How are you making so many MPGs!?!

[Rybold]

Originally Posted by Argyle

OK, now I am confused. I seem to hear a lot about Pulse & Glide (which might be a good name for a sex lubricant) where you purposely avoid a constant speed. The way I understand it (and I could be wrong) rather than driving a constant 60 MPH, you pulse up to 70 and glide down to 50 and repeat. It sounds dreadful and counter intuitive.

I was thinking the same thing... instead of going back and forth from 50 to 70, why not just drive a constant 60? So I started thinking about this. 70mph, you are better off going a constant 60 because it will take you 15 to 20 seconds (or more) to [efficiently] accelerate from 50 to 70, yet if you take your foot off the gas, your car will quickly slow from 70 to 50 in very few seconds. The added wind resistance at 61,62,63,64,65,66,67,68,69,70mph will negate the "glide" benefits, and you would be better off just going a constant 60mph. However, if you are not on the highway/expressway/freeway, and you are pulse and gliding between 50 and zero (example) miles per hour and of course accelerating very slowly, then wind resistance will not outweigh your benefits from gliding.

note: although I clearly sensed the sarcasm/joking of your list of improvements, the flapping of the Hefty bags in the windows might actually create more drag force than weight-saving benefit. It would depend on whether you do more city or highway driving. When I was around 16yrs old (back in the day), my brother had a van for his first vehicle and I used to help him remove the 2nd and 3rd row bench seats and it took two of us because those seats weighed about 100 pounds each. The 0-60 acceleration improved very noticably when those seats were out of the vehicle; so I have been able to experience first-hand the benefits of removing seats from a vehicle. Of course, we can all experiment with this by comparing your cars 0-60 with driver only, versus having all four seats occupied by passengers. Yes, 0-60 is not fuel efficient; however, it is a great way to demonstrate the difference in vehicle performance when weight is added or subtracted. [/nerd]

[morpheusx]

It's all about tire pressure and not driving like a sh!thead

[Argyle]

Originally Posted by morpheusx

It's all about tire pressure and not driving like a sh!thead

That is a bit simplistic. Weight counts for a lot. Which is supposedly why you can't get the SR in the V, to make the weight to get the mileage.

[wfolta]

Originally Posted by Rybold

70mph, you are better off going a constant 60 because it will take you 15 to 20 seconds (or more) to [efficiently] accelerate from 50 to 70,

I think you've not got "efficiency" correct here. It's more like drive-train efficiency, not "keep the instantaneous MPG up" efficiency. I haven't seen times specified, but I've seen P&G in terms of accelerating at an indicated 15 MPG instantaneous, which you might be calling "inefficient". I haven't learned this technique yet, but I don't imagine it takes 20 seconds to go from low to high end of the band.

A band from 50-70 is probably high, due to wind resistance at 70, though.

[ksstathead]

A couple of points re: pulse & glide.

The theory of pulsing is to use the engine in an efficient (somewhat hard) way, then not use it all during the glide. Wind resistance does make this a PITA for little gain at freeway speed. But it is a powerful tool at lower speeds where wind resistance is a smaller factor.

Gliding is not coasting. Gliding requires a slight pedal pressure to negate the regen of a coast. When needing to lose speed, let completely off the pedal to capture some of the energy in the battery. For gliding, give just enough pedal to let it roll freely.

[hansgrason1]

Originally Posted by nullxposur

This question is not just for Gen3 but for Gen2 as well. I have a Gen3 II and am making 40-42 mpgs. Granted, I had a 2006 Civic before and I was making 26 on the city, 36 or so on the highway.

On the Civic, I drove like a maniac on the city. On the highway, I'd range between 70, 80, or sometimes 100 when on free range. With the new Pri, I don't drive like a sh!thead, but I don't, by far, hypermile. I do slowish take offs but still get around 60-70 on the city (lots of interstate roads).

My question is, how are you all making such huge MPGs? I must say, I'm quite please that I'm not driving as bad as before but still not limiting myself and am getting 40-42. That, to me, is impressive. Still, I see others making 60+ and I must just wonder.

Hi,
well I have basically tried to stop the "jack rabbit" starts. Not that I had a heavy foot before I bought my 2010 IV, but from time to time I'd like to "break away from the pack". I used to drive a 4 cyl Camry.
Anyway, I'm getting 48 to 50 just being a bit more conservative on my accelerations from dead stops. Also, I tend to be in stop and go traffic during most of my commute, so I'm using the battery big time.

[Rybold]

Originally Posted by ksstathead

Gliding is not coasting. Gliding requires a slight pedal pressure to negate the regen of a coast.

You're right. Thank you for reminding me. We've been over this before. Since I drive a Corolla (with aspirations for a 2010 Prius), my experiences are based on my Corolla (43mpg is my best, with average of about 35mpg). I think of pulse and glide as coasting, but if the person who originally invented the phrase was referring to battery-assisted maintenance of constant speed with the engine off, then that is that. What is the maximum speed you can glide in a GenII and in a GenIII ? Thank you.

Wfolta, I could accelerate from 50 to 70 in my next door neighbors Porsche Turbo in about 1.5 sec, but I wouldn't be getting very good MPG. If you want to maintain good MPG, it will take you about 20 seconds to accelerate from 50 to 70 (that's one second per mpH). Try it on your way to work or on your way home today and let me know what your experience is. For extra credit, when you get to 70, take your foot 100% off the gas and see how long it takes to slow back to 50. I'm going to make myself a reminder note right now. I'll evaluate this also.

[wfolta]

Originally Posted by Rybold

I could accelerate from 50 to 70 in my next door neighbors Porsche Turbo in about 1.5 sec, but I wouldn't be getting very good MPG. If you want to maintain good MPG, it will take you about 20 seconds to accelerate from 50 to 70 (that's one second per

I've read several articles on it, and from what I understand you're not looking at it correctly. P&G is all about the efficiency of the engine. (It works in non-hybrids as well.) An engine is not most efficient when accelerating slowly, but rather in a particular band of load/RPM. The rest of the drivetrain has similar efficiency bands.

The Pulse phase is intended to gain speed at the vehicle's most efficient band, which may be faster than you imagine. The Glide phase is purely coasting. (In the Prius, you must press the accelerator slightly, to eliminate the artificial "engine braking" that Toyota has designed in when you lift your foot entirely off of the accelerator. People use the phrase "glide" to distinguish these two states; you're not actually using electric power*, but you are pushing on the accelerator slightly.)

I'll try it today to get actual numbers, but if I accelerate at 20 MPG for 8 seconds, then glide at 100 MPG for 8 seconds, I'm achieving something like 60 MPG. (It's more complex than that, I think, but.)

For extra credit, when you get to 70, take your foot 100% off the gas and see how long it takes to slow back to 50. I'm going to make myself a reminder note right now. I'll evaluate this also.

100% off of the gas will slow quickly because Toyota has added a fake engine braking (by regen) when you let off the gas entirely. So I would glide instead, and with a drag coefficient of 0.25 and low-resistance tires inflated to 40, it will go quite a lot farther than you think. (In fact, I am amazed how far I can glide at times.) The issue, of course, is 70 MPH: I believe wind resistance increases with the square of your speed, which is why P&G works best at speeds below 50 MPH. (That, plus 45 MPH is a magic number in the 2010 Prius because the gasoline engine will start spinning at that speed, even if it's off, in order to protect the electric motors from damage.)

Hopefully a P&G expert will chime in. I've just read about it and drive in traffic that really doesn't allow it on a long-term basis anyhow.

* Actually, it appears that you do use a small amount of electric power, I believe approximately twice as much as if you threw it into Neutral instead. This provides a light electrical boost.

[wfolta]

Rybold: I don't drive on many flat roads, but I tried my best this morning on the way in, and gliding it takes me about 12 seconds to drop from 70 to 60. It should take longer to go from 60 to 50 (I wasn't going to try it in morning traffic), so I'd say we're talking zero gasoline usage for 25-30 seconds in a 70-50 glide.

I forgot to look at how long it takes me at 15-20 MPG to go from 60 to 70.

EDIT: I'll add it here instead of replying to myself again:

"When accelerating, the engine should be kept in the peak of the torque curve. A slow acceleration is less efficient." -- From a typermiling wiki.

That's acceleration from a stop, and it's a more complicated affair for a Prius, but I guess the point I'm trying to make is that you can accelerate too slowly in a mistaken belief that "really fast is bad, then really slow must be good".

[ksstathead]

Glide max without spinning ICE in D:
Gen II 41 mph
Gen III 45 mph