pre 2008 models do not have brake override??

My 2006 has brake override. I believe all Prius have it.

Tom

 

My 2007 also has it.

 

Toyota has said that the engine override feature is an essential component of the Hybrid Synergy Drive, and that all cars with HSD have it. That includes all Prius years and models.

 

Lets just say that the lack of knowledge of some car dealers is unbounded.

 

deh2k really answered this:

The key is that the Prius does not have a SPECIFIC overide system because the function is inherently provided by the HSD. It is something that has always been there and it is not something that is on the car's feature list or something.

I tried out this system the other day, floored the car and when I got to 80 I applied the brakes. The ICE stopped and the car slowed down - BUT when I released the brakes (with the gas floored) the car sped back up. From what I understand, with a traditional Brake Override System (on a non-hybrid car) that the engine would have been totally shut down. So what the Prius has is somewhat different.

 

Of course, this assumes that the computers that do all of this always work properly!!

What is the protection if HSD goes haywire (and leaves no record that it has)

An entirely seperate Brake Override would provide a redundant backup - just in case.

 

If the HSD computer malfunctions and allows the gasoline engine to rev up to maximum RPMs and continue to run even as you stomp on the brakes to stop the car, it will destroy the transaxle due to the way it's geared (cause the MG1 electric motor in the transaxle to burn out).

I can't think of a better brake override than a destroyed transaxle.

If that happens, your Prius WILL come to a stop, PERMANENTLY. And will NOT move again without a new transaxle.

 

If that is so, then if you try to go 100mph won't the transaxle be destroyed?

Is not the issue that there are an infinate number of ways that the HSD computer could go wild?

 

No. The transaxle won't be destroyed when you are going 100mph, because the gasoline engine is directing its torque towards MG2, which is the outer ring gear that is drivechained to the wheels.

When you brake MG2 / outer ring gear using the front disc brakes down to very low speeds, it forces a runaway gasoline engine to direct more and more of its power to the center sun gear in the HSD (the MG1 electric motor). Remember the HSD planetary gearset is a DIFFERENTIAL.

The MG1 electric motor has a safety limit of 10,000 RPM. When the gasoline engine is revving at its maximum 4500 RPM while the car is being hydraulically braked to a stop (MG2/outer ring gear going to 0 RPM), the planetary gearset will direct the full brunt of the gasoline engine's power to MG1, causing it to spin at 16,000 RPM. That's 6,000 RPMs over its safety limit. Burnt-out MG1.

 

I believe the brake override only works with WOT, not partial throttle.

 

Well it is, if you know nothing about computers.

Do you have any documents (Ideally not documents by a lawyer trying to extort money from a manufacturer) that back up your claim?

 

Not just WOT. The override will kick in anytime MG1 reaches the 10,000-RPM safety limit.

If MG1 is spinning at 10,000 RPM, two things can be done to bring MG1's RPMs down below 10,000 RPM:

1) The HSD computer commands the gasoline engine to slow down, or

2) you release the brakes so the gasoline engine is allowed to send its torque to MG2/outer ring gear/drive wheels rather than to MG1/center sun gear.

 

Actually, I DO know a bit about computers (and real time software development). That's why I made that statement. However, I don't know much about the HSD controller, but I don;t think that it is exempt from Murphy's law.

I'm not trying to provoke an argument nor am I trying to promote some conspiracy theory or something - but I do believe that it is possible for "phantom" unintended acceleration to occur. I also believe that once these Toyota problems hit the press that all kinds of nuts come out of the woodwork. But issues with folks that don't know the difference between the accelerator and the brake, and out and out idiots who don't understand the difference between "Park" and "Neutral" are also obscuring real issues.

 

I confess that my 20 years in software development were mostly in Inventory and Financial systems. Perhaps Real time controller compilers are more lenient than financial language compilers, (RPG, COBOL, PL/SQL, etc.) but I never felt there were infinite ways to write bad code.

 

I'm not sure what you mean by "more lenient". If the code compiles, it is syntactically correct, but that doesn't mean it's good. Also, I would say there are infinite ways to write bad code.