Driven to Save -- Opinions Needed! (hypermiling book author seeking feedback)

[MetroMPG]

For context I'll also say: I used to P&G a lot (even on long rural highway trips if there wasn't anyone behind me). I mostly gave it up though, because I found it tiring, and it's arguably mechanically harder on the car than cruising. But I still do it strategically in other circumstances.

[NachtRitter]

Book sounds great! Agree with Darin's inputs so far.

[Frank Lee]

Originally Posted by MetroMPG

For context I'll also say: I used to P&G a lot (even on long rural highway trips if there wasn't anyone behind me). I mostly gave it up though, because I found it tiring, and it's arguably mechanically harder on the car than cruising. But I still do it strategically in other circumstances.

Me too. P&G is definitely effective, and it's definitely annoying too, out on the open road. Now I only do it sometimes when having to stop anyway.

[wdb]

Originally Posted by MetroMPG

For context I'll also say: I used to P&G a lot (even on long rural highway trips if there wasn't anyone behind me). I mostly gave it up though, because I found it tiring, and it's arguably mechanically harder on the car than cruising. But I still do it strategically in other circumstances.

Be still my heart! I never expected to hear the venerable folks here admit to giving up on P&G. I gave it up after a couple of weeks, for the same reasons you mention. (I still use the technique, sort of, in rolling terrain.)

[brucepick]

At the risk of going off topic (too late!!) - - -

I've been using P&G on the interstates here over the past couple months, varying between about 55-70 or so. We have hills so I adjust technique as needed for terrain, but still P&G nearly always.

Admittedly traffic in my area is generally light. That said, I can see that other drivers are confused by my driving technique and they get frustrated. I'm a bit heartless that way. Too bad for them, they can pass me if they want.

I also use P&G when traffic is stop + go, or very slow and moving in pulses. Leave enough room ahead to coast through available space, accelerate when traffic demands it. Of course brake when traffic demands it - but if you can leave space and watch out ahead, you will be braking far less than other drivers.

Yes it's tiring, but very good for fuel economy.

[redpoint5]

Book Feedback

Correction: BSFC stands for Brake Specific Fuel Consumption. BSFC- How to Feed a Horse section.

In the chemical energy section torque is defined as the energy required to move 1lb a distance of 1ft. I'm not sure this is an accurate description of torque, as torque is merely a static force. Once an object begins to move, that torque produces power (HP) and performs work. Anytime movement is involved in the discussion, we are really talking about work performed at a certain power (rate of work).

I'm really enjoying the book so far, and I've learned some things from it. It might take me another week to finish though due to work and social obligations.

As to the discussion on P&G, I don't use the technique on a flat road, but I do use it for hill climbs when I can almost maintain speed on the glide down the back side. I also use it in traffic as long as I'm not causing people to miss traffic lights or otherwise slow their journey. I've managed to get slightly better mpg in stop and go driving than steady state 70mph freeway.

[PaleMelanesian]

I just now found that (thanks Darin!). I have only seen what's here on this thread so I don't know what else is in the book.

Darin is right - the glide is at least half the magic of p&g and leaving it in gear will possibly cost you instead of helping. It depends on how the car handles the in-gear-no-throttle state, but I know that Honda automatics go into heavy engine braking that eats up any potential gains. Neutral is required.

A trip average mpg gauge is hugely beneficial to learning p&g. If you don't have one, it's easy to do it wrong and lose fuel instead of gaining.

I p&g always in a manual. Half the time in an automatic. Even on the highway, even on flat ground. It's work, yes, but it makes the drive more interactive and prevents "highway hypnosis" as well as saving fuel.

Keeping an eye out and adjusting your cycle for other traffic can make your p&g nearly invisible to the rest of traffic. Even in high-speed rush hour traffic, you can do mini-p&g and find good gains without being disruptive.

[MetroMPG]

From: Green Means Go, Yellow Means Go Faster

Don't think that speeding up to get through a yellow light is a mortal sin or anything; yellow means “clear the intersection,” not “prepare to stop.”

Is this the common rule in the U.S.?

In Ontario, amber means stop, unless you cannot safely stop.

Every driver approaching a traffic control signal showing a circular amber (yellow) light and facing the light shall stop his or her vehicle if he or she can do so safely, otherwise he or she may proceed with caution. Ontario Highway Traffic Act 144.15

[Diesel_Dave]

In my opinion, the notion that fuel-cutoff is the holy grail is one of the biggest falicies out there in hypermiling. While it is true that you're not using any fuel at the moment, the engine is providing a considerable drag on the vehicle (hence the term "engine braking"). That drag is going to slow your vehicle down and you're going to have to make up for it later. The ideal of course is engine off in neutral, but in some cases even idling in neutral is better than motoring with fuel-cutoff.

[jamesqf]

Originally Posted by redpoint5

In the chemical energy section torque is defined as the energy required to move 1lb a distance of 1ft. I'm not sure this is an accurate description of torque, as torque is merely a static force.

That's wrong, because torque is an angular quantity. It's the product of a force applied times the distance from the axis at which it's applied. (Think of a torque wrench.) And of course pounds and feet are just English units: in metric it'd be measured in newton-meters.