I thought about just sending this question directly to you AdrianD, but I guess this thread is designed to allow the community to discuss and explore what might be possible. We might as well examine the entire range of potential mods, not just the more fuel, more air that many tunes focus on.
So, it would appear we have a drivers wish map for high range, a different one for low range.
We also have different shift schedules available for high range and low range.
The transfer case switch appears to be connected to the ECU, not TCU, therefore the low range signal must be sent to the TCU via comms.
My goal with tuning is to improve relaxed drivability. So, I am aiming for increased bottom end torque, lower shift schedule, earlier TC lock. All great stuff for lightly loaded conditions.
Problem is when it comes to towing. Sure I could just try and fine tune the DW map with regards to throttle input, but I think that would result in a less smooth experience.
Now for all those people reading, this is just a theory question for now.Trying to put some thought into what might be possible. Food for thought.
What do you think would be the result of the list below?
Take the wires from the transfer case switch up to a manual switch on the dash.
Adjust the TCU high range shift schedule to match my relaxed lower reving driving style.
Adjust the ECU high range DW map to provide lower boost at lower throttles for economy AFR, but then increased boost/IQ at lower rpm and mid throttle for the low down torque when needed.
Adjust the TCU low range shift schedule to up the RPM a bit and provide a more responsive engine.
Adjust the ECU low range DW map to provide more boost at lighter throttles to keep the exhaust temperatures down.
Adjust the TCU low range ratio to 1.
As far as I can tell, the transfer case is an entirely mechanical device and doesn't care about fancy programing.
So with the transfer case in high range. The switch on the dash could be used to change between the relaxed map, and towing map in both the ECU and TCU.
Problem would come when actually selecting low range. If I am looking at this correctly, this would result in extremely low rpm gear changes as the output shaft of the transmission is expecting to see a 1/1 ratio in it, but instead is 2.72/1.
Obviously this is a really bad situation. Now this bit is where we are all different, but I rarely, if ever, go off-road anymore. It would mean that on the extremely rare occasions that I hit low range, I would need to manually select each gear to bring the rpm back to normal.
For me, and my driving style, I think I could handle this. The benefit of having a normal mode, and towing mode in the ECU and TCU tune would far outweigh the hassle caused to the actual low range driving.
Oh, and I guess heading off for a weekend of off-road driving would be a planned thing for me, so I could just whack the original TCU tune in for that time if really required.
What do you think? Potential area to explore, or crazy idea that will result in a fireball parked by the side of the road?
|