Driving 55mph instread of 65mph -Just hit 32.5 MPG (honda accord)
- Thread starter goodoleboy
- Start date
- Status
But were you still in Kansas, when you looked out the window afterwards?
Here are some pictures. The weather warmed up and got rainy, so I've had to take most of it off, but I stuck some on again for the pictures. There's a problem with dust scratching the paint, so next time I do a test, I'll put a layer of tape on the paint, to protect it, then put the cardboard, or water resistant corrugated plastic, on top.
The gap above the headlight was sealed with a gasket, but the bottom had an open gap. I sealed that with silicone (see arrow in upper.jpg), putting waxed paper under it so it wouldn't stick to the bumper.
This image shows where the fog lights would go on this car. There was a plastic mesh cover over the hole, that let high pressure air inside, causing drag.
This is a picture of somene else's car, and you can see how the fog lights are deeply recessed into the bumper. This was probably done to protect them from damage in case you drive into something, but it also increases drag. You could stretch a sheet of paper across the bumper, rub a pencil along the edges to trace the outline, and then cut out a piece of clear acrylic to cover that hole.
During cold weather, the dark open area under the license plate on this car could be covered, reducing drag.
[ April 21, 2005, 06:23 PM: Message edited by: oilyriser ]
labman, when will you realize that logic and reason has absolutely nothing to do with this!
Seriously, while the aerodynamics streamlining stuff does make good discussion, from an economical sense it is pointless. Chalk it up to a hobby, you're fine. Claim you actually save money, you're only fooling yourself.
I am still in the process of "fine tuning" my scangauge so it gets the same mpg that my calculations with actual milage and gals pumped. I am doing this by changing the calibration for miles per hour (on the scangauge). The scangauge speedometer will be inaccurate as well as the trip length. But right now I'm interested in mpg.
I am then gonna pick a section of highway near my house and by checking instaneous mpg at the same spot vs speed try to come up with fairly accurate mpg vs speed. Preliminary results show about 37 mpg at 60 mph, 40/41 mpg at 55 mph, and 33 mpg at 65. Now this is instaneous milage which means on a trip I won't get this high of milage.
But today on a 230 mile trip on the Pa. Turnpike driving at about 62 my actual mpg was 36.6. I have a 2L, 145 HP Sentra (2001-auto)
I respectfully disagree with the idea that the foglight on that pontiac is causing drag. There should be a "bubble" of air in front of the lens that deflects oncoming air around the bumper. (I assume the fog light lens to be airtight against its surroundings.) The same premise makes some pickup trucks more efficient with the tailgate up: The bed is a bubble invisible to aerodynamics and the tailgate smooths the air back into place with less draft. If I had no foglights, I might consider filling the hole.
The wheel fairings and grill cover I agree with though. I bet they have enough grill opening for 110'F heat to supply enough air for cooling; when it's cooler you can deflect air out and around more. It's actually interesting once air goes through the radiator where it goes next; it can't get out the top or sides so sort of gets forced around the engine and under the floorpan. It's more complicated than I can comprehend, or explain. Removing the weather strip at the rear of the hood, by the firewall, has possible negative consequences (to offset what should be a positive, better cooling) that I cannot quote the source or logic of.
You'll notice in Nascar they run enough grill tape for aerodynamics but not too much or the car overheats. They tweak it during races when they see how hot the cars get. Naturally in Nascar they want the cars going fast and glued to the track; if you're shooting for ultimate economy you might not mind a little "float" in the drive.
In winter, if I had to block off my rad, I'd do it below the bumper where that scoop fairing sits. I'd make a downward wedge out of cardboard. That's where a lot of (possibly uneccessary cold) air enters the rad through on my cars; I might only make it halfway across. That air will get forced out under my floorpan anyway; I might as well do it before it gets more disturbed. Also the engine will warm up slightly faster with less air rushing over it.
The wheel fairings and grill cover I agree with though. I bet they have enough grill opening for 110'F heat to supply enough air for cooling; when it's cooler you can deflect air out and around more. It's actually interesting once air goes through the radiator where it goes next; it can't get out the top or sides so sort of gets forced around the engine and under the floorpan. It's more complicated than I can comprehend, or explain. Removing the weather strip at the rear of the hood, by the firewall, has possible negative consequences (to offset what should be a positive, better cooling) that I cannot quote the source or logic of.
You'll notice in Nascar they run enough grill tape for aerodynamics but not too much or the car overheats. They tweak it during races when they see how hot the cars get. Naturally in Nascar they want the cars going fast and glued to the track; if you're shooting for ultimate economy you might not mind a little "float" in the drive.
In winter, if I had to block off my rad, I'd do it below the bumper where that scoop fairing sits. I'd make a downward wedge out of cardboard. That's where a lot of (possibly uneccessary cold) air enters the rad through on my cars; I might only make it halfway across. That air will get forced out under my floorpan anyway; I might as well do it before it gets more disturbed. Also the engine will warm up slightly faster with less air rushing over it.
I didn't actually measure the wind direction near the fog light, but assumed the air would be flowing sideways near the outer edges of the bumper, so there might be some drag.
An interesting thing to calculate is the energy needed to push a side mirror through the air for a million miles at 60 mph, such as on a truck. A video camera system would have much less drag than a mirror.
If the mirror causes 4 lbs of drag, moving at 60 mph (88 feet per second) gives a power of 352 ft-lbs/sec. A million miles, at 60 mph, takes 60 million seconds. So, the mirror will consume 60 million X 352 ft-lbs of energy, or 21.12 billion ft-lbs.
1 BTU = 778.3 ft-lbs
A gallon of diesel fuel has 150,000 BTU.
21.12 billion / 778.3 = 27.14 million BTU
27.14 million / 150,000 = 181 gallons of diesel fuel, if you can get 100% of it's heat energy converted into motion. But the engine and drivetrain is only about 35% efficient, so you really need 181/0.35 = 517 gallons of fuel to move that mirror a million miles.
An interesting thing to calculate is the energy needed to push a side mirror through the air for a million miles at 60 mph, such as on a truck. A video camera system would have much less drag than a mirror.
If the mirror causes 4 lbs of drag, moving at 60 mph (88 feet per second) gives a power of 352 ft-lbs/sec. A million miles, at 60 mph, takes 60 million seconds. So, the mirror will consume 60 million X 352 ft-lbs of energy, or 21.12 billion ft-lbs.
1 BTU = 778.3 ft-lbs
A gallon of diesel fuel has 150,000 BTU.
21.12 billion / 778.3 = 27.14 million BTU
27.14 million / 150,000 = 181 gallons of diesel fuel, if you can get 100% of it's heat energy converted into motion. But the engine and drivetrain is only about 35% efficient, so you really need 181/0.35 = 517 gallons of fuel to move that mirror a million miles.
I realise it is slightly off-topic, but how do you change MPH settings in ScanGauge? I fine-tune its MPG readings by varying the engine size coefficient which does not affect MPH or distance readings...
I would like to know also. If I were to fine tune my scanguage MPG readings, I would also vary
the engine size coefficient, as you are doing.
Would seem as if a "changed MPH setting" would throw off the trip mileage.
OOPS, to edit, just saw this in ALs post:
Yea it does throw the trip off. But that's the breaks. Changind the size of the engine didn't change the mpg. It probably only works for GM vehicles. But anyway I corrected my miles down to -13% and I'm now gonna wait to see what's happening. The other thing is that -3% made me agree with my trip meter installed in my car (milage) so with 13 percent..if Scan gauge says I went 100miles I just tack on 10% more.
My scangauge still doesn't turn itself on so I have to press "Home". But that's no big deal.
I love this gizmo
goodoleboy, I consistently average better that 35mpg cruising the interstates at 70mph with the AC off in my 2001 Accord (same 2.3L as yours). Sounds like it's time for you to change your air filter and plugs.
I'm currently at 142,000 miles plus.
[ April 25, 2005, 02:51 PM: Message edited by: mike1qaz ]
Mike brings up an issue that I always have wondered about. I owned a Volvo 960 at one time and got around 22-23mpg which I thought was OK for that size car. I was visiting a Volvo forum and a guy claimed that he usually got over 30mpg. I chimed in and said that people often claim higher mileage than they actually get, due to rounding of their calc or not actually doing an accurate calc. So, the guy emails me his maintenance log for the life of the car. He logged the amount of the fill-up for the 90k that he owned it. He proved me wrong! I still cant understand the large discrepancies that people get for mileage on the same car.
We got 36 mpg (well 35.9 and 36.1) in two 2005 Chevy Cavalier 5 speeds on a recent caravan. One started the trip with 2500 miles and the other had 1500 miles. Mine had M1 5w30 and cruise control. I got the lower MPG. Hmmm. I do have a lead foot from the rest stops though...
It also matters where the car is driven. If your in the middle of Kansas your going to get better mileage than someone that living in the mountains of WVA. Those hills make a big difference to your gas mileage. When I make a run from Pittsburgh to Naples Fl in my 87 745 Turbo I always get the best gas mileage from Charlotte to Naples. The mileage from Pittsburgh to Charlotte is always 2 to 3 mpg less than from Charlotte to Naples. The flip side to that is the car being driven with the AC on or off more than someone else. Someone driving around Brownsville Texas is probably running the AC a lot more than someone living in Chicago Ill. You have to compare Apples to Apples and Oranges to Oranges.
I read that post on the 960 and I'm hoping I can get that kind of mileage out my newly acquired 97 960 (67K miles) I'm still on my 2nd tank of gas since Jan. so I have no idea what it is really getting in mileage.
When I make my run to Florida 1177 miles I make it in 18.5 to 19 hours running straight through.
Usually with stops I average 63 mph running the speed limit all the way down. The difference between running 55 to 60 mph and running the speed limits would mean another 2.5 to 3 hours in time with a savings of maybe $6.00 in gas each way. That $2.00 per extra hour on the road is not worth the extra time driving. There is no way I would want to make the drive between Ocala and Naples on I-75 at 55 mph. Its over 3.5 hours now at 70 mph. At 55 mph I'd have to add another hour
to my trip just on that 250 mile stretch. And after 15 to 16 hours on the road coming from Pittsburgh another hour is a killer on the mind.
Now I do advocate driving slower on shorter trips of an hour or less to save gas. I would never expect someone to drive 55 mph on a 200 mile or longer trip. Heck our time is worth more that the amount of gasoline saved by driving slower on those longer trips.
Usually with stops I average 63 mph running the speed limit all the way down. The difference between running 55 to 60 mph and running the speed limits would mean another 2.5 to 3 hours in time with a savings of maybe $6.00 in gas each way. That $2.00 per extra hour on the road is not worth the extra time driving. There is no way I would want to make the drive between Ocala and Naples on I-75 at 55 mph. Its over 3.5 hours now at 70 mph. At 55 mph I'd have to add another hour
to my trip just on that 250 mile stretch. And after 15 to 16 hours on the road coming from Pittsburgh another hour is a killer on the mind.
Now I do advocate driving slower on shorter trips of an hour or less to save gas. I would never expect someone to drive 55 mph on a 200 mile or longer trip. Heck our time is worth more that the amount of gasoline saved by driving slower on those longer trips.
Ouch.
I got 25mpg on my Grand Cherokee.. 70mph... the key.. DON'T USE THE AC!!!! I hit 24-25mpg this past weekend, with strong winds. Not bad for a Jeep.
I made a long interstate drive a couple of months ago and was getting 28 MPG in my '04 Deville at the posted speed of 70. I was pleased but as an experiment dropped my speed to 55 and on the next tank got a tad over 33 MPG. The only problem was I was having to drive looking in the rear view mirror too much. Driving 55 can be dangerous.
- Status
Similar threads
