Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
I f you will reread my op in this thread you'll see that we achieved higher fuel mileage when we were slowed to 55 mph. We had already been running at the company's mandatory top speed of 65 mph and getting less fuel mileage.
Yeah, but you're also a big heavy truck--even unloaded. I made the suggestion that a LIGHT vehicle, being pushed by a big engine, could definitely go faster than 55 mph and get mileage results just as good as at 55 mph.
I was making the suggestion that, when fully loaded, your mileage was not going to be as high as it was unloaded. Because you're heavier, and harder to "push".
Yeah, but you're also a big heavy truck--even unloaded. I made the suggestion that a LIGHT vehicle, being pushed by a big engine, could definitely go faster than 55 mph and get mileage results just as good as at 55 mph.
I was making the suggestion that, when fully loaded, your mileage was not going to be as high as it was unloaded. Because you're heavier, and harder to "push".
Larger more powerful oversized engines pushing smaller & lighter vehicles along at higher speeds with the expectation that better economy will be archived than at slower speeds simply doesn't add up, in the real world.
The smaller lighter vehicle will have to be beefed up in order to handle the larger more powerful engines performance which adds additional weight to the no longer smaller & lighter vehicle.
As for stripping down ( removing weight ) an already larger more powerful vehicle in order to achieve economy, that won't work either because of the limited amount of economy available in the larger engine. No matter how much weight you strip from the vehicle the larger more powerful engine will always consume much more fuel as was originally intended.
For example we drove some converted fuel trucks that were originally designed to haul crude oil at a gross weight of nearly two hundred thousand pounds. Even with all the extra unneeded weight stripped off so the truck could haul gas like all the rest of our gas trucks, the fuel burn was so bad they were removed from service.
The drivers loved the performance, but that wasn't enough of a reason to keep the trucks in service
Last edited by Tanque Verde; 01-05-2010 at 12:45 PM..
Use more gas to go fast. Go slow to take more time. You are just trading money for time.
At any given relative ground and air speed the way to improve gas mileage is to remove excess weight (do you really need to carry all that junk in the trunk), set tires a slightly higher pressure than recommended (putting up with the harsher ride), decrease drag (take the roof rack off when not using it) and go slower with less acceleration. Or do all this and buy a hybrid.
If you want to buy more fuel you can accelerate hard with an overloaded van on soft tires with a roof rack and big engine and go 80 mph.
I like the idea of a 55 mph speed limit but would appreciate an exemption for Subaru and Buick wagons and any motorcycle.
Or from a librul point of view you are wasting our nations precious resources for a little convenience. Given enough time we'll al be commuting in public transportation if were not careful.
With less wind resistance, and lower engine RPM, it makes no sense that an engine would burn more fuel at a 55 than at higher speeds, unless you're talking coasting down hill (none of us do that, right )
It all depends on how the vehicle is designed. A 4 speed transmission in the same car will likely have worse mileage than a 5 speed transmission. You can see this on existing products on the market the ones with more transmission gears have higher MPG. A drivetrain can be adjusted to have optimal (minimal) RPM at a certain speed, so it could be at 65 or 55 or 70, etc... There are other issue of course, but when all else is equal the transmission gearing changes things.
The Chevy Malibu is a real world example, the 4 speed transmission has 3 MPG less on highway than the 6 speed model with the same engine. Conversely, the 6 speed car could drive faster but with the same MPG as the 4 speed model.
It all depends on how the vehicle is designed. A 4 speed transmission in the same car will likely have worse mileage than a 5 speed transmission. You can see this on existing products on the market the ones with more transmission gears have higher MPG. A drivetrain can be adjusted to have optimal (minimal) RPM at a certain speed, so it could be at 65 or 55 or 70, etc... There are other issue of course, but when all else is equal the transmission gearing changes things.
The Chevy Malibu is a real world example, the 4 speed transmission has 3 MPG less on highway than the 6 speed model with the same engine. Conversely, the 6 speed car could drive faster but with the same MPG as the 4 speed model.
The number of gears isn't the only factor there, the gear ratios come into play as well. For example, a 2010 Toyota Tacoma 4 liter V6 engine and 4x4 is estimated by the EPA to get 20 miles per gallon on the highway with a 5 speed automatic transmission. The 6 speed manual transmission is estimated at 18 miles per gallon on the highway.
It makes no logical sense, but I can only conclude that 5th gear in the automatic turns a lower RPM than 6th gear in the manual. Why on earth it would be made that way, I have no idea.
You guys are arguing about different vehicles but comparing them at stated, constant speeds. Given the same vehicle specs, it will almost always take less energy input (fuel and throttle setting) to run at a lower speed than at a higher speed. Of course, if we dedicate and optimize the design to achieve best performance at a given speed (aerodynamics, engine rpms best suited to that engine's design and specific fuel consumption number), we can achieve fuel consumption results that are the same, or better, at 65 than another vehicle's consumption at 55.
The air resistance increases with the square of the increase in speed. Other friction values also increase exponentially.
A far better approach is to determine what speeds the public wants or needs to travel at so as not to feel like they'll be out in central Montana all one day and into the next day, just to get part-ways across! If 65 or 70, or even 85, is the target number, let's optimize for that, and then accept the costs.
Time is money in this country. We could conduct all travel business by horse-drawn wagon or steam powered passenger train but it would cost our economy dearly. Far better that we concentrate on alternate fuel sources (the car switches to induced electricity when it merges onto a next-generation Interstate, for example, and then runs off the grid's power until it exits) than simply slowing down all the existing traffic and to heck with the consequences!
The number of gears isn't the only factor there, the gear ratios come into play as well. For example, a 2010 Toyota Tacoma 4 liter V6 engine and 4x4 is estimated by the EPA to get 20 miles per gallon on the highway with a 5 speed automatic transmission. The 6 speed manual transmission is estimated at 18 miles per gallon on the highway.
It makes no logical sense, but I can only conclude that 5th gear in the automatic turns a lower RPM than 6th gear in the manual. Why on earth it would be made that way, I have no idea.
It makes sense because, as in the example I gave, it depends on the design and how "new" the technology is. If the automatic is a newer design than they could theoretically optimize it better. No different than an engine from today versus the same size engine from 10 years ago, the modern engine, while being the same size, can be more efficient and powerful.
You guys are arguing about different vehicles but comparing them at stated, constant speeds. Given the same vehicle specs, it will almost always take less energy input (fuel and throttle setting) to run at a lower speed than at a higher speed. Of course, if we dedicate and optimize the design to achieve best performance at a given speed (aerodynamics, engine rpms best suited to that engine's design and specific fuel consumption number), we can achieve fuel consumption results that are the same, or better, at 65 than another vehicle's consumption at 55.
Of course, but I'm just pointing out that it depends on what range of speed people are talking about. Basically I believe the cars are optimized to get a very good rating on the EPA mileage test so they can get the best numbers for sales/marketing and to meet the CAFE standards (since they must meet these standards). However, the mileage test is slower than many people drive and can be slower than the speed limit in many places. So theoretically, the vehicles are not optimal for many typical driving patterns.
As far as the safety issue goes the autobahn has no speed limit in places and is safer road than here. The difference being is they heavily enforce traffic laws like staying in the right lane unless you're passing, no passing on the left etc.
Interesting article here on Montana when they lifted the speed limits, fatalities decreased. Shortly after imposing a speed limit again fatalities increased.
For the last 5 months of no daytime limits in Montana, the period after its Supreme Court had ruled that the Reasonable and Prudent law was unconstitutional, reported fatal accident rate declined to a record low. Fixed speed limits were reinstated on Memorial Day weekend 1999. Since then, fatal accidents have begun to rise again.
This begs the question, do people change the way they drive when there is no speed limit? The evidence suggests the answer is yes. The measured vehicle speeds only changed a few miles per hour as predicted - comparable to data collected from other western states. What changed? The two most obvious changes were improved lane courtesy and increased seat belt use. Did other driving habits and patterns change as well?
When I'm driving on the interstate I don't even look at speedometer, I drive with traffic or what I'm comfortable driving. If most people did that speeds of 90+ could easily be maintained safely on most interstates with lower accidents and much less traffic congestion.
We don;t need lower speed limits, we need high minimum speed limits and heavy enforcement to get the idiots off the road such as the guy clogging up the passing lane, aggressive drivers etc.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
but that wasn't enough of a reason to keep the trucks in service
)
