Driving trick

good to know! thanks

 

don't worry it'll get warm on the next stretch, till you get caught at the next light.

 

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As explained in the owners manual, the B position is for "engine braking" and does not increase the amount of energy recovered. If you are driving around in, or downshifting to the B position, you are wasting energy with unnecessary engine compression losses. The B position is for long downhill slopes where you would increase speed if you tried to coast, and you don't want to ride the brakes.

I have noticed that with the heater running, when I pull up to a light, the engine may continue to run to try to heat up the coolant. If I either turn down the temperature, or turn off the Auto A/C, the engine will stop. When the light turns green, I'll turn the temperature back up as soon as the ICE kicks in. I'm not obsessive about fuel consumption, I just don't like the way the car idles when it's in this "I'm only running because the heater is on and the coolant isn't hot" mode. Instead of the normal idle, the engine runs rough, like only one or two cylinders are getting fuel. I'm sure it was done for a reason, and I assume the reason was that the engine will heat up just as fast even if it is barely running. I have confidence that the Toyota engineers have not programmed the system so that the ICE is adversely affected for the sake of fuel economy.

 

Could you explain by we are losing energy due to "engine compression losses" in the "B" engine braking mode?

I understood from discussions here and the owners manual that the engine braking mode simply cuts off the flow of fuel to the cylinders...I find it is an excellent assist if I need to stop in a shorter distance than brakes alone, particularly in unpredictable stop and go traffic, in addition to the steep hills. There are also times I use it to "downshift" even though it technically is not a lower gear, but can be used at any speed (the owners manual recommends its use to slow down when the cruise control increases speed to an undesirable level.)

wildplaces

 

When you apply the brakes to slow down, some of the energy is saved in the battery by the regenerative braking system. But all the energy that is consumed by engine drag is lost. You may also find you're slowing down more than you indend to at times, which must be compensated for by more acceleration.

One thing that's not clear to me is if "B" mode increases the regen rate that always takes place when you take your foot off the accelerator. If it does, then using "B" mode may not be significantly wasteful in stop-and-go traffic. But I believe that its intended purpose is to save the brakes on long downhill slopes.

 

I'm not sure that "B" increases the regen rate...that should be determined by the number of rotations of the generator...and that is dependent on both the number of drive train rotations (regenerative braking) and the number of RPMs over and above what the accelerator is calling for at optimum engine output.

I would not use "B" over a long distance unless the conditions seem to warrant it (e.g. new snow or icy conditions, stop and go traffic in close quarters where my reaction time may not stop me as quickly as with the engine braking.)

I'm not sure how to quantify this in terms of MPG or emissions.

wildplaces

 

I disagree with the original post 100%. If the system is cold, the engine will run to warm it up. Also if the heater is on, the engine may run to supply heat. And, as I've discovered to my dismay, in sub-zero weather the engine almost never shuts off.

However, in normal weather, after the engine has warmed up sufficiently, if you have gotten into S4 operation (explained HERE) the engine will shut off as soon as you lift your foot from the pedal to begin slowing down.

Also, B is not "energy-recovery braking." B is engine braking, analogous to the jake brakes on a semi. According to Toyota (and many old-time posters here) B should only be used on long downhill slopes, when use of the brakes would first completely charge the battery, and then switch to friction brakes and overheat them.

On the other hand, if you have an EV switch, you can shut off the engine sooner than the car would do on its own, if conditions allow EV mode. This is especially true if the engine is warm but not yet hot, or if you are still in S3 operation.

 

That may accomplish ICE shut down, but it would seem that this technique defeats the minimum ICE temperature required for low emissions...at the expense of higher MPG

wildplaces