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Is there any possible damage to the powertrain/electrical system of my Prius by employing the "pulse and glide" technique on a frequent basis?
 

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Absolutely not. It simply takes advantage of the system to it's most efficient level of function.
 

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I would think that gliding in neutral would be a bad thing, considering that in neutral you loose the simulated automatic tranny drag that is programmed into the regenerative braking system and on top of that neutral prevents the vehicle from self charging with the ICE.

Toyota recommends against this mode unless there is a genuine utility reason for this.
 

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Neutral

Nothing is achieved in Neutral either, no regeneration and it is not recommended.
With pulse/glide you make the best use of the aerodynamics of this car. Design really makes this the most efficient way to drive.
 

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We're not talking about REMAINING in neutral, but rather going into neutral during the 'glide' portion of the pulse-glide.

I see no harm in it. Some came up with the possible problem of over-reving MG1 since ICE cannot be started if in neutral. But unless you are gliding downhill, you wouldn't be accelerating in neutral, but rather slowing down. If ICE rotation was needed to protect MG1, it will already be spinning when you go into neutral. If it wasn't needed and wasn't spinning, it is not likely it would be needed during the time you are in neutral.
For THSII, MG1 can rev to 10K rather than the original 6.5K RPM in the classic, so you have additional protection there.
 

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Dan, do you have some speed values associated with damage to MG1 in neutral? I can see someone perhaps hitting the shifter and getting into N without being aware, then speeding up down a hill as expected. If the damage is at a speed over 80mph, I wouldn't give it any mind. If it can happen at lower speeds, then this could be a problem. Going down long stretches like the Grapevine on I-5 or Cajon Pass on I-15 can get you well over 100 mph if you let it. I could see slacking the throttle at the top of a grade, stopping the ICE, then gaining speed as you go downhill. Do you know at what road speed the damage might occur?
 

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With the classic, where MG1 RPM limit is 6500, it was calculated that the car would have to travel 42MPH or above before ICE spin was needed.

With the MG1 RPM limit raised to 10K, the magic speed is about 64 MPH. However, it has been found that ICE still is spun at 42MPH.
 

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So if I understand correctly, if I drive uphill at 40mph, let up on the gas as I crest the hill, shift to neutral, then let the car speed up past 65mph, I risk damaging MG1?
 

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That is the theory, since HV would not be allowed to start the ICE since you are in neutral, and thus MG1 would exceed the 10K RPM limit.
If you glided only with the accelerator, then ICE would be started, though barely fueled, though you will probably find it next to impossible to achieve a no-arrow glide at that speed.
 

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Would I risk the same damage if I started from a stop on a downhill slant, foot off the gas in neutral, and just let it coast until it exceeded 65mph?

Not a common thing, but not impossible if you live at the top of a long hill. Costing in neutral is harmless in other catrs, so there would not be any expectation that this would casue damage.

Is there any warning under these conditions? Any DTC codes or master warning light?
 

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What confuses me about why Pulse and Glide is so efficent is, why is using the battery a bad thing? Is it less efficient to charge the battery with the ICE, then drive the power train with the EM, than it is to drive the power train directly with the ICE?

Does this mean that driving at low speeds using just the EM and not the ICE is also a bad thing?

TIA for info.

Miracle Max
 

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MiracleMax said:
What confuses me about why Pulse and Glide is so efficent is, why is using the battery a bad thing? Is it less efficient to charge the battery with the ICE, then drive the power train with the EM, than it is to drive the power train directly with the ICE?

Does this mean that driving at low speeds using just the EM and not the ICE is also a bad thing?

TIA for info.

Miracle Max
Yes, it is less efficient, under most conditions, to use the battery. There are energy losses (mostly as heat) when the energy is convertered from one mode to another for storage, then more loss when convertered back from the battery. Remember that the inverter gets hot enough to require it's own radiator/cooling system. Heat is energy.

That said, there are times where the ICE is less efficient than the battery powered car even taking the conversion losses into account.
 
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