Some Cold/Low Load & RPM Surge - Piston Slap Spark and Cold Launch Spark Questions

Guys, I am getting some surge feeling at time when cold and low speed. I get some in 6th-8th when the TCC locks, it goes away when warm.

I also get it when pulling out of the parking spot headed home from work.

Looking at the log, the spark is quite low when this happens. It almost feels like a miss, but I am also looking to see what the TPS is doing to make sure it isn't trying to vary and maintain idle airflow.

One thing I wondered since it seems to come back a little after startup is some of these startup modifiers. The piston slap spark and cold launch spark is about all I see. I assume these remove timing and do not add? That is the main thing I wanted to clarify before messing with it. I also wanted to see if anyone else had any feedback on these tables based on their changes.

Thanks.

When the car is cold and in Cat warmup, it will pull a lot of timing via Torque Management Advance to heat up the cats. I see total timing of -8 to -12 degrees at idle right after a cold start until the water temps come up a little. Only take a bout a minute. During this time the car is a little bit jumpy but it's not really an issue since I have a manual transmission.

There are a couple of things you can try. First, by reducing the Virtual Torque Tables in the idle and off idle area, it will reduce the Torque Management Advance affect. But also the Idle External Load and the Idle Speed Control Reserve tables have a direct effect on throttle position and timing to maintain idle and just off idle torque values. Kind of like the old airflow tables but now with timing logic added to maintain an RPM based on what the ECU thinks the engines torque output is and what it wants. Additionally Idle Torque Limit Offset value is the maximum amount the ECU is allowed to add/remove from the External Load Table to reach the target idle/torque. If this value is too high it can cause surging and wild idle swings. If it is too low it can cause stalling.

As for piston slap, that is a thing of the past I thought. Your tables are likely zero'd out right? Cold Launch Spark I've never touched. I ASSUME it is a spark adder table to offset the Torque Management Advance when the car is cold. It would make sense that it could help by adjusting this but I still think the above mentioned items would be the proper way to go. That table might only be uses my Manual cars just like the Launch Assist table.

I will see if I have the tables you mention.

No, my tables are not zero. I have areas at 20 deg in the piston slap and 10+ in launch. Cold in the AM when I let the truck idle to move my wife's car I am fine. In the afternoon I take off faster and notice it. That is why I was thinking the launch table (with a run timer on the left axis) may be part of it. I am going to try to see today what it does when I leave work.

If they are adders, they are crazy high in my opinion, but if they offset the other tables it may be OK. If these are additional subtractions, it seems excessive. I wish I could log those values to see what it is doing.

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Originally Posted by WS6FirebirdTA00

I will see if I have the tables you mention.

No, my tables are not zero. I have areas at 20 deg in the piston slap and 10+ in launch. Cold in the AM when I let the truck idle to move my wife's car I am fine. In the afternoon I take off faster and notice it. That is why I was thinking the launch table (with a run timer on the left axis) may be part of it. I am going to try to see today what it does when I leave work.

If they are adders, they are crazy high in my opinion, but if they offset the other tables it may be OK. If these are additional subtractions, it seems excessive. I wish I could log those values to see what it is doing.

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Torque Management Advance is also much more aggressive during a cold start so your final timing value is much much lower when cold than it is warm. Torque Management Advance subtracts from the final spark value. So after the base table is referenced, then all of the adders and multipliers are considered, TMA subtracts from that value. My Final timing is around 30 degrees at idle, but TMA pulls out 40 degrees during cold start and my cold idle timing is negative 10 degrees. Once the car warms up the TMA only pulls around 15 degrees so my warm idle timing fluctuates around 12-15 degrees.

Anyhow, you can log Base Spark, Final spark, Torque management Spark and even others if necessary. Then start the car and immediately start data logging. You will be able to see what the timing logic is doing and have a better idea of what is going on. Then you can adjust the tables and see what affect it has on each of the spark values. If you get get a log of that it might help.

I did see the values in the scanner so I have it set up to look at those now too. Thanks!

So, my idle external load table had a jump at 1300 RPM. I looked at a 2016 (5.3) and 2018 (6.2) calibration and they do not have this.

I see some odd stuff happen around 1000 RPM, so I am going to try to smooth these values out to see if that helps.

Anyone else seeing odd jumps in the calibration? There have been a few tables I have seen like this which don't flow as you would expect.

I disabled cat warmup and still get some hesitation when it is cold.

Looking at torque values and fluctuating timing and throttle I can only assume cold it is making more torque and affecting the driving feel.

I need to look through cold start modifiers to see if there is anything there. I just feel like there is a table that can use some smoothing to fix cold driving.

Have you tried messing with the External Load Torque under the Idle Tab? Not sure if it will help but you can lower the values in the cold start temp range and see if it helps.

I have but only in the warm cells. I will try the cold ones. The warm issue seems to be solved by lowering cat warmup.

From what I see I am questioning if it is a miss or torque converter issue. Being the 8 speed I always questions the transmission. It almost feels more like a bucking at low throttle until about 30 seconds or so pass.

I am going to start a new post. I am seeing a few random misfires cold that I think is related to fueling or the DI plug temp range.

Fixed it, decreased the VVT vs ECT multiplier to less than 1.0 up to 68C ECT. It runs great cold now, just as well as when warm and no matter the load.