B Lever on Dashboard

What does this mean?

Tom

 

Going on up to friction brakes from regen is not just a question of panic stops or the extreme slow end.

The 90 Ampere or so regenerative maximum is an impressive stopping force and deceleration rate at 20 mph, but at 70 mph it is a rather modest amount which is really easy to exceed. Even at 40 mph braking down to stoplight from 50 mph on a downhill I find it pretty easy to use up my quota.

The single information upgrade on Toyota's energy flow display I'd think most useful would be an indication of braking effort share between regen and friction brakes. If true proportion indication were judged too complex for our little minds, then a simple two-state indicator (perhaps an icon for a disc brake) that turned on any time friction brake share was over a threshold, say perhaps 30%, by changing color would still be an improvement.

It is a pity we need to buy a ScangaugeII or such to see that.

 

See this discussion:

http://priuschat.com/forums/prius-main-forum/3659-what-exactly-happens-when-you-brake.html

Actually I guess it was about 3 or 4 documents. I've found this one:

http://priuschat.com/forums/attachm...y-how-do-friction-brakes-work-prius-brake.pdf

If someone has the time to find them all, it wouldn't be a bad idea to put them together into a single post in the Knowledge Base forum, or into the File Library.

 

Wrong forum. Please take such comments to "Fred's House of Politics". Thank you.

 

Thank you for that information. I had understood that friction took over around 7-8 mph. Now I won't be quite as concerned about wearing out brakes before a possible 100,000 miles. FYI, I also drive a 97 F250 Powerstroke with 219,000 miles. Two of the brakes, I can't remember which axle, are the originals. Now I'm wondering which vehicle will wear out brakes first.

 

By the way. F.Y.I. I learned something about our 2000 Avalon XLS, using the ScanguageII, that I never realized. I remember a couple of members mentioned having Avalons. Monitoring the GPH & HPR I noticed, on downhill situations, they both go to 00.0. I didn't realize that it cut the injectors off completely. I didn't think that technology came along until later models, although I now remember that the "instant economy" or mpg went to 99.9. I should have guested. I never use instant because it's too erratic, all over the place. I always kept it in "average economy" or mpg, which doesn't make the changes as obvious. That's why I like the HPR. You have a better feel of what's happening. It really helps you to learn to develop a light touch on the gas pedal. It also shows, immediately, what effects accessories such as A/C and even headlights (Silverstar Ultras) have on the GPH & HPR. A/C requires an extra 2-3hp @ idle to maintain rpm. This may be more difficult to determine in the Prius, since the ICE charges the battery which powers the A/C. We used to leave the A/C on all the time thinking the Climate Control would only use it if needed to maintain temp, evidently not so. Now we only turn the A/C on if we're uncomfortable, too hot or too humid. We've increased our MPG around 10%, that's about 2mpg.
Thought this may help others with non-hybrids, if your letting your Climate Control determine when to call for the A/C. It took our city from 17/19 to 19/20. We've kept a log from delivery. All 108k. Date, miles driven, odometer reading, gals, $$$, $/gal, mpg, per fillup. 25/26 highway. Haven't taken any trips since using ScanguageII, but I assume only A/C will affect mileage, since I use CC whenever practical. Having oil change tomorrow. Switching to Mobil1, not sure of viscousity yet. Goint to decide on that tonight.
I realize that most of my remblings are old hat to most of you. But I like to share just in case it helps some of the new drivers. I had my dad. Rebuilt my G'Pa's "49 Pontiac, straight 8, 2 door torpedo back. Pistons like coffee cans. That's when you could actually climb into the engine compartment to work on it. He taught me alot about cars. Passed it on to our son and daughter. Probably some of the few today that can change a tire, check/change tire pressure, check/add/change the fluids, replace lights/headlamps. Used to change our own oil, shocks, brake pads, etc. All required before I let them go for their licenses. Didn't want them stranded. Of course, we need to know all that, since the cars weren't anywhere near as reliable as they are today, or as complicated. Anyway. Drive careful and never let yourself be dead-right. Let the person, in the wrong, have his/her accident somewhere else.

 

A side note on engine/compression braking and gas mileage.

If someone says engine braking costs gas, it does because even with no load, an ICE injects some amount of gas while running. The faster the RPM, the more gas is being burned compared to idling.

A motorcycle (with a high-compression motor) engine brakes naturally just by rolling back on the throttle...even in higher gears. A car (with standard-compression motor) only effectively engine brake in lower gears, but it will still burn more gas in gear coasting down a long, steep hill than if it was in neutral because the engagement of the transmission to the motor forces the engine to spin faster.

Good to know that when the Prius battery is full, the B mode is somewhat pointless and that it's less effective than normal braking unless you are on a steep hill and want the extra help from engine braking.

 

It's not all that pointless. B mode comes on by all by itself on a long downhill, if the battery is full. No need to select it. And in the Prius it doesn't consume gas, that I am aware of. Yes, not a real major stopping force, but it does help keep the wear off the brakes. I use it all the time on my very long downhill mountain driving.

 

Correct. The Prius and most vehicles made in the last 15 years have what is called Deceleration Fuel CutOff (DFCO) which kills the injectors and turns the engine into an air pump. Different models have different criteria for doing DFCO, such as speed or RPM at the time you lift off the throttle.

 

That must refer to carbureted and older fuel injected engines. My last pre-hybrid, a 1997 model, doesn't inject fuel during engine braking, and I'd be quite surprised if it was the first to apply this savings.