Lets lower speed limits because gas costs too much

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05-13-08, 05:55 PM
Benyen Soljax

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by Kham

ghostrider is idiot. at 120mph and in 30 min, you'll probly dumping more gas than 1hr and half speed.

i dont believe you. how can you reject the SCIENCE behind ghostriders claims?!?!?!

:twitch::twitch::twitch::twitch:
05-13-08, 05:59 PM
taxonomy

Re: Lets lower speed limits because gas costs too much

You know, I thought I would be pissed off reading this thread. But I am not, it's fun.
05-13-08, 09:22 PM
superbrew

Re: Lets lower speed limits because gas costs too much

I know this is about planes, but the theory applies.Like Motorists, Airlines Are Reducing Their Speed to Save Fuel Costs
05-13-08, 10:10 PM
*GhostRide37

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by Kham

if aerodynamic is a myth, they would stick jet engine and some wings on a bus and fly. know how paddling boat work?

ghostrider is idiot. at 120mph and in 30 min, you'll probly dumping more gas than 1hr and half speed.

yeah, you said "probly" (probably) dumping more gas at 1hr half speed. with you saying "probably", ill take my chances and get there half hour earlier. unless you're 100 % sure...

and air resistance is an entire different story. if you were in an airless vacuum doing 80 at low rpm and doing 30 at high rpm, youd probably use more gas doing 30.

*but anyway, before people get carried away here...much of what i said is just me and my sarcastically extremist views for shock value......but in all seriousness.....if you drive slow but do gas-brake-gas-brake....or drive fast and just dont brake until your there....youll use the same amount of gas (if not less for not breaking and accelerating)
05-14-08, 07:48 AM
TheIglu

Re: Lets lower speed limits because gas costs too much

No.
05-14-08, 08:25 AM
ultraTwist

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by tsanto

As fuel prices rise, some speedometer needles fall - Boston.com

This is so ridiculous. I dont know much about aerodynamics but on a modern car the difference in 65mph and 75mph cant be that much in gas milage.

If you read the whole article, they quote a state rep from alabama proposing "we'll lower the speed limits when gas prices get high and raise them when prices are low." Yeah ok buddy I'm sure you'll raise speed limits once prices are low (which wont happen for awhile anyway).

When gas prices soar people get these crazy ideas to lower speed limits and go buy vespas.

Which means there's probably going to be a lot of new riders with little to no experience riding around on two wheels trying to save a buck this summer.

And possibly lower speed limits.

The energy required to overcome aerodynamic resistance goes with the square of the speed in theory and is likely worse than that in real life. That's why a 160bhp car can not go twice as fast an 80bhp car. You use a lot more energy (gas) to a little bit faster. If you have a car with a computer that measures mph, drive around at 80-83mph and notice you gas consumption, then to the same at around 50-55.

If the cross section on you car is twice as large then the aerodynamic drag goes up in a linear fashion, that is twice as much, the same goes for cd. So if you are in a pickup that is twice as large as a small car and has a cd twice as big again you are going to get about 4 times less mpg for the same speed.

Those are the biggest factors in mph, secondary effects include your cars total mechanical friction and differences in the thermodynamic effiecncy of the engines (lots of small cylinders are better than less big ones (or the other way around)).
05-14-08, 09:12 AM
Benyen Soljax

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by *GhostRide37

......but in all seriousness.....if you drive slow but do gas-brake-gas-brake....or drive fast and just dont brake until your there....youll use the same amount of gas (if not less for not breaking and accelerating)

:mope::mope::mope:

too many assumptions, too little science.

have you ever ridden in 6th gear? you dont have to be using "high rpms" to go slower. i can go 25 and be in 5th or 6th just fine. im betting im going to use less gas than you going faster and using "lower rpms". id put a mortgage on it if i had one.
05-14-08, 09:13 AM
tsanto

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by *GhostRide37

yeah, you said "probly" (probably) dumping more gas at 1hr half speed. with you saying "probably", ill take my chances and get there half hour earlier. unless you're 100 % sure...

and air resistance is an entire different story. if you were in an airless vacuum doing 80 at low rpm and doing 30 at high rpm, youd probably use more gas doing 30.

*but anyway, before people get carried away here...much of what i said is just me and my sarcastically extremist views for shock value......but in all seriousness.....if you drive slow but do gas-brake-gas-brake....or drive fast and just dont brake until your there....youll use the same amount of gas (if not less for not breaking and accelerating)

I'll get carried away i guess:

Basic thermal eff.

Nth= Wout / Qin

Where Nth= engine efficiency Wout= energy from force out
Qin= energy in (fuel)

Basic translation is Efficiency equals the % of heat transformed into work (energy).

Engine eff. is roughly 25% due to losses in the engine (engine heat, friction, work used to turn engine equipment)

This simply means that out of 100% energy that fuel contains (Kinetic energy), only 25% is actually utilized to create work (move your car).

At high rpms your engine needs to works harder to create the same out of Wout at a lower rpm due to higher friction losses, more engine heat, etc.

Basically the total Wout will be less because your Wlost is higher at high engine speed.

Havent you seen that old school quaker state motor oil commercial with Dennis Leary?

HEAT is bad for engines, and in thermal efficiency terms you see bigger losses the harder the engine runs and the hotter it gets

Nth=Wout/Qin

When engine runs at high rpm, Wloss increase. Which means Wout is less.

For example

Nth1=Wout/Qin @ 65mph

Nth2=1/2Wout/Qin @120mph

Nth1 > Nth2
05-14-08, 09:18 AM
Benyen Soljax

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by ultraTwist

(lots of small cylinders are better than less big ones (or the other way around)).

its also the way the cylinders are designed, not just how many there are. usually engines that rev higher are designed with a shorter stroke, and bigger bore, this reduces the momentum from the pistons that the crankshaft has to stop. i would also assume this has some effect on the amount of friction and losses in the engine, but who knows if its better or worse. :dunno: im not even going to pretend i know about all the intricacies of engine design.
05-14-08, 09:29 AM
taxonomy

Re: Lets lower speed limits because gas costs too much

From Wikipedia Fuel economy-maximizing behaviors - Wikipedia, the free encyclopedia

I did some hypermiling this winter in my car, I found I could do about 10-15% better traveling at lower speeds and working to minimize braking. Most of what I have read points to max efficiency around 40 MPH.

Efficient Speeds

Maintaining an efficient speed is an important factor in fuel efficiency.[citation needed] [1] Optimal efficiency can be expected while cruising with no stops, at minimal throttle[citation needed] and with the transmission in the highest gear[citation needed]. The optimum speed varies with the type of vehicle, although it is usually reported to be in the range of 35 to 55 mph[9][10] [11]. For instance a 2004 Chevrolet Impala had an optimum at 42 mph (70 kph), and was within 15% of that from 29 to 57 mph (45 to 95 kph)[9]. Drivers of vehicles with fuel-economy displays can check their own vehicles by cruising at different speeds and monitoring the readout.
05-14-08, 10:01 AM
ChrisNoF4i

Re: Lets lower speed limits because gas costs too much

You fuckin' science geeks are all alike. You probably believe in gravity too. :squint: Just another scam.
05-14-08, 10:11 AM
taxonomy

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by ChrisNoF4i

You fuckin' science geeks are all alike. You probably believe in gravity too. :squint: Just another scam.

Hooray for science!

The people that brought you trauma surgery, indoor lighting, the telephone, blender, well the list goes on and on. Hazzah! for peer review!
05-14-08, 10:57 AM
ultraTwist

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by Benyen Soljax

its also the way the cylinders are designed, not just how many there are. usually engines that rev higher are designed with a shorter stroke, and bigger bore, this reduces the momentum from the pistons that the crankshaft has to stop. i would also assume this has some effect on the amount of friction and losses in the engine, but who knows if its better or worse. :dunno: im not even going to pretend i know about all the intricacies of engine design.

No this is a purely thermal issue associated with the ration of the volume to surface area. Thermal guys can jump in. But there's no free lunch, if lots of small pistions are better, you then need to pay for more fiction in the way of more values, cams and chains.
05-14-08, 11:16 AM
stoinkythepig

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by ultraTwist

No this is a purely thermal issue associated with the ration of the volume to surface area. Thermal guys can jump in. But there's no free lunch, if lots of small pistions are better, you then need to pay for more fiction in the way of more values, cams and chains.

Lots of small pistons moving fast are better for generating HP for a given displacement (due to a higher rev ceiling), not necessarily for better fuel efficiency. For fuel efficiency in today's engines, you want a slow turning engine operating at WOT under heavy load, at the engine's torque peak, all the time to reduce pumping losses. This is one of the reasons why diesels are so efficient, they run slowly (compared to gas engines) and have no throttle to restrict airflow. They also run best under a heavy load (at least 70% of their rated output)

The latest Cycle World magazine has a great Kevin Cameron essay about improving efficiency of gasoline engines. He's a MA native (I'm pretty sure) and one of my favorite writers.
05-14-08, 11:38 AM
taxonomy

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by stoinkythepig

The latest Cycle World magazine has a great Kevin Cameron essay about improving efficiency of gasoline engines. He's a MA native (I'm pretty sure) and one of my favorite writers.

Kevin is a MA native. I am a librarian in Western MA. Kevin has agreed to do an author reading of his new book Top Dead Center. It'll be in September. There will also be some sort of ride that afternoon with the Yankee Beemers.

It's looking like September 6th at the Forbes Library. Date and location remain slightly up in the air. More details and they come.
05-14-08, 12:53 PM
stoinkythepig

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by taxonomy

Kevin is a MA native. I am a librarian in Western MA. Kevin has agreed to do an author reading of his new book Top Dead Center. It'll be in September. There will also be some sort of ride that afternoon with the Yankee Beemers.

It's looking like September 6th at the Forbes Library. Date and location remain slightly up in the air. More details and they come.

Thanks for the heads up
05-14-08, 12:54 PM
ultraTwist

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by stoinkythepig

Lots of small pistons moving fast are better for generating HP for a given displacement (due to a higher rev ceiling), not necessarily for better fuel efficiency. For fuel efficiency in today's engines, you want a slow turning engine operating at WOT under heavy load, at the engine's torque peak, all the time to reduce pumping losses. This is one of the reasons why diesels are so efficient, they run slowly (compared to gas engines) and have no throttle to restrict airflow. They also run best under a heavy load (at least 70% of their rated output)

The latest Cycle World magazine has a great Kevin Cameron essay about improving efficiency of gasoline engines. He's a MA native (I'm pretty sure) and one of my favorite writers.

[/I]

I understand but you are a little off track. I was trying to keep it simple and assume people were driving about the same vehicle. The Diesel is an entire different cycle and from what I remember makes great gains from high compression. I was trying to give the guy some guidelines to making an informded decision about what to buy. Diesels are a great choice and I personally would consider any VW 2.0l turbo if I could.

Yes, small pistions have less mass and can change direction faster. Their valve trains have less mass and can turn faster. This is why more small pistons turning faster will have more hp compared to less big ones that can not turn as fast per the same displacement, they simply move more air and therefore can burn more gas which has nothing to do with mpg if you lose it all to heat.

So since no thermal guys jumped in I did a quick look to refresh my memory. If the surface to volume ratio is large you lose more heat, hence your mpg goes down as your engine can not convert this heat lose to motion. I then wrote a small program to calculate this ratio and found that really big cylinders should save you a lot of heat.

So this guy should buy a small car, with great cd that has an engine with one huge cylinder. If I'm right. That should reduce internal friction as well. I wonder what the mpg of my tractor is?
05-14-08, 01:14 PM
enzo_f1

Re: Lets lower speed limits because gas costs too much

I feel that anyone that wants to drive 55 MPH should. Just keep out of the fast lane.
05-14-08, 04:09 PM
CEO

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by *GhostRide37

what people fail to realize is that, yes, maybe slower driving uses less gas to run the engine at that moment, but if you drive faster, you get to your destination faster...at which point you turn the vehicle off and stop using gas (rather than still driving at a slower speed and using less gas for a longer period)

in the end it all cancels out and its the same.

Quote:

Originally Posted by *GhostRide37

nope, why would i be kidding. its true when you think about.

you can drive 60 miles for 1 hour doing 60mph

or drive 60 miles in 30 min doing 120 mph (using these #s for the sake of argument)

the gas you use up from going so fast is going to be about the same as the gas you WOULD HAVE used if you were still driving that extra half hour. at least thats the way i look at it.:wink:

Quote:

Originally Posted by *GhostRide37

yeah, you said "probly" (probably) dumping more gas at 1hr half speed. with you saying "probably", ill take my chances and get there half hour earlier. unless you're 100 % sure...

and air resistance is an entire different story. if you were in an airless vacuum doing 80 at low rpm and doing 30 at high rpm, youd probably use more gas doing 30.

*but anyway, before people get carried away here...much of what i said is just me and my sarcastically extremist views for shock value......but in all seriousness.....if you drive slow but do gas-brake-gas-brake....or drive fast and just dont brake until your there....youll use the same amount of gas (if not less for not breaking and accelerating)

After these three posts, I'm 100% positive that you are clinically and legally retarded.

You should apply for a handicapped plate/permit with your retardation. Then you could use the gas you saved driving faster to drive closer to the building for parking and not have to walk as far.
05-14-08, 04:18 PM
Benyen Soljax

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by ceo012384

After these three posts, I'm 100% positive that you are clinically and legally retarded.

You should apply for a handicapped plate/permit with your retardation. Then you could use the gas you saved driving faster to drive closer to the building for parking and not have to walk as far.

:lol:
05-15-08, 07:39 AM
*GhostRide37

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by Benyen Soljax

:mope::mope::mope:

too many assumptions, too little science.

have you ever ridden in 6th gear? you dont have to be using "high rpms" to go slower. i can go 25 and be in 5th or 6th just fine. im betting im going to use less gas than you going faster and using "lower rpms". id put a mortgage on it if i had one.

Quote:

Originally Posted by tsanto

I'll get carried away i guess:

Basic thermal eff.

Nth= Wout / Qin

Where Nth= engine efficiency Wout= energy from force out
Qin= energy in (fuel)

Basic translation is Efficiency equals the % of heat transformed into work (energy).

Engine eff. is roughly 25% due to losses in the engine (engine heat, friction, work used to turn engine equipment)

This simply means that out of 100% energy that fuel contains (Kinetic energy), only 25% is actually utilized to create work (move your car).

At high rpms your engine needs to works harder to create the same out of Wout at a lower rpm due to higher friction losses, more engine heat, etc.

Basically the total Wout will be less because your Wlost is higher at high engine speed.

Havent you seen that old school quaker state motor oil commercial with Dennis Leary?

HEAT is bad for engines, and in thermal efficiency terms you see bigger losses the harder the engine runs and the hotter it gets

Nth=Wout/Qin

When engine runs at high rpm, Wloss increase. Which means Wout is less.

For example

Nth1=Wout/Qin @ 65mph

Nth2=1/2Wout/Qin @120mph

Nth1 > Nth2

well that guy just did a whole shitload of science to say some of what i said, higer rpms usually means more gas. (of course 120 mph was an exaggeration...at that speed the wind resistance is extremely high)
05-15-08, 07:42 AM
*GhostRide37

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by ceo012384

After these three posts, I'm 100% positive that you are clinically and legally retarded.

You should apply for a handicapped plate/permit with your retardation. Then you could use the gas you saved driving faster to drive closer to the building for parking and not have to walk as far.

definitely the most origianal message board diss ever. maybe youre the retarded one though if you think a legally retarded person can make that much sense on a silly topic. like i said, those post were half joking. i use a stephen colbertish type of humor, obviously you cant pick up on it.
05-15-08, 08:08 AM
ZX-12R

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by *GhostRide37

...youre...

Argh! You were so close!
05-16-08, 06:30 AM
*GhostRide37

Re: Lets lower speed limits because gas costs too much

Quote:

Originally Posted by ZX-12R

Argh! You were so close!

so close? what is incorrect about "youre", besides i didnt type the apostrophe?...hopefully you dont think it sould be spelled "your" in that context, or else youre the one who was so close
05-16-08, 07:41 AM
Woodsy

Re: Lets lower speed limits because gas costs too much

This is just a thinly veiled attempt to extort more money out of the tax payer. They say “hey, we are lowering the speed limit so it will save you gas” if I wanted to slow down to save gas, I would! I do not need a speed sign to tell me that. Also how many people actually drive 65 to begin with? 70-75 at an average right? So let say you actually get pulled over for that 75mph that is a 10mph diff not a huge ticket, but under our eco friendly system it turns into a 20mph dif which is a fairly heavy ticket. So who is making out? The tax payer who could drive 55 anyways but probably wont or the state with their greatly increased revenue. It basically turns the whole state into a speed trap

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