How can I put negative timing values in $12P

Charlescrown · Post by **Charlescrown** » Thu Feb 12, 2015 2:16 pm

Need a little help with this one.
Is there something I can change in the $12P XDF that will allow me to put negative timing figures into the spark table?

Post by **Holden202T** » Thu Feb 12, 2015 2:32 pm

hmmm ... well I don't believe so .... but I also have to ask, why would you want to ?

Charlescrown · Post by **Charlescrown** » Thu Feb 12, 2015 2:46 pm

New that question would come up. I have a Starion that I fitted Delco to and also have a Mitsu EVO4. I looked at the stock EVO map and they have some serious retard at high boost so what I wanted to do is start with the base map and tune from there. I figured it would be a good starting point. Not that my car will see that much boost it still has a few minuses in the map.

Post by **VL400** » Thu Feb 12, 2015 3:31 pm

The ECU is capable of negative timing but you cannot have a negative value in the main table.

There are a few ways fudge this if you really want negative spark. Some tables and scalars allow for spark subtraction, first check that "EST params - Maximum Spark Retard from TDC" allows for negative values (normally its about -15 by default.

Then use the item "EST params - Coolant Advance Table Bias Term". Default is 20 deg, change this to 25 deg to pull 5 deg from everything. If you open the tables "EST - Coolant Advance vs MAP and Temp" (there is a boost table also) will now see a stack of negative numbers. If you have 0 in the main table and the coolant advance table has -5 the delivered advance will be -5deg (and will see this logged so its not as hacky as fudging the ref angle).

Charlescrown · Post by **Charlescrown** » Thu Feb 12, 2015 3:51 pm

Thanks VL400 new you would let me know a way. I don't think I will ever get into the negative zone but just in case I get adventurous in the future.

Post by **Holden202T** » Thu Feb 12, 2015 6:05 pm

I cant really under stand the reason needing a negative ... if the evo4 has it ... why not just have zero ... in theory if it gets past TDC without detonating why would you need a negative value ?

Charlescrown · Post by **Charlescrown** » Thu Feb 12, 2015 6:16 pm

Detonation occurs well after TDC to as far as 50 degrees after. It never occurs BTDC unless there are some really really serious issues but I am not sure why Mitsu go so far as 10 degrees after in the maps. I had a close look and would think my car would not get into that zone unless I get some serious boost at very low RPM. At the moment I have set all the regions to 0. Maybe it's to get more boost happening with a bit of after burning or to get engine preservation in a stupid zone.

How can I put negative timing values in $12P

How can I put negative timing values in $12P

Re: How can I put negative timing values in $12P

Re: How can I put negative timing values in $12P

Re: How can I put negative timing values in $12P

Re: How can I put negative timing values in $12P

Re: How can I put negative timing values in $12P

Re: How can I put negative timing values in $12P