Ignition Angle and Air/Fuel Ratio

[Demetris Nenes]

Hi all,

 

Recently purchased a durametric tool and am having great time with data logging the engine info on my 2003 996 Turbo (stock).

A few question for your guys:

 

1) My Ignition angle goes up to 40 when running the engine up to 4K RPM. Idle is about 6

From your experience does this sound normal?

 

2) My Oxygen Sensing values for both banks is 1 all the times, except when I go in boost mode which then it pushes up to 5. So 1 for no boost and then 5 when we have a boost.

From your experience does this sound normal? Does this indicate that maybe there is a boost leak in the system? The max boost seems to be 0.6 - have not seen a 0.7, but then again never pushed the engine yet above 5K rpm.

 

Thank you

[Silver_TT]

I don't know what an ignition angle is.  Do you mean the cam deviation?  That is measured at idle with the engine at operating temperature.  6 degrees would be pretty high, how many miles are on your engine?  It's not common but the Mezger can stretch chains as I have discussed with Jake Raby in the past.

[JFP in PA]

I think he is referring to ignition timing as "ignition angle".

[Silver_TT]

Thank you, I think you are right.  The degrees make me wonder if it is a reference to the vane cell camshaft adjustor's position as this is also closely related to the ignition timing (it's job is to advance or retard it).  I expect that it would be fully advanced, somewhere near 40 degrees, at WOT or high RPMs when the timing gets advanced.  The numbers sound normal to me except if this is the case the 6 degrees at idle is too much.

[Silver_TT]

Correction to my post above.  Your numbers look similar to this:

Tests

WWW.SYSTEMSC.COM

---

Automotive Electronics for BMW, Porsche, Mercedes Benz, and Asian vehicles

 

Your 996 numbers are very close (appears to be for all 996s both NA and turbo, which makes sense I think):

Porsche 986/996 MAF & DME System Data

 

RPM	MAF (volts)	Mass Flow	Ignition Timing	Load (ms)	Pulse (ms)
Idle	1.30	15	5.0	1.10	2.6
1000	1.35	20	10	1.20	2.6
2000	1.70	40	23	1.20	2.7
3000	1.90	60	32	1.20	2.7
4000	2.11	80	36	1.20	2.6

 

Edited December 27, 2023 by Silver_TT

[JFP in PA]

1 hour ago, Silver_TT said:

Thank you, I think you are right.  The degrees make me wonder if it is a reference to the vane cell camshaft adjustor's position as this is also closely related to the ignition timing (it's job is to advance or retard it).  I expect that it would be fully advanced, somewhere near 40 degrees, at WOT or high RPMs when the timing gets advanced.  The numbers sound normal to me except if this is the case the 6 degrees at idle is too much.

They may be the result of a DME "tune", common aftermarket tune factors are more timing and more boost.

[Demetris Nenes]

On 12/27/2023 at 8:27 PM, Silver_TT said:

Correction to my post above.  Your numbers look similar to this:

Tests

WWW.SYSTEMSC.COM

---

Automotive Electronics for BMW, Porsche, Mercedes Benz, and Asian vehicles

 

Your 996 numbers are very close (appears to be for all 996s both NA and turbo, which makes sense I think):

Porsche 986/996 MAF & DME System Data

 

RPM	MAF (volts)	Mass Flow	Ignition Timing	Load (ms)	Pulse (ms)
Idle	1.30	15	5.0	1.10	2.6
1000	1.35	20	10	1.20	2.6
2000	1.70	40	23	1.20	2.7
3000	1.90	60	32	1.20	2.7
4000	2.11	80	36	1.20	2.6

 

Thank you so much for sharing this. I will check the above parameters on my next Durametric check.

[Demetris Nenes]

Durametric refers to this as "Ignition Angle" - and believe it has to do with the "advancement" or "retardation" of the ignition.

[Demetris Nenes]

On 12/27/2023 at 9:55 PM, JFP in PA said:

They may be the result of a DME "tune", common aftermarket tune factors are more timing and more boost.

Thanks guys for your replies. My engine has 196K on it and i am not sure if there is a "tune" on the DME.

How can I check if there is a DME on it? Can Porsche dealership "reprogram" the DME? 

 

Also do you have any idea about the second question i had about the Oxygen Sensing?

[Silver_TT]

You guys are correct about ignition angle, different OEMs refer to it differently and I had forgotten this is what the variable is called in Durametric.  You should also check the Camshaft Position Deviations, which is effectively the angular deviation from what the vane cell adjustor is supposed to be advancing or retarding the timing.  Generally the timing is locked in the fully retarded position to start and then is advanced by the DME using oil pressure and a solenoid.

 

A PIWIS can tell if the car has been tuned but there is no way that I know of in Durametric.  If Durametric has a field for the number of times the ECU has been flashed as some do, this could be an indicator.  If it was tuned, Porsche or the tuner should be able to set it back to stock.

 

For your question about o2 sensors, are you looking at the precat or postcat value?  The post cat value should not "follow" the precat value.  For my naturally aspirated 996 here is an old thread of mine with relevant notes, I would think it should apply to the turbo as well overall:

 

Going back and reading that thread of what I did 10 years ago is pretty funny... I never would buy the O2 sensors on Amazon now like I did back then.  I am wiser now... but also older 😉  

Edited December 29, 2023 by Silver_TT

[Demetris Nenes]

On 12/29/2023 at 11:32 AM, Demetris Nenes said:

Thanks guys for your replies. My engine has 196K on it and i am not sure if there is a "tune" on the DME.

How can I check if there is a DME on it? Can Porsche dealership "reprogram" the DME? 

 

Also do you have any idea about the second question i had about the Oxygen Sensing?

I had Porsche reprogram my DME, which they guaranteed the car would return to stock performance. Well what a difference did that make to the car. The car is idling on lower RPM, "feels" less powerful on lower RPM, but at the same time it is much more smooth. Of course once you are above 3500 RPM the car is transformed! 🙂

 

I need to hook up the durametric tool and see what are now the ignition angle values!