How do BLM modifications affect tuning?
Thread Starter
Staging Lane
Joined: Jun 2004
Posts: 76
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How do BLM modifications affect tuning? Yesterday, I was at the track (quarter mile) and my first run of the day was 14 seconds. This is a lot slower than I am used to running, so I pulled codes and found that my PCM was reporting a problem with the sense on the knock sensor.
I pulled the connector for the knoch sensor apart and found that it was full of water. I had washed my engine a few days earlier.
I blew the connector out and that fixed the problem.
For the next five run, the car kept getting faster and faster (dropping between .2 and .3 seconds every run unit it got to about 12.9 seconds.
It appears to me that it was "relearning". If that is in fact the case, how do we ever really do any tuning. Doesn't the engine continue to learn after a parameter is changed (say timing at a particular map and RPM). This would seem to be something that could make tuning very difficult. Maybe what this says is that I am no where near tuned... (if the BLM tables affect things so much).
Is there a way to save the BLM tables? If so, what function governs this under HPTuners?
Or... is something else going on?
Sam
I pulled the connector for the knoch sensor apart and found that it was full of water. I had washed my engine a few days earlier.
I blew the connector out and that fixed the problem.
For the next five run, the car kept getting faster and faster (dropping between .2 and .3 seconds every run unit it got to about 12.9 seconds.
It appears to me that it was "relearning". If that is in fact the case, how do we ever really do any tuning. Doesn't the engine continue to learn after a parameter is changed (say timing at a particular map and RPM). This would seem to be something that could make tuning very difficult. Maybe what this says is that I am no where near tuned... (if the BLM tables affect things so much).
Is there a way to save the BLM tables? If so, what function governs this under HPTuners?
Or... is something else going on?
Sam
What you experienced is the transition from the low octane spark map to the high octane spark map. I know in EFILive, the scaler PID is called GM.ASPARK. Basically, when the knock sensors go off continuously, the scaler pushes the PCM to use the values in the low octane table. This was ideally developed as a preventative measure incase you got a batch of bad gas or the motor started showing signs of detonation from some sort of part fairlure. Once you fixed the issue with the knock sensor, the PCM stopped receiving the (false) signal and the ASPARK gradually moved back towards the high octane spark map.
The PCM doesn't really learn optimals. It just adjusts things to be safe if it receives certain "bad" signals...like knock. The problem when tuning modified cars can be knowing what's real vs. what's false coming from the various sensors. Knock sensors, misfire detections and O2 sensors are classic examples of this problem.
The PCM doesn't really learn optimals. It just adjusts things to be safe if it receives certain "bad" signals...like knock. The problem when tuning modified cars can be knowing what's real vs. what's false coming from the various sensors. Knock sensors, misfire detections and O2 sensors are classic examples of this problem.
Thread Starter
Staging Lane
Joined: Jun 2004
Posts: 76
Likes: 0
Originally Posted by SSpdDmon
What you experienced is the transition from the low octane spark map to the high octane spark map. I know in EFILive, the scaler PID is called GM.ASPARK. Basically, when the knock sensors go off continuously, the scaler pushes the PCM to use the values in the low octane table. This was ideally developed as a preventative measure incase you got a batch of bad gas or the motor started showing signs of detonation from some sort of part fairlure. Once you fixed the issue with the knock sensor, the PCM stopped receiving the (false) signal and the ASPARK gradually moved back towards the high octane spark map.
The PCM doesn't really learn optimals. It just adjusts things to be safe if it receives certain "bad" signals...like knock. The problem when tuning modified cars can be knowing what's real vs. what's false coming from the various sensors. Knock sensors, misfire detections and O2 sensors are classic examples of this problem.
The PCM doesn't really learn optimals. It just adjusts things to be safe if it receives certain "bad" signals...like knock. The problem when tuning modified cars can be knowing what's real vs. what's false coming from the various sensors. Knock sensors, misfire detections and O2 sensors are classic examples of this problem.
I don't think so. I copied the high octane table into the low octane table ages ago. Is there a "limp home mode" in these PCMs? Also, I wasn't getting knocks. The pcm was reporting a low sense voltage (due to the mild short caused by the water in the connector). This would not cause false knocks. It would eliminate the ability to pick up a real knock.
Sam
Originally Posted by samgm2
It appears to me that it was "relearning". If that is in fact the case, how do we ever really do any tuning. Doesn't the engine continue to learn after a parameter is changed (say timing at a particular map and RPM). This would seem to be something that could make tuning very difficult. Maybe what this says is that I am no where near tuned... (if the BLM tables affect things so much).
Sam
Sam
