pulse & glide... accelerate fast or slow?

The engine is sucking up those MPG. The arrows show energy flow. There is no indicator to show that the engine (ICE) is running. When it is cold, the ICE will run to heat itself, the catalytic converter, and heat the cabin, all without showing arrows on the screen.

Tom

 

perfect sense, thanks qb !

 

Thanks patsparks, ken1784, and JimboK for your knowledge and experiences!
It looks to me like they are in agreement with the Prius always adding just a little extra power while gliding to significantly reduce drag.

I think this could also explain JimboK's 38 mph neutral glide release point. At 38 mph MG1 is spinning at about 5500rpm (right?). In neutral, without the extra anti drag power of the normal glide, that requires a significant amount of torque to keep it spinning. Through the PSD, the ICE must also always share a proportional amount of that torque (72% of total IIRC). When the torque is high enough, apparently at about 38 mph, then it overcomes the static friction and compression resistance of the ICE, and the ICE starts spinning. After it starts spinning, the torque required to overcome dynamic friction and keep it spinning is less, and MG1 also requires less torque because it then spins slower. So the torque i.e. drag suddenly decreases, and a slight increase in acceleration might be felt.
In a normal glide, MG1 is supplied with enough anti drag power to keep the ICE from spinning until 42mph, and then it is immediately spun up to a certain rpm IIRC.

If this is true, then it may have some other interesting implications:
1. Normal glide with anti drag power might be more efficient than neutral glide.
2. Neutral glide above about 38 mph might cause increased engine wear if the engine is not being spun fast enough to produce sufficient oil pressure.

 

You're correct about the 5500 MG1 RPM at 38 MPH and ICE RPM of zero. But whatever the state of the ICE when the car goes into N, it remains in that state. If it's on it stays on, and if it's at zero RPM it stays at zero. Which is why warp neutral (allowing a neutral glide to continue while crossing the 40 MPH threshold on a downhill) prevents the spinning of the ICE that you would otherwise see when letting off the gas pedal at higher speeds. With that, there is a theoretical concern of allowing MG1 to over-rev. But others much more knowledgeable about the engineering of the car than I (Hobbit being chief among them - he routinely uses warp neutral) seem confident that MG1 is OK below 10000 RPM (warp neutral at ~63 MPH).

 

Adding to Tom's comment... There is another situation seeing no arrow and non 99.9mpg gliding.
After completion of warming up (above 70C:158F coolant temp), Prius goes to S3, then the engine continues to run until the idling check ceremony.

Ken@Japan

 

KISS.... keeping it simple.... (it seems this is being made way to complex). You are after better MPG's, right? That is Miles over Gallons or distance traveled over fuel used.

So do your acceleration over a short distance uses most of your fuel over a short distance ..... lets say accelerate at a brisk rate in the first 500 feet, leaves the remaining 4780 feet of the mile pretty much gas free.

 

This might be a really stupid question, but:

Where do I find the RPM on my display?

 

Not a stupid question. It doesn't exist on a stock Prius, you need to get extra instrumentation like scangauge.

 

Can the scangauge display MG1 RPM?

Ken@Japan