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| Secrets to fuel mileage. (Page 3/5) |
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williegoat
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MAY 02, 04:40 PM
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| quote | Originally posted by Notorio:
So that looks like the biggest variable in your list. Can you describe what the Efficient Drivers are doing that is so beneficial? My dad always warned against jackrabbit stops/starts and speeding. What else is there? |
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Depending on the types of roads you operate on and the types of vehicles, there are some very useful and proven techniques that I used to teach to both beginning and experienced drivers. Each of these techniques also has other benefits in safety and can reduce wear and tear on vehicle components.
It is important to be aware of your surroundings. Look ahead to where you will be 15-20 seconds in the future. Make note of potential hazards so you can position yourself in such a way that sudden movements will be less likely. Every time you use your brakes, you have to make up for it by using the throttle. That costs fuel.
Be aware of the condition of the traffic light ahead. If it is red and there is stopped traffic, go ahead and let up on the throttle and with some timing and practice, you will be able to go through traffic lights without coming to a complete stop and possibly in a higher gear. I learned to teach this trick in downtown L.A. and would demonstrate it on a weekly basis to a group of experienced truck drivers in downtown Phoenix. Don't tell me it can't be done.
There is a technique known as "progressive shifting" (no, not like the current administration) where you shift out of the lower gears at a lower RPM, progressively increasing that engine speed with each higher gear. In other words, get out of each gear as soon as possible. You don't need all of that torque in the lower gears.
There are also obvious things like trip planning and keeping idle times to a minimum.[This message has been edited by williegoat (edited 05-02-2021).]
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cvxjet
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MAY 02, 05:53 PM
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I wanted to state something about Aerodynamics vs Trucks; There has always been the big debate about the tailgate being up or down- either is still (Basically) bad, aero-wise; Two ways to go for improved aero on a pickup truck; A) Install a lid or tonneau cover...This a big improvement.....But by far the best thing to do is to B) Install a camper shell even with the roof of the cab- The flat back-end is (Basically) a Kamm effect situation where the air-flow breaks cleanly from the vehicle....This seems contradictory to people with limited Aerodynamic knowledge.
My father was an aircraft worker/ Foreman/Supervisor at NAS Alameda, so I was completely immersed in all thing aero from a young age.
I also did some diagrams of how different wing/spoiler setups on our Fieros can create down-force vs Drag...
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williegoat
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MAY 02, 06:32 PM
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| quote | Originally posted by cvxjet:
The flat back-end is (Basically) a Kamm effect situation where the air-flow breaks cleanly from the vehicle....This seems contradictory to people with limited Aerodynamic knowledge.
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That is simply not true. The Kamm tail effect depends on some taper. This is obvious to anyone who has ever followed a tractor-trailer on a motorcycle. There is quite a bit of turbulence even sixty to eighty feet back from the trailer. A tapered tail cone on a trailer can net a fuel savings of better than six percent.
| quote | Originally posted by williegoat:
This is something I studied thoroughly in the last 15 years of my career.
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 [This message has been edited by williegoat (edited 05-02-2021).]
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blackrams
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MAY 02, 06:47 PM
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| quote | Originally posted by cvxjet:
I wanted to state something about Aerodynamics vs Trucks; There has always been the big debate about the tailgate being up or down- either is still (Basically) bad, aero-wise; Two ways to go for improved aero on a pickup truck; A) Install a lid or tonneau cover...This a big improvement.....But by far the best thing to do is to B) Install a camper shell even with the roof of the cab- The flat back-end is (Basically) a Kamm effect situation where the air-flow breaks cleanly from the vehicle....This seems contradictory to people with limited Aerodynamic knowledge.
My father was an aircraft worker/ Foreman/Supervisor at NAS Alameda, so I was completely immersed in all thing aero from a young age.
I also did some diagrams of how different wing/spoiler setups on our Fieros can create down-force vs Drag...
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You do have a point reference the airflow going over/around pickup points but, what you are omitting is the flat ass end on trucks. Even on pickups. To smooth out that airflow, the ass end of the pickup with tail gate or, the back of the cab without a tail gait still provides for that area where the vehicle must over come the aerodynamic affects of that surface. Aerodynamic Engineers always attempt to smooth out the airflow characteristics of all aircraft. One would have to assume that automotive engineers are attempting to do the same thing. That low pressure area you're describing has to be reduced to the lowest value possible to actually increase fuel mileage.
| quote | Originally posted by williegoat:
That is simply not true. The Kamm tail effect depends on some taper. This is obvious to anyone who has ever followed a tractor-trailer on a motorcycle. There is quite a bit of turbulence even sixty to eighty feet back from the trailer. A tapered tail cone on a trailer can net a fuel savings of better than six percent.
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This is factual. Anything with a flat ass end has a portion of that area that is actually holding back the vehicle as in a vacuum situation. A tapered wind flow device smooths out the air flow. A few years ago there were a group of hypermilers that were trying to build tapered cones for the back or their Honda, Toyotas or other fuel efficient vehicles. Some got some amazing fuel mileage numbers.
https://www.wikihow.com/Hypermile
Rams[This message has been edited by blackrams (edited 05-02-2021).]
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williegoat
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MAY 02, 06:55 PM
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The Kamm tail was a compromise between the reduced drag and the unwanted lift of the tapered tail.
A few years later, a guy from Texas did a lot of work on the lift problems.
Look at the ass end of a modern LMP car.[This message has been edited by williegoat (edited 05-02-2021).]
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cvxjet
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MAY 02, 07:44 PM
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Obviously, it would be better to have (Very) gentle taper to the rear- But how would that work on a Pickup? Or a semi? If you have a steep taper it will create lift and drag. Remember the rear of the incredibly ugly 3rd-gen (92-95) Taurus? It was all rounded and tapered....and it's aero was bad......It is better to chop the tail off clean rather than have the air slowly trying to disengage while creating more drag.
On my 1973 Mustang I made an airdam that rammed the air in from directly in front of the radiator >>Below the Bumper<< while the air to the sides was deflected outward....And then I completely blocked off the GRILL- even used foam strips to seal around the headlights and between the grill and the hood. I had driven it in a cross-head-wind once and the front was floating- Uncontrollable above 60 mph; ALL of the air that hit below the hood-line was (Originally) rammed under the hood, which had 3000 square inches of surface- so 1/10 PSI would create 300 lbs of lift!
After my mods I had it up to 95 mph passing 3 semis and 2 cars on highway 97 above Mt. Shasta- it was rock-solid.
If you want to put a 100 foot taper on the back of a semi then you can have better aero- but it will be a ***** to back-up.....
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williegoat
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MAY 02, 08:03 PM
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Here is some food for thought, something to read, or just look at the pretty moving pictures put together by some that you would probably describe as "people with limited Aerodynamic knowledge".
a study from 2007: https://www.osti.gov/servlets/purl/926158
Pay attention to 1:17
Maybe you could call these guys and explain aerodynamics to them. I just don't understand what you are saying, being an old retired gearjammer and stuff.
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blackrams
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MAY 02, 08:11 PM
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| quote | Originally posted by cvxjet:
If you want to put a 100 foot taper on the back of a semi then you can have better aero- but it will be a ***** to back-up..... |
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Just the first time............ 
Rams
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cliffw
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MAY 03, 02:55 PM
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| quote | Originally posted by maryjane:
Does the same hold true in space?
Not 'much' drag other than the pull of gravity, but is it truly zero drag?
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Going into, or with an asteroid belt ? Can you draft an asteroid, or get "push" ?
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theogre
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MAY 03, 08:12 PM
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| quote | Originally posted by cvxjet:
I wanted to state something about Aerodynamics vs Trucks; There has always been the big debate about the tailgate being up or down- either is still (Basically) bad, aero-wise; Two ways to go for improved aero on a pickup truck; A) Install a lid or tonneau cover...This a big improvement.....But by far the best thing to do is to B) Install a camper shell even with the roof of the cab- The flat back-end is (Basically) a Kamm effect situation where the air-flow breaks cleanly from the vehicle....This seems contradictory to people with limited Aerodynamic knowledge. |
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Mythbusters and others including Truck manufacturers has done gate up vs down for years for light trucks and other types...
Gate up and air Roll in the bed and little compress so air moves very well around the rest of the body to get best MPH.
Tonneau cover is close to same.
Gate Down or Off get Worse MPH cause by Drag.
Most to all Bed Caps does Not get best MPG and have other problems.
These act like most Vans and have big flat rear w/ issues of air sucking on the back of truck.
Many that drives on Dirt Roads or in Winter often have a hard time seeing thru back windows on vans, truck w/ caps, and "old school" Station Wagons because low pressure air there drops dust snow etc. Rear glass wipers often don't help for same reason.
While makers of these vehicles have reduce the air flow problems w/ rolled edges etc. still happens.------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave
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