SOT -Negative spark advance, seeing this on my VW Tiguan Options

[fixer34]

Doesn't appear to be causing a problem, just never seen (looked?) it before. Had an OBD II scanner hooked up which also does real time monitoring. Was driving around and noticed that stopped/at idle, rpm was 750-800 and spark advance was -15 (15 ATDC?). Normal around town it runs about 2000rpm and +15, peaking to +20/25 at 3000.
Redline is about 5000, haven't pushed it near that.

Also noticed when backing off, even at 1500/2000, the advance will go negative.

Is this all part of the computer controlled emissions system?

[technicalninja]

Yes, normal operation, especially at idle.

The first variation of computer control on an ICE engine was idle alone.

Those late 70 early 80s cars were IMPOSSIBLE to set base timing on without putting them into "base mode". With GMs you crossed two terminals in the ALDL (check engine light) connector. Almost everything else had a "timing adjustment" connector somewhere.
Sometimes they were front and center in the engine compartment (like Toyota) and sometimes they were so hidden unless you knew exactly where to look you were screwed.
The OBD2 connectors made life SO much easier but by that time most adjustable timing distributors were gone so no more timing adjustments.

You'd set timing normally and pull the short. In computer control you might see 30 degrees either way and it would vary wildly. Most of the time you couldn't even see the timing mark. Looked like chaos!

Seeing something constantly stuck one direction was a cause for concern.

Unless you are also seeing DTCs in computer memory you have nothing to worry about.

[technicalninja]

You want to really see something wild?

On a car with an ETB (electronic throttle body) the throttle will not close immediately after removing your foot from the pedal. It will stay the same or OPEN MORE during engine deceleration to reduce throttle closure mixture spike to rich.

The ECU decelerates the engine via ignition timing and injector pulse width modulation and the throttle stays OPEN a LONG time.

This is part of the programming on all of the Chrysler high output hemis. Owners HATE this as you can't "rump rump" the throttle at idle.
You can accelerate the engine quickly; it takes a long time to come back to idle.

And the first mod most folks do to those is throttle remapping to allow them to do this.

So, for noise alone, folks are willing to break Federal emission laws!

800+ hp legally and they modify for this...
(IMG:style_emoticons/default/screwy.gif) (IMG:style_emoticons/default/screwy.gif)

[emerygt350]

My mustang does this and it's an 84. Tfi on Ford's require you to disconnect a wire near the tfi module (spout connector) and then you set your timing.

[fixer34]

Thanks guys, figured it was 'normal' since there weren't any codes and it seemed to run fine. I just never remembered ever setting timing for ATDC, but then again, that was back when cars had distributors...