Hypermiling: The Gasoline Squeeze

Is the euro plate street legal in TEXAS?

Inquiring minds want to know...

milo

Florida does not have front plates, so you could get away with it, but that picture isn't mine anyway, but it looks the same.

By the way, just to give you an interesting perspective, the car has 400 hp (not a turbo), top speed of 191 mph, 0 to 60 in about 4 heartbeats, yet I can get 32.2 mpg at 67 mph (with AC off). When I turned the AC on and cruise at 80 mph it dropped down between 27 to 28 mpg on my last trip.

We recently did "the trip" to see our kids in Cairns. I remembered some discussion about this topic and drove accordingly. I was surprised how effective it was to drive passively. I didn't do any proper measurements but it was obvious that we used less gas. It took us about 15 minutes longer but correlated with other parameters we won. Some cars less powerful than ours overtook, which was the worst feeling of all. We were driving a Nissan Skyline,6cyl, straight extractors. My son, who advises me on cars, calls it Godzilla. Very powerful if need be.

Try it if you want to save a few $$. You need some accountant's blood in your veins to get a high but it worked for us. Ky.

Skyline is an amazing car. The new one even more so.

I haven't driven my car in three months. I put homemade racks on my homemade e-motor assisted bike and use it for errands.

please send photos.

milo

My apologies. I don't have a working camera.

I built the whole thing from scratch, improving it over the years.

Excellent link! I have added it to my fav's for reflection and sent it around the office for others to benifit from i give you a good answer .

many thanks for the link to that site, it is now on my favorites.

Some of the techniques employed by the hard-core hypermilers are dangerous, and some are even illegal.

Drafting can reduce drag a little, but if you are far enough back to be safe, you get into turbulence that actually cuts mileage. Close enough to be efficient, you had better hope that a) his brake lights work, b) your reflexes are quicker than his, and c) your brakes are more effective than his.

Also, the business of "coasting" with the engine shut off is NOT LEGAL here in the U.S. - check your state statutes rather than taking my word for it though...

Nobody said to tailgate which is illegal. Mythbusters did a segment on drafting. At 100 ft, you can get around 50-70 mpg while following a big SUV or Semi without a side wind. I have a manual transmission and do not shut my engine off while coasting. Only the extreme hypermilers shut off their engines. I also manually cycle my A/C. I don't go over 75 mph.

There are many tactics that help with gas mileage that are safe. It is up to each individual person on which they can live with.

No disagreement from me! I just felt it necessary to point out (for those who might not realize it) that some practices can be unsafe, and some against the law. Please do be safe, and enjoy the mileage you can get longer!

Nobody said to tailgate which is illegal. At 100 ft, you can get around 50-70 mpg while following a big SUV or Semi without a side wind.

70 MPH = 102 FPS (MPH = Mile Per Hour, FPS = Feet Per Second)

50 MPH = 73.3 FPS

Don't most states in the USA require a following distance of no less than 2 or 3 seconds?

Isn't anything less than that distance considered tailgating?

Excellent point!

I was taught and always told by everyone to have "one car length per 10 mph". At 70 mph with a 15ft car, that is 105 feet. I guess that I am going to have to do some research into Indiana law to make sure that I don't set myself up for a ticket. Most people on the roads today are in violation of this law. I have driven most of the interstates in the Midwest and most people only leave about 1 car length. Following this closely causes the slinky effect and reduces gas mileage.

Anyway, here is a brief of what mythbusters said that I found on treehugger.com.

"Tim Haab at Environmental Economics shows test results from Mythbusters:

* In scaled wind-tunnel tests, driving 100 feet behind a semi at 55 mph will reduce drag on your car by 40%. The drag reduction increases as you approach the bumper of the truck until you get a 93% drag reduction at a distance of 2 feet.

* In road tests, the testers achieved an almost 20% improvement in gas mileage at a distance of 100 feet (at 55 mph) and a 45% improvement at 10 feet.

Tim also calculates that at 100 feet you have 1.25 seconds to respond if the truck slams on the brakes, (keep off that cell phone) and at ten feet you have .124 seconds. The reccommended distance at 55 miles per hour is 150 feet."

Whatever distance you feel is acceptable, please pay attention to the roads. The number of wrecks are getting outrageous and sitting in a traffic jam gets everyone 0 mpg.

Well, the old rule of thumb was car length, but a better rule is via time (easier to estimate than physical distance). 2 seconds is probably a minimum and 3 is more likely to be a better number (under ideal conditions).

The whole thing revolves around maintaining control in the event of something unplanned. Unplanned events take many forms. For instance, there is simply having a vehicle slow down for traffic or changing direction. There are emergency avoidance braking.

The worst scenario is when the vehicle in front actually hits something and you no longer have the normal stopping distance. I have seen this happen many times and with fatal results.

I recommend that people be aware of reaction time, road conditions, and driving conditions and factor those into their following distances.

I tend to drive conservative with my car because I have no intention of wrapping $80 - $100K of car into someone's bumper. However, my brakes are superior to most cars, so when I stomp on them I have to look behind me, too. I have had two instances in the last two months where a quick stop was required and I had to allow for the bad driving habits of the car behind me following too close. In both instances the operator complained . One driver told me I had superior brakes and I should take into account that he did not! Why it did not occur to him that maybe he should increase his following distance is beyond me.

The following website has this to say about reaction time:

Expectation

Reaction times are greatly affected by whether the driver is alert to the need to brake. I've found it useful to divide alertness into three classes:

• Expected: the driver is alert and aware of the good possibility that braking will be necessary. This is the absolute best reaction time possible. The best estimate is 0.7 second. Of this, 0.5 is perception and 0.2 is movement, the time required to release the accelerator and to depress the brake pedal.
• Unexpected: the driver detects a common road signal such as a brake from the car ahead or from a traffic signal. Reaction time is somewhat slower, about 1.25 seconds. This is due to the increase in perception time to over a second with movement time still about 0.2 second.
• Surprise: the drive encounters a very unusual circumstance, such as a pedestrian or another car crossing the road in the near distance. There is extra time needed to interpret the event and to decide upon response. Reaction time depends to some extent on the distance to the obstacle and whether it is approaching from the side and is first seen in peripheral vision. The best estimate is 1.5 seconds for side incursions and perhaps a few tenths of a second faster for straight-ahead obstacles. Perception time is 1.2 seconds while movement time lengthens to 0.3 second.

If you do the math it is easy to see why so many people end up in rear-end collisions. This doesn't even take into consideration wet or snowy roads.

Typically, yes. Less than that causes those 17-car chain reaction pileups you see on the news every so often. Can't recommend being in that newscast...

The speed difference between the two cars is not 70MPH. It is likely only a few MPH for the first 2-3 seconds. This means that you do have more than 2-3 seconds to react unless that car can stop instantaneously.

The speed difference between the two cars is not 70MPH.

Correct. It is 0 MPH. Tailgating implies that you are closely following a vehicle in front of you. I merely pointed out that 100 feet would be considered tailgating. AH pointed out the reaction time.

"I used locked wheel because it is the fastest a vehicle can stop."

Sorry, I thought that the fastest a vehicle can stop was JUST BEFORE lockup...seems to me a locked wheel has almost no traction...maybe i missed something

The physics actually is a little more complicated, but locked wheel braking has a number of effects. One is that the tire heats up more and its friction increases as it heats. The second major component is the bias of weight of the car shifts forward onto the front wheels where the bulk of the stopping power is. Yes, the rear tires loose down force, but the gain in stopping power of the front wheels exceeds the loss of traction of the rear wheels.

Nevertheless, as long as both cars experience the same level of braking, the results I cited will be the same. I just happened to have a chart showing locked wheel braking at hand and used it.

You are absolutely correct. Locked wheel stopping is not the fastest stopping method. Hence anti lock braking. Yes, they also allow directional control but at the same time provide the shortest stopping distance and time.

Impressive graphs and data but also incorrect. Anonymous Hero needs to do a little more homework.

Cheers,

Demon4

Here is a little more homework, well, at least one citation. Locked wheel braking is the shorter stopping distance, with the possible exception of a wet road as compared to ABS.

http://www.freescale.com/webapp/sps/site/application.jsp?nodeId=02Wcbf07jSKy5P

http://www.mucda.mb.ca/aboutabs.htm

http://www.drivingfast.net/car_control/braking.htm

Note that the third link introduces a method that stops faster called Threshold Breaking, where the break pressure slows the wheels down to the point just before lockup.

The bottom line for ABS is that it improves the control of a car in slippery conditions or when both stopping and turning are required. However, on dry, clear pavement, straight line performance is not quite as good. While today's ABS systems are very, very, good, and the stopping distance difference is not that significant, it is not true to assume that ABS will always yield the shortest stopping distance.

When ABS brakes were introduced the number of auto accidents and fatalities actually went up. The reason was not due to the performance of the brakes, but people had a misconception that ABS was a magic bullet. That misconception, obviously, still exists today.

This was exactly my point for displaying graphs and "data". Following too close to the next vehicle is dangerous. If you still doubt me, just look up the statistics for the number of rear end collisions yourself. The butt you save may just be mine!

Okay, I'm not lobbying for less following distance, but your very compelling argument has a couple mathematical omissions in it.

First, your Vf = Vi + ... equation omits the .75 G factor, so the result should be 72 fps, not 62 fps.

Second, in your next statement you assert that the 128 feet you have traveled has eaten up 128 feet of vehicle separation. In actuality, only about 19 feet of separation have been lost because the front vehicle has traveled about 109 feet during that 1.25 seconds also.

With those corrections made, you will still have twenty-some feet of separation when you both come to a halt, but that doesn't mean you won't have to clean out your nickers! That is not exactly a comfortable margin.

Yes, I neglected to divide the acceleration 32.2 by 3/4 (1 G = 32.2 feet per second per second). Good catch!

Would you mind reposting the corrected information? I'd like to use this as a safety briefing, but would prefer it to be as accurate as possible...

Opps. I had a nice Excel file that I created, but threw it out after the discussion. If I get time I'll recreate it. Sorry.

Even coasting with the vehicle out of gear (engine running) is illegal in every US state I have lived in...

I read an article about hypermiling and decided to try it on my '79 Honda GL1000. Since I live out in the country, I even tried shutting the engine off and coasting (easy and not so dangerous to do on a bike). I found that there was no difference between hypermiling and just driving easy. Obviously there was a difference between the hypermiling and the occasional "need for speed." I'm wondering if the carburettor set up on a bike accounts for the lack of difference.

I have a 1998 Jeep TJ(Wrangler) 4.0L straight 6 engine with almost 200K Miles. I was only getting 16mpg and I have acheived 35-40mpg when hypermiling.!!

Pumping tires to maximum is dangerous, I drive a landcruiser Prado and at the highest tyre pressure given by Toyota unless the vehicle is heavily loaded slight drift starts to occur (nothing wrong with alignment or tryes). Go up a few pounds more with no load and you can feel the vehicle is loosing traction (steering becomes lighter and vague), pump it up to full sidewall pressure and a light wind would blow it off the road.

You also void your insurance by inflating tyres above the advised pressure so when you have the crash your sure to have, you not only lose the cost of your vehicle but you get fined for having an unroadworthy vehicle, dangerous driving and driving a vehicle without insurance. That cost far outwieghs the cost of the fuel you saved. Drafting with high tyre pressures you will never stop if the vehicle in front slows down fast as at higher speeds you can lose up to 75% of your braking tread contact, in wet weather just don't use your brakes they won't stop you any way.