Brake Throttle Override
 

There is another conversation on this topic buried amidst a thread with covering a few different topics
...but I thought this deserved a separate thread so people could focus on it.

The point is ... there is a difference of opinion as to whether the TCH has the 'override' or not.
Dealer's service department managers and the media say the TCH does...however, user experiences might say otherwise.
I have the 2008 TCH VIN starting with 4T1 (US made).
I floored the gas and then applied the brakes.
The car slowed down (which was a good thing!)
However, the engine was still racing (while my foot was on the accelerator).
This implies that the brakes are stronger than the gas...NOT that there was any software override of the throttle system.
My MPG meter indicated low fuel efficiency, the graphic showed power from the engine and I could hear the engine racing (at a very high level).
Wouldn't a true override system cancel (or reduce) the input signal from the accelerator and tell the engine to rev more slowly (or not at all)?

So, in my ever so simple experiment, the TCH does not have an override system, or at least, if it does, it's not an effective one.
Is there a speed of acceleration where the brakes aren't capable of trumping the gas...or are brakes always superior?

In any event, if there is a software upgrade to these cars, I think we should be part of it. I'm unsure why there is so much misinformation out there.

I'm NOT a mechanic, nor auto expert.

Thanks!

Re: Brake Throttle Override
 

:D
next week it will be another problem lol!

Re: Brake Throttle Override
 

What happens in neutral if you "floor" the gas pedal, does the engine rev up...??

And if it does I assume the TCH still doesn't move....

With the TCH, neutral doesn't mean the drivetrain output isn't still connected to the axles, it just means that the PSD will not allow ICE "drive" to reach the drive axles.

I'm not saying with any authority or conclusiveness that the PSD operation is limiting the ICE torque to the axles, just that it could be so.

Re: Brake Throttle Override
 

Makes sense...but then, we have no way of knowing for if it works, or not.
How do we know that it's just the braking power overriding the acceleration?

I'd expect an override system to operate in a different way than revving in neutral.
If it's an override, assuming I understand how it should work, the signal from the accelerator should be ignored when the brakes are simultaneously applied. That's how the video portrayed it.
In this regard, we are to take it as a leap of faith that the engine is revving but the transmission (or what ever connects the engine to the wheels) is not connected.

You see my confusion?

Re: Brake Throttle Override
 

Re: Brake Throttle Override
 

You're probably right...
I guess the only way to know for sure is to see how long it takes to come to a complete stop from a certain speed with moderate to heavy braking pressure (no need jam on the brakes and kiss the windshield) and then compare that to the braking distance with the same braking pressure while accelerating.
If it's the same, I guess the system works as you suggest.
If not, then the extra braking distance would be a reflection of the brakes being more powerful than the acceleration...which would still be taking place.
Right?

Re: Brake Throttle Override
 

I will add that my own little tests, similar to Larry's, gave the same results as his and also that any BTO function supposedly present in my 09 TCH was certainly not adequate to provide any relief during my floor-mat-induced UA incidents.

After the BTO flash is completed on my car this afternoon, I'll see if it works any better.

Re: Brake Throttle Override
 

Vera confusing...

It would be the absolute ULTIMATE in engineering stupidity to not "disengage the clutch" (use the AC motors to "counter" ICE input to the PSD) when the brake is depressed.

We already know that HIGH ICE RPM, say to quickly recharge the hybrid battery, does not necessarily result in higher roadspeed since the PSD can easily accommodate that situation.

Re: Brake Throttle Override
 

As I posted in the other thread, and as Willard predicted, they did not do the BTO flash.

Also, I have done some further reflection on the inadequacy of the existing ability of this car to deal effectively with brake-accelerator pedal conflicts.

I seems to me now that the system may have some ability to ameliorate the result when the accelerator pedal is stuck and then the brake is applied, but it seems to be little or no help if the accelerator pedal is pushed further AFTER and WHILE the brakes are applied.

This would explain why any inherent BTO capability on my car did not help me out in my floor-mat-induced UA incidents. (As explained previously, the mat can get under the brake pedal and over the gas pedal so that pressure on the brake pedal can further depress the accelerator pedal.)

I would also explain why Toyota needs to do the pedal and floor mat modifications on the Camry Hybrid in spite of their contention that the PSD hybrids have an inherent BTO function.

Re: Brake Throttle Override
 

How "butchered" does the accelerator pedal look after the modification? Can you post a picture?

Re: Brake Throttle Override
 

It is really not bad at all.

I would advise everyone to get the modification. The floor-mat-induced UA is a very real possibility and it is life threatening.

I'm usually very careful about these things, and I took care to use a genuine Toyota mat specifically designed for this car and installed exactly according to instructions, and it happened to me - twice!

Even if you have no floor mats at all, there is always the possibility that one of our cars could one day wind up in the hands of someone else unaware of the danger. We could be saving their life.

Will post a picture over the weekend.

Re: Brake Throttle Override
 

I tested tonight ... when it's in neutral I put me foot all the way down and nothing happened. The ICE didn't rev at all.

Re: Brake Throttle Override
 

Exactly as advertised (and very different from what it does in any other shifter selection).

That is precisely why the very best way to deal with an unintended acceleration is to shift immediately into neutral.

This worked like a charm for me in mt second UA event.

Re: Brake Throttle Override
 

Haroldo had the same results as I did. Move the lever to neutral and the engine goes to idle. The gas pedal becomes useless If sitting still the car won't even move in neutral, even if you floor the accelerator.

Warning, if you move the selector to neutral while driving, your now on your physical brakes. Although they will slow the car rapidly you may have to use added brake pedal pressure to do so.

I confused myself in thinking, press the brakes would release the accelerator when. Now I know, I was thinking of it releasing the cruise control instead.

Re: Brake Throttle Override
 

Not to nitpick, but idle is, I believe, a low rate of RPM of the engine. In my experiment, ICE was off completely. Is that what you meant?

Re: Brake Throttle Override
 

Jimmy said:

"Haroldo had the same results as I did. Move the lever to neutral and the engine goes to idle. "

Larry clarified"

In the middle, I had said:

"Exactly as advertised (and very different from what it does in any other shifter selection).

That is precisely why the very best way to deal with an unintended acceleration is to shift immediately into neutral.

This worked like a charm for me in mt second UA event."

Further to this, I add:

I observe that shifting to neutral results in the system exchanging no power to (or from) the wheels and it also either sets the engine to idle or shuts it off (probably cuts fuel) according to whether or not the system needs to run the engine; e.g. to warm up.

It seems to me that the engine is either idled or shut off according to conditions in the the same manner as it would be in drive with foot off of accelerator pedal; e.g while stopped in drive.

Re: Brake Throttle Override
 

How did the mat get loose from the retaining clip? I tried to remove mine for cleaning but gave up because it was too difficult.

Re: Brake Throttle Override
 

Apparently some floor mats are long enough and with forward ridges that even properly restrained the bottom of the gas pedal gets stuck in a ridge.

Re: Brake Throttle Override
 

Why? I believe the TCH brakes are not dependent on engine vacuum. I believe they are electrically assisted as in the Prius. Steering assist is also electric as is the A/C etc.

Re: Brake Throttle Override
 

The Prius has an electric Brake Boost pump and a small accumulator tank to store the energy.

JeffD

Re: Brake Throttle Override
 

It would not be difficult for someone to make floor mats that look just like genuine OEM floor mats. Some dealers do sell non-Toyota accessories, either because the markup is higher, or because they don't like the Toyota design. And, a lot of people buy floor mats from sources other than the dealer.

I would be very surprised if there are not some knock-off "genuine Toyota" floor mats out there that were not actually made by Toyota. I was offered a "genuine Rolex" watch, just last week, for only $59.

Re: Brake Throttle Override
 

That's why the modified all weather mat has a much larger cutout under the gas pedal along with a molded in warning regarding proper installation.

Re: Brake Throttle Override
 

I suspect.....physical = frictional

Re: Brake Throttle Override
 

Good question, Eric.

As I posted earlier, the errant mats in m case (and other similar cases posted in these forums) were not the standard carpeted mats that hook into the prongs. The mat that caused my UA was a clear plastic mat intended to protect the carpeted mat. It was a genuine Toyota part, purchased from the Toyota Dealer in March 2009, and specifically designed for the 07 to 09 Camry. And it was installed exactly per clear instructions, and it fit really well.

The mat is designed to be installed over the carpeted mat, and is precisely the size and shape of the carpeted mat. It fits quite nicely and snugly. It comes with a binding clip intended to bind it to the carpeted mat, and it has hundreds of cleats to grip the carpet below. In that way it is intended to rely on the carpet mat being secured to its own hook prongs to keep the two bound mats in place.

It all seemed quite secure, but it proved out to be not secure enough, "in the field" as 007 used to tell Q.

Thinking back, I was wearing athletic shoes with very sticky soles at the times of UA.

Re: Brake Throttle Override
 

Quick (amateur) test of my 09 TCH (purchased new July 2009..US built) ...roughly 3/4 pedal acceleration from stop, speed about 35mph, ICE on... I then applied brakes quickly as in a panic stop, while maintaining accelerator pressure, felt influence of brakes...car began to stop, then very quickly felt engine cut power...I then pressed harder on the accelerator, it felt like it wasn't applying any further acceleration. I believe car would have stopped completely in a "normal" distance with accelerator pedal depressed.

Further testing, (as others have noted) moving gear selector to Neutral, also cuts power, in fact, the accelerator pedal has absolutely no effect with selector in Neutral.

I, (and more importantly, my wife) am completely satisfied with this test that our car will stop. We never use anything but the factory carpet floormats, that are secured by the factory hooks.

With all this said, I wonder if there were any BTO system/calibration running changes in the prodcution cars of the 2009 year, as it was a very long run, perhaps 18 months? When I bought my 09 TCH, some 2010's were on the lots.

Re: Brake Throttle Override
 

Jeff,

Thanks for that interesting thought. I may check into that, as my 09 TCH was an early production - on the dealer's lot in Feb. 2008.

Re: Brake Throttle Override
 

Ya know you shouldn't be afraid to try a "full throttle" max brake application. Find a nice clear road, floor it, then stop the car with the brakes while leaving the throttle on the floor. I've done it on every car I've owned at least once.

It's better to know what it's like under a controlled condition than when you least expect it.

Two mistakes people make.
1) It takes quite a hard brake application to stop. More than you might think is normal.
2) Don't try to control the speed of the car. You can overheat your brakes quite quickly. Just get the car stopped as soon as you can.

Cheers!

Dang

Re: Brake Throttle Override
 

Just suppose...

The "reflash" was not only a BTO upgrade but also a fix for a firmware bug that was/is resulting in UA incidents...??

How, who, would ever know...??

Re: Brake Throttle Override
 

Please see picture in the new thread, "SSC 90L Recall work on 2009 Camry Hybrid"

Re: Brake Throttle Override
 

Checked BTO on my 2007 TCH, and it appears to be there. Both break and throttle applied, engine did not rev, car stopped easily.

Re: Brake Throttle Override
 

I checked the BTO out a little more thoroughly, and it appears that the engine does continue to rev under light braking with throttle applied. However, when the brake peddle was pushed further, the engine did return to idle. Felt like it took about 1/2 of the brake peddle travel to engage BTO.

Re: Brake Throttle Override
 

Thanks to cp_tch for the thoroughness and for stating the observation so clearly !

I had noticed something similar in my informal tests, but I had not thought it out this clearly.

Now this latest observation would, at least qualitatively, explain why the inherent BTO functionality in the Camry Hybrid (as well as in the Prius) has proven inadequate to prevent the mat-induced UA incidents in which the mat became trapped under the brake pedal and on top of the accelerator pedal.

It would also explain why it makes sense for Toyota to do the carpet and pedal modification recall on the TCH in spite of the fact that the car has the inherent BTO functionality.

Excellent work, cp_tch ! Thanks again for sharing your observation.

Re: Brake Throttle Override
 

The Toyota HSD's ICE can be revving at 5,000RPM and not deliver a single erg of energy to the drive wheels.

Re: Brake Throttle Override
 

In my observation, the engine did feel like it was delivering power to the wheels until the rev's dropped. However, my experiment was pretty "informal" also...

Re: Brake Throttle Override
 

Thanks to cp for posting this clarification.

My own obsrevation was similar.

Hence my conclusions,

"Now this latest observation would, at least qualitatively, explain why the inherent BTO functionality in the Camry Hybrid (as well as in the Prius) has proven inadequate to prevent the mat-induced UA incidents in which the mat became trapped under the brake pedal and on top of the accelerator pedal.

"It would also explain why it makes sense for Toyota to do the carpet and pedal modification recall on the TCH in spite of the fact that the car has the inherent BTO functionality."

Re: Brake Throttle Override
 

What about the inverse of this, floor the pedal THEN shift to neutral.
I expect the same to happen, ie the engine does not continue to rev.

Re: Brake Throttle Override
 

Upon shift to neutral, the ICE will be either idled or shut off, depending upon temperature and state of charge. It will do this regardless of accelerator pedal position or engine speed or car speed.

This is why in the TCh this is absolutely the best way to manage a UA event. I know this from first hand experience.

Re: Brake Throttle Override
 

My understanding of the toyota HSD planetary gear system is that a MG1 must be operating in order for the engine to provide any power to the drive shaft. This is different from a standard transmission that could, possibly, in theory, "torque lock" or not shift to neutral at very high speed or engine rev levels (any gearheads that could explain this would be greatly appreciated).
When a HSD is shifted to neutral the hybrid control system simply cuts power to MG1 which causes the planetary gear to freewheel after a second or two depending on the speed. with the planetary gear "unlocked" from the drive shaft only MG2 (drive motor) could move the vehicle, but the control system would not power the motor since the shift selector is not in Drive.
Given this gear setup, I dont believe a torque lock would be possible as in a standard transmission, since there is nothing physically shifting in a HSD planetary gear system, just gears syncing or freewheeling and the ratio of which controls transfer of power from the engine to the drive shaft.

taken from http://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

Re: Brake Throttle Override
 

Modern transmissions will shift to neutral at high rpm or under a high load condition. The shifts are done by solenoids and controlled by the ECU unit. The only other "control" mechanism in the tranny is the valve body which controls the fluid flow. I will defer to a Toyota transmission expert but the ones I am familar with will not suffer from "torque lock". It might happen, but I very much doubt it.

Re: Brake Throttle Override
 

So in a car with a gas engine and an automatic transmission, even in a wide open throttle condition, it should always be possible to put the transmission into neutral removing power from the wheels.

There has been so much (mis)information thrown around in the press about this whole unintended acceleration problem, "brakes not having any effect", "shifting to neutral does nothing", I'm trying to get a better technical understanding what failure modes really do exist.