Finally -- I've felt surging in the ICE

HighBreed · 12-15-2007, 01:51 PM

Quote:

Originally Posted by bwilson4web

One of my 'lessons learned' is to keep a guard-band around 42 mph. I'll slow down to 38 mph or speed up to 46 mph but I try to minimize transitions through 42 mph. My mileage data using cruise control to govern the speed showed that 42 mph in city driving gives a the worst mileage. Yet in controlled tests on level roads without other traffic, 42 mph fits on the drag curve.

Bob Wilson

Anather uh-ha! for me. great tip

Mawcawfee · 12-18-2007, 06:22 PM

The surging around 40mph is normal behavior. In fact, I have yet to drive a Prius that doesn't do it. I have a habit of driving on secondary roads right around the magical 40mph surging point on the Prius, where the powertrain starts constantly pulsing like you describe. I can duplicate it in less than five minutes. Don't sweat it. They all do it. It's normal. Try to keep your speed a bit higher or lower.

fruzzetti · 12-18-2007, 11:48 PM

I felt it for the first or maybe second time today. It's the first time I can be certain I felt it. And I figured out and can replicate exactly the conditions to make it happen:

accelerating somewhat hard up a hill (parallel hybrid at least), and as you top out at or around the low 40s, you let off the throttle to start decelerating. The ICE shuts down. But then you start demanding a bit more power, right as it's shutting down, and it will hesitate -- as if it can't decide whether to be starting or stopping.

It was much easier in the earlier version of the car; in fact, that's essentially what caused the occasional startup lag when in ready mode with engine already shut down, in thinking about it.

~ dan ~

douglas001001 · 12-19-2007, 04:52 PM

If you watch rpm as you coast down from 42-40, rpm briefly jumps from 960 to ~1180. There is some sort of fuel squirt around that threshold even if you're coasting.

I think this happens if you're coasting down a hill and go from 40-42, can anyone verify?

But what Bob said, minimize crossovers between 40 and 42 in either direction. I try not to cross 40 accelerating unless I know I'm going all the way to 50 or higher.

12-18-2007, 06:22 PM	#12
Mawcawfee Prius-less (for now) Join Date: Dec 2007 Location: The Free State Posts: 98 My Car: Other Non-Hybrid Package: N/A Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: Finally -- I've felt surging in the ICE The surging around 40mph is normal behavior. In fact, I have yet to drive a Prius that doesn't do it. I have a habit of driving on secondary roads right around the magical 40mph surging point on the Prius, where the powertrain starts constantly pulsing like you describe. I can duplicate it in less than five minutes. Don't sweat it. They all do it. It's normal. Try to keep your speed a bit higher or lower.

12-18-2007, 11:48 PM	#13
fruzzetti Customization-Obsessed Join Date: Dec 2007 Location: Hayward, CA USA Posts: 337 My Car: 2006 Prius Package: #7 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Re: Finally -- I've felt surging in the ICE I felt it for the first or maybe second time today. It's the first time I can be certain I felt it. And I figured out and can replicate exactly the conditions to make it happen: accelerating somewhat hard up a hill (parallel hybrid at least), and as you top out at or around the low 40s, you let off the throttle to start decelerating. The ICE shuts down. But then you start demanding a bit more power, right as it's shutting down, and it will hesitate -- as if it can't decide whether to be starting or stopping. It was much easier in the earlier version of the car; in fact, that's essentially what caused the occasional startup lag when in ready mode with engine already shut down, in thinking about it. ~ dan ~

12-19-2007, 04:52 PM	#14
douglas001001 smug doug Join Date: Mar 2007 Location: Chicago Posts: 206 My Car: 2007 Prius Package: #6 Touring Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 1	Re: Finally -- I've felt surging in the ICE If you watch rpm as you coast down from 42-40, rpm briefly jumps from 960 to ~1180. There is some sort of fuel squirt around that threshold even if you're coasting. I think this happens if you're coasting down a hill and go from 40-42, can anyone verify? But what Bob said, minimize crossovers between 40 and 42 in either direction. I try not to cross 40 accelerating unless I know I'm going all the way to 50 or higher.