going down a slippery hill

[tjoe78]

Going down a 1/2 mile yest. road was really sloppy--the trac. control light kept flashing the whole way--really scared me--never had it stay on so long. Kept light pressure on the brakes. I was able to stop almost at the end where I have to turn. I have winter tires. Would it be better to shift to B?

[efusco]

I see absolutely NO advantage to using B-mode in this situation. Also, can't see why the TRAC would kick in going down hill...it only works when accelerating and it senses tire spin.

Do you think it might have been the VSC doing it's job to keep you on the road...a car without probably would've been in the ditch. Sounds like everything worked perfectly to me.

[qbee42]

No advantage to B mode. As for VSC, did you get a chime along with the trac control light?

Tom

[pinball]

Hang on a sec - B is exactly what you need to deploy. There's much less chance of locking the tyres and skidding when using the ICE/motors to slow you down than brakes alone.

[DaveG]

<div class='quotetop'>QUOTE(pinball @ Dec 9 2006, 10:47 AM) [snapback]359782[/snapback]</div>

Hang on a sec - B is exactly what you need to deploy. There's much less chance of locking the tyres and skidding when using the ICE/motors to slow you down than brakes alone.
[/b]

I'm not sure that's entirely accurate for the Prius - after all, when you're slowing, it's actually using the electric motor to slow you down as it regenerates power anyway so there wouldn't be much difference between the electric motor slowing the car as it regenerates, and the ICE slowing the car in B mode.

Dave

[cairo94507]

<div class='quotetop'>QUOTE(efusco @ Dec 9 2006, 08:08 AM) [snapback]359672[/snapback]</div>

I see absolutely NO advantage to using B-mode in this situation. Also, can't see why the TRAC would kick in going down hill...it only works when accelerating and it senses tire spin.

Do you think it might have been the VSC doing it's job to keep you on the road...a car without probably would've been in the ditch. Sounds like everything worked perfectly to me.
[/b]

With respect I completely disagree. My traction light illuminates when ever I am coming to a stop and my front tires slip on a man hole cover in the street. I am not on the gas and I am lightly braking when that happens. So I believe the condition as described exists. I would think B mode would assist with this problem too.

[efusco]

Despite the disagreement, I absolutely stand by my statement that B-mode is not indicated here. ABS is the part responsible for preventing skidding...it offers active control...b-mode blindly slows without regard to skidding/slipping.

I may be mistaken about the trac coming on during slipping while moving forward, and it will flash on briefly when the VSC activates, but I don't think it should kick on repeatedly during a long slippery downhill...that sounds like VSC.

[hobbit]

While it's usually a disadvantage to use "B" other than when needing
to blow off a little more downhill energy than the battery can suck
up, in the case of slippery roads all bets about energy recovery are
off and "B" actually helps keep a constant retardation going but
not wheel lockup [which, of course, would immediately be compensated
for by ABS but possibly not in a way the driver expects]. Near the
end of the B-mode article is some discussion about potential uses
of the "falls on its face" feeling when coming off the accelerator,
and snow and the like are probably one of those situations where you
want that. In a MT car you'd be gearing down, and possibly dropping
an automatic into "L" for the same effect.
.
But use your best judgement, find situations where you've got the
leisure to experiment, and PRACTICE to determine what works best.
You aren't likely to get great, efficient regen on stuff like that
so it should take a back seat to control.
.
_H*

[pinball]

For many years I lived in the Italian mountains teaching skiing.
The best mountain car I ever had was a VW Beetle.
With the engine over the rear wheels it had great traction on steep icy roads both up and down.
I only ever had to put chains on twice in 8 years.
The trick was to keep it in 2nd - and sometimes 1st gear, using the engine to slow you down rather than brake and risk inducing a skid.
Usually it was a bit of both....however - lock your wheels up on an icy downhill bend and you end up in the ditch - I know !
Incidentally in the mountains (Italy) the car coming down the hill has the right of way - think about it .

Anyway, I just applied the same principles to Prius on the basis that anything that will reduce your momentum down an icy slope has to be a good idea - except when skiing !
You'll also find that lowering the pressure in your tyres will give you a little more traction - but it'll affect your mpg.
Don't try getting into B half way down the slope either !!
Its either from the top or not all

[efusco]

<div class='quotetop'>QUOTE(pinball @ Dec 10 2006, 04:34 AM) [snapback]359984[/snapback]</div>

For many years I lived in the Italian mountains teaching skiing.
The best mountain car I ever had was a VW Beetle.
With the engine over the rear wheels it had great traction on steep icy roads both up and down.
I only ever had to put chains on twice in 8 years.
The trick was to keep it in 2nd - and sometimes 1st gear, using the engine to slow you down rather than brake and risk inducing a skid.
Usually it was a bit of both....however - lock your wheels up on an icy downhill bend and you end up in the ditch - I know !
Incidentally in the mountains (Italy) the car coming down the hill has the right of way - think about it .

Anyway, I just applied the same principles to Prius on the basis that anything that will reduce your momentum down an icy slope has to be a good idea - except when skiing !
You'll also find that lowering the pressure in your tyres will give you a little more traction - but it'll affect your mpg.
Don't try getting into B half way down the slope either !!
Its either from the top or not all
[/b]

A thing or two have changed in automotive technology since the old VW!

Namely, ABS and VSC. The risk of skidding, even with firm braking, is markedly reduced with these.

I do, however, fully agree that if one is going to use B-mode (which I still see no point in b/c of the ABS) that it should not be used to slow down once one has gained momentum...start it at the top as a speed control measure down the slope or not at all.