3rd Gen Traction Control Modes Explained

And what, technically, is "throttle intervention"? I saw a user on page 6 describe his truck rev limiting at 2K RPM in 4HI, yet in 4HI all TRAC throttle intervention is disabled (and VSC shouldn't be kicking in unless he was sliding). Wouldn't a 2K limit be considered throttle intervention?

Unless, of course, there is in error in the chart as @ShimStack mentioned and there actually is TRAC throttle intervention in 4HI TRAC.

 

Yes, that would be throttle intervention. Anything that cuts engine power/output and/or restricts engine speed is throttle intervention.

 

If this is true, @Doggman, can we confirm that this is correct on the chart?

Disregard, it seems post #129 answered my questions. I am curious as to why there is engine regulation in 2WD but not 4WD.

 

Also, the description for AUTO LSD on the home page might need revised:

"AUTO LSD(Automatic Limited Slip Differential) is a 2wd only mode that has TRAC turned on and VSC turned off. Meaning you get the brake simulated LSD functionality from TRAC while preventing VSC from intervening and cutting engine power. This is useful for powering out of situations where VSC is preventing you from getting out/started because it is constantly cutting engine power."

Since VSC is controlled by yaw sensors and has nothing to do with traction, AUTO LSD is not preventing VSC from intervening, but it is preventing the throttle intervention from TRAC from intervening, correct? VSC should never prevent the truck from getting unstuck since the vehicle is moving close to 0 MPH.

 

I also believe there is from what I have experienced. You’ll notice it happening the most when your pedal input is more than what is occurring at the wheel(s) slippage. Like the fella said in the video, you won’t know TRAC is working because no lights go off in 4HI/LO. It just does.

Be careful in 4LO, and climbing a steep hill. I once lost traction heading up at a good pace, and gave it too much throttle, the motor’s power was cut out, and I snail crawled up and over. The TRAC system would not allow the motor/gearing to wind back up to a “comfortable” pace.

It’s an awesome system that is working in the background, the majority of the time unnoticed.

On a side note, for brake actuation, I erased a comment about a “possible” Locker TRAC system, but got it all goofed up and made it sound like it was only occuring on one wheel. I know, hard to believe, sounds like BS, and beyond logic. But from what the patterns showed on the ground, I have no doubt TRAC is working even though the locker is engaged and the sensors should not detect any “abnormalities.”

I’ll have to get some rollers. It’s the only way to know for sure. But if the traction control comes on in 2WD/Rear Locker/ALSD engaged, then I have no doubt TRAC does too, even though both wheels are turning at the same time.

 

Maybe there isn't engine regulation. There was a MORR video where they struggled with a Tacoma engine cutting out in sand but it's possible it was something different going on. The traction control problem is a little more difficult in 4wd than 2wd because there's no good easy speed reference to characterize slip. Maybe that's why it would be brake simulated LSD only because slip across the axle is still straightforward to measure in 4wd as is measuring vehicle skid for the VSC.

 

Did they have it in 4HI? If the engine was cutting out, wouldn't that lend more towards the possibility that there is throttle regulation?

What do you mean by "no easy speed reference to characterize slip"? If I recall correctly, the entire TRAC system operates by using speed sensors, hence the brake LSD choice by Toyota and not an internal clutch pack system. Therefore, wouldn't all 4 wheels' speed be measured to characterize slip?

 

That's the thing, I have no idea. Hence my hesitancy to take it as more than weak evidence. They attempted to explain but who knows. If it *was* cutting then that's definitely throttle intervention.

They're all measured, but in 4wd you can't easily characterize slip because each axle is driven the same speed. In 2wd to know if the powered rears are slipping it's compared to the rolling speed of the fronts. The rolling front tires are an accurate ground speed reference. In 4WD, if the rears are slipping, so are the fronts. So how do you know if they're all slipping or if the truck's just driving along at that speed? It's doable but it's a more difficult problem.

 

I see. This makes sense, thanks. As you said, I think this is why we only get brake assist during 4HI TRAC.

 

Sorry dont feel like reading over 500 comments.
How do you turn all these electronic traction control stuff off so i can actually do a donut in the mud ??? Must do donuts!!

 

In 2WD, hold down the VSC button for 3 seconds. Then you’re good to go.

 

Last one for the road and a hell of a read to understanding Toyota’s TRAC system. Originally developed for the 1994 Turbo Supra.

TRAC is one hell of an engineering feat.

Later Days

http://autoshop101.com/forms/brake12.pdf

 

Great information! Thanks for sharing!