Fuelly Forums - Playing with my Smart

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I had never driven a Smart fortwo or even seen one. I had studied it to death but, still, getting in one and immediately heading onto Los Angeles freeways heralded a pleasant surprise. I had not expected a quick vehicle so I was utterly amazed to be passing anyone I chose with confidence. I had heard complaints about the transmission, but I have a Tiptronic in the Volvo so I found the Smart transmission absolutely delightful in the manual mode.

Climbing out of the basin to the high desert, the Smart Fortwo held 65 mph up 2000 ft Cajon Pass. I was in a state of shock. Sure, you do want to hold your speed, not let it fall off and then attempt to bring the rpms back up. I have no tach as of yet but I could tell by the engine's song where the torque curve peaked. Boy, is that a sweet little tune! Keep that rev up and she's a mountain-climber in 5th!

It was raining and the winds were strong, The car is responsive to the wind but I learned to hold the wheel still to minimize the slight tendancy to wander. I drove 65-70 mph all the way back home. It was very comfortable. Very pleasent. I went through a Burger King at the halfway point and every employee in there stuck their head out the drive-up window to comment on the Smart.

The Smart got 38 mpg being abused like this so early in life. I'm going to try high-mileage techniques next.

I'm very pleased. The dealer offered me the 100,000 warranty. I took it. Kudo's to the Japanese team who redesigned that Mitsubishi powerplant and to Mercedes for making me believe I'm driving a sports car!

Premium Gas
It is a common misconception to believe that using premium fuel in an engine designed for it entails a loss of value compared to one using regular unleaded. Reason A, realize that this is not an American car and regular unleaded has a higher octane rating in Europe and possibly in Japan where the Mitsubishi engine is manufactured. This is because fuel costs so much more over there that manufacturers do everything they can to wring every last bit of power out of the fuel. Over in the States, nobody cared that much, until recently, about fuel efficiency.

The Mitsubishi's 657cc base engine design had a compression ratio of 10.8:1. Then this engine was redesigned for the Smart Fortwo: bored and stroked to meet the demands for power of the NA market. Reason B, because the compression ratio was quite high, it requires premium for two reasons. One, for maximum efficiency the progress of the flash through the air/fuel mixture in the combustion chamber has to be slowed down to provide optimum expansion during the power stroke. Remember, because they increased the stroke, the piston has farther to travel and you want to have the gas expanding at such a rate as to deliver steady power throughout the entire length of the downstroke. This is what the magic of higher octane does. It makes the fuel burn slower to deliver more power and better mileage. Surprise. Most folks think it is just the opposite. But if you were to run unleaded regular, the air/fuel mix would flash faster, delivering too much power at the top of the down stroke and not enough toward the bottom. See? Using lower octane WASTES fuel.

Second, to protect the engine from predetonation, you need this slower-burning fuel to avoid damaging the piston head. As an old California hotrodder, I would not even consider running low octane (below 91) in an engine with a compression ratio above 11:1. The most important thing you can carry away with you from all this is that the engine runs a lot better with premium. So much better, in fact, that you will actually end up paying MORE in fuel costs trying to run it on regular. So the whole premium concern is really a non-issue. Look, it's a Mercedes. Put premium in it with a smile on your face.

The Smart Transmission
The biggest key to high mileage in the Smart is probably understanding the transmission. A lot of people - and a lot of journalists who should know better - seem to think the Smart has an automatic transmission and it has a problem of being too slow between gears. But that's not the case at all. The Smart has a manual transmission with an automatic cluch that shifts according to an optimized high mileage program. It is marvelous and it works perfectly. It even allows you to defeat the high mileage overlay with manual shifting similar to a Tiptronic that you find in high end sports cars and sports sedans.

This is the first transmission I have ever seen that is designed to do this. It even took me a while to figure out what it was. I was also under the illusion that the transmission was faulty in some way. I was even told at the dealer that I should lift my foot between shifts for proper operation. That is not the case. Lifting your foot just forces the transmission out of economy range and defeats the economy program.

One can make the Smart behave like a performance car and impress people who think its really cool to go fast and waste energy. I've been there, done that, and if that's where you want to be, there are a lot of cars that will make you very happy and do a much better job than the Smart. This is because the Smart was designed to go a long way on a tank of gas. That was the primary design goal, urban or highway. That's why I bought it. I'm a hypermiler.

Most of all, the Smart reminds me of big, big trucks. Not in size, of course, but the way it shifts. some of you have probably driven big trucks. Big two axle, three axle, maybe some eighteen wheelers with 5 axles. Possibly a few of you pulled the heaviest 5-axle jobs, bulk liquids with a gross vehicle weight of 80,000 pounds. But I'm talking about the trucks I drove in the western states. Supertrains. Tank trucks with two trailers. 9 axles. 34 wheels. 120 thousand pounds. 105 feet long. Big, big trucks. Over mountains. Big, big mountains.

Those trucks are so heavy you don't use a clutch. You'd burn it up in one trip. Instead, you dog clutch through all 15 or 20 gears. That's right. You put it in low gear and drop the clutch at idle to get going. The flywheel gives you the momentum to start moving. Not the engine. Not the clutch slipping. From there on, you never touch the clutch again. You match the gears. You match the gears perfectly for every shift, for thousands of shifts. You pull through the torque curve, let off the accelerator, slip the shift lever into neutral, drop the revs to the insertion point for the next lower ratio gear, slip into perfect engagement, give it throttle, then repeat the process. You don't rely on the synchros to make your shifts work. Pros like me use the tach to slip the transmission teeth in neatly. We know every shift point for every gear, upshift or down shift. Our lives depend on it. So do yours if you are on the highway with us.

Anyway, I don't do that anymore. But the Smart shifts like that. Try it. Put the transmission in D and give the Smart a tiny bit of gas and lock your foot against the carpet to the right of the pedal to hold it in place. Don't move it. Moving the pedal wastes gasoline. The Smart knows what to do to give you the best economy possible. It moves you up through first gear, stops delivering fuel to the engine (even though your pedal's down), gives the engine just a little fuel to match the revs for the next gear, smoothly engages the teeth, then brings the power up to your pedal setting and repeats the process through all five gears. After w while, you'll be going fast. The more patient you are, the better your gas mileage will be.

To this old truck driver, that is not a fault. That is magnificent technology, perfectly applied for optimum economy and power delivery. It is hard to improve on that but you can really screw it up by not understanding it.

February 26, 2008 Genuine 54 mpg on 84 mile trip today, 50 mph average speed, driver with very pleased medium sized dog in back.

MILEAGE TEST ON MOUNTAIN ROADS
-- Partial hypermiling on 347 mile trip on rural highways and mountain roads.
-- Smart ForTwo Pure (with 265 lbs above empty dryweight: a/c off)
-- California Hy 395 to 14 to 58 to Bakersfield to mountain road Hy 178 to 14 to 395
-- Exactly 7 gallons 91-grade premium cost $27.93.
-- MILEAGE: Just a hair shy of 50 mpg

March 8, 2008 When I could, I drove at 50 or slightly below, but on 2-lanes and busy 4-lanes I had to maintain traffic speed of 65mph. In Bakersfield I demonstrated to several people how fast the Smart could accelerate and corner, and I added about 30 miles around town in traffic. I drove winding Kern River Canyon (Hy 178) using constant throttle position techniques as opposed to a wasteful cruise control (which I don't have.). Despite being Friday, the road was almost deserted and this allowed me to climb 5250 ft Walker Pass from 200 ft Bakersfield using the same fuel delivery rate that would propell the Smart at 50 mph on a level road. I used manual shifting techniques on this mountain road, dropping out of 5th into 4th at 40 mph; out of 4th into 3rd at 30; and out of 3rd into 2nd at 20 mph. (I don't have a tach.)

I crested the pass at 20 mph on the steepest part.. There was no traffic so this was safe. One must always compromise on the side of safety when hypermiling. The 3-cylinder engine was was not working very hard in any gear at any time - which is why you get your best mileage doing this regardless of terrain.

CONSTANT THROTTLE VS. CRUISE CONTROL
Myth has it that cruise control provides better economy than manual control. This is true for people with twitchy feet but for those who are seeking high mileage performance, constant throttle is the number one way to succeed. True constant throttle, that being constant except for falling off in rpms to catch the next gear, then resuming fuel feed without actuating a wasteful carburator accelerator pump is impossible in carburated vehicles and is pretty much impossible to maintain on nearly every fuel-injected vehicle other than the Smart with its fabulous automatically shifted manual transmission. This technique is usually self-defeating with most automatic transmissions, even "lock-ups", because of necessary torque-convertor slippage during shifts. Every gear is "locked" with the Smart. There is no wasteful torque convertor. There is no slippage. Hence no fuel is wasted during shifting. Power is only applied when the gear is locked. This is where the silly complaints about transmission drag come from. People are used to wasteful automatics that slip and gobble gas. The Smart is not one of these vehicles and should not be expected to act like one. The transmission is designed for high mileage performance. This has to be understood to get results.

The constant throttle technique limits the load imposed on the engine, and therefore the fuel usage, to a predetermined limit. You can chose a fuel-useage limit by identifying the accelerator depression point required to maintain constant speed at your hypermiling maximum. This is a subjective choice. You can decide to hypermile at 65mph if you want to. Some people place a little marker, like a dowl or screw, to the right of the pedal to help them maintain this position. You can also set a lower limit where you will begin to apply throttle to maintain a speed that you do not wish to fall below. For instance, you could decide before a trip to hypermile between 65 and 55 mph. If you have never done this, you will REALLY notice the difference.

Never lock the throttle with a mechanical device. This can be dangerous and will defeat high mileage on variable terrain where you will want to let up on downgrades. Of course, you do not accelerate on upgrades, but rather lett the speed fall off, grabbing a lower (higher ratio) gear when necessary. For this trip I chose 50 mph with safety compromises to gradually accelerate to highway traffic speed when necessary, which places my driving in the "Real World Mileage" category.

Drafting
Another way to achieve a dramatic distance is to actually chose a truck to follow over a long distance. Not all trucks are the same. I like semi box trailers with flaps that extend across the entire rear. You can follow one of these (or better yet, several) at a safe and legal 2-second distance for an an additional 10 MPG. People say a lot of bad things about drafting trucks. I don't understand this. I've never heard of somebody running into a truck while drafting. And if you do, so what? Your closing speed would be real low. You'd crumple your hood. No way could you hurt the truck with a Smart. Big deal.

And here's a tip from a truck driver you'll appreciate. Loaded trucks actually stop better than empty trucks. Empty trailers will lock up their wheels and flat-spot the tires if the driver slams on the brakes. They will catch hell back at the yard if this happens. They are also paying more attention because they know this. This is also why you'll sometimes see a flatbed carrying it's empty trailer on the rebound.

When you chose a truck to draft closely, look for one that's riding stiffly on the rear springs. He'll be empty. About 20% of box trailers are always empty. He'll be an ideal candidate for close drafting because he can't stop as fast as you and won't even try. Even with as little as one second following distance, you're probably good (unless he hits something!) If you have trouble identifying spring load, just start watching trucks on the highway as you travel. After a while, after watching a hundred or so, it becomes obvious.

After years of drafting trucks, I avoid less than 1 second following distance because the money you save on gas is lost when a pebble thrown up by a rear trailer tire breaks your windshield. Then again, I've enjoyed telling people, "That little star was made on my trip to Albuquerque in 2003 when I got 32 mpg in this station wagon by drafting trucks on Hy 40!" So go figure.

CALIFORNIA VEHICLE CODE
:: SECTION 22400-22413 California vehicle codes index

22400. (a) No person shall drive upon a highway at such a slow
speed as to impede or block the normal and reasonable movement of
traffic unless the reduced speed is necessary for safe operation,
because of a grade, or in compliance with law.
No person shall bring a vehicle to a complete stop upon a highway
so as to impede or block the normal and reasonable movement of
traffic unless the stop is necessary for safe operation or in
compliance with law.
(b) Whenever the Department of Transportation determines on the
basis of an engineering and traffic survey that slow speeds on any
part of a state highway consistently impede the normal and reasonable
movement of traffic, the department may determine and declare a
minimum speed limit below which no person shall drive a vehicle,
except when necessary for safe operation or in compliance with law,
when appropriate signs giving notice thereof are erected along the
part of the highway for which a minimum speed limit is established.
Subdivision (b) of this section shall apply only to vehicles
subject to registration.

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I'll do 50 on a 4-lane in the slow lane with cops around. I only go slower when nobody's around. 55 mph is a maximum speed for many vehicles, after all. The CHP hasn't ever given me a second look and I've been doing this for years. I never let more than 2 or 3 cars pile up behind me. I'll speed up. But if I ever do get pulled over, the officer has no basis to give me a ticket if I simply agree to speed up. Heck, I see cops weaving across all lanes all the time to slow people down.

So good luck and be careful. I'll keep posting my results with the Smart as the mood strikes me.