Here's some things to think through on how to solve, you have three options
- run two PCMs (one for the drivetrain and the stock LS PCM for everything else)
- run only a new PCM that will work on the new drivetrain and everything else
- run the stock LS PCM and mate the new drivetrain to it
- run two PCMs (one for the drivetrain and the stock LS PCM for everything else)
remember - modern cars are not simply wires coming from a sensor to a pin on the PCM, many of the signal are caommand issued to a bus that the several computers share, pickup the messages for themselves and drop new messages for other systems on the bus to handle.
- since the engine management needs to control the fuel - the LS FEM will not be used for that, but will you still use it for fuel level? The 4.6L typically uses a seperate FPDM for the fuel pump and not the FEM system. How are you goning to integrate to the dash?
- since the dash is connected to the LS PCM, you will not get things like RPM, unless you do what the other two guys did and swap dashes with a custom solution. Then you lose little things like your PATs, trip computer, ...etc.
- things like ABS, traction control and SRS are not allowed to be 'modified' since the car pass DOT with it, that why you cannot pass inspection with those item in an error condition, you can disable them but only with using a factory feature. Another example, you cannot legally pull the steering wheel airbag and put a TV screen there... So with ABS - the PCM need to use the wheel sensors and other car sensors to determine that although the driver appears to be braking hard, the vehicle is still moving alothough the tires have stopped rotating (or some of them have) - then it modulates the brake pressure to allow the tires to keep from skidding. if you run two PCMs - which one has all though inputs to do this? the stock LS PCM will likely still control the brakes, ABS, but don't you have to feed the wheel sensor input to the dash to a speedo? which PCM is controlling that?
If you are going the route to pull the stock PCM and replace it with a single new engine management solution - then you have to think through all the issues of controlling things lights, turn signals, ...etc. the turn stock on the steering wheel simply tells the FEM that the driver pushed the turn stock down, the FEM then manages which lights come on. it seems to be difficult to replace that functionality with a standalone PCM, or trying to re-wire a different PCM to work with the FEM.
If you are going to try to mate a different drive train to the stock LS PCM - would seem to be the easiest way - however we currently do not have enough deep control over the PCM code to change things like crank counts, or cam shaft teeth - so the 4.6L and the 3.9L are different, and I believe the only way to fix this is $custom$ tuning by SCT themselves to dig that deep into the code - which I believe is what Ken is doing.
All three options are posible, although it seems that the two PCM route is really the only practical one.
