Hi,
I have a LS1 with 4L65E in a fairly light Ford -32 hot rod. The transmission tune is all stock from a Camaro Z28 2002. The issue I have is when I go from neutral to drive at 650 rpm idle it drives forward too much. I have to push hard on the brake to prevent it from jumping forward.
Is there some parameter I can prevent it from pushing hard forward at idle?
PS
I'm experienced with the HP Tuner, but only at the engine side.
DS
Thank you!
There is nothing in the tune that can make the torque converter 'looser'. You'd have to buy a different, higher-stall converter, if that's really the cause of your issue.
But, is it adding too much idle airflow on the P/N-to-drive transition? Look at the Idle > Airflow: Base Running Airflow. See that the 'Gear' row has higher numbers than the 'P/N'? The goal of that is to keep the same idle speed even though load increases when it goes into gear. If that table's not right it could be adding too much air and making it push through the brakes. If the engine speed doesn't increase when it goes into gear then this isn't your problem, you just need a looser converter.
You'd really need to log all the idle parameters in the scanner, and compare to what's in the tune file. (you'll get better answers if you post a tune file & log with things like this)
Thank you blindsquirrel for your reply! The idle airflow is perfectly tuned and the in-gear values are in fact the same as the P/N values. The STIT is close to zero all the time at idle and the rpm is steady and the same both in P/N and in-gear. I guess I have to get another converter.
TCC isn't stuck on, is it? If you hold the brake enough to keep it from moving and go from P to D how much does engine RPM drop?
Originally Posted by bson
When you fail to post your current calibration (tune), it is impossible for anyone to make specific comments - everything becomes a generalized guess.
You mentioned using a 2002 Camaro transmission (4L60) calibration - did you actually mean that you are using a stock OEM 2002 Camaro calibration in the entire PCM ?
This vintage of Camaro programming was unique - and most often does not work well in a conversion vehicle, without some adjustments.
If you look at the tables for Idle Spark Advance - In Park, and Idle Spark Advance - In Gear, and compare these tables to calibrations from a Corvette or a Truck - it will become evident that the Camaro calibration is a bit odd.
The above mention table when in Park - usually has an Idle Spark Advance of around 18 degrees.
The above mention table when in Gear - usually has an Idle Spark Advance that jumps to around 28 degrees. This can cause a conversion vehicle to push forward - requiring the driver to use a lot of brake pressure to keep the vehicle stationary.
Looking at 2002 calibrations from a Corvette or Truck - the above mentioned tables are more similar than they are different.
As an initial test, I would suggest copying the values from the Idle Spark Advance - In Park table, and pasting these values into the Idle Spark Advance - In Gear table.
The next area to examine is as blindsquirrel had suggested - any related airflow parameter, table, or modifier.
Thanks for all feedback!
Here is my tune file. The engine tune has been modified a lot since I've made several modifications to the engine. The engine is, in my opinion, is running fine.
The transmission tune has not be modified and should be stock Camaro 2002.
Copying "idle spark advance in park" table to "idle spark advance in drive" was one of the first things I did to calm it down a bit when going from neutral to drive. The idle airflow has been tuned fine in my opinion. No sudden changes in airflow in the log when going from neutral to drive.
There is a tiny bit of adjustability in the baseline transmission pressure for closed throttle. I Would check the pressure at idle and see if it is reasonable, 60psi or 100psi or something I would think. It might be too high.
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