Anyone know any more about this equation
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Anyone know any more about this equation
A quote from the ecomodder website:
A debate has been going on about wheel size, weight, and rotational mass. I have a set of 15" rota slips weighing in at 11.9 lbs. I am being told that I need to switch to a 14" Honda Civic HX wheel which weighs in at 11.75 lbs. The weight is negligible so then it goes to wheel mass that a 15" tire weighs more than the 14" tire.
I can see that argument but with the mentioned equation would it really make a difference?
Blue Bomber Man said - To get an idea of the impact of lighter wheels, take your vehicles weight and divide it by your HP. This will tell you how much weight each HP drives. Say you have a 100 hp car that weighs 2000 lbs. Works out to 20 lbs/hp. So cutting 20 pounds from your car would be the equivalent to improving your engine by 1 hp.
Now this isn't really a comparison of apples to apples because the wheels are rotational mass. I think the conversion is roughly 4:1 so if you cut 20 pounds of wheel mass it is the same as cutting 80 pounds off the car.
Now this isn't really a comparison of apples to apples because the wheels are rotational mass. I think the conversion is roughly 4:1 so if you cut 20 pounds of wheel mass it is the same as cutting 80 pounds off the car.
I can see that argument but with the mentioned equation would it really make a difference?
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I see people out there spending money on the car to improve it … If you spend half that effort just working on your driving skills, making you and the car work together as a team, then you’ll go faster – period. To make the car go a second faster on the track takes a lot more energy and money than making yourself drive it one second faster.
– the late Tom Thrash SCCA Solo E Production
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I agree with the formula, as I've experienced it, and I've even seen the results of reduced inertial weight (flywheel and lightweight wheels) on a dyno.
The difference between 14 and 15" wheels that have the same weight, the same width tire, and the same overall diameter isn't going to be enough to worry about, though. The 15" tire may be a touch heavier, it all depends on what size and what model of tire you choose. The difference can be a pound... or it can be 3 pounds, just depends on the tire.
Odds are that you can ultimately find a narrower and lighter 14" tire, however. But, from what I've read, going with a low rolling resistance tire will pay off more than downsizing the tire.
Tires : Test Results : The Tire Rack
Even then, you're only looking at maybe 1-2 mpg difference for a typical car.
The difference between 14 and 15" wheels that have the same weight, the same width tire, and the same overall diameter isn't going to be enough to worry about, though. The 15" tire may be a touch heavier, it all depends on what size and what model of tire you choose. The difference can be a pound... or it can be 3 pounds, just depends on the tire.
Odds are that you can ultimately find a narrower and lighter 14" tire, however. But, from what I've read, going with a low rolling resistance tire will pay off more than downsizing the tire.
Tires : Test Results : The Tire Rack
Even then, you're only looking at maybe 1-2 mpg difference for a typical car.
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Would you notice the difference? Almost certainly not outside of a lab. There would be an added advantage from the decreased rotational inertia since the 14" wheels are smaller (obviously) than the 15" wheels.
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You'd notice a 3 pound difference on a lightweight Honda, but I'm sure she already knows that.
1 pound difference? Nah. You'd probably not even be able to identify it statistically, it's just not going to make that much difference.
1 pound difference? Nah. You'd probably not even be able to identify it statistically, it's just not going to make that much difference.
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The thing about reducing weight is you have to keep in mind what you are compromising. I'm planning to move up in wheel diameter, width, tire width and as a consequence rotational weight but I'm doing this for other reasons. My car is missing about 400-500lbs of dead weight, including cruise control which is one of those things that might help gas mileage....if it doesn't make me fall asleep and crash into a tree during a 50 mile plus drive.
The lower you go in weight the more it matters of course, going from 6000 to 5800 is laughable in a full sized truck but even 100lbs from an old VW (that weighs under 1800lbs) can be HUGE. F1 teams at some point complained to Champion I believe that the spark plug was THE densest part in their cars, as a result the spark plug design seen to the left was put into production, on the far right is a Ford Taurus plug for comparison's sake.
http://www.caranddriver.com/var/ezwe...line_image.jpg
You just have to ask yourself "how serious am I about this?".
The lower you go in weight the more it matters of course, going from 6000 to 5800 is laughable in a full sized truck but even 100lbs from an old VW (that weighs under 1800lbs) can be HUGE. F1 teams at some point complained to Champion I believe that the spark plug was THE densest part in their cars, as a result the spark plug design seen to the left was put into production, on the far right is a Ford Taurus plug for comparison's sake.
http://www.caranddriver.com/var/ezwe...line_image.jpg
You just have to ask yourself "how serious am I about this?".
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Cruise control only helps fuel economy if you're a driver with a lead foot. Using technology to keep your speed in check will return better economy than driving 10-15-20 mph faster.
But, if you're capable of employing "hypermiling" techniques on your own, you'll return at least 10% better than cruise control will.
But, if you're capable of employing "hypermiling" techniques on your own, you'll return at least 10% better than cruise control will.
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You'd notice a 3 pound difference on a lightweight Honda, but I'm sure she already knows that.
1 pound difference? Nah. You'd probably not even be able to identify it statistically, it's just not going to make that much difference.
The difference between 14 and 15" wheels that have the same weight, the same width tire, and the same overall diameter isn't going to be enough to worry about, though. The 15" tire may be a touch heavier, it all depends on what size and what model of tire you choose. The difference can be a pound... or it can be 3 pounds, just depends on the tire.
1 pound difference? Nah. You'd probably not even be able to identify it statistically, it's just not going to make that much difference.
The difference between 14 and 15" wheels that have the same weight, the same width tire, and the same overall diameter isn't going to be enough to worry about, though. The 15" tire may be a touch heavier, it all depends on what size and what model of tire you choose. The difference can be a pound... or it can be 3 pounds, just depends on the tire.
The Model of tire has been difficult to choose. I need something for the street that is good to go on the drag strip as well. I am looking at the Falken Azeni 65-K. I wonder what the weight difference is from the 14" to the 15"?
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if you can only race me in a straight line then whats the point ...91 SMF SCCA
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I see people out there spending money on the car to improve it … If you spend half that effort just working on your driving skills, making you and the car work together as a team, then you’ll go faster – period. To make the car go a second faster on the track takes a lot more energy and money than making yourself drive it one second faster.
– the late Tom Thrash SCCA Solo E Production
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! Ne shab'rud'ni !
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The thing about reducing weight is you have to keep in mind what you are compromising. I'm planning to move up in wheel diameter, width, tire width and as a consequence rotational weight but I'm doing this for other reasons. My car is missing about 400-500lbs of dead weight, including cruise control which is one of those things that might help gas mileage....if it doesn't make me fall asleep and crash into a tree during a 50 mile plus drive.
The lower you go in weight the more it matters of course, going from 6000 to 5800 is laughable in a full sized truck but even 100lbs from an old VW (that weighs under 1800lbs) can be HUGE. F1 teams at some point complained to Champion I believe that the spark plug was THE densest part in their cars, as a result the spark plug design seen to the left was put into production, on the far right is a Ford Taurus plug for comparison's sake.
http://www.caranddriver.com/var/ezwe...line_image.jpg
You just have to ask yourself "how serious am I about this?".
The lower you go in weight the more it matters of course, going from 6000 to 5800 is laughable in a full sized truck but even 100lbs from an old VW (that weighs under 1800lbs) can be HUGE. F1 teams at some point complained to Champion I believe that the spark plug was THE densest part in their cars, as a result the spark plug design seen to the left was put into production, on the far right is a Ford Taurus plug for comparison's sake.
http://www.caranddriver.com/var/ezwe...line_image.jpg
You just have to ask yourself "how serious am I about this?".
I've never seen a spark plug design like that before.
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if you can only race me in a straight line then whats the point ...91 SMF SCCA
...91 SMF SCCAhttp://www.flickr.com/photos/8341770@N07/5601083432/http://www.flickr.com/photos/8341770@N07/5601083432/ by http://www.flickr.com/people/8341770@N07/, on Flickr
I see people out there spending money on the car to improve it … If you spend half that effort just working on your driving skills, making you and the car work together as a team, then you’ll go faster – period. To make the car go a second faster on the track takes a lot more energy and money than making yourself drive it one second faster.
– the late Tom Thrash SCCA Solo E Production
I race sailboats
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Cruise control yields better MPG for my car. But its kind of an odd case. Cruising on the interstate at constant speed with/without cruise yields a 2-3 mpg difference on the instantaneous MPG readout. I think it has something to do with the ECU controlling the throttle and having a good idea about whats coming next as far as injector timing, etc.
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Angela, I'm pretty sure you'll notice 3 pounds difference in several ways. Let us know.
On the tangent topic of cruise control, CC will probably appear to be giving you better MPG as long as the road is straight and flat. Where it fails is when you introduce hills. CC wants to maintain speed above all else, that's its mission in life. So, when you start up a hill and speed starts to decline, CC punches the throttle as hard as necessary to maintain speed. Now, you, as a mpg-concious hypermiler, will see the hill before you get there and maybe breathe on the throttle just a little more to gain 5 mph before you get to the hill... and then allow the car to lose 5-10 mph on the way up the hill, and then on the downhill side, you'll gently regain your speed and then some... all while using less fuel than your CC would have.
On the tangent topic of cruise control, CC will probably appear to be giving you better MPG as long as the road is straight and flat. Where it fails is when you introduce hills. CC wants to maintain speed above all else, that's its mission in life. So, when you start up a hill and speed starts to decline, CC punches the throttle as hard as necessary to maintain speed. Now, you, as a mpg-concious hypermiler, will see the hill before you get there and maybe breathe on the throttle just a little more to gain 5 mph before you get to the hill... and then allow the car to lose 5-10 mph on the way up the hill, and then on the downhill side, you'll gently regain your speed and then some... all while using less fuel than your CC would have.
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