Engine Braking at High Speed

Marvinh · 07-12-2007, 02:29 PM

Hello - 'newbie' here. I have my Prius about a week and I already have almost 500 miles on it. AND I'm loving it!!

I have a question on 'B' mode at high speeds: If I'm on a highway at 60mph or faster and I encounter a hill that requires a 'lower gear', can I enter 'B' mode at such a high speed?

Will engine braking kick in and really cause an abrupt slow down from 60mph? Or is it gradual?

Thanks! Marvin

qbee42 · 07-12-2007, 04:10 PM

Yes, you can use B, but unless the hill is very long, you are better off leaving the Prius in D. B mode deliberately wastes energy by spinning the ICE. This is fine if that's what you want to do, but normally it's better to put that energy to use by saving it in the traction battery. Use B only on those long mountain roads where you know the battery will be fully charged before getting to the bottom.

Tom

NoMoShocks · 07-12-2007, 04:52 PM

Someone will correct me if I say this wrong, but with Prius, riding the brakes is not such a bad thing as it is with conventional cars. I spent quite a while teaching my other family members not to ride the brakes because they overheat. I even was in the habit of looking down on others if I saw them riding the brakes down a hill.

But with a Prius, light brake pressure regenerates energy. Unless the hill is extremely steep and you are doing some fairly substantial braking, it doesn't seem like you will liekly overheat the brakes.

I wish there was a MFD display that tells you if the friction brakes are employed. I have not been able to feel them kick in as I drop below 7 MPH, but that is actually pretty slow.

Bill Merchant · 07-13-2007, 02:57 AM

Welcome to PriusChat, Marvin!

If you are traveling at highway speeds going down a hill and you fill the HV Battery (it goes solid green) you can really feel the friction brakes kick in as the car stops putting the regen charge into the battery. That is definitely a time for B mode. It's hard to feel the mechanical friction brakes at low speed, which is how it should be.

The Prius is smart and won't let you hurt it. You can put the shift switch into any gear you want, like bumping it into R at 60 MPH, and the car will ignore you. If you're cruising around town and press the Power button, the car ignores you, unless you press and hold it, signaling an emergency shutdown. Same thing is true of the Park switch; if you're moving, you're not parking, so the car ignores your press. And not to suggest being lazy or anything, but if you come to a stop with your foot on the brake and press the Power button, your smart Prius will put itself in Park and then shut down.

usbseawolf2000 · 07-13-2007, 10:06 AM

<div class='quotetop'>QUOTE(Marvinh @ Jul 12 2007, 02:29 PM) [snapback]477615[/snapback]</div>

Quote:

Will engine braking kick in and really cause an abrupt slow down from 60mph? Or is it gradual?

Thanks! Marvin
[/b]

You can notice when the engine braking kicks in (right away). The force you feel is not gradual but happens as soon as you are in B. It feels like you suddenly slam on the brake maybe 1/4 pedal distance to the floor. You will probably gradually slow down but I have not use it until it comes to a complete stop. I have only use it for maybe 3-4 seconds because I hate wasting energy.

If someone is behind you, be very careful using it. The driver behind will not see you brake (no brake light) and get off guard.

Whiteyprius · 02-27-2008, 04:53 PM

Quote:

Originally Posted by Bill Merchant

Welcome to PriusChat, Marvin!

If you are traveling at highway speeds going down a hill and you fill the HV Battery (it goes solid green) you can really feel the friction brakes kick in as the car stops putting the regen charge into the battery. That is definitely a time for B mode. It's hard to feel the mechanical friction brakes at low speed, which is how it should be.

The Prius is smart and won't let you hurt it. You can put the shift switch into any gear you want, like bumping it into R at 60 MPH, and the car will ignore you. If you're cruising around town and press the Power button, the car ignores you, unless you press and hold it, signaling an emergency shutdown. Same thing is true of the Park switch; if you're moving, you're not parking, so the car ignores your press. And not to suggest being lazy or anything, but if you come to a stop with your foot on the brake and press the Power button, your smart Prius will put itself in Park and then shut down.

Your last comment here was a question I've had - When you shut her down, it's really not necessary to go "P" then "Power off" - one can just press "Power off," right?

JimboK · 02-27-2008, 05:19 PM

Quote:

Originally Posted by Whiteyprius

Your last comment here was a question I've had - When you shut her down, it's really not necessary to go "P" then "Power off" - one can just press "Power off," right?

Yes, I do it all the time.

Bill Merchant · 02-28-2008, 02:19 AM

That's what I said...

Bob64 · 03-03-2008, 12:02 AM

Hmm... What would happen if someone held down the power button (until it turned off) at 60mph or so? Would the parking paw engage?

**efusco** · 03-03-2008, 12:18 AM

Quote:

Originally Posted by Bob64

Hmm... What would happen if someone held down the power button (until it turned off) at 60mph or so? Would the parking paw engage?

Just goes into neutral. You gotta try harder than that to destroy your car!

07-12-2007, 04:52 PM	#3
NoMoShocks Electrical Engineer Join Date: Jan 2007 Location: Camas, WA Posts: 1,219 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 2 Thanked 49 Times in 31 Posts Friends: 1	Someone will correct me if I say this wrong, but with Prius, riding the brakes is not such a bad thing as it is with conventional cars. I spent quite a while teaching my other family members not to ride the brakes because they overheat. I even was in the habit of looking down on others if I saw them riding the brakes down a hill. But with a Prius, light brake pressure regenerates energy. Unless the hill is extremely steep and you are doing some fairly substantial braking, it doesn't seem like you will liekly overheat the brakes. I wish there was a MFD display that tells you if the friction brakes are employed. I have not been able to feel them kick in as I drop below 7 MPH, but that is actually pretty slow. __________________ Lightning Green McQueen Jr. and owner Larry 2010 Blue Ribbon Pkg IV with Solar Moon Roof Picked up on 5/20/2009. Lighning Green McQueen Sr. is 2007 Silver Pine Mica Pkg 5 who was named for his appearance, sustainability and resemblance to Lightnig McQueen, star of Pixar's movie "Cars". Jr. carries on the family name, even though he is Blue Ribbon Metalic in Color.

07-13-2007, 02:57 AM	#4
Bill Merchant absit invidia Join Date: May 2005 Location: USA \| Oregon \| Portland area \| 97004 \| Posts: 4,100 My Car: 2007 Prius Model: Package: #5 Thanks: 18 Thanked 10 Times in 8 Posts Friends: 60	Welcome to PriusChat, Marvin! If you are traveling at highway speeds going down a hill and you fill the HV Battery (it goes solid green) you can really feel the friction brakes kick in as the car stops putting the regen charge into the battery. That is definitely a time for B mode. It's hard to feel the mechanical friction brakes at low speed, which is how it should be. The Prius is smart and won't let you hurt it. You can put the shift switch into any gear you want, like bumping it into R at 60 MPH, and the car will ignore you. If you're cruising around town and press the Power button, the car ignores you, unless you press and hold it, signaling an emergency shutdown. Same thing is true of the Park switch; if you're moving, you're not parking, so the car ignores your press. And not to suggest being lazy or anything, but if you come to a stop with your foot on the brake and press the Power button, your smart Prius will put itself in Park and then shut down. __________________ Bill Bill.Merchant@PortlandHSD.info 2007 NL 5 Silver Wraith • 2005 BC 6 Silver Cloud Portland Area HSD Meetup Group: PortlandHSD.info Become carbon neutral: Carbonfund.org or TerraPass.com > < Follow me on

02-28-2008, 02:19 AM	#8
Bill Merchant absit invidia Join Date: May 2005 Location: USA \| Oregon \| Portland area \| 97004 \| Posts: 4,100 My Car: 2007 Prius Model: Package: #5 Thanks: 18 Thanked 10 Times in 8 Posts Friends: 60	Re: Engine Braking at High Speed That's what I said...

03-03-2008, 12:02 AM	#9
Bob64 Sapphire of the Blue Sky Join Date: Apr 2007 Location: Virginia Posts: 1,135 My Car: 2007 Prius Model: N/A Package: #2 Thanks: 3 Thanked 9 Times in 9 Posts Friends: 0	Re: Engine Braking at High Speed Hmm... What would happen if someone held down the power button (until it turned off) at 60mph or so? Would the parking paw engage?

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07-12-2007, 02:29 PM	#1
Marvinh Marvin Join Date: Jul 2007 Location: NY - Long Island Posts: 138 My Car: 2007 Prius Model: Package: #5 Thanks: 0 Thanked 1 Time in 1 Post Friends: 0	Hello - 'newbie' here. I have my Prius about a week and I already have almost 500 miles on it. AND I'm loving it!! I have a question on 'B' mode at high speeds: If I'm on a highway at 60mph or faster and I encounter a hill that requires a 'lower gear', can I enter 'B' mode at such a high speed? Will engine braking kick in and really cause an abrupt slow down from 60mph? Or is it gradual? Thanks! Marvin

07-12-2007, 04:10 PM	#2
qbee42 Senior Member Join Date: Mar 2006 Location: Northern Michigan Posts: 10,477 My Car: 2006 Prius Model: Package: #7 Thanks: 95 Thanked 391 Times in 290 Posts Friends: 10	Yes, you can use B, but unless the hill is very long, you are better off leaving the Prius in D. B mode deliberately wastes energy by spinning the ICE. This is fine if that's what you want to do, but normally it's better to put that energy to use by saving it in the traction battery. Use B only on those long mountain roads where you know the battery will be fully charged before getting to the bottom. Tom