[20swrt]

I found this cool site. It gives a better idea what happens during normal MG1 and MG2 interactions. One question i have is - does the ICE ever go backwards even slightly ? Perhaps due to the forces excerted by the MG1 and MG2 rotations.

Secondly, I was trying to look for dyno results for Toyota Hybrids vehicles - but found very little. Here is one with a very surprising result. It seems like a big difference between normal modes and "power" mode.

Dynoed my prius

Recently entered a competitive event that required entrants to dyno their cars. Did three pulls on the dyno. Pull 1 was in normal mode. Hp 102.83...

priuschat.com

 

[exmachina08]

Those results are more likely varying due to the regen power reclaimed off the dyno after pull 1. This would give you more electric power to draw from on the second pull. As for changing the drive modes, it doesn't do anything beyond apply a more aggressive throttle response curve.

The ICE also decouples from the gearing when operating under EV power. No possibility for the crankshaft to ever run backwards. Pretty clever engineering/programming to make such a smooth and reliable system. Wiki has a great article on the Hybrid Synergy Drive if you want to understand how it works.

https://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

 

[jseyfert3]

I found this cool site. It gives a better idea what happens during normal MG1 and MG2 interactions. One question i have is - does the ICE ever go backwards even slightly ? Perhaps due to the forces excerted by the MG1 and MG2 rotations.

I don't believe it ever would move backwards.

The ICE also decouples from the gearing when operating under EV power. No possibility for the crankshaft to ever run backwards. Pretty clever engineering/programming to make such a smooth and reliable system. Wiki has a great article on the Hybrid Synergy Drive if you want to understand how it works.

It does? Do you have more info on that? The professor in the amazing video from Weber Automotive mentioned a torque limiting clutch or something like that, but didn't describe it, and didn't say it could be disconnected on command. There shouldn't be a reason it needs to be disconnected (besides a torque limiting/slip clutch in case something goes wrong).

 

[exmachina08]

Took some digging to come to the right answer, but it utilizes a one way clutch on the drive shaft so it can't spin backwards. Advancement of Toyota Hybrid System II (THS-II) | Toyota Motor Corporation Official Global Website

Edit: Holdup this appears to be specific to the Prime Hybrid Drivetrain. Trying to find some good documentation on the non-prime version and how it keeps the motor from free wheeling when not needed for power.

Edit 2: Alright so the ICE never truly "disconnects" on a standard HSD setup (Prime systems it has that Sprag clutch). But the ICE is directly connected to the carrier (C below) on the planetary setup. Therefore ICE can be stopped and the Sun and Outer ring gears driven by MG1 and MG2. Pretty clever engineering! Take a look at this simulator and pay attention to ICE at 0 RPM Toyota Prius - Power Split Device

Schematic view of the First-Generation Toyota Hybrid transmission system (S: central Sun" gear, C: planetary Carrier, R: outer Ring gear, Motor-Generators MG1 and MG2, Internal Combustion Engine ICE)

 

[20swrt]

Those results are more likely varying due to the regen power reclaimed off the dyno after pull 1. This would give you more electric power to draw from on the second pull. As for changing the drive modes, it doesn't do anything beyond apply a more aggressive throttle response curve.

Are you suggesting the amount of power hybrid system can put out is dependent on the condition of how much charge there is in the HV ? i.e. the higher the charge the more power you get from the hybrid drive ?

I always had the understanding that as long as there is enough minimum voltage, the hybrid system will perform the same way (either half charged or fully charged battery) - everything held equal.

In other words. 0-60 times of the Sienna that has 4 bars HV charge will have the same 0-60 time if that same vehicle had 7 bars of charge.

 

[exmachina08]

Are you suggesting the amount of power hybrid system can put out is dependent on the condition of how much charge there is in the HV ? i.e. the higher the charge the more power you get from the hybrid drive ?

In my previous experience it does. That thread doesn't tell us much about what battery pack he has on that Gen 4 Prius but I believe the majority of 2016+ were lion which has less voltage sag that the NiMH in Gen 3 and below. In my Gen 2 you could feel the charge difference in the seat of your pants when taking off from the line. Wasn't as pronounced in my Gen 4, but I know you could chirp the tires when you had a full charge. I do not feel that it would explain 100% of the discrepancy between pulls but likely accounts for a portion. Reading further down the thread, it does appear that there are some issues with the Dyno RPM calibration that would have misrepresented the HP and Torque calculations. Wheel HP @ 102 over rated 122 seems inline with transmission loss. If this wasn't a cattle call Dyno test on a race day, this would probably be better data. Just speculating based on anecdotal knowledge

 

[20swrt]

In my previous experience it does. That thread doesn't tell us much about what battery pack he has on that Gen 4 Prius but I believe the majority of 2016+ were lion which has less voltage sag that the NiMH in Gen 3 and below. In my Gen 2 you could feel the charge difference in the seat of your pants when taking off from the line. Wasn't as pronounced in my Gen 4, but I know you could chirp the tires when you had a full charge. I do not feel that it would explain 100% of the discrepancy between pulls but likely accounts for a portion. Reading further down the thread, it does appear that there are some issues with the Dyno RPM calibration that would have misrepresented the HP and Torque calculations. Wheel HP @ 102 over rated 122 seems inline with transmission loss. If this wasn't a cattle call Dyno test on a race day, this would probably be better data. Just speculating based on anecdotal knowledge

Thats good to hear. I really hope its true. My wife is taking delivery of a 2023 Corolla Hybrid that has a Li-Ion HV battery. I will compare that with our Sienna and post results here. Thanks for the replies.