Audi 40V 4.2 V8 - no power, gas guzzler

[elaw]

Well I stand corrected about the timing mark... that is really weird! Although there might be a TDC #1 mark on the flywheel?

But if you look at that PDF you linked, it actually tells you the tooth #1 angle! That's assuming you are using the factory crank/cam sensors and have the trigger edges correct.

On page 40 of the document it shows the tooth pattern on the crank signal and a "software reference mark" at 66 degrees BTDC #1 which is a little confusing. But if you look at the diagram, it appears that mark is tooth #2. So doing a little math: with a 60-tooth wheel each tooth is 6 degrees of crank, so tooth #1 should be at 72 degrees BTDC #1 (based on tooth #2 being at 66 degrees).

[benjaminearle]

Unfortunately we're not using the factory timing wheel (not sure why, exactly) and since it's all on the flywheel (which is conveniently located inside the non transparent bellhousing, we're stuck to the timing light / cyl #5 technique. There IS another mark on the balancer which may be #1 but it's just as easy to time against #5 as it is #1 as long as you're using the right mark.

[benjaminearle]

OK, rigged a HT lead and grounded a plug - got it sparking and found 93.3 on the timing light lines up the crank pulley mark.

So, then I put 93.3 into the "Tooth #1 Angle" (deg BTDC), set the timing light back to 0, maintain static timing at 0, and the light doesn't flash on the timing mark.

In a word (or phrase) WTF?

On the encoder wheel the 15th physical tooth is lined up with the variable reluctance sensor when Cyl #1 is at compression TDC - per the fab drawings we found.
It's a Bosch-style 60-2 so 58 physical teeth follow by a double gap of no teeth. Is this 15th tooth #15 or #16?

Also - maybe worth noting - the wheel is on the flywheel, not the balancer. 360-93.3 maybe?

[slow_hemi6]

Did you do the test with fixed timing set or MS commanding the timing?
Either way, what was MS calling for when you did the test? Whatever it was, unless it was fixed to 0, that will be an offset you have to allow for in the tooth angle if you are strobing for TDC/0deg.

[benjaminearle]

Fixed timing
0 deg advance
no prediction
0 deg cranking advance

[slow_hemi6]

Oh are you using a dial back timing light? I hate those things. They never seem to work with non distributor based ignitions.

[benjaminearle]

OK, so it looked about 45deg retarded when i finally found the mark with the 93.3 in the Tooth #1 angle, so i took that out of my 93.3 and started fooling around. 46.3 in the tooth #1 field made the line go where it should be.

Still have fixed advance @ 0
Still have no prediction
trigger offset (ignored anyway) @ 0
crank offset @ 0

This should be it, right? Unless I'm timed at TDC Exhaust (COP Wasted Spark) and that should show up if my advance numbers to run seem 360deg off, right? Then I'd add 360 to my 46.3? Or, since I'm wasted spark there's no way to know?

[slow_hemi6]

If it is 360 off it will run as wasted but won't run as sequential COP.

[benjaminearle]

Thanks Luke. Will have to wait until we have the cam sensor working to run true sequential. Guess my only tell for now will be if the injector timing doesn't make sense.

[benjaminearle]

I'd really like to know how in the world it makes sense that a 93.3 on the timing light translates into a 46.3 in the Tooth #1 angle. That's a 47degree difference.

I'm and engineer, so just HAVING a number the works isn't sufficient - i need to know WHY it works.

Possibly because we have a -2 wheel instead of -1? so divide the timing light advance by the number of missing teeth to get the #1 offset?

[slow_hemi6]

Was it a dial back timing light?

[Paul_VR6]

All the other vag 4 and 6 cyl are 78deg trigger. You sure you are using the right marks?

I agree try with a std no dial light and your own verified cyl1 tdc mark.

[benjaminearle]

This is the timing light we're using:

http://www.amazon.com/Actron-CP7529-Dig ... ming+light

It's a V8, not a 4 or 6.

The "internal use only" manual clearly says the timing mark (and the pulley is keyed) is for #5 (first cylinder on bank 2).

The trigger wheel is NOT the VAG trigger wheel - it's a custom 60-2 (custom flywheel/clutch wouldn't accommodate the stock wheel)

The installation diagram that is supposed to show how it was installed insinuates 84deg between #1TDC and the first physical tooth (meaning the two missing teeth are 59 and 0 (or 60).

Could this be a result of corrupted firmware in the MS3/MS3X?

[jsmcortina]

Could this be a result of corrupted firmware in the MS3/MS3X?

Very unlikely.

I use a similar timing light to that. Make sure that if you run wasted spark (or wasted COP) that you turn on the 2-stroke setting.
An incorrect setting on the light will show up as double or half rpm.

James

[slow_hemi6]

Nah that timing light has too many complicated features for use on wasted spark, cnp or cop. Anything with complicated electronic tach or dial back features hasn't worked for me. Basic featureless timing light and timing tape on the balancer, that's what works for me. That model you linked to has a real mixed bag of feedback comments as well. As an engineer you would appreciate that results are only as good as the equipment used to get them.

[elaw]

I'd really like to know how in the world it makes sense that a 93.3 on the timing light translates into a 46.3 in the Tooth #1 angle. That's a 47degree difference.

I'm and engineer, so just HAVING a number the works isn't sufficient - i need to know WHY it works.

Possibly because we have a -2 wheel instead of -1? so divide the timing light advance by the number of missing teeth to get the #1 offset?

You're running wasted-spark, right? If so, do you have the timing light set to "2-cycle" mode?

With wasted spark in 4-cycle mode, the timing light is going to think RPM is twice what it actually is since it's expecting one spark per 2 revolutions, but actually getting one spark each revolution. And as a result, it'll think the advance is twice what it actually is. If you divide 93.3 in half, you get 46.65 which is darn close to 46.3. The difference could be explained by the VR sensor being slightly out of position, MS triggering on the tooth edge but the wheel being positioned based on the tooth center, etc.

Anyhow, here's the test - that timing light displays RPM, right? With the engine idling at a reasonably known RPM, see if the RPM displayed on the light seems doubled. If it is, the advance will be doubled too.

[benjaminearle]

Eric,

You have made my day. And, made me feel somewhat a fool. All in that's not so bad.

[benjaminearle]

It's been a few months and no much happened on this car through the winter (Was working on a truck project which got stolen).

We figured out the bizzare timing problem - the 60-2 wheel was slipping around the flywheel adapter changing the tooth #1 angle every so often. Wow, that made it difficult to tune.

New problem is a weird non-sync spot at 1700rpm (missing tooth goes missing). I have another thread on it. Running only the 60-2 wheel but it acts like an engine with a cam tooth and crank tooth lining up.