PCM power questions - 2 power sources?
02-20-2012, 09:53 AM
#1
PCM power questions - 2 power sources? I'm completely rewiring my LT1 and have a question regarding the power sources to the PCM. Forget the OEM wiring harness for a minute...it's long gone 
In the FSM, there are two PCM power sources -
---ALWAYS HOT
---HOT IN RUN
What is the purpose of the two power sources?
My thought is that the ALWAYS HOT keeps power to the PCM via the battery while the car is off so it does not have to re-learn every time the car is started. This is a race car, so I only really need it to perform under WOT conditions - these parameters don't need to be re-learned.
I'm also wiring a master cutoff switch on the rear bumper, so if the PCM DOES need an ALWAYS HOT feed, I need to rethink how I'm wiring this. If I only need the HOT IN RUN (switched 12v) power, then this is a non-issue.
Advice?
In the FSM, there are two PCM power sources -
---ALWAYS HOT
---HOT IN RUN
What is the purpose of the two power sources?
My thought is that the ALWAYS HOT keeps power to the PCM via the battery while the car is off so it does not have to re-learn every time the car is started. This is a race car, so I only really need it to perform under WOT conditions - these parameters don't need to be re-learned.
I'm also wiring a master cutoff switch on the rear bumper, so if the PCM DOES need an ALWAYS HOT feed, I need to rethink how I'm wiring this. If I only need the HOT IN RUN (switched 12v) power, then this is a non-issue.
Advice?
02-20-2012, 10:16 AM
#2
Since it's only a race car, I wouldn't worry about keeping power to the PCM.
You don't want it applying the trims from idle, or whatever cell it happens to be in when you snap to WOT, anyway.
If you're dyno tuned and you're on top of maintenance, changes in performance, etc., then you want the BLM's locked at 128 for WOT anyway.
You don't want it applying the trims from idle, or whatever cell it happens to be in when you snap to WOT, anyway.
If you're dyno tuned and you're on top of maintenance, changes in performance, etc., then you want the BLM's locked at 128 for WOT anyway.
02-20-2012, 02:03 PM
#4
..to read all the sensors and make the adjustments.
The power required just to store its trims is miniscule ("always hot"). This can be fed by your "hot in run" supply for a race car.
The power required for processing would kill your battery if left on continuously ("hot in run").
The power required just to store its trims is miniscule ("always hot"). This can be fed by your "hot in run" supply for a race car.
The power required for processing would kill your battery if left on continuously ("hot in run").
