Computers

[juane]

I had planned a nice quite little camping trip to Canyonlands - three nights in Devil's Kitchen - girlfriend and I, and our four kids. Deb had never seen the Needles and I knew she'd get a kick out of it. And what a kid's paradise.

Well, the word got out - we ended up with six vehicles and 30 people including 14 kids ages 3 to 12. This happens quite often in Salida.

Anyway, I found myself as reluctant trip leader getting five stock vehicles and drivers of various experience over Elephant Hill. The two Four Runners did great as did the two full size pickups. I was amazed - both late model double cabs with 8 foot beds - a Dodge Cummins and a Chevy. With some judicious spotting they had absolutely no problems.

Any issues we had was with a Sequoia. The driver (and wife) were a bit freaked. Street tires and running boards and NO articulation and NO traction. The vehicle had some sort of traction control, but other than flashing lights on the dash we did not see any benefit.

In order to fool the car into providing traction to the tires sitting on the rocks I had Mike use both feet - constant RPM on the gas with left foot on the brakes to modulate the momentum. (This technique also works great with automatics by keeping the torque converter spooled up).

But the car seemed to be questioning why this moron human was pressing the gas and brakes at the same time. The throttle response was really erratic and lurching. Not good given the situation. Shutting the engine off and restarting seemed to reboot the system and smooth things out for a while.

With quite a bit of rock stacking, finagling, and my driving we finally got him into camp. The drive out went better and Mike finished up the last switch back with a great big old grin on his face.

I'm guessing this car is totally computer controlled with throttle by wire and the software engineers never anticipated this sort of driver input.
Any insights from you techies?

juane

 

[1911]

The FJC is totally throttle-by-wire and has tons of ECU's and ECM's, but still responds quite well to left-foot braking. Probably as you say the software for the 4WD ECM is different.

You have my admiration for getting a stock Sequoia over Elephant Hill! Was just there a couple of weeks ago and did it in my 40; not sure I would want to try in a stock Sequoia.

 

[marcfj60]

It was a challenge in my nearly stock 100 due to the size, loss of articulation/traction inherent to IFS and lack of armor. I know a Sequoia is a few inches bigger in every direction. I have AT tires and a rear e-locker. I cannot imagine how difficult it would be with street tires, bigger size, no locker and computers making it harder. The only computer issue I had was the ABS system didn't like the amount of time I spent pressing on the brake pedal. The ABS light would come on and the owner's manual said I was supposed to take it to a service center immediately when this happens. Thankfully, the light would turn off after I stopped wheeling.

 

[evanz80]

Juane -

It sounds like a fun trip, even with the problem Sequoia. At least the owner had a smile on his face by the end of the trip!

I can't even begin to speculate about the computer issues, but this story made me remember that Bill Burke (4WD America, or whatever his company is called) wheeled a Sequoia at Cruise Moab this year. As you'd expect, I think it had been slightly modified (I didn't see it). But maybe his was an older model that didn't have quite so much "interaction" with traction control, etc.

Evan

 

[OGBeno]

The traction control can be disabled. The system is the same across all of Toyota's vehicles that use ATRAC (4Runner/FJC/Sequoia/Land Cruiser).

 

[sirenmoses]

^ Does that also apply to our new Pierce 75' Ladder Truck w/ ATRAC?

Just curious. I offered to attend the training for it on my own time, but they said no, so when I'm assigned to drive it, the in-house ff does. Rides mighty sweet in the 3rd seat: not nearly the lumbar pain as in previous rigs.

 

[alia176]

The ATRAC is a very advanced system but it all comes down to the driver. Someone more knowledgeable need to correct me on this but I think the computer needs to see a steady throttle input. The ATRAC program needs to assess quickly and adjust the engine output and control the ABS/traction control only if the user doesn't fluctuate the gas pedal. Every time the pedal fluctuates, the program tries to change algorithm which may take too long for the given situation.

At least that's my rudimentary understanding of that system.

In light of the recent Toyota runaway issue, I think the new ECU program will stop the engine if the ECU sees that the brake and the gas pedal on at the same time, or some such thing.

 

[gr8wrk]

My Tacoma has ATRAC. I know nothing of their programming but Ali is right, it seems to be happiest with a steady throttle input. It's no locker, but in many situations it's light years head of an open diff or even limited slip. It takes a little getting used to but there is a big button to turn it of with. I think that with a crawl box, on many trails you'd never miss having a front locker. But it'll be way down the road before I can substantiate that. With all that said, it's still run by a computer.

 

[juane]

Found this on another forum (http://www.tundrasolutions.com):

"I've been having a discussion about the Sequoia 4wd system performance in another thread in the Sequoia Forum, but it should probably be here.....

And, I want to follow-up on my earlier discussion of the Sequoia's real world 4wd functioning.

I was on this southern california trail last weekend in my stock 06 4wd Seq. Pics are in my Photo Gallery. It is rated most difficult and had a lot of rutted spots where I lost traction to opposing wheels (for example: front left and rear right).

Earlier discussions in the other thread talked about what would happen in this situation - that ATRAC should lock the wheels without traction and keep me moving. What I found, however, was that in 4Lo w/locked Center Diff if I was creeping along I would lose traction and be unable to move. The lifted tires would spin - no amount of power would create a differential between the spinning/non spinning tires to trigger ATRAC. The tires spun like mad. It would not move forward so I had to back down and make another approach - I always got through, but still....

What I found was that as long as I had some forward motion, the ATRAC would brake the spinning tire or tires and keep me moving forward. In some cases, however, the obstacles were very significant and slamming into a boulder with momentum was pretty painful!

Has anyone else experienced this and can you comment on the effectiveness of 4Hi vs 4Lo Locked/Unlocked in this situation? After the fact, I wonder if the ATRAC setting in Locked Center Diff is not more adapted to sand/mud than situations where I am constantly lifting a wheel or two. Would the more sensitive ATRAC setting when unlocked center dif have worked better for the ruts and rocks I was navigating.

In any case, my buddy and I had a great time! And, the jeepers I was with were amazed. It doesn't get an better than an 8 passenger luxury SUV that'll go most anywhere! Considering a small lift, sliders, skid plates and 32's anway for next time..."

 

[TOYOTARIG]

All I know is that I love my Sequoia, and am also planning a slight lift with some 285/75's. It seems to be the best truck for the family, all except the lack of aftermarket support. Juane were are your photos of the Cali trip? I am very curious to see the Sequoia off road!

 

[TroutRunner]

I've got the 04 4runner with atrac. I'm with Ali on this one, for mine you need to maintain the rpm's above 2500. You will start to hear the clicking fo the ABS actuating and off you go even in a twisted situation. This is in 4lo with center locked.

My tundra has about 16 pages in the manual on the 6 different computer modes to run the ATRAC and LSD. I'll pull the book out if I need it.

G

 

[1911]

I think that with a crawl box, on many trails you'd never miss having a front locker. But it'll be way down the road before I can substantiate that. With all that said, it's still run by a computer.

I have a crawl box and a front locker on my FJC, and I never use A-Trac any more, and the front locker only rarely. Personally, I don't like A-Trac though a lot of folks do. I don't like the feedback from it, feels like I'm not in complete control when it kicks in. I suspect it's also hard on the CV's to modulate the applied torque that quickly, but have no hard facts for that. If I don't want to lock the diff(s) for whatever reason I just use left-foot braking to do the same thing as A-Trac but more smoothly.

 

[juane]

Oh Yeah,
We were driving back to camp when around the corner who should I meet in a lavender 80 with dinosaur stickers???