~3k RPM Rev Limiter on 4Lo??

[borfoo3]

~3k RPM Rev Limiter on 4Lo w/A-TRAC??

Hey guys, interesting one here.

Was doing quite a bit of sand driving when I stumbled upon something. Here's what happened:

Faced a steep hill of soft sand, so wanted to get some momentum. Was already on 4Hi
Stopped, held down traction off for 5 sec to disable both Traction control and VSC. Both lights came on showing both are indeed disabled.
Attempted hill on 4Hi, didn't work
Stopped, went into 4Lo, Rear diff lock on, A-TRAC on
backed up, floored it, engine revving high and started climbing when I noticed the RPM needle sinking down and holding steady at 3000 RPM.. Pedal was all the way down but feels like engine power was being cut from me somehow and ceased my progress.. Took me a few attempts but finally got through.

So what happened here?? Is it A-TRAC limiting things down? Or is the ECU nanny kicking in to prevent over-stressing the drive-train? (read that somewhere online but not sure if its true)

Curious to hear if anyone faced the same thing. If so, how would you stop that and get maximum power continuously through all 4 tires?

 

[marshal]

Never experienced this before. Mine revs all the way through, but I didn't have atrac on. Just went straight for the locker

 

[4Rager]

I haven't experienced this either, but it does sound like something traction control would do. As you're aware, 4Lo automatically disables the standard traction control and vsc, so the only times I've used A-TRAC is to get up an obstacle and I was stationary aka low rpms. The times I've been in 4Lo without A-TRAC it revs to redline if you want it to. Judging by how A-TRAC works, it seems logical that it would limit revs and power. If it's trying to apply brake to the tractionless wheel while you're flooring it, that doesn't sound good for the brakes. I wonder how it would have tackled it if you used the MTS set to "Sand".

 

[borfoo3]

I haven't experienced this either, but it does sound like something traction control would do. As you're aware, 4Lo automatically disables the standard traction control and vsc, so the only times I've used A-TRAC is to get up an obstacle and I was stationary aka low rpms. The times I've been in 4Lo without A-TRAC it revs to redline if you want it to. Judging by how A-TRAC works, it seems logical that it would limit revs and power. If it's trying to apply brake to the tractionless wheel while you're flooring it, that doesn't sound good for the brakes. I wonder how it would have tackled it if you used the MTS set to "Sand".

Actually had it at "Sand" first, which seemed to 'relax' the traction control nanny, but honestly don't like it as when it gets too deep and things get real slippy it cuts too much power.

Another interesting thing I learned about A-TRAC, was that it only works within a certain "window" of gas pedal action.. too little gas pedal input, nothing happens up front. Too much pedal = revs high for a bit and no A-TRAC action up front. Seems like A-TRAC works within a ~2k-3.5k RPM range. Continuous full gas pedal revs things high, then sinks down to the magic range as I mentioned earlier..

 

[wfo9]

I've been in one sandy steep hill climb situation that required lots of momentum and wheel spin... I tried with ATRAC on and it failed miserably. Seemed like the ATRAC was fighting itself...

Backed down and flipped on my lockers and went right up no problem.

In most crawl situations ATRAC has worked fairly well. High RPM/SPIN scenarios seem to be problematic for it, but I rarely come across those situations in my wheeling adventures.

 

[borfoo3]

I've been in one sandy steep hill climb situation that required lots of momentum and wheel spin... I tried with ATRAC on and it failed miserably. Seemed like the ATRAC was fighting itself...

Backed down and flipped on my lockers and went right up no problem.

In most crawl situations ATRAC has worked fairly well. High RPM/SPIN scenarios seem to be problematic for it, but I rarely come across those situations in my wheeling adventures.

Hmm now that I've found a clip of it seems like the case.. Video doesn't do the spot justice as many ATV's and quads were getting stuck around here as well.

2nd Attempt in the vid, gas pedal was ALL THE WAY DOWN from the get go, but notice it cutting back for some reason.. Barely made it at the end.

<iframe width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid878.photobucket.com%2Falbums%2Fab341%2Fborfoo3%2F4Runner%2F20150810_180905.mp4&title=T4R%20TEP%20Sandy%20hill">

End of the day, pretty darn impressed on how capable this 4800lb grocery getter is! Even without a real mug holder or Supercharger... :behindsofa:

 

[borfoo3]

I've been in one sandy steep hill climb situation that required lots of momentum and wheel spin... I tried with ATRAC on and it failed miserably. Seemed like the ATRAC was fighting itself...

Backed down and flipped on my lockers and went right up no problem.

In most crawl situations ATRAC has worked fairly well. High RPM/SPIN scenarios seem to be problematic for it, but I rarely come across those situations in my wheeling adventures.

Hmm now that I've found a clip of it seems like the case.. Video doesn't do the spot justice as many ATV's and quads were getting stuck around here as well.

2nd Attempt in the vid, gas pedal was ALL THE WAY DOWN from the get go, but notice it cutting back for some reason.. Barely made it at the end.

<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid878.photobucket.com%2Falbums%2Fab341%2Fborfoo3%2F4Runner%2F20150810_180905.mp4&title=T4R%20TEP%20Sandy%20hill">

End of the day, pretty darn impressed on how capable this 4800lb grocery getter is! Even without a real mug holder or Supercharger... :behindsofa:

 

[rnb754]

in for some info....

I do more wheeling in the sand and normally use 4high. tried 4l and it was okay. 4l with a-trac is awesome but I have yet to try it on a sand hill

 

[BlackWorksInc]

I vaguely remember something in Toyota's literature that their A-TRAC/TRAC system when in 4Lo works best/is designed to work in the sub-3k RPM range. Otherwise the system stops trying to "lock" the axles (I imagine it's because at those higher speeds there's greater potential to cause damage to the drivetrain and/or the ABS system works too hard.)