ECU Added Timing As A Result Of Low IAT2 Temps??

[throttle jockey]

Does the ECU add timing when the charge temps/IAT2 temps get below a certain temperature?

In a recent post a member stated that in the OEM tune the ECU adds timing for charge temps below 105*. I've never heard this before. Can someone verify this for me? If this is correct, how is timing added by the ECU? Is this a parameter that can be adjusted in the tune? If so, do most tuners adjust this parameter?

Here's the post that peaked my curiosity about this:
The National Lightning Owners Club Inc - View Single Post - Stock bottom ends FTMFL!!!


I'm a fairly conservative driver, especially in cooler temps. I have a cold weather/91 octane tune intended for 50* ambient temps or less but I really have no need for the tune since I generally avoid going WOT in temps lower than 60-65*. I refuse to go WOT in anything less than 50* ambient.

I've been trying the past couple of weeks to hit the track in the cool winter temps hoping they will aid me in getting into the 11s, but I've decided to pass on racing each time since ambient temps have been in the low-to-mid 50s or lower. My race tune has 16* of timing running 104 octane. With my use of the Killer Chiller greatly reducing charge temps in conjunction with the cool winter temps I suspect (at least early in the pass) that my IAT2 temps will be below 105*. I just don't want my timing to get too aggressive in the event the ECU does in fact add timing when IAT2 temps are below 105*.

 

[LightningClint]

Subscribing for one of the best questions I've heard in a while

 

[throttle jockey]

For anyone interested here's a thorough explaination from a member on one of the other forums:

The EEC will indeed subtract and add timing to the border line knock table up to the point of the maximum values contained in the base spark tables (sometimes called max spark tables, depends on the eec), some tables are called the MBT (Max. Brake Torque)tables. Just as said above, the EEC will in fact add timing unless the tuner zero'd out adding timing below 105* IAT2. The EEC is continuously comparing the different timing tables and will alway choose the timing map with the lowest timing. So if the tuner maxed out the base timing table at say 14* degrees and the borderline table on a cold day will exceed it because of low IAT2, then the borderline table will not be the table used. Most tuners change all the tables, some lock the timing to a maximum amount, but not always, some choose to ignore the other timing tables completely which will account for added timing during IAT's below 105 degrees. I routinely change this in the tuning software and have personally data logged this and know it to be true.
PS, I may be able to get a screen shot of the software I use later today.

 

[LightningLou]

Yes, it's true. If you reduce the MBT table to the max timing you'd like then it will not exceed those values. The MBT table is really the "limiter" so to speak in timing. When your IAT2's are very low the PCM can add maybe 3-5 degrees of timing in that load/rpm value. This is what I noticed when datalogging and it drove me nuts because I was afraid of blowing my block.

 

[Bird]

Yes, it's true. If you reduce the MBT table to the max timing you'd like then it will not exceed those values. The MBT table is really the "limiter" so to speak in timing. When your IAT2's are very low the PCM can add maybe 3-5 degrees of timing in that load/rpm value. This is what I noticed when datalogging and it drove me nuts because I was afraid of blowing my block.

FWIW - the MBT table is used only for torque calulation - the MAXIMUM ALLOWED SPARK table is what limits the total spark.