke on the wife's car?

My 03 Golf is like yours...it starts instantly...it almost feels like it doesn't even turn over...just touch the key, and it goes.

How are the glow plugs in both cars? I can't remember...does the 2000 model tell you if individual glow-plugs are bad like the later ALH cars do?

Of course there could be differences between the two that are not easy to check or change...like compression, etc...maybe your car has slightly better numbers than hers?

You could try bumping the timing up a bit on her car to see what happens. Jack the mechanical timing up to the top line (70 or so) and see how it starts there. The SOI valve numbers will effect normal driving/operation. Where you set the pulley on the pump effects starting.

Is her car able to meet all of the specified numbers for the SOI valve?

 

[Rembrant]

PS: I'm going to play around with some timing stuff today on my Golf, so if you need any VCDS comparison info, I can post some numbers.

 

[ymz]

my wife's car's TB was done by a dealer, in which case I'd figure that they actually timed it.

I'd be surprised if they did anything of the sort... I'd also guess that they overfilled the coolant tank... (that is, if they replaced the water pump at the time - we've heard of a number of dealerships who don't bother replacing either the water pump or the idlers during a timing belt change...)

Since you have VCDS, do run a Basic Settings timing checker... just for giggles...

Yuri

 

[Rembrant]

I'd be surprised if they did anything of the sort...

I know we should be optimistic about "dealer service", but with the age of the Mk4 platform now, I think it really would depend on how long the particular dealer mechanic has been working on VW's.

My 03 Golf was at a VW dealer for low power issues a month before I bought it....and I have the receipts and paperwork for the work performed. They replaced the VNT actuator and neglected to install the circlip on the VNT lever, and wrote on the work order that the car was tested and was making boost. The missing circlip was the good news...the VNT mechanism barely moved at all, the intake was plugged solid, the timing was off, and the MAF sensor was bad.

I think it was simply a new/inexperienced mechanic working on the car, and he just didn't know much about the old ALH. (Or he told the customer there were 10 other problems with the car and the customer declined to repair...but they usually note all those things on work orders).

 

[UhOh]

Are you referring to the slower starting and smoke on the wife's car?

Yes.

My 03 Golf is like yours...it starts instantly...it almost feels like it doesn't even turn over...just touch the key, and it goes.

Yeah, to me that's saying that things have to be pretty much spot-on.

How are the glow plugs in both cars? I can't remember...does the 2000 model tell you if individual glow-plugs are bad like the later ALH cars do?

I haven't checked on the GPs. Correct me if I'm wrong, but I am of the understanding that they don't come in to play with air temps over 40: right now it's well above that: watched her car start for the first time in the day yesterday with the temps above 80 and still the same- whir, whir and then puff, puff. Once it's started it's much better behaving. I could almost explain it as being associated with the CTS, but it's not being recognized as a problem by VCDS: ironically, the CTS in my car is faulty (per VCDS, and per actual observed operations; it's on my todo list).

Not sure about the ability to isolate bad GPs. I believe that this granularity isn't possible on this model year.

Of course there could be differences between the two that are not easy to check or change...like compression, etc...maybe your car has slightly better numbers than hers?

Possible, yes. But that aside, and for this discussion/thread, I was looking to understand what kind of numbers, all else being equal, one could expect to find that would correlate to the issues I'm seeing with her car. That is, if the numbers on my car looked perfect, and the reality is is that it's running, I believe, almost perfectly, then how could I modify the settings on my car to behave like hers? (not that I'm wanting to!)

You could try bumping the timing up a bit on her car to see what happens. Jack the mechanical timing up to the top line (70 or so) and see how it starts there. The SOI valve numbers will effect normal driving/operation. Where you set the pulley on the pump effects starting.

My take on this thread is that the mechanical pump setting provides the actual playing field that the ECU can operate under and that the ECU only knows what its maps tell it to do and assumes that the playing field is "legit" (within expected parameters, not "out of the park"). My further understanding is that adaptations can slightly skew the view as seen by the ECU/maps (feedbacks then provide the necessary instructions to the ECU/maps to match what is being asked for- if what is being asked for cannot happen because the playing field is too far skewed then the engine will either struggle to achieve what it's being command or it will fail, which will result in poor performance of one thing and or another).

Is her car able to meet all of the specified numbers for the SOI valve?

I'm kind of back-dooring this here I'm asking folks what kinds of numbers that I should end up seeing. Let's just say that I "do know," but that I'm not saying until the class submits it's papers But, in reality, I don't know what the numbers are at this time: I will, for sure, get them!

 

[Rembrant]

I haven't checked on the GPs. Correct me if I'm wrong, but I am of the understanding that they don't come in to play with air temps over 40: right now it's well above that: watched her car start for the first time in the day yesterday with the temps above 80 and still the same- whir, whir and then puff, puff. Once it's started it's much better behaving. I could almost explain it as being associated with the CTS, but it's not being recognized as a problem by VCDS: ironically, the CTS in my car is faulty (per VCDS, and per actual observed operations; it's on my todo list).

The glow plugs should be activated every time you start the car, it's just that above 40 degrees, they don't come on for the preheat stage. Somebody can correct me on that, but it was my understanding that they're always on for much longer than the light on the dash indicates. I was just thinking out loud...above 80 degrees, they shouldn't be needed at anyway. What is the actual coolant temp in the morning @ first start? I assume it would be close the night time temps (assuming the car sat all night).

My take on this thread is that the mechanical pump setting provides the actual playing field that the ECU can operate under and that the ECU only knows what its maps tell it to do and assumes that the playing field is "legit" (within expected parameters, not "out of the park"). My further understanding is that adaptations can slightly skew the view as seen by the ECU/maps (feedbacks then provide the necessary instructions to the ECU/maps to match what is being asked for- if what is being asked for cannot happen because the playing field is too far skewed then the engine will either struggle to achieve what it's being command or it will fail, which will result in poor performance of one thing and or another).

All correct. The adaptation changes the entire map by the amount you adapt it to. If you adapt it to add 3 degrees, it will add 3 degrees to every cell in the map. I'm not suggesting timing adaptation for your issue though.

The mechanical adjustment of the IP sprocket will effect starting injection timing. The SOI valve adjusts the timing advance/retard once the car is running, but it can't do so until then. So yes, the mechanical adjustment of the IP does dictate the SOI playing field as it were, but there is no playing field until the car is actually running. For starting purposes, it's the mechanical adjustment that matters, and then the ECU takes over once the car is running (the low pressure pump in the IP provides the fuel flow that the SOI valve uses to adjust the SOI).

Fuel temp plays a role too...compare those readings between the two cars.

Since the issue is with starting (and not running) I would try adjusting the mechanical timing to see if it improves. If you advance it too much, like up to the top line in the graph (70-ish) it may start better, but you may find that the SOI valve is not able to retard fully at idle to meet specified. It might be off by a couple degrees.

It wouldn't hurt to check it first and see if the SOI can meet the specified timing during cold idle. I don't know what mine is when cold, but when it's warm, it's specifying 0.4 degrees timing (or something like that) at idle.

Sounds like your wife's car may have a slightly different 'sweet spot' than yours does.

 

[UhOh]

Rembrant, as usual, thanks for the great info! This thread has really helped to set my understanding of these engines.

Her car was started cold when outside temps were 80+. Prior to then I was only witnessing it being cold started in the early mornings (prior to work; yesterday she was off work).

I am pretty sure that this was addressed somewhere in this thread, but what again, exactly, is the VCDS timing graph telling/showing? Are the lower and upper bounds centered around the physical setting of the IP, or are they the map boundaries and the number (per the yellow line) is a percentage value within these bounds (with the lower being zero and the upper being one hundred)?

Should one look to ignore this graph completely and rely on, as someone suggested, only Group 004 settings (matching Requested and Actual, and that the Cold Start be in the proper range [not 2.8, more in the middle?])?

 

[RacerTodd]

I am pretty sure that this was addressed somewhere in this thread, but what again, exactly, is the VCDS timing graph telling/showing? Are the lower and upper bounds centered around the physical setting of the IP, or are they the map boundaries and the number (per the yellow line) is a percentage value within these bounds (with the lower being zero and the upper being one hundred)?

The key is that when checking timing with VCDS the ECU is in "basic settings" mode. What that means is that the ECU is not dynamically changing timing based on sensor inputs. What the timing graph shows is mechanical timing only. The ECU will then advance or retard timing from that baseline.
The red and green lines are the minimum and maximum specified timing. The blue line is just halfway in between those two.

Think of like an ignition distributor. You set the base timing by physically rotating the distributor and reading the timing light until you get the correct number. Then, while running, the mechanical and vacuum advance mechanisms will adjust timing accordingly from that base setting.

In the TDI, you read the mechanical timing advance with VCDS. Then you physically adjust the pump. Then you check it with VCDS. Once it's set, the ECU will advance or retard timing from that baseline depending on input from the various sensors.

As for starting, the ECU does not begin dynamically adjusting timing until the engine is at idle speed. So, during cranking it's using straight mechanical timing. Retarded timing (near the red line) will generally result in slower starting, especially in cold climates. If you live in a cold climate, having timing near the top (green line) will help starting.
In our mild Pacific NW climate, proabably not a huge deal.

I did go through a slow starting issue a couple of years ago. I was kinda random - sometimes started slow, sometimes not. Did it in winter and summer. I checked timing and found it between the blue and green, so no problem there. I checked RPM during cranking and found rpms during starting at around 175rpm. 250rpm is generally considered what you'd like to see. Put in a new starter and I was back to nice quick starts all year long.

 

[UhOh]

Todd, great reply, thanks! Putting in a more mechanical context works for me as I'm still new to the computer controlled aspects of engines: I've got an old IDI Ford truck and an IDI tractor- ALL mechanical.

I did a quick look at my car and now realize why the engine tone changes when switching to basic settings! Someone noted that you're likely dead-on if there's little change when switching here. Seems, then, that my car isn't so dead-on as I might think it is: this is actually good news as it means that I should be able to improve it even more!

I'm still a bit perplexed as to how nearly identical timing graphs can result in different behaviors. Pretty sure that both cars can benefit from a resetting of the physical timing. I suspect that there might be an non-related timing issue with my wife's car, possibly injector issues: I was planning on doing a Diesel Purge on it in about 5k miles when I replace the fuel filter; am also planning on new nozzles and install with calibration.

Anyway, I appreciate the education here, and don't mean to hijack this thread. Just thinking that I might have a good case study going. Will report back on how this goes.

 

[Rembrant]

Yeah, nice explanation Todd. Beat me to it.

Uhoh,

The ECU has a range ('window') of timing it want's to be in relative to TDC:

072 Start of Injection - Specification (Idle): 12...75 (2 °ATDC ... 4 °BTDC) | (Full Load): 137...215 (8...14 °BTDC)

The IP has a range ('window') it operates in. This is based on the movement of the piston in the bottom of the IP that advances and retards the timing. There is a spring on one side of that piston pushing it to retard ignition. The other side of the piston gets fuel pressure applied to it via the SOI valve. This is why the ECU cannot adjust the timing until the car is running and the low pressure pump in the IP has built up case pressure.

Ideally, you move the IP until the range of the IP properly matches the range the ECU is looking for relative to TDC.

When the timing is advanced too far to the top of the graph, the ECU may not be able to retard the timing far enough to meet specified at idle...or during low load driving. The spring is pushing the SOI piston in the pump, but it physically cannot move further to retard.

For example, I have my mechanical timing set @ 70/110, and the SOI cannot retard timing past about 2 degrees BTDC, even if the ECU is asking for 0.5 degrees BTDC.

Where you set it depends on who you talk to...but I'm pretty sure a VW dealer tech would set it so that the actual timing can meet specified at all times. I've tried mine advanced for awhile now, but I'm going to play around with it to do some MPG tests...make sure I find my car's sweet spot. My car is working so darn good, I almost hate to touch it...lol, but I can't seem to leave the thing alone...not yet at least.

 

[UhOh]

Well, I'm about as confused as I can be now after taking a look at my wife's car. Here's a slice:

,15.08,903,Late,4.2,49.0,,,,,,,,,,
,15.44,903,Late,4.0,46.6,,,,,,,,,,
,15.79,903,Late,4.0,45.4,,,,,,,,,,
,16.15,903,Late,4.0,46.6,,,,,,,,,,
,16.50,903,Late,3.7,45.0,,,,,,,,,,
,16.85,903,Late,4.0,45.0,,,,,,,,,,
,17.21,903,Late,4.0,45.0,,,,,,,,,,
,17.56,903,Early,4.0,47.0,,,,,,,,,,
,17.91,903,Early,7.3,58.6,,,,,,,,,,
,18.27,903,Early,7.7,59.0,,,,,,,,,,
,18.62,903,Early,7.5,56.6,,,,,,,,,,

"Late," and then "Early," huh? Is this IP starting to flake out?

Just to make sure I've got this right, when probing via Basic Settings I'm effectively looking at the raw timing, correct? Is this the same for the timing graph, which, I'm not sure, is from the same Basic Settings function?

A few days ago I'd looked and I could have sworn that the timing was showing up in the mid way between the mid and upper bounds. Today I saw the graph with the timing hitting at and slightly above the upper bound. Fuel temp was significantly warmer too: it's been in the upper 80s here of late; when I last looked at the timing the outside temps weren't this high.

Here's a sliced output on my car (had logged extra stuff):

,26.12,903,0.4,1.8,2.8,26.51,903,0.0, 0 1 0,89.1,25.72,903,2.6,1.660,90.0
,27.23,903,0.4,1.8,2.8,27.59,903,0.0, 0 1 0,89.1,26.88,903,3.0,1.680,89.1
,28.31,903,0.4,1.8,2.8,28.67,903,0.0, 0 1 0,90.0,27.95,903,2.8,1.680,89.1
,29.39,903,0.4,1.8,2.8,29.75,903,0.0, 0 1 0,90.0,29.03,903,2.8,1.700,90.0

 

[RacerTodd]

Just to make sure I've got this right, when probing via Basic Settings I'm effectively looking at the raw timing, correct? Is this the same for the timing graph, which, I'm not sure, is from the same Basic Settings function?

Correct, in Basic Settings you are looking at the raw, mechanical timing only. The graph uses the same numbers, just puts them in an easier to read form.
Without the graph, you'd have to look up your fuel temp (box 9 in Group 000, IIRC) then the Start Of Injection in box 2 (I think), then look in the manual to see what the correct range for SOI was for that fuel temp. Much easier with a graph!
On the graph, fuel temp is across the bottom, SOI on the vertical axis. Note the upper and lower timing limits changes with fuel temp.

A few days ago I'd looked and I could have sworn that the timing was showing up in the mid way between the mid and upper bounds. Today I saw the graph with the timing hitting at and slightly above the upper bound. Fuel temp was significantly warmer too: it's been in the upper 80s here of late; when I last looked at the timing the outside temps weren't this high.

One thing that can trip you up when graphing timing is you need to select the correct engine in the bottom right of the graph. Different engines use different number ranges. Using the wrong engine type can result in faulty assumptions.
Also, the engine needs to be warmed up fully. If you read timing with the engine not fully warm, you could get incorrect readings.

As for the difference in the two cars. Fuel timing isn't the only variable that'll affect things like power, mpg, starting, etc. Condition of the pump internals, injector nozzles, etc can have an influence.

 

[UhOh]

Todd, thanks for the input.

What's baffling me is how the requested SOI jumps around from Early to Late like that. How can that happen? Is that because the cold start injection is cycling higher?

Since my car is more stable (even the data suggests such), am I safe to interpret its numbers as being just slightly advanced? Does it even look like there's any call for adjustment here?

 

[Rembrant]

Todd, thanks for the input.

What's baffling me is how the requested SOI jumps around from Early to Late like that. How can that happen? Is that because the cold start injection is cycling higher?

Since my car is more stable (even the data suggests such), am I safe to interpret its numbers as being just slightly advanced? Does it even look like there's any call for adjustment here?

Where did you log that section for your wife's car that it shows early and late? I've not seen this before. Is it showing early and late instead of the actual degrees BTDC and ATDC?

The SOI will climb closer and closer to the top of the graph as the fuel temp increases.

I'm just trying to interpret what you logged here...I can see time, idle, etc...but what are the other columns? I'm used to looking at the raw numbers instead of what they're converted to.

 

[UhOh]

Where did you log that section for your wife's car that it shows early and late? I've not seen this before. Is it showing early and late instead of the actual degrees BTDC and ATDC?

The SOI will climb closer and closer to the top of the graph as the fuel temp increases.

I'm just trying to interpret what you logged here...I can see time, idle, etc...but what are the other columns? I'm used to looking at the raw numbers instead of what they're converted to.

Engine, Basic Settings, Group 004. Just clipped from the log. I was surprised to see these as well. I suspect that they're far out of range(?) and that's the default display value for the upper or lower bounds. For my wife's car it was ONLY Group 004: time stamp, Requested SOI, Actual SOI, Cold Start Injection, (then a bunch of empty columns).

 

[Rembrant]

Engine, Basic Settings, Group 004. Just clipped from the log. I was surprised to see these as well. I suspect that they're far out of range(?) and that's the default display value for the upper or lower bounds. For my wife's car it was ONLY Group 004: time stamp, Requested SOI, Actual SOI, Cold Start Injection, (then a bunch of empty columns).

Ok...I'll have to take a look at mine tonight, but I've never seen that late/early business. Somebody else with more experience than me can chime in here...but I've only ever seen the timing numbers (in degrees or the range of numbers that the ECU uses).

Was her car idling during this time, and was it up to operating temp? Requesting 4-7.5 degrees ignition advance is weird if so...

I'm not sure why VW called the SOI valve the "Cold Start Injector"...that's not really correct imho. Some call it the commencement valve as well...but I've gotten used to SOI valve. In any case, the Cold Start Injector seems like a mis-label.

Since my car is more stable (even the data suggests such), am I safe to interpret its numbers as being just slightly advanced? Does it even look like there's any call for adjustment here?

According to the log data you posted for your car, your mechanical timing is slightly advanced. The ECU is requesting 0.4 degrees BTDC, and your actual is at 1.8 degrees BTDC, and the SOI valve duty cycle is at 2.8 (this is max retard). So, the ECU is requesting slightly more ignition retard than the SOI valve is capable of. You'd have to retard the pump timing slightly if you want actual to meet specified.

The timing on my car is also slightly advanced...almost identical to yours, and it works great.