Does using "B" mode to generate more charge?
#11
04-19-2011, 09:03 PM
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Re: Does using "B" mode to generate more charge?
My Brake-mode experience..
Coming down a long moderately steep grade on a straight highway for 3 miles. I got to test the B-mode when the car was rather new. At the top of the mountain I started off around 30 mph. The car sped up as I put it in the B-mode. The car slowed quickly as I thought the regeneration was maybe 3 times faster than normal when braking. I watched the traction battery indicator as close as I could. It shows the usual 80% full charge but half way down the grade it was at 100% so the generator or generators shut off. The engine if it was gearing down was not felt till it really revved up near 50 mph at around 5000 rpm. I didn't like the revving and engine noise being that high so I put the lever in drive. I tried using the brake pedal but it did not slow the car much even though I was pressing rather hard. The brakes may have been hot from using the B-mode for for over a mile.
The way I overcame this problem. Is at the top of the 6000 or so foot mountain I slow to 5 mph in the right lane. I let any string of traffic to go on by. I start out slowly rolling down the mountain in drive. I get up to 40 mph I ease on the brakes to use the regeneration. I pull the car down about 5 mph but the car quickly speeds up to 50 so I ease the brakes on again. I do this about 2 or 3 times and am up to 60 mph when I get into the foothills and 4 wide lanes. The speed limit is 60 on in toward Las Cruces, NM from that point.
Using the brakes for regeneration gently slowing down and not riding them seems to me works better then the B-mode. I do use the B-mode on any really steep grades at slow speeds, only if it's a 1/4 mile or shorter.
Last edited by rburt07; 04-22-2011 at 01:21 AM.
#12
04-21-2011, 08:41 AM
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Re: Does using "B" mode to generate more charge?
Your right, high revving while gearing down the engine can elongate the rods and rod bearings. Exaggeration would be to think of a circle compared to a egg shape. The large end of the rod and bearings on the crankshaft have to be round. This is to allow oil pressure to flow evenly inside the crank to each rod bearing to get ample oil.
My B-mode experience..
Coming down a long moderately steep grade on a straight highway for 3 miles. I got to test the B-mode when the car was rather new. At the top of the mountain I started off around 30 mph. The car sped up as I put it in the B-mode. The car slowed quickly as I thought the regeneration was maybe 2 or 3 times faster then normal when braking. I watched the traction batter indicator as close as I could. It shows the usual 80% full charge but half way down the grade it was at 100% so the generator or generators shut off. The engine if it was gearing down was not felt till it really revved up around 50 mph. I didn't like the revving ending that high so I put the lever in drive. I tried using the brake pedal but it did not slow the car much even though I was pressing rather hard. Evidently the brakes were hot from using the B-mode for longer than usual.
The way I overcame this problem. Is at the top of the 6000 or so foot mountain I slow to 5 mph in the right lane. I let any string of traffic to go on by. I start out slowly rolling down the mountain in drive. I get up to 40 mph I ease on the brakes to use the regeneration. I pull the car down about 5 mph but the car quickly speeds up to 50 so I ease the brakes on again. I do this about 3 times and am up to 60 mph when I get into the foothills and 4 wide lanes. The speed limit is 60 on in toward Las Cruces, NM from that point.
Using the brakes for regeneration gently slowing down and not riding them seems to me works better then the B-mode. I do use the B-mode on any really steep grades at slow speeds, only if it's a 1/4 mile or shorter.
My B-mode experience..
Coming down a long moderately steep grade on a straight highway for 3 miles. I got to test the B-mode when the car was rather new. At the top of the mountain I started off around 30 mph. The car sped up as I put it in the B-mode. The car slowed quickly as I thought the regeneration was maybe 2 or 3 times faster then normal when braking. I watched the traction batter indicator as close as I could. It shows the usual 80% full charge but half way down the grade it was at 100% so the generator or generators shut off. The engine if it was gearing down was not felt till it really revved up around 50 mph. I didn't like the revving ending that high so I put the lever in drive. I tried using the brake pedal but it did not slow the car much even though I was pressing rather hard. Evidently the brakes were hot from using the B-mode for longer than usual.
The way I overcame this problem. Is at the top of the 6000 or so foot mountain I slow to 5 mph in the right lane. I let any string of traffic to go on by. I start out slowly rolling down the mountain in drive. I get up to 40 mph I ease on the brakes to use the regeneration. I pull the car down about 5 mph but the car quickly speeds up to 50 so I ease the brakes on again. I do this about 3 times and am up to 60 mph when I get into the foothills and 4 wide lanes. The speed limit is 60 on in toward Las Cruces, NM from that point.
Using the brakes for regeneration gently slowing down and not riding them seems to me works better then the B-mode. I do use the B-mode on any really steep grades at slow speeds, only if it's a 1/4 mile or shorter.
#13
04-21-2011, 08:46 AM
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Re: Does using "B" mode to generate more charge?
Altima Hybrid has Toyota HSD in it.
I found one psychological disadvantage to using B mode. I use it when I go downhill to decelerate and to take sharp curves, like clover type off ramps, at higher speed and less brakes use. anyhow, my downhill use terminates in usually red light. call me stupid, but it's a long downhill, and I caught myself several times that I relied on B deceleration so much, that I almost forgot to use brakes to stop at the red light. Sort of allowed car to stop it for me.
Also, Toyota states that continuous use of B mode will "damage certain bearings".
I found one psychological disadvantage to using B mode. I use it when I go downhill to decelerate and to take sharp curves, like clover type off ramps, at higher speed and less brakes use. anyhow, my downhill use terminates in usually red light. call me stupid, but it's a long downhill, and I caught myself several times that I relied on B deceleration so much, that I almost forgot to use brakes to stop at the red light. Sort of allowed car to stop it for me.
Also, Toyota states that continuous use of B mode will "damage certain bearings".
Can you refer me to the document or site wherein Toyota has made such a statement..?
I'm a disbeliever....
#14
04-21-2011, 12:18 PM
Re: Does using "B" mode to generate more charge?
people are like belly buttons, everyone has an opinion.
i had quotation posted with this here couple mths ago, should be easy to find. otherwise, you can look up HSD articles on Wikipedia, it's there. of course, for many, Wiki is is not a good source either. but that's where it came from.
i had quotation posted with this here couple mths ago, should be easy to find. otherwise, you can look up HSD articles on Wikipedia, it's there. of course, for many, Wiki is is not a good source either. but that's where it came from.
#15
04-21-2011, 12:27 PM
Re: Does using "B" mode to generate more charge?
1. for starters, there's a very good technical article on HSDs floating around here, that says ICE never revs. it always runs at specific, most efficient rpm level, controlled by ECM.
2. to my knowledge, ANY braking done by TCH involves 2 phases. phase a is deceleration done by MG; phase b is deceleration done by hydraulic brakes. the way it said this was "initial braking is done by MG" with later switchover to hydraulics. i do not know what is the boarder line. now, this is WHEN YOU PRESS ON THE BRAKE PEDAL.
so, in either B or D modes, deceleration is done by MG anyway. just to a different extent. mof, i can hear it when i roll down the hill, and GENTLY press brake pedal.
3. i have been in this quarrel here before. Toyota user manual says you can drive with gear selector in either B or D modes. yes, it does contradict what Wiki says about "certain bearings damage". why would you tell someone to use mode that can lead to a damage?
2. to my knowledge, ANY braking done by TCH involves 2 phases. phase a is deceleration done by MG; phase b is deceleration done by hydraulic brakes. the way it said this was "initial braking is done by MG" with later switchover to hydraulics. i do not know what is the boarder line. now, this is WHEN YOU PRESS ON THE BRAKE PEDAL.
so, in either B or D modes, deceleration is done by MG anyway. just to a different extent. mof, i can hear it when i roll down the hill, and GENTLY press brake pedal.
3. i have been in this quarrel here before. Toyota user manual says you can drive with gear selector in either B or D modes. yes, it does contradict what Wiki says about "certain bearings damage". why would you tell someone to use mode that can lead to a damage?
#16
04-21-2011, 12:47 PM
Re: Does using "B" mode to generate more charge?
ok, here's ur source:
# gradual braking: Regenerative brakes re-use the energy of braking, but cannot absorb energy as fast as conventional brakes. Gradual braking recovers energy for re-use, boosting mileage; hard braking wastes the energy as heat, just as for a conventional car. Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.[9] Use of "B" constantly is discouraged by Toyota as it may promote excessive wear on certain gears.[10]
with source quoted being Prius owner manual.
does ICE rev or not? apparently, it may for this particular situation:
Compression braking: The HSD system has a special transmission setting labelled 'B' (for Brake), that takes the place of a conventional automatic transmission's 'L' setting, providing engine braking on hills. This can be manually selected in place of regenerative braking. During braking when the battery is approaching potentially damaging high charge levels, the electronic control system automatically switches to conventional compression braking, drawing power from MG2 and shunting it to MG1, speeding the engine with throttle closed to absorb energy and decelerate the vehicle.
regenerative braking
Regenerative braking: By drawing power from MG2 and depositing it into the battery pack, the HSD can simulate the deceleration of normal compression braking while saving the power for future boost. The regenerative brakes in an HSD system absorb a significant amount of the normal braking load, so the conventional brakes on HSD vehicles are undersized compared to brakes on a conventional car of similar mass.
i guess, this is the answer to the original topic question?
Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.
# gradual braking: Regenerative brakes re-use the energy of braking, but cannot absorb energy as fast as conventional brakes. Gradual braking recovers energy for re-use, boosting mileage; hard braking wastes the energy as heat, just as for a conventional car. Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.[9] Use of "B" constantly is discouraged by Toyota as it may promote excessive wear on certain gears.[10]
with source quoted being Prius owner manual.
does ICE rev or not? apparently, it may for this particular situation:
Compression braking: The HSD system has a special transmission setting labelled 'B' (for Brake), that takes the place of a conventional automatic transmission's 'L' setting, providing engine braking on hills. This can be manually selected in place of regenerative braking. During braking when the battery is approaching potentially damaging high charge levels, the electronic control system automatically switches to conventional compression braking, drawing power from MG2 and shunting it to MG1, speeding the engine with throttle closed to absorb energy and decelerate the vehicle.
regenerative braking
Regenerative braking: By drawing power from MG2 and depositing it into the battery pack, the HSD can simulate the deceleration of normal compression braking while saving the power for future boost. The regenerative brakes in an HSD system absorb a significant amount of the normal braking load, so the conventional brakes on HSD vehicles are undersized compared to brakes on a conventional car of similar mass.
i guess, this is the answer to the original topic question?
Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.
#17
04-21-2011, 12:47 PM
Re: Does using "B" mode to generate more charge?
ok, here's ur source:
# gradual braking: Regenerative brakes re-use the energy of braking, but cannot absorb energy as fast as conventional brakes. Gradual braking recovers energy for re-use, boosting mileage; hard braking wastes the energy as heat, just as for a conventional car. Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.[9] Use of "B" constantly is discouraged by Toyota as it may promote excessive wear on certain gears.[10]
with source quoted being Prius owner manual.
does ICE rev or not? apparently, it may for this particular situation:
Compression braking: The HSD system has a special transmission setting labelled 'B' (for Brake), that takes the place of a conventional automatic transmission's 'L' setting, providing engine braking on hills. This can be manually selected in place of regenerative braking. During braking when the battery is approaching potentially damaging high charge levels, the electronic control system automatically switches to conventional compression braking, drawing power from MG2 and shunting it to MG1, speeding the engine with throttle closed to absorb energy and decelerate the vehicle.
regenerative braking
Regenerative braking: By drawing power from MG2 and depositing it into the battery pack, the HSD can simulate the deceleration of normal compression braking while saving the power for future boost. The regenerative brakes in an HSD system absorb a significant amount of the normal braking load, so the conventional brakes on HSD vehicles are undersized compared to brakes on a conventional car of similar mass.
i guess, this is the answer to the original topic question?
Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.
# gradual braking: Regenerative brakes re-use the energy of braking, but cannot absorb energy as fast as conventional brakes. Gradual braking recovers energy for re-use, boosting mileage; hard braking wastes the energy as heat, just as for a conventional car. Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.[9] Use of "B" constantly is discouraged by Toyota as it may promote excessive wear on certain gears.[10]
with source quoted being Prius owner manual.
does ICE rev or not? apparently, it may for this particular situation:
Compression braking: The HSD system has a special transmission setting labelled 'B' (for Brake), that takes the place of a conventional automatic transmission's 'L' setting, providing engine braking on hills. This can be manually selected in place of regenerative braking. During braking when the battery is approaching potentially damaging high charge levels, the electronic control system automatically switches to conventional compression braking, drawing power from MG2 and shunting it to MG1, speeding the engine with throttle closed to absorb energy and decelerate the vehicle.
regenerative braking
Regenerative braking: By drawing power from MG2 and depositing it into the battery pack, the HSD can simulate the deceleration of normal compression braking while saving the power for future boost. The regenerative brakes in an HSD system absorb a significant amount of the normal braking load, so the conventional brakes on HSD vehicles are undersized compared to brakes on a conventional car of similar mass.
i guess, this is the answer to the original topic question?
Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.
#18
04-21-2011, 06:18 PM
Re: Does using "B" mode to generate more charge?
this is even better:
Whereas during coasting MG2 produces some generator drag to simulate engine braking, when the brake pedal is pressed, the electrical power generation of MG2 is stepped up and a much greater generator drag contributes to slowing the car. Unlike friction brakes, which waste the car's kinetic energy as heat, the electrical power produced by regenerative braking is stored in the battery and will be re-used later. The computer calculates how much deceleration will be produced by regenerative braking and reduces the hydraulic force transmitted to the friction brakes by an appropriate amount.
In a conventional car on a steep hill, you might decide to change to a low gear to increase the intensity of engine braking. The engine spins more rapidly and holds the car back more, helping the brakes to slow it. The same option is available in the Prius should you decide to use it. If you move the mode selector lever to the "B" position, the engine will be used for engine braking. Whereas normally the engine is stopped during braking, in this mode the computer and motor/generators arrange for it to turn over without fuel and with an almost closed throttle. The resistance it offers slows the car, reducing brake heating and allowing you to ease up a little on the pedal.
so, no, engine is not revved. it is simply used as "weight" or "pendulum" to slow down car without wasting energy into hydraulic braking.
Whereas during coasting MG2 produces some generator drag to simulate engine braking, when the brake pedal is pressed, the electrical power generation of MG2 is stepped up and a much greater generator drag contributes to slowing the car. Unlike friction brakes, which waste the car's kinetic energy as heat, the electrical power produced by regenerative braking is stored in the battery and will be re-used later. The computer calculates how much deceleration will be produced by regenerative braking and reduces the hydraulic force transmitted to the friction brakes by an appropriate amount.
In a conventional car on a steep hill, you might decide to change to a low gear to increase the intensity of engine braking. The engine spins more rapidly and holds the car back more, helping the brakes to slow it. The same option is available in the Prius should you decide to use it. If you move the mode selector lever to the "B" position, the engine will be used for engine braking. Whereas normally the engine is stopped during braking, in this mode the computer and motor/generators arrange for it to turn over without fuel and with an almost closed throttle. The resistance it offers slows the car, reducing brake heating and allowing you to ease up a little on the pedal.
so, no, engine is not revved. it is simply used as "weight" or "pendulum" to slow down car without wasting energy into hydraulic braking.
#19
04-22-2011, 09:21 AM
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Re: Does using "B" mode to generate more charge?
"..engine is not revved..."
Clarification only.
The engine is not revved in the normal way, fuel supply. It is, however, "revved" due to the forces provided by gravity acting on the drive wheels. Just as in a normal vehicle as the level of compression braking grows the higher the engine will "rev".
Clarification only.
The engine is not revved in the normal way, fuel supply. It is, however, "revved" due to the forces provided by gravity acting on the drive wheels. Just as in a normal vehicle as the level of compression braking grows the higher the engine will "rev".
#20
04-23-2011, 02:11 PM
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Re: Does using "B" mode to generate more charge?
ukrkoz, please don't take this wrong. I'm not saying you are wrong - I don't trust Wikipedia 100%. I'm glad they press contributors for references - as in this case. If one doesn't believe, one can check the reference...
Regarding "bearing damage". Quote [10] simply references the 2007 Prius Owners Manual. No page #, or any other detail.
I just went to Toyota's website, downloaded parts of the maual and looked for that reference. All I could find was the following (copied directly from the .pdf - page 146). "2007 Prius: "power" Switch, Transmission and Parking Brake"
Regarding "undersized brakes": "The regenerative brakes in an HSD system absorb a significant amount of the normal braking load, so the conventional brakes on HSD vehicles are undersized compared to brakes on a conventional car of similar mass"
Regarding "bearing damage". Quote [10] simply references the 2007 Prius Owners Manual. No page #, or any other detail.
I just went to Toyota's website, downloaded parts of the maual and looked for that reference. All I could find was the following (copied directly from the .pdf - page 146). "2007 Prius: "power" Switch, Transmission and Parking Brake"
(d) Using engine braking
To use engine braking, shift the shift lever to “B” position.
During high speed driving, you may feel that deceleration by engine braking is less than that of a typical vehicle.
Do not continue normal driving with the transaxle in “B” for a long time. This may cause decreased fuel economy. To prevent this, use “D” for normal driving.
When you shift the transaxle to “B” from a position other than “D”, an alarm sounds and the transaxle is automatically shifted to “N”.
I couldn't find any reference to what Wikipedia quotes. Can anyone find this reference?To use engine braking, shift the shift lever to “B” position.
During high speed driving, you may feel that deceleration by engine braking is less than that of a typical vehicle.
Do not continue normal driving with the transaxle in “B” for a long time. This may cause decreased fuel economy. To prevent this, use “D” for normal driving.
When you shift the transaxle to “B” from a position other than “D”, an alarm sounds and the transaxle is automatically shifted to “N”.
Regarding "undersized brakes": "The regenerative brakes in an HSD system absorb a significant amount of the normal braking load, so the conventional brakes on HSD vehicles are undersized compared to brakes on a conventional car of similar mass"
I don't have a Toyota part number guide. And this is simply my opinion - but I will bet a good dinner that the Camry Hybrid brakes (rotors, calipers and pads) are IDENTICAL to those of the non-hybrids.
And I will bet a good lunch that the Prius brakes are similarly sized to those of a Yaris or Corolla.
I have a friend at work with a 2007 XLE. I have the 2007 Hybrid. The brakes look identical. Any good car maker will re-use parts wherever possible.
Plus Toyota can't depend on regeneration. If one brakes hard, regeneration simply shuts off.
And I will bet a good lunch that the Prius brakes are similarly sized to those of a Yaris or Corolla.
I have a friend at work with a 2007 XLE. I have the 2007 Hybrid. The brakes look identical. Any good car maker will re-use parts wherever possible.
Plus Toyota can't depend on regeneration. If one brakes hard, regeneration simply shuts off.
