Please bear with me as I pose this question to all the mechanical gurus, it may sound ridiculous.My girl is the one with the 04 G35X and loves the car overall. But her and I don't prefer the RWD bias in inclement weather until slip is noticed, and therefore we need some more input.

This is were my quandry lies, would it be possible to reprogram the G35X when it is in snow mode. Instead of the car reverting back to 100% RWD bias over 18mph(not exactly sure the speed), would it be possible to reprogram the computer or piggy back it so that the car is atleast a 25/75 split all the time when snow mode is engaged, or just something better than the 0/100 split until slip is noticed.

Remember now, I am not familiar with the mechanics of AWD. What would limit someone from doing this, does the problem lie in programming the cars computer or do the mechanics of the awd system limit this from being possible.

I think I read that the new G35X is actually a 25/75 split in snow mode despite the speed.(Even over 18mph)

Thanks for the help and I look forward to all responses.

without speaking to some Gx specifics I am not familiar with...

The issue on most cars nowadays is that all the electrical systems are integrated. That doesn't mean it on has one computer, often it has many. Depending on how your G is equipped it will have one for the navigation, and for the climate control (maybe the same box maybe different), one for the 4 wheel steer 9maybe), and also have ones for the engine, the transmission, and the AWD system. This can lead to problems in making all of the systems communicate when they communicate via the CAN bus.

Its not as simple as turning a knob. Any system like this uses a set of algorithms and a lot of sensor input to decide when and how much power to transfer. Because of the way these are setup, your not going to see a lot of piggy back capability for somethign like this. Maybe there will be more interest if the new GTR uses a similar system in getting a tuner setup for the AWD but right now thats gonna stay a luxury car. Doing a piggy back on the AWD controller might also require electronic surgery because I doubt the AWD controller has a OBDII port on it.

The G is also designed as a RWD platform that has to be adapted to AWD (effectively adding FWD). This can lead to inefficient packaging (old GTR's with a driveshaft through the oilpan) and many other problems. The end result may be the use of parts that aren't as strong. The system may just not be capable of sustaining higher power levels in the front than what the system currently transfers.

Hope that helps a little bit...the way cars are done now, its becoming harder and harder to just piggyback major functions.

Thanks for the informative answer, but I am wondering how much reprogramming would have to go into only changing one particular area (Snow Mode button reprogramming) The AWD system in good weather is flawless and would not want to mess with any of this function.

So my logic is that since the car is already programmed to act differently during snow mode activation, would it be that hard to just change that part of the AWD system.

In addition to the mechanical problems, would the CV joints/axles really have a hard time holding up due to prolonged driving with a 50/50 split. Because at low speeds with snow mode enabled, all 4 wheels are driving, hence a ton of stress is put on the vehicle and there is no adverse effects from this. Why would it be any different of a scenario at speeds in excess of 18mph, isnt most torque initiated at startup in bad weather.

pits200 wrote:So my logic is that since the car is already programmed to act differently during snow mode activation, would it be that hard to just change that part of the AWD system.

It really depends. The problem is that if you don't have a programmable controller already built for the unit your gonna be outta luck. If you have ever seen screenshots of somethign like engine mapping that is probably what your thinking of changing. Unfortunnately, its not that simple. Those systems can generate those plots by interpreting what the controller is saying. To get those plots from a engine ECU you have to be brave (or smart) enough to backtrack through all the software and reverse engineer it to give you the information you want. Only then can you design an interface to change what you want and its still going to require significant testing. Also, the snow mode is probably more than just the AWD system. I'm willing to bet (again I don't know specifics) that it probably adjusts the activity of the electronic throttle, the shifting of the transmission, and maybe even the antilock brake controller. You would be amazed at how in depth these things are nowadays its kinda scary. theres some serious tricks to be played with.

pits200 wrote:In addition to the mechanical problems, would the CV joints/axles really have a hard time holding up due to prolonged driving with a 50/50 split. Because at low speeds with snow mode enabled, all 4 wheels are driving, hence a ton of stress is put on the vehicle and there is no adverse effects from this. Why would it be any different of a scenario at speeds in excess of 18mph, isnt most torque initiated at startup in bad weather.

It really depends on the system. It shouldn't in the short run but if your talking about going to a much more front dependant drive system there are second and third order effects to think about on the syste...what torque were the couplings and shafts and clutches meant to take.

It would THEORETICALLY be possible to adjust torque bias through wheel sizing if the system wasn't that smart...although it would also change relative wheel speed.

Ha, you know way to much, not many other people are giving me any love, so thanks for the time. I have no more rebuttals, now comes my grief.

Why the hell didn't Nissan program the snow mode to be more aggressive in snow and forget about the performance aspect of 0/100 ratio.

Is there something that I am missing with this.

your welcome

what your missing is that snow mode is a mode to HELP snow handling...it is not glue, you still must drive with care. In snow the FWD RWD difference is amplified. The reason FWD fails is the same. Your asking to much of the front tires. When the coefficient of friction goes down (snow) it becomes more of a problem because simple manuevering (changing lanes while accelerating) can cause loss of traction. in RWD the wheels have their own roles in both cases. The difference is keeping the car in a straight line when things go wrong. A FWD will default to that because of the rear wheels still having traction (god willing lol) and wanting to continue rolling in a straight line. In RWD, all the wheels are less loaded and less is asked of them...failure mode (loss of traction) is just more serious (fun).

The terrific thing about AWD is that when one end goes, they both go.Up until that point, you have control and abilities that are downright eerie.... and often lead the incautious driver straight into trouble.I can't begin to think of the sorts of mischief people would be getting themselves into, let alone what it would do to the hardware, if we were allowed to start fiddling with torque splits.