Gas Mileage Build, Whats ur take on it..
04-23-2013, 09:17 AM
#61
So now you're saying that it does matter...so which is it?
Noone said how significant of a difference it is, just that there is a difference.
Noone said how significant of a difference it is, just that there is a difference.
Since you haven't seemed to grasp the gist of my post, allow me to clarify.
When you accelerate a mass from a rest, you burn a lot more fuel moving a heavier load than a light one. When you are at a steady state cruise, you aren't accelerating that mass, so a change in mass has little effect on hwy mpg, or even top speed for that matter, since aerodynamic forces dominate above 50-60 mph. Yes, rolling resistance can be measured, as others have noted, but its effect is smaller than aero drag and cruising RPM.
Last edited by DoctorV8; 04-23-2013 at 11:00 AM.
04-23-2013, 09:28 AM
#62
You tell me if you think taking 300 lbs out of a 3000 lb car for a 1.4% improvement in highway mileage matters. That's the difference between 25 mpg and 25.35 mpg at 75 mph. Can you even measure that? What if you had a 5 mph tailwind that day, or if a cool front dropped your tire pressure by 2psi?
Weight does NOT matter in steady state cruising.
04-23-2013, 09:55 AM
#65
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It's a minor player compared most of the other factors you mentioned. The EPA notes a 10% weight reduction leads to a whopping 1.4% improvement at a steady 75 mph.
http://green.autoblog.com/2009/10/29...es-efficiency/
I've gone to much wider, stickier tires with heavier, larger wheels many times in the past, and even added weight from turbos, intercoolers, and big stereos to my cars in the past couple decades, and real world MPG decrements from driving all over Texas are in line with what the EPA found. OTOH, putting a shorter axle ratio, or worse yet, losing 5th gear and cruising home in 4th....now that's what sucks down the gas.
Probably the biggest, most common offense to cruising economy is also the most preventable....driving on underinflated tires.
http://green.autoblog.com/2009/10/29...es-efficiency/
I've gone to much wider, stickier tires with heavier, larger wheels many times in the past, and even added weight from turbos, intercoolers, and big stereos to my cars in the past couple decades, and real world MPG decrements from driving all over Texas are in line with what the EPA found. OTOH, putting a shorter axle ratio, or worse yet, losing 5th gear and cruising home in 4th....now that's what sucks down the gas.
Probably the biggest, most common offense to cruising economy is also the most preventable....driving on underinflated tires.
04-23-2013, 09:55 AM
#66
04-23-2013, 10:08 AM
#68
Yes, I stand corrected. It does. The same way having a BM affects your weight. ;-)
If you can measure a 1.4% difference with all the uncertainties that contribute to manually calculating fuel economy, you're a better man than me.
Now, if you do more city driving, weight matters. Big time.
If you can measure a 1.4% difference with all the uncertainties that contribute to manually calculating fuel economy, you're a better man than me.
Now, if you do more city driving, weight matters. Big time.
04-23-2013, 12:45 PM
#69
Anyone that tows a trailer can answer that question....more weight burns more gas cruising. "Steady state" or whatever you want to call it.
It takes more gas to keep 12klbs moving then it does 7klbs. I do it quite a bit and have the time putting gas back in the truck to prove it.
Unloaded 18-wheelers get far better gas mileage than loaded ones.
Turning a molehill into a mountain here.
It takes more gas to keep 12klbs moving then it does 7klbs. I do it quite a bit and have the time putting gas back in the truck to prove it.
Unloaded 18-wheelers get far better gas mileage than loaded ones.
Turning a molehill into a mountain here.
04-23-2013, 01:02 PM
#70
Unloaded 18-wheelers get far better gas mileage than loaded ones.
Turning a molehill into a mountain here.
Turning a molehill into a mountain here.
In the passenger car realm, weight has little to no meaningful effect on steady state fuel economy, or top speed for that matter. It's mostly aerodynamic drag, more so the faster ya go.
04-23-2013, 01:09 PM
#71
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This is a topic that we should all find interesting. It's crazy how much a gallon of gas costs nowadays.
I've got to say...there is a lot of misinformation in this thread. Someone even said to bump up the compression ratio and switch to E85. Lol. I hope I don't sound like a know-it-all, but E85 isn't a good solution for fuel economy.
Elsewhere in this thread, there was a suggestion to build a bigger engine. That's not the best solution either.
The smaller engines (4.8L instead of 6.0L) will be more efficient.
Another point that was just mentioned...weight does matter for steady state fuel economy. Weight is a major part of the rolling resistance calculation, and is easily quantified. Frr=W x Crr
Rolling Resistance Force = Weight x Rolling Resistance Coefficient
A faster PCM isn't the solution either. The current OE processors do a pretty nice job. There's room for improvement, but they're not bad.
There have been several good points mentioned. I'll start a list.
Aerodynamics
Proper Tire inflation
Lightweight vehicle
Overdrive transmissions
More gear ratios in the transmissions
More efficient engine
Smaller engine
More compression
Better cam design
Direct Injection
Here are a few more to think about.
Synthetic Lubricants
Thermal Coatings
Under drive pulleys
More Efficient Induction and Exhaust Systems
Aerodynamic tricks (such as automatically closing the grill opening at highway speeds)
Belly pans
Smaller mirrors
We can make a list of other improvements as well.
I'm thinking I may just hook a tow rope to my next door neighbor's back bumper. That should help my fuel economy!
I've got to say...there is a lot of misinformation in this thread. Someone even said to bump up the compression ratio and switch to E85. Lol. I hope I don't sound like a know-it-all, but E85 isn't a good solution for fuel economy.
Elsewhere in this thread, there was a suggestion to build a bigger engine. That's not the best solution either.
The smaller engines (4.8L instead of 6.0L) will be more efficient.
Another point that was just mentioned...weight does matter for steady state fuel economy. Weight is a major part of the rolling resistance calculation, and is easily quantified. Frr=W x Crr
Rolling Resistance Force = Weight x Rolling Resistance Coefficient
A faster PCM isn't the solution either. The current OE processors do a pretty nice job. There's room for improvement, but they're not bad.
There have been several good points mentioned. I'll start a list.
Aerodynamics
Proper Tire inflation
Lightweight vehicle
Overdrive transmissions
More gear ratios in the transmissions
More efficient engine
Smaller engine
More compression
Better cam design
Direct Injection
Here are a few more to think about.
Synthetic Lubricants
Thermal Coatings
Under drive pulleys
More Efficient Induction and Exhaust Systems
Aerodynamic tricks (such as automatically closing the grill opening at highway speeds)
Belly pans
Smaller mirrors
We can make a list of other improvements as well.
I'm thinking I may just hook a tow rope to my next door neighbor's back bumper. That should help my fuel economy!
Pretty much EXACTLY what he said lol
04-23-2013, 01:43 PM
#72
Na..just applying common sense to the girly argument on hand.
Weight and aerodynamics are a factor..dur. I'm sure I can convince a 12yr old with down syndrome that after he gets done eating his crayons.
You contradicted yourself a few times already..you sure you know what you are trying to accomplish?
Weight and aerodynamics are a factor..dur. I'm sure I can convince a 12yr old with down syndrome that after he gets done eating his crayons.
You contradicted yourself a few times already..you sure you know what you are trying to accomplish?
04-23-2013, 01:57 PM
#73
Actually, I didn't. The EPA graph I posted supports my statements, unless you are in the camp with a couple others here who enjoy splitting hairs and having a less that 1% standard deviation in everything you do.
When it takes a substantial 10% weight loss to effect a 1.4% improvement in steady state fuel economy, that frankly is within the margin of error by which we mere mortals measure fuel economy on the road, not in a lab.
I didn't realize I had to be so specific with my qualifiers, but for the topic at hand, in a passenger car with +/- a couple hundred pounds of vehicle load, not towing a box trailer full of dead hookers uphill both ways to the dumpster, weight does not matter to a significant degree in steady state cruising.
Aero/gearing/tire pressure are key, esp for those of us that tend to exceed the speed limit from time to time.
When it takes a substantial 10% weight loss to effect a 1.4% improvement in steady state fuel economy, that frankly is within the margin of error by which we mere mortals measure fuel economy on the road, not in a lab.
I didn't realize I had to be so specific with my qualifiers, but for the topic at hand, in a passenger car with +/- a couple hundred pounds of vehicle load, not towing a box trailer full of dead hookers uphill both ways to the dumpster, weight does not matter to a significant degree in steady state cruising.
Aero/gearing/tire pressure are key, esp for those of us that tend to exceed the speed limit from time to time.
04-23-2013, 02:23 PM
#75
That 2 sec google search result from the EPA was aimed at putting the weight issue in perspective after kevin87turbot's excellent detailed post.
Still curious as to how you think I contradicted myself, since I apparently lack the common sense to come to that conclusion on my own.
I would have (maybe should have) kept to myself, if it weren't for people mistakenly synonymizing "weight" and "drag," and talking about hills in the context of "steady state" cruising.
04-23-2013, 03:08 PM
#77
The more weight, the more drag, it is that simple. The more drag, the more effort needed to counter that to maintain a constant speed. It's basic mathematics. You can't take a variable in an equation and make it smaller/larger and expect to come out with the same answer without changing at minimum one other.
Common sense..
And yes Aero Drag is different from Mass Drag, I use that term referring to the movement of parts in the vehicle..Bearings, Gears meshing, etc.
Common sense..
And yes Aero Drag is different from Mass Drag, I use that term referring to the movement of parts in the vehicle..Bearings, Gears meshing, etc.
04-23-2013, 03:13 PM
#78
Did you ever, by any chance, study the scientific method? And how it's important to eliminate variables if you want to arrive at any meaningful conclusions? How's the guy driving a Camaro in Denver supposed to compare his fuel economy to the dude driving his LS powered G body in New Orleans?
Hence the need for STEADY STATE numbers and the now famous YMMV disclaimer.
I don't envy those EPA engineers. Not an easy job.
(still waiting for you to explain how I contradicted myself, Merv...PM me if don't mind....I doubt anyone else cares to hear your reply....)
04-23-2013, 03:16 PM
#79
04-23-2013, 03:19 PM
#80
Theory and real life are two whole different things..those of us that actually encounter real life understand that..again, we come to the term "common sense".
And my common sense is good enough to tell when it's a null argument because the other party can't grasp that concept.
And my common sense is good enough to tell when it's a null argument because the other party can't grasp that concept.