2010 Prius engine braking down very, very steep slope!

There's a difference in degree when you're coasting, but if you press on the brake a bit in D to match the drag you get in B, then it'll use more engine braking. The only difference being that B just naturally gives you more drag, whether from regen or engine braking, and D you have to press the brake a bit to get the same amount. Only if you press harder will they both start to use the friction brakes.

 

If you go down really slow, you could give it a try in R to empty the battery ...

 

I don't have much of a good solution to your dilemma

Roll down your windows and jack up the A/C all the way, at worst it should help a little.

Take off your hub caps

Install off road / winter tires

I'm not saying these are good suggestions, just suggestions.

 

Sorry, I am not sure I understand what exactly you are after.
Do you wish the prius to be designed to take your "dirty steep road" with engine and regen braking without using friction brakes? It probably could have been designed that way, are you prepared to pay for it?
Or maybe you wish the friction brakes to be designed to take it without overheating? It could have been designed that way, are you prepared to pay for it?
A mass production car is a compromise, it cannot be designed for a very extreme case only one in 3 million users tackles.
My advice to you: be careful there and let the brakes cool down - same as you are doing with your Odyssey minivan.

 

Is there any chance the CC provides some braking, somehow? I'm new to the hybrid world, I live at about 2100 feet, and descend to 300 feet in relatively few miles every day to work. It seemed like we've gone slower when I had the CC on, and one time, the CC was off, and we ended up going a little faster than my comfort zone. [70 or so] Light regen braking easily fixed that. Or is it engine temp related? Still rather warm around in the the Central Valley, but slowly getting cooler in the mornings.
Love the car, just getting used to its nuances.

 

CC can apply the brakes, but it doesn't have access to any additional braking. In other words, there is no braking advantage to using CC.

Tom

 

I live in the mountains above Denver, and have a daily commute with about 3000ft in elevation change, mostly in one 2500ft highway drop over 10 miles. The engine braking has actually been enough for that average grade but sounds pretty terrible at some of the steeper parts.

What I've generally been doing is alternating between engine braking and wheel braking (once the battery is full, which it is, after like, half a mile of that) every few turns... i.e. i'll engine brake through a couple of turns, sometimes while still accelerating, then I'll lay into the brake pads for one particularly steep curve, then switch back to engine braking for another couple of curves to give the pads a chance to cool, etc.

Seems to mostly work, but I do feel the pain. I wish that the plug mods allowed you to apply regen back into the bigger lithium battery, if i had 4-6kwh back there I think I could make it most of the way down just with the regen.

 

Eltee, in your situation there is no good reason to alternate between engine braking and normal braking. Assuming you need to brake, keep it in B mode and apply accelerator or brake as necessary.

Tom

 

Gbee42, that was exactly what I was thinking - coming down over 3000 feet from a mountain pass in southern Colorado, I simply put it in B and braked as necessary.

 

I just got back from trip to Breckenridge from my home near Denver. This was my first significant mountain foray with my 2010 prius. I experimented with B mode, but the cruise control held speed great (I set it between 60 and 70, depending on the road conditions. It did rev the engine quite high (by ear) to increase engine braking to hold speed on the long downhills; it seemed a lot more than B mode would do. I worried a little that cruise control on long mountain downhills could damage the engine. Should I have used B mode and brakes instead of criuse control?

Thanks, Bill

 

My new Prius should be delivered this upcoming week. I have a question based on billshadow00's post. Can one not use "B" mode and cruise control at the same time?


iPad ?

 

Cruise control is disabled in B mode. I found this out when I accidently hit the shifter and was in B mode and started wondering why my cruise control wouldn't come on. Took a minute to figure that one out.

 

It's actually not any more than B would do; however, the amount of engine braking used (aka the engine RPMs) will vary based on a number of factors, including at least battery temperature, battery SoC, amount of braking requested, etc. So if you've used B mode before when your battery wasn't 100% full (not just full on the display), you weren't hearing the full extent of the engine revving.

The Prius "redlines" around 4500 RPM, by which I mean the computer won't let it go any higher than that; it'll switch to friction brakes or regen for additional braking beyond what it is capable of. And I don't think it's particularly damaging; it tends to run pretty cool when this happens, since it's not burning any fuel.

 

I'm a new Prius III owner; our other vehicle is a Subaru Legacy with "Sport" shifter that easily allows downshifting.
I can confirm that low fixed gear helps on Pike's Peak: going downhill in the Subie I simply toggle between L1 and L2 depending on the slope and traffic speed... never have to put on the brakes at all. The brake-check attendants are always amazed that my brakes are completely cool
Have yet to try it in our Prius (only had it 24 hours!)... I suspect B mode will be my friend here in Colorado... and appreciate the heads-up here about being careful with braking.

Thanks!
Pete

 

I think the OP might be referring to the NF road as seen here. BigHorn Mountains Red Grade Road - YouTube The video is driving up the hill. Coming back down you use 4x4 low range or ride your brakes at 10mph plus or minus. Regen in the Prius might be disabled because of the low speed < 7mph. and the Prius doesn't have much brake pad or disks to dissipate heat.

 

Will it be safe to apply reverse and use pedal to control speed while you are moving forward downhill?

 

maybe drag an anchor?

 

That is NOT a good idea!
Just put it in neutral, the battery does not charge in neutral.

 

The car will not let you switch to reverse while moving forward. Strangely enough, flicking the shift knob to Reverse while driving ahead will put the car in Neutral.

However, being in neutral while going downhill is undesirable because it disables 2 braking systems (regen, engine braking) of the 3 available, and has you relying solely on friction braking for control.

It is far more desirable to be in B mode. Once the HV battery fills up with recovered energy and regen is turned off, one would at least be left with friction and engine braking. In order to reactivate regen, one might try to reduce the battery SOC by burning off the recovered energy. Turning the AC to its coldest setting, opening the windows (which also increases aerodynamic drag), turning the stereo on at full blast can all help, but only up to a point.

If regen and/or engine braking are not enough to maintain a steady speed, use the friction brakes intermittently as needed to slow down. When those get too hot, pull over and wait for them to cool down, and then resume your descent.

I understand that taking breaks may seem disruptive, but it is ultimately the safer choice in a vehicle that was likely not designed for such extreme terrain.