Drop in fuel mileage

Ok, here is a follow-up. I went for a 150 mile ride yesterday. Over a
mountain pass at maybe 8500 feet, starting in SLC at maybe 4700 feet.

Mileage is back up in the high 40+mpg range. Up from maybe 34 mpg on the
previous tank. I switched from mid-grade fuel to the highest octane. The
trip conisisted of half freeway / half twisty mountain roads. Speeds ranged
from 70-90mph, slower in the twisties.

I will have to assume the low fuel mileage tank was just an anomoly or
perhaps bad fuel.

I always check my mileage at every fill up, so I will continue to monitor.
Good chance it is time for a tune up anyway.

Bryan

 

"Altitude? My fuel-injected Triumph 955i gets 40-42 mpg at sea level
and almost 50 mpg at 4000 ft elevation. Thin air requires less fuel
to maintain proper air/fuel mix. Less power, but better mileage. "

And also less aerodynamic drag due to the lower air density.

 

---------------------------------------^^^^^^^^^^^^^^^^^^^^
Sounds like something for nothing or Sounds like something for nothing
or perpetual motion (see below)

This is a very short sited explanation. Maybe, just maybe, the mapping
on yout 955i is set too rich at sea level and too lean at altitude.
It's a known fact that without turbocharging or supercharging that
piston engines ALL lose power at altitude. Sure wind resistance is
lower but unless you have more wing area, it takes higher power
settings to keep you aloft. What's this got to your 955i? Drag vs HP
settings, that's what.


Bob Nixon, Chandler AZ
01 Sprint ST "RED" 50K miles
http://bigrex.net/pictures

 

I have been getting 10-20% less distance on Utah's gas every time i pass
thru. Oregon's fuel is getting worse, too.

 

They're likely throwing in increasingly more alcohol or MTBE thus
reducing the BTUs/gallon and therefore reducing fuel economy due you
having to run at higher throttle settings (higher oxidations levels).
IOW, they're screwing us more than by just raising the prices. And
they can get away with it in the name of cleaner burning (oxygenated
fuels). Blame in on greed via the oil companies. IOW, if the price per
barrel goes up $1.00 then everyone in the fuel chain has an excuse to
eek out more profits. Basic supply & demand principles. It's gonna get
worse, right TTT?


Bob Nixon, Chandler AZ
01 Sprint ST "RED" 50K miles
http://bigrex.net/pictures

 

It's true that reduced air density affects the dynamic pressure of air
acting upon wings and fuselage, but pilots at cruising altitude are
actually setting their throttles at 80%, leaning up their mixtures for
economy and trimming the elevator to reduce angle of attack, decreasing
induced drag.

Yeah. What does it have to do with a wingless vehicle?

In a piston engined vehicle the reduction in aerodynamic drag and the
loss of horsepower due to decreased air density cancel each other out.
The reason for flying in the stratosphere has to do with smoother air
and the better efficiency of the gas turbine engine in the cooler
temperature up there.

 

This is sort of true up to maybe 10,000ft with a NA piston engine.
Above that, fuel economy will drop without turbo charging.

Gas turbines are a different story. More engine air volume and like
you said much colder inlet temps equal greater efficiencies up to 40K
ft. (above that air temps don't drop anymore) Much higher and you must
have a ramjet to take advantage of the lower air density. (like the
dual stage SR-71).

Then, the higher you go the faster you go and skin temps balance due
to the thinner air. IOW, the Mach 3.3 top speed of the A-12. SR71
blackbird was for classification reasons or an artificial ceiling
based on 80,000 ft. Above that, who knows?, -


Bob Nixon, Chandler AZ
01 Sprint ST "RED" 50K miles
http://bigrex.net/pictures

 

The aerodynamic drag at 5000' msl is nominally 75% of the drag at sea
level assuming a standard atmosphere and all other conditions the same.

In addition an engine will have less pumping loss (throttling loss) at
altitude although this is a factor of interest to mostly piston
airplane drivers. For that reason engines will be most efficient (i.
e. have the lowest specific fuel consumption) at the altitude that
allows them to operate with the throttle wide open and fully leaned
out. This may not be the best range for an airplane however as the
airframe aerodynamics have a more complex effect on things.

In an airplane, the aerodynamic drag goes up with speed, is at a
minumum at a moderate speed, and goes up again as the speed is reduced
to stall.

On a motorcycle, the drag only goes up with speed squared.

 

It ain't gonna get better...until we get a decent recession going anyway.
And you want to know what we are ALL going to notice this winter? Higher
natural gas prices, you heat your house with it, or your utility generates
its electricity with it, and things are going UP!

 

Yup just heard natural gas up here is going to $12.00 & change a
gigajoule up here next month. I think they said that is three times
what it cost in October last year.

I hope it's not too cold next month.
--


Don
RCOS# 7

2000 - Yamaha Venture Millennium Edition

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http://www3.telus.net/public/dbinns/calgarybrowning.htm

 

You might have to start looking at coal as a fuel. It is a resource that
is plentiful and cheap. The tree huggers won't be happy and you might
have to scrounge a bit to get it, but you will be warm this winter.

pierce

 

Scrounge, hell, Alberta is the coal capital of North America. I think
most of it is shipped overseas.

I must have a vision problem cuz I just can't see myself shoveling
coal all winter.
--


Don
RCOS# 7

2000 - Yamaha Venture Millennium Edition

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Buffalo chips or cow pies! Cheap! Doesn't annoy the tree huggers! Burns
well, gives off lots of heat and..... bonus! They're aromatic!

 

If everyone starts burning coal, it will accelerate global warming,
meaning you won't need heating in winter in years to come......a win,
win situation (unless you own beachfront property)

Three times the price in a year is too steep for gas. There will be some
cold pensioners this winter. Maybe one of them will shovel for you for a
bit of cash to pay their bills......

 

All kidding aside it is a tremendous increase in a commodity you can't
do without. We do have a government subsidy for the winter months but
it doesn't kick in until November.
--


Don
RCOS# 7

2000 - Yamaha Venture Millennium Edition

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Blame in on greed via the oil companies. IOW, if the price per

Me too. Plus, in a meeting today, me and boss were speculating on $20/Mcf
based on what we are hearing coming up outta the Gulf.

 

Can anyone say Powder River Basin Baby!

 

And you can gaurantee any subsidy won't cover the price rise.Home
heating is more critical than your V8 running out of petrol, especially
if it snows where you live (The only snow around here stays on the
mountain where it belongs) and you are on a fixed income. Time to but
some shares in the gas company?


We are having an 'electricity crisis' every year....because demand
'might' go up over winter, and the lake levels 'may' get low, they put
the price up to discourage people using too much. We have coal and oil
fired power stations, but getting resource consent from the govt. to
fire them up is a nightmare. Everyone wants their TV, video, stereo,
computer, fridge/freezer, heaters, hot water etc. etc., but when it
comes to using fossil fuels to generate power, it's a big no-no.

 

I wonder what would happen if you found a geothermal vent on your
property. The heat is free, there is near zero pollution and everyone is
happy. You would make the cover of "Green Magazine". Wealth, fame,
women! What more could you ask for. >)

pierce

 

Everyone wants their TV, video, stereo, computer, fridge/freezer, heaters,

Well, except for the 75% of the countries TOTAL electricity which comes from
burning fossil fuels. 75% seems like a big number for the worlds largest
power consumer for it to be that much of a "no-no". More difficult to build
nowadays perhaps, but it still happens, its just more difficult.