Set Ignition to after TDC in ign. table. Possible?

[tweak]

Not sure if this is covered somewhere else, but i fire off a topic at it.

I'm now involunteerly running my Audi ABY on 95" RON,  subsequently i got a problem with knock under load at very low RPM (0-1400)

I set the advance to 0° and it got better, but the knock is still there.
I think that we have to forget about knock sensors for now, so i need further retard of ignition by a fixed setting.
Setting it to a minus value does not seem to work, it just defaults back to 0°
In a test i moved the primary trigger another 10° back and the knock was gone. So i know that appox. 10° after TDC i'm knock free. 
So the question is, can i  somehow get the value in the ign table to a value after TDC?

[gunni]

You can do that with anytrim table.

In anytrim control go into the 3rd anytrim control and set it to ignition correction.

Then select MAP as the input source. Then adjust the curve so that at a specific boost level you get more retarding happening.

This will solve your current problem.

Also go into Ignition settings and adjust the "Ignition retard clamp" to your latest possible spark time.

Say -10 or -20 degrees. otherwise the ecu will not allow you to retard below the current value.

[mattias]

I've never come across this situation. 
How can you be sure it's knock and not just mechanical vibrations caused by the slow speed? This is common, if you try 5th gear at 1000 rpm, most gearboxes and drivelines can make horrific noise in that situation.

[tweak]

Gunni, thank you, but
In the Anytrim table, how do i get it to the correct rpm area?
I don't want a general retard by map only, but at a certain map+rpm area.
I'm only able to see a map range from 0-1024 and a anytrim scale bin with possible values from 78 to 178


Mattias.
I can never say for sure without a pressure sensor in the cylinder or at least a working knock sensor, but there is things pointing me in that direction.

- The "Knitrande lyd"  always come at 0-1400 rpm in any gear, can even be heard at a split second when you rev it from idle.
- Driving on 95
- Had to blow the crankhouse ventilation back into the turbo d/t icing problem last winter, still don't fixed.
- Sound gone in test with -10° primary trigger.
- Sound is even more in cold and wet condition.

I can make a recording but quality likely to be bad...

[audis2turbo]

I'am interested to her the record.please make a good record to hear for us;-)

[gunni]

Gunni, thank you, but
In the Anytrim table, how do i get it to the correct rpm area?
I don't want a general retard by map only, but at a certain map+rpm area.
I'm only able to see a map range from 0-1024 and a anytrim scale bin with possible values from 78 to 178


Mattias.
I can never say for sure without a pressure sensor in the cylinder or at least a working knock sensor, but there is things pointing me in that direction.

- The "Knitrande lyd"  always come at 0-1400 rpm in any gear, can even be heard at a split second when you rev it from idle.
- Driving on 95
- Had to blow the crankhouse ventilation back into the turbo d/t icing problem last winter, still don't fixed.
- Sound gone in test with -10° primary trigger.
- Sound is even more in cold and wet condition.

I can make a recording but quality likely to be bad...

In this case your best bet is to fool the ecu into thinking that -10 actual ignition timing is 0. You do that with the trigger reference setting
then change the whole map by 10deg and retune the problem area. Not exactly a clean solution

[GintsK]

Negative values are required quite often. E.g BMW M50 - it came from production with negative values in low <1000rpm area. Potentially any engine with high CR and narrow cam phases needs negative angles...

[GTOBB]

strange, never hear it in my s2 , but i have got lower CR pistons and always use 98oct.

[Ignitec]

Than you don't need atdc ignition
My c20xe isn't very happy at load at low rpm with 11.5:1 and 95 fuel (no 98 here), but it can run 1-2-3 degrees before tdc, WOТ, 1000rpm. However, it depends on fuel quality.

[tweak]

I have orginal pistons and C/R. What i did was to raise the ingition significantly according to another topic here which reports good experience with values over 40° and up to 50° BTDC. I tried this, of course after filling correct fuel. Did not check the fuel perfomance, but after a longer trip this low rpm knocking got less, and was completly gone for a while at warm engine, but returned after a few days and can be heard specially with cold engine.

I suspect carbon buildup on the pistons and too high C/R causing compression knock.