Automatic Throttle Reduction during braking??

[jondoe1482]

5th gen TRD Pro 2016. So, I went to the 4WD-101 course at Uwharrie a couple weeks ago (great course, definitely recommend). We were learning about brake throttle modulation and two foot driving, ways to trick your differential into powering all 4 tires without diff lock or the fancy computerized controllers (MultiTerrain Select and Crawl control). I realize that these systems will perform this duty way better than I can with two pedals and two feet, however, I do think it is a valuable technique to learn and be able to implement.

I was using this technique (without MultiTerrain or crawl, in 4Lo, 1st gear) going up a steep hill with a mogul in the middle, knowing I would lift a wheel and need to apply a little brake to power the opposite wheel. I felt the momentum drop as I was going through the mogul (lifting a tire) and applied a little more brake (slightly riding the brake all the way up (only maybe 5-7 s total) to distribute power through the diff. I felt the car continue to move up the hill for a second, then I suddenly lost power. Pushed the gas more and nothing happened. Engine just at idle. Came of the gas completely and then I could throttle up again, but, alas, it was too late. I lost my momentum and had to back down and start again. The trainer said, "You came off the throttle, I heard the RPMs drop. " I thought, well maybe I did, though I didn't really think that I did, because I distinctly remember trying to add more gas and nothing happened. The next run I just turned on MultiTerrain and drove up, not worrying about the braking technique.

I have since recreated this on pavement, (albeit in 2wd with standard traction control on, etc.) After a few seconds of driving with light brake and RPM 1200-1500 range, I lose power completely down to idle, until I release the gas all the way.

Is this some kind of safety mechanism? It basically precludes us from using that driving technique, though I will say it worked in other situations without powering down. Any insight??

BTW, the runner performed really well out there. MultiTerrain Select and Crawl control are like having Cheat mode on a video game.

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[1jzgte]

No experience with your situation but i wouldnt be surprised if a safety were put in place to combat the whole unintended acceleration nonsense years ago.

 

[nb rob]

does it behave the same when you hold the trac off button until both trac off and the slip off (not what it's called--- but the second light that illuminates after holding it in some time) light illuminate?

I know that it cuts the power when the trac light lights up and the system applies brake to the slipping wheel. I would imagine the same would be true if the brake were depressed while traction control is on (default)

 

[spetka]

I noticed mine doing this on a recent drive up to the mountains, and actually mentioned it to my wife, that it felt like the car was using the motor to assist the braking.

 

[wfo9]

Most of the traction control nannies are turned off in 4-lo automatically, but it is possible the ECU will limit throttle when brakes are applied. It limits throttle all the time... you just don't really notice it.

Bottom line.. the technique you learned is of little use on the 4runner. It helps a tiny bit in rare scenarios... with open diffs (works really well with a torsen diffs). But you have A-trac which works much better, so just use that. Still not a substitute for a locker, but I would not waste my time with manually applying the brakes and throttle and putting a lot of unnecessary wear and tear on the drive-line. There is way too much bias on the front for it to be effective, plus it does not work that good anyway. Let the computer attempt to equalize each wheel speed when needed.

The post just above this is talking about grade braking... Totally different subject. And yes the ECU will command the transmission to do that in an attempt to save some brake wear and heat/fade.

 

[(none)]

Haven't tried it in 4wd much, but i can tell you that doesn't happen in 2wd with the traction control off... Wet road, hold the brake, stomp the gas at a stop and these things do a pretty good burnout

 

[1000MPH]

Part of the STAR Safety System so you hopefully avoid running over little Johnny when your throttle gets stuck WFO.

"Smart Stop Technology: This technology is the simplest to understand. It automatically stops the vehicle when both the accelerator and the brake pedal is pressed at the same time, just in case you need to bring your new Toyota to a quick stop! "

 

[raptore]

Went through the same thing. Simply press brake and lose throttle response for second or two. Unless you can reprogram the computer, sit back and enjoy the ride.