NefMoto

Hi guys!
I have just bought a Porsche 997 Turbo to use as an extra daily driver when my Seat Leon 20VT needs a rest. The Porsche sometimes has a slight hesitation during full load acceleration. It happens around 3000-5000 RPM and not exactly the same every time. It's like a quick decline in acceleration, and a non-car guy might not even notice it. I have been trying to figure out what causes it, and the first step was to log timing with the Torque app and ELM327 adapter. Timing values look pretty similar to my Seat's, dropping to maybe 10-12 degrees mid range and increasing to 17-18 higher up.

The question is, what is the timing value from the standard PID telling me about the complete timing situation? I read somewhere that the PID shows cylinder 1 only, so could I have massive timing retard on other cylinders and not know it? Or will knock on a few cylinders cause all the others to retard as well, in which case I would see it on my log?

The ECU is a Bosch unit called DME-something. I figured someone on this forum might know something.  :)

There is no KR PID.

I know, but there is one for timing advance, right? Just trying to figure out if it is at all useful.

No, there is no ignition timing PID.

Recovery from KR is via basic hysteresis

He's talking about OBD PIDs https://en.wikipedia.org/wiki/OBD-II_PIDs not about PID controllers IMHO.

Oops, sorry about the confusion.   ;) Yes, I'm talking about the OBD PID (Parameter ID) for timing advance.

What I want to know is basically if what I'm seeing on the PID is just cylinder 1 (it says so at some places online), and if I would have crazy amounts of knock retard on another cylinder, would all others be retarded as well, so that I would see something on the PID signal?

It's not the smoothest signal in the world, but it's pretty consistant over several pulls so I think it should be somewhat representative for what's going on.

Plugs replaced recently? Correctly gapped?

Yep, plugs are only 1300 miles old. Replaced by certified Porsche Dealership so I would hope thay are correctly gapped. I didn't own the car at the time.

What gear was that log done in? Resolution looks piss-poor to me, but I'd say there isn't much wrong with 12.5 degrees timing at 4500 on a stock 997TT, so not sure what the "problem" is here.

3:rd gear. Right, good to hear from someone else that the timing looks pretty normal. The thing is I do feel a slight shutter in the car during hard acceleration that I'm pretty sure shouldn't be there, but I guess it's not from KR then. It sort of feels like the traction control is doing something, even though traction shouldn't be a problem at those speeds.

Shudder usually means misfire

Automatic?
Could be one of the torque limiters.

Check yours DVs

Yes, automatic!

Sounds interesting, could you elaborate? Anywhere I can read about how that works?

These models have poor ignition coils. Replace them.

Thanks for the input guys! I think the coils might be the prime suspect at this point. I'll order a new set.

You should be able to see which cylinder(s) are missing under load with a higher end scan tool. Could be only 1 weak coil.