18 March 2012

"Mad Max" hypermiler questions and comments answered



As I am very sure that anyone who has found this blog is already aware, me and my work truck were recently featured on  TreeHugger, Huffington Post, HighT3CH, and Faircompanies.com, among others, for my new video (shot, edited, and posted to Youtube by Faircompanies' Kirsten Dirksen)

It is 14 minutes long, which is long by modern internet video standards, but still was only enough time to provide a little snapshot into the entire concept.
I've been crawling the web for the various re-posts and the comments on them.  Not surprisingly, given how unorthodox everything I'm doing is and how unfamiliar the general public is with the idea of hypermiling, there are a lot of questions and criticisms and misconceptions.
First, I'm not in or from LA.  I live in the San Francisco Bay Area.

Also, the grill block is not made of concrete!! :P
That error is just bizarre.  I wrote to treehugger's editor about it, but I haven't heard back yet...
[update: he wrote back, and fixed it]


Some of the more common questions and comments I have noticed follow:



Why don't you just use a smaller truck (or, "I get better mileage than that in my compact truck")?

What you see in that video is just one random day.  On other days I have to move a couple tons of soil or concrete, or the entire contents of a 1-bedroom apartment including furniture:

































I recently had to move an original painting that was 5ft x 8ft.  Being able to lay it down flat with the cover on allowed me to transport it safe, clean, dry, and out of the wind and direct sunlight from the artist's home to the gallery.  Monday I will be needing to get several full size sheets of plywood, which can only lie flat in a full bed.
While most would put loads this size into a box truck or a flat bed, or even a dump truck, I am using a 170HP full-size pick-up. 
When you look at it this way, my truck could be considered small.

Of course, if you aren't a hauler, there is no reason you should be driving a full size truck.
Everyone should use the absolutely smallest vehicle that meets their needs.  For the majority of Americans that probably means a compact car, or even a motorcycle.

The point of the video isn't the specific number "30".  The point is that it is 15mpg better than when I started.  The same can be done with any vehicle.  If you are currently getting 30mpg, apply the same ideas and you could be getting 45.  If you drive a Prius, you should be getting at least 70.  But since most Prius drivers drive like regular Americans, the real world reported mileage is closer to 45.

The best example of the same ideas applied to a small car is the Aerocivic



100+mpg in a regular old, non-hybrid car with no special engine technology.


Doesn't it take more fuel to start than it does to idle?
No.
No it doesn't.

That is an incredibly common misconception, that was started back before fuel injection and computer controlled engines were invented.  Even back then, it was likely only true for idling under 45-60 seconds, especially if the engine wasn't warm yet.  It certainly was never true for idling 5 minutes while you wait for the person you are picking up to come downstairs, or even at a 2 minute long stoplight.

In a modern car, if you are at a stand still for more than 10 seconds, you are wasting more fuel by idling than it takes to start the car again.

http://www.iwilltry.org/b/projects/how-many-seconds-of-idling-is-equivalent-to-starting-your-engine/
(note that the number 10 is very generously rounded up from 0.2 seconds!)

Another example: http://ecomodder.com/forum/showthread.php/fuel-used-idling-vs-restarting-5144.html

The moral of the story is this:  NEVER IDLE.  You are getting 0 mpg.  You are not getting anywhere any faster.
It is about the same as taking a dollar bill out of your pocket and lighting it on fire.
Both in that it wastes your money, and that it causes unnecessary pollution.

Do not start your car until after you are fully settled, seat belt is on, foot on the brake, and you are ready to put it in gear and go.
Modern cars do not need to warm up.  There is literally no benefit to warming up a car before you start driving.
If you have to wait for someone to run in the store "real quick", turn off the engine.  If you know that the stop light you are at is extra long, shut the engine.  While you are waiting in the drive-through, shut the engine...
Actually, no! Just park, and get out!  Seriously, how lazy can we get?  It's a few feet to walk from the parking lot to the door. You get at least a tiny bit of exercise to burn off what you are about to eat.  And you'll get your food faster, because the line at the drive-through is longer than the line inside.  But I digress...


You are going to wear out your starter / clutch
Maybe, eventually...

First, it takes much less force to start the engine once it is already warm than it did first thing in the morning.

Second, if done correctly, bump starting uses very little clutch (and no starter).
The trick is a technique called double clutching - very similar to the technique used by semi-truck and race-car drivers.  Basically, when used in hypermiling, you shift into the highest gear and very briefly 'tap' the clutch up until it just barely engages, and then immediately depress it again.  Instead of fully engaging the engine with the wheels, you just 'bump' the engine a partial turn.  When the engine is warm, this is enough to re-start it.  Once it starts you step on the accelerator enough to match the engine RPMs to the transmission RPMs, and when they match (or close to it) you then release the clutch again.  This entire process takes place in about a second.  If you look closely, you can see me doing it at 5:02 in the video.

It may be that in the long run the clutch and/or starter lasts a few months less than they would have otherwise. 
If you buy a replacement starter from an auto parts store, they come with a lifetime warranty.
I've had to replace a couple (long before I started shutting the engine to save fuel), and all you do is walk in with a faulty starter, tell them your phone number (because I had lost the receipt but they keep records in the computer) and walk out with a new starter (also with the same lifetime warranty.)
So for the cost of replacing the starter just once you get a lifetime of starting it at every stoplight.
As far as the environmental impact, the starters you buy are refurbished, and the old one you turn in for the deposit is refurbished in turn.

Given that hypermiling saves hundreds or even thousands a year as well as preventing an equivalent amount of pollution, the occasional odd extra starter is more than worth it.



Accelerating takes more fuel than driving steady state, so why do you repeatedly accelerate and then coast - doesn't take that more fuel?
Accelerating does take more fuel than driving steady, and so that is an understandable confusion.
If car engines were 100% efficient, (or even remotely close to it) then the hypermiling technique, known as "pulse and glide" (P&G) would use more fuel than driving steady.

But engines are not 100% efficient.
The basic laws of physics dictate that no heat engine (which includes everything from gas and diesel engines to steam engines and coal power plants) can ever be 100% efficient.
No matter what technology produces in the future, any flammable fuel powered vehicle (including natural gas, biodiesel, anything that burns) will waste some of its energy on heat.

In a typical gas engine, efficiency is only around 25%.

In order to understand how much internal resistance is in a car engine, try this:
-Park on a perfectly flat area.  Make sure there are no parked cars, small children, or cliffs in front of you.
-Turn off the engine.
-Put the car in neutral and take off the parking brake. 
-Get out, and try to push the car.
You will be able to.  No matter how small you are, and how big the car is, you will be able to move it (albiet slowly) on flat ground in neutral.

-Now put the car into gear (engine still off)
-Get back out and try to push it again.
You will not be able to, no matter how big and strong you are. 

The difference you feel between the first try in neutral and the second in gear, that is the engine's resistance to turning.
Every time the engine is on, it has to overcome that internal friction with each and every rotation it makes - and it makes about 100 rotations every single second! 

In other words fully 75% of the energy in the fuel is used just to overcome internal resistance, to turn the engine itself. 
That's why it gets so hot (and why it needs a radiator).
75% of the money you spend on gas is not used to move you and your car around, it is used to make your engine hot.

On top of that, belt driven engine accessories and drivetrain losses absorb another 5-10% of the energy in the fuel.

That means all together, when the engine is running, well over 3/4 of the energy never even reaches the wheels.
And that is in optimal conditions, at the peak of the BSFC curve!*

Any time the engine is off, you are not wasting that 85%.

As noted earlier, accelerating takes more energy than steadystate driving, however, the internal losses don't change (a significant amount) in acceleration vs stead state.

So, if you can P&G with a 1:3 ratio (10 sec pulse, 30 sec glide) the engine is off 3/4 of the time. Over that 40 sec span, the 85% of potentially wasted fuel energy is conserved.
In order for that not to save fuel compared to stead state, it would have to require 4x more fuel to accelerate - and of course that is before even taking into account pumping losses or the fact that acceleration puts the engine in a more efficient part of the BSFC curve.

*(BSFC refers to the fact that an engine is more efficient at some speeds and loads than others. The peak is where you get the most torque for the least fuel, and what RPM and throttle position that corresponds to varies from one car to another, but it is always at least slightly more efficient during acceleration)

While coasting is more efficient in any car, it shouldn't be done in many cars.  Most cars with an automatic transmission should not coast at high speed or for large distances, as the engine circulates the transmission fluid that lubricates and cools the transmission.  Cars with a turbo charger should also be wary of turning the engine off during transit.  And of course, unless you have a very old car or have modified it, turning off the engine will change the steering feel and limit the number of power assisted stops (more on that later)


Driving slow is illegal

Driving excessively slow is illegal in some places.  Laws vary from state to state.  In my state it is not illegal to drive at 45mph on highways. 
I am not aware of any state which has minimum speed laws higher than 45mph.  In fact, the maximum speed for commercial trucks in my state is 55mph - only 10mph higher than the lowest speed I go. 
(Anything slower than that does not increase efficiency anyway, because it requires shifting to a lower gear, which raises engine RPM.  In most modern cars optimal speed is between 50 and 60mph, give or take.)

When there is a specific minimum limit, it is usually (but not always) marked:



In practice
its rare for drivers to drive below the maximum speed limit, but it is important to remember that the number on the sign is just that: a MAXIMUM.  It is not a requirement.  It is not even a recommendation.  And it is most certainly not a minimum.

If where you live there are highways that have a minimum speed of 50 or 55, I don't recommend driving slower than that.

For many vehicles, driving slower than that offers no benefit anyway.  Various factors determine the optimal speed for each vehicle; primarily how the transmission is geared, followed by how aerodynamic it is.  Optimal speed will usually be at whatever speed the transmission shifts into its higher gear (or the lowest RPMs in high gear without lugging, in the case of a manual).  For most modern cars this will be somewhere in the range of 45mph to 60mph. Unless you have a very old vehicle, its unlikely you will gain any benefit driving slower than that.


Driving slowly is dangerous

This misconception is almost as common as the myth that it takes more fuel to start than it does to idle.
And like that one, it is understandable how it got started:
Some traffic studies have found an increased accident rate for drivers driving below the average speed of drivers around them.

But here is the really important part:
Studies have also found that the rate of accidents that involve INJURY OR FATALITY goes down with a decrease in speed.

In other words, driving slow will increase the risk that you get a dent or scratch on your nice shiny car.  At the same time, it will also decrease the risk that you die in a fiery car crash!! 


So, given that there is a trade off, you have to ask yourself:  "which would I rather avoid: a dent - or losing a limb?"
Driving fast is the single biggest factor in injury and fatality accidents - more than drinking, more the cell phones, more than teenage drivers.  Speed has an exponentially bigger impact on accident severity than the weight of the vehicle.  In other words, driving 45 in a compact car is safer than driving 75 in a big SUV.
This is due to basic laws of physics, so it will never change, no matter what new safety features come out.
I could go on, but I already dedicated an entire blog entry to the topic, so if you are still unconvinced, you can see the math as well as the traffic study references there:
http://biodieselhauling.blogspot.com/2012/03/slow-down-my-philosophy-for-life-also.html

The fact that everyone around you is breaking the law, wasting gas, and endangering their lives, does not legally or morally obligate you to also break the law and endanger your own life to avoid inconveniencing them.  Even if every single other person on the highway is speeding, it is still all of them who are in the wrong.



You are interfering with traffic

Good hypermiling takes road and traffic conditions into account, and changes appropriately. 
In the video I am driving on a 4 lane highway with light traffic.  On a 4 lane highway there is no possible way for me to impede traffic.
I think this is common knowledge:  The left-most lane is considered the "fast" or "passing" lane.  The right-most lane is the "slow" or "merging" lane.  If you want to drive fast you should be in the fast-lane.
Kind of makes sense, right?
But the law says the maximum speed limit is 65mph (on most highways in my area, replace that number with whatever is your local limit).  That means the fastest car in the fast lane should be going 65mph.  That is the law.  I'm sorry, I don't make the rules. 
This means that every lane to the right of the left most lane should be going slower than 65mph, with the slowest traffic in the right most lane.
On a 4-lane highway, no one should be going significantly faster than me in the slow lane.
If they want to pass, they can change lanes.

In heavy traffic, hypermiling strategy changes.  I didn't happen to get stuck in any, so you don't see an example of it in my video, but someone else has made an excellent video with an example of how to drive efficiently in heavy traffic:


(click through to the original youtube page to see an excellent write up by wbeaty, the person in the video)

As you can see in this video, the act of driving efficiently actually makes traffic SMOOTHER for everyone behind you.  It is everyone else's erratic and aggressive driving which actually causes (or contributes to) the traffic jam in the first place.  If everyone drove this way, everyone would get where they were going much faster, much like walking in a calm single file line will get you out of a burning building faster than trying to shove everyone else aside. 

True, coasting to a stop light sometimes agitates drivers behind me who are used to driving full speed toward red lights and then hitting the brakes at the last moment.  But they would have had to come to a full stop anyway, so being "stuck" behind me is costing them zero seconds of time.  Do I feel bad for forcing them to save a little gas and help their brakes last longer?  I do not.


Isn't it illegal to turn the engine off while you are moving?

I might well ask you whether it is illegal to drive 66mph in a 65 zone, or to cross the street in the middle of a block with no crosswalk.
No, no, no, I'm not suggesting that this is a stupid and unenforceable law...
What I will say is that law varies from state to state.
In some states it is legal to coast in neutral, as long as the engine is on.
If you happen to live where that is the case, P&G is still beneficial, even if you coast while the engine is idleing (although not by as much).  (This is also important to note because automatics should not coast with the engine off at high speeds or for long distances)
In other states there is no rule about whether the engine is on or off, but you aren't supposed to be in neutral - but that doesn't mean you can't hold in the clutch while still leaving the transmission in gear.

What is perhaps even more important than the finer technicalities of the law is whether or not it is safe.
As noted earlier, by driving well below "normal" speeds (i.e. slightly above the legal lower limit) hypermiling is already much safer than regular driving.  In addition, to avoid having to brake, all hypermilers leave large following distances between them and the car ahead.  This, obviously, increases safety by a huge margin.
Finally, by being constantly aware of the road, conditions, and other vehicles around you, very little takes you by surprise.

There are no accidents.  There is only negligence. 

Regarding having the engine off specifically:  in most modern cars both the brakes and the steering are enhanced with help from the engine.
This is because Americans are incredibly lazy and spoiled.  I'm sorry.  I shouldn't rant.  Power steering just really bugs me.  I mean, really really really bugs me.  It is so stupid.  It is not hard to turn a steering wheel with a manual steering gear.  I mean, not even a little.  My first "car" was a 15ft long camper van with manual steering.  My current work truck has manual steering.  The ONLY time it is even slightly difficult is parallel parking.  Then it is some effort.  Nothing like running a 5k or bench pressing 100lbs, but it is more than no effort.  99.9% of the time behind the wheel is not spent parallel parking. 
So, in order to avoid having to put in a little bit of effort 0.1% of the time, car manufactures build in a complicated expensive system that sucks up 1-3mpg at all times.  It is hard to find a car, even an entry level model, that doesn't have power steering standard.  It is perhaps a reflection of us as a society that we are so fat and lazy that even after having had a gas engine do all the work of moving us from one place to another, we can't even be bothered to take the effort to turn a wheel in order to park the machine.
[end rant]

Where was I? 
Oh, right... shutting off the engine will take away the power steering.
The steering wheel will still work, but you will definitely feel the difference.
The best way to avoid that, (and improve your mpg at all times, any maybe even build a tiny bit of muscle during your daily drive), is to simply remove your power steering.  This is easier than you may think.  My girlfriend did it on her own, with basically no previous mechanical experience.** Basically you need to do just two things:
1) disconnect the lines from the pump goes to the steering axle, and
2) remove / replace the engine belt with one that bypasses the pump pulley. 

As far as the brakes go, there is a reservoir of brake boost, so after you cut the engine there is still brake assist for at least 1, usually 2 or 3, good hard brake pumps, enough for a panic stop in an emergency (which is less likely to happen if you are driving slow and have a good following distance, but its still better to have the option)

The last potential issue is turning the key too far, and locking the steering wheel.
I don't recommend turning the key one click too far and locking the wheel while moving.
In fact, I'm going to go ahead and word that a little more strongly:
Don't do that.
That would be bad.

All that is for a typical, unmodified car.
I have modded my truck specifically to accommodate engine off coasting.
My brake booster is electric.
My steering is manual (I actually installed a factory original manual steering gear, as it was optional equipment when it was sold - in other words, it is all OEM parts, although I personally did the downgrade)
I have an engine kill switch and starter on the gear shift column so I don't have to touch the key.

All of this means that all of the control systems function identically whether the engine is off or on, and therefor there is no increased risk from coasting.


**Specifically, she had done 1 oil change, and changed 1 flat tire before tackling the power steering delete project.



 Why don't you just buy something newer / better / hybrid / electric?

First of all, there are no hybrid or electric trucks available in the US that can handle the loads I move.

Second, newer vehicles are not significantly more efficient than old ones.
They SHOULD be, because engine technology has improved considerably, however those improvements have been used to make cars and trucks heavier, more powerful, and more feature rich.  My truck is powerful enough, and I don't need "features".

Third, my truck cost $2000.  I spent about another $800 on the mods.  And I ended up with a truck that gets better mileage than a brand new truck of comparable capacity would.  In fact, it gets better mpg than the average passenger car on US roads gets.

Fourth, by buying used I avoiding having additional mining and energy use in building and transporting another new vehicle.  Buying used is (almost) always easier on the environment than buying new, no matter how "green" the product or how "sustainable" the production process.

In the end, being environmentally responsible (contrary to popular belief) goes hand-in-hand with saving money.  Saving lots and lots of money.
Its win/win

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I think that covers just about everything.
I'm not suggesting that everyone go out and do everything exactly the way I did.
But I do hope people will think twice about what things they can do differently.
Small changes taken by large numbers of people has a greater impact than big changes done by just a few people.  If you do nothing differently after reading this besides driving slower and never idleing, I will have made a bigger impact on the world by writing this than I have by all of my biodiesel-solar panel-vegetarianism ways ever could.
So help me out.
Help out the Earth and the country, and as a side-effect keep a little more money in your own pocket next time you head to the gas station.



4 comments:

  1. you walk the talk! Aerodynamically though, would you not like to try changing the shape of your truck like was done on the aerocivic? A transparant sheet from the front of the hood to the top of your windshield, and then the same but detachable (for hauling big stuff) at the back...
    That's not beyond your modding capabilities is it?

    ReplyDelete
  2. Interesting idea.
    Can't say I'm opposed to it, but I'm trying to strike a balance between mileage and practicality / useability. I know many people would think I'm already way over that line, but the line still exists. For example, my rollup cover is very quick and easy to remove in the field for big stuff and for accessing stuff in the back, whereas if I had a detachable aero cover I'd have to detach it before leaving home if I thought I'd need access (and I'd have no place to store it!)
    The front might be feasible, but how would I access the hood (which I need to daily to charge the batteries)
    Anyway, thanks for the idea, its something for me to think about

    ReplyDelete
  3. Cool truck! Your rear bumper looks very heavy. I bet getting rid of it would save a few mpg. You could mount your hitch ball elsewhere.

    Thank you Bakari for the interesting video.

    ReplyDelete
    Replies
    1. Hi Ben,
      thanks for the comment.
      I haven't really put any effort into weight reduction - even though I know it has a significant impact on fuel economy - because I sometimes need to tow, and in order to tow safely, the tow vehicle has to have a certain minimum weight relative to the trailer, for control reasons.
      If I were going for maximum possible mileage... well, I'd start with a very different vehicle! but this truck's meant for working, and that is always the first consideration

      Delete

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