I just increased my 80's MPG for free and you can too! (1 Viewer)
- Thread starter msapers
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Yea i plan on a basket for now its just the bars, I mean they remove easy, but still.
ranma21
Supporting Vendor
If you want best mpg, stay stock height, stock size tire and no roof rack.
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Its hard to haha. I dont care so much about MPG. itd be nice but it is what it is. plus lately weve been DD my GFs 87 camry That thing gets 28mpg and runs 2 weeks off 12 gallons lol
A Prius is a great companion for the 80. Just saying.
That said, we get 15-18mpg depending on how we drive. No third-row seats, no rear seats at all, no interior, period. So it's lighter than a normal 80, probably. But the absolute most important factor regarding mileage is your right foot. The slower you safely go (to a point), the better. Drive at 55mph on the interstate and you can just about make it to 19mpg. We hit 20mpg once. You can also draft at a safe distance behind a slow-moving semi, though this may result in the engine warming up.
There have been many arguments regarding efficiency of the AC vs having the windows down, and for many smaller cars. It turns out that at highway speeds, the AC is more efficient than having the windows down, because at those speeds, aerodynamic drag is the predominant force affecting fuel efficiency. At slower speeds, it's better to have the windows down, since the aerodynamic drag is a function of v^2 (a function of velocity squared).
It is an open question as to whether any of this applies to a vehicle with a drag coefficient (Cd) as high as the 80's must be. The parasitic affects of windows down may only match those of the AC compressor at very high speeds. This is because C_d is probably not increased greatly by opening the windows.
So let's calculate the force on the 80 for fun.
Fd is the drag force of an object, and:
Fd = .5 * Cd * v^2 * ρ * A, where
Cd is the drag coefficient, which we don't know and I couldn't find. According to wikipedia, it's Cd=0.35–0.45. It's an 80, so let's not pretend it's not 0.45 or higher. So we'll take Cd = 0.45. ρ is the density of our fluid, which in this case, is air at 68 degrees Fahrenheit and at sea level. It's equal to 1.2 kilograms per cubic meter; v is our speed (suppose 60kph or 25 meters per second); and finally, A is the area of the front of the 80.
We went outside and took a (very) rough measurement of the 80's frontal area, which was 1.2192m tall * 1.9304m wide. This is 2.353 square meters. This does not include the correction for windshield rake, because a) it's not very steep, and b) it probably changes by a few degrees depending on conditions and whether you're stink-bugging it. This does not include tires or suspension or your 8-inch HIDs and roof rack and the deer you've got dangling from the ARB bumper.
Therefore, we have, at 90 kph, or 25 m/s:
Fd = .5 * 0.45 * (25)^2 * 1.2 * 2.353 is roughly equal to 397.069 Newtons. This is the force your truck must overcome at 90kph to keep moving forward.
Yep, it's a pig. Now pop those windows down and I'm guessing your Cd = 0.5.
So that becomes:
Fd = .5 * 0.45 * (25)^2 * 1.2 * 2.353 is roughly equal to 441.187 Newtons.
So at 90kph, the difference in drag is about 44.19 Newtons if the windows are open at 90kph. When does the AC compressor create a drag equivalent to 44.19 Newtons? Someone who knows those systems will need to chime in, because I don't know that. Bear in mind a lot of these numbers are made up, but it should help put everything into perspective.
That said, we get 15-18mpg depending on how we drive. No third-row seats, no rear seats at all, no interior, period. So it's lighter than a normal 80, probably. But the absolute most important factor regarding mileage is your right foot. The slower you safely go (to a point), the better. Drive at 55mph on the interstate and you can just about make it to 19mpg. We hit 20mpg once. You can also draft at a safe distance behind a slow-moving semi, though this may result in the engine warming up.
There have been many arguments regarding efficiency of the AC vs having the windows down, and for many smaller cars. It turns out that at highway speeds, the AC is more efficient than having the windows down, because at those speeds, aerodynamic drag is the predominant force affecting fuel efficiency. At slower speeds, it's better to have the windows down, since the aerodynamic drag is a function of v^2 (a function of velocity squared).
It is an open question as to whether any of this applies to a vehicle with a drag coefficient (Cd) as high as the 80's must be. The parasitic affects of windows down may only match those of the AC compressor at very high speeds. This is because C_d is probably not increased greatly by opening the windows.
So let's calculate the force on the 80 for fun.
Fd is the drag force of an object, and:
Fd = .5 * Cd * v^2 * ρ * A, where
Cd is the drag coefficient, which we don't know and I couldn't find. According to wikipedia, it's Cd=0.35–0.45. It's an 80, so let's not pretend it's not 0.45 or higher. So we'll take Cd = 0.45. ρ is the density of our fluid, which in this case, is air at 68 degrees Fahrenheit and at sea level. It's equal to 1.2 kilograms per cubic meter; v is our speed (suppose 60kph or 25 meters per second); and finally, A is the area of the front of the 80.
We went outside and took a (very) rough measurement of the 80's frontal area, which was 1.2192m tall * 1.9304m wide. This is 2.353 square meters. This does not include the correction for windshield rake, because a) it's not very steep, and b) it probably changes by a few degrees depending on conditions and whether you're stink-bugging it. This does not include tires or suspension or your 8-inch HIDs and roof rack and the deer you've got dangling from the ARB bumper.
Therefore, we have, at 90 kph, or 25 m/s:
Fd = .5 * 0.45 * (25)^2 * 1.2 * 2.353 is roughly equal to 397.069 Newtons. This is the force your truck must overcome at 90kph to keep moving forward.
Yep, it's a pig. Now pop those windows down and I'm guessing your Cd = 0.5.
So that becomes:
Fd = .5 * 0.45 * (25)^2 * 1.2 * 2.353 is roughly equal to 441.187 Newtons.
So at 90kph, the difference in drag is about 44.19 Newtons if the windows are open at 90kph. When does the AC compressor create a drag equivalent to 44.19 Newtons? Someone who knows those systems will need to chime in, because I don't know that. Bear in mind a lot of these numbers are made up, but it should help put everything into perspective.
Can you put that in american? Lol
That's the trick on the highway. No rack (ever), 33" skinnies, stock height suspension.
It's always 10 mpg around town, except it drops to maybe 9 mpg in the winter.
On the highway, on the level, the truck can regularly achieve 17 mpg with A/C at 70 mph. Go uphill and it drops off considerably.
No, the drag equation works best in metric. Dunno how to calculate it in miles and inches and stuff without converting to metric first. But for some perspective, the bite force of the average human is like 720 Newtons, so it's basically the force of a nibble or something. I don't know, I couldn't find a good comparison, ha.
Awesome, I might have to do that. And I agree, I rarely look at the scanguage avgmpg.. i just enjoy the experience of my rig.
And to piss off some I might add a Boxster engine to a Prius.
How many more MPG should I expect after a apply a Hybrid sticker on the rear window?
Your answer could also be in metric too, it doesn't matter that much because I got an app for that.
Your answer could also be in metric too, it doesn't matter that much because I got an app for that.
Slomo
It's Complicated
I have a completely different approach. I park the 80 during the week and drive a Prius to work!
You're a better man than me Brent. I couldn't do it...
EVER!
I've heard the "break even point" for rolling the windows up and switching the AC on is around 70km/h (44mph), although I'm sure it varies from vehicle to vehicle, etc.
If you're still working at Mission and living in the same place, your commute is a whole lot shorter than mine too!
Let's put it in different terms when I was working over in Scottsdale. Less than one tank, about 10 gallons to drive the 400 miles over there in the Prius. The one time I drove the truck over, I barely made it out of CA before stopping for gas in Quartzite, AZ! It took about 30+ gallons in the truck to get there!
richardlillard1
SILVER Star
You mean Land Cruisers don't get good gas mileage compared to purpose-built economy cars?
What about switching the AC compressor to an electric driven compressor instead of belt driven?
I've fantasized about using a Prius compressor on the 80 before, but lack the technical skills at present time to do so. It would be more efficient, but the main benefit is that you could run the AC in the truck without the engine on. Helpful for sleeping in the truck during the boiling hot Florida summers. Probably a pretty pointless project when it's cheaper and easier to just suffer through the heat, though. There's always the "lay on a tarp in the mud" method of cooling off...
richardlillard1
SILVER Star
So you can put more draw on the alternator, forcing it to suck more horsepower to produce enough electricity to cool you?
What about switching the AC compressor to an electric driven compressor instead of belt driven?
Is that a joke?
Do you think that converting mechanical energy to electrical and back to mechanical is somehow more efficient?
I wonder how much HP an AC compressor uses and how massive an electric motor/alternator it would take...
Crap, we'll need a electric motor-driven alternator to drive our electric compressor!
Oh, wait...
Again, just put a "Hybrid" sticker on your 80. That's all it takes.
