Please check my Calculations

IIRC Honda didn't get that, the EPA did. Overall my '03 Accord EX sedan
w/automatic has gotten 26 mpg (12,500 miles). I consistently get > 30
mph on the highway, with a max going to NC of 34 mpg (absolutely NO city
driving & no A/C).

 

You are getting terrible mileage out of your 04 Accord. 8km/l (or
12.5litres/100km) is 18 mpg, which is far below the fuel efficiency of
an Accord 4-cyl.

My 01 Prelude (which is far less fuel efficient than a 04 Accord)
consumes about 11 litres/100km (21.4mpg), in city driving. On the
highway I am getting about 9 litres/100km (26.1mpg). My old 94 Accord
EXR was getting slightly better numbers than my 01 Prelude.

So there is either something wrong with your car, or you are a very
agressive driver.

Cosmin

 

You are getting terrible mileage out of your 04 Accord. 8km/l (or
12.5litres/100km) is 18 mpg, which is far below the fuel efficiency of
an Accord 4-cyl.

My 01 Prelude (which is far less fuel efficient than a 04 Accord)
consumes about 11 litres/100km (21.4mpg), in city driving. On the
highway I am getting about 9 litres/100km (26.1mpg). My old 94 Accord
EXR was getting slightly better numbers than my 01 Prelude.

So there is either something wrong with your car, or you are a very
agressive driver.

Cosmin

 

What I'm seeing generally supports this. For the interested car enthusiast, see
for example:

1.
http://wahiduddin.net/calc/calc_hp_dp.htm and
http://wahiduddin.net/calc/cf.htm, along with the pointers from these sites.

2.
"The correlation between altitude and power goes like this: a gasoline engine
loses three percent of its horsepower output for every thousand feet of
altitude, a function of relative oxygen scarcity as the altimeter needle
climbs."
http://www.caranddriver.com/article.asp?section_id=4&article_id=8074 But again,
this was for racing cars, presumably operating at maximum possible horsepower.

For the same temperatue and relative humidity but two different altitudes, air
pressure varies very close to perfectly inversely with altitude, at least for
altitudes from sea level to 15,000 feet. I believe the percent oxygen that air
contains is fairly fixed with altitude (again, assuming constant temperature and
relative humidity).

After experimenting with the numbers and calculator above, the 3% hp lost/1000
feet of altitude appears to me to be a "not bad" rule of thumb.

So small as to be negligible, at least for my move from sea level to a mile
high.

 

What I'm seeing generally supports this. For the interested car enthusiast, see
for example:

1.
http://wahiduddin.net/calc/calc_hp_dp.htm and
http://wahiduddin.net/calc/cf.htm, along with the pointers from these sites.

2.
"The correlation between altitude and power goes like this: a gasoline engine
loses three percent of its horsepower output for every thousand feet of
altitude, a function of relative oxygen scarcity as the altimeter needle
climbs."
http://www.caranddriver.com/article.asp?section_id=4&article_id=8074 But again,
this was for racing cars, presumably operating at maximum possible horsepower.

For the same temperatue and relative humidity but two different altitudes, air
pressure varies very close to perfectly inversely with altitude, at least for
altitudes from sea level to 15,000 feet. I believe the percent oxygen that air
contains is fairly fixed with altitude (again, assuming constant temperature and
relative humidity).

After experimenting with the numbers and calculator above, the 3% hp lost/1000
feet of altitude appears to me to be a "not bad" rule of thumb.

So small as to be negligible, at least for my move from sea level to a mile
high.

 

Thanks,

I am a fairly aggressive driver (not that much, tho), and the kind of
driving is pure stop & go. Absolutely no highway. (Not a good combo).

I tried "premium" gas to see if it helped. It didn't, so I am back to
regular now.

Still, I'll talk to the dealer when it goes to its 5000K checkup.

-Indirecto

 

Thanks,

I am a fairly aggressive driver (not that much, tho), and the kind of
driving is pure stop & go. Absolutely no highway. (Not a good combo).

I tried "premium" gas to see if it helped. It didn't, so I am back to
regular now.

Still, I'll talk to the dealer when it goes to its 5000K checkup.

-Indirecto

 

Hey Yahmed,

Yeah, I'm trying. If you're interested you can see my post awhile back
(http://tinyurl.com/3ceyd). I'm using tanks of gas burned during my commute
as the benchmark (its about 6 miles of residential drives and roadways, and
10 miles of expressway I guess). I just added some more data to that
thread. I'm not certain that anyone is too interested though!

The problem is I'm not sure I'm going to be able to provide statically
meaningful data. There are a lot of variables (outside temp, if I use the
car for other stuff besides the commute, if I drive more gingerly or more
aggressively etc.)

-Arthur

 

OK, I looked at this further, & at meaningful automotive altitudes I
agree you can loosly approximate it at 3% per thousand feet. It has a
much bigger effect at higher altitudes. My bad.

JM

 

OK, I looked at this further, & at meaningful automotive altitudes I
agree you can loosly approximate it at 3% per thousand feet. It has a
much bigger effect at higher altitudes. My bad.

JM

 

Hey, no bad. I didn't think anything meaningful happened at high altitudes. On
the contrary, your first observation about the consensus where you live being
"hp lost is about 11% at 3000 feet" is a great guideline.

I figure most folks who have any Western mountain driving experience know the HP
is going to get worse--but not unmanageable--at the usual driving higher
altitudes. It's better at lower altitudes. So it seems a bit intuitive that HP
variation with altitude is very crudely (but still usefully) linear.

Shoulda figured this from my summer running a little cross-country near Boulder,
Colorado.

 

Hey, no bad. I didn't think anything meaningful happened at high altitudes. On
the contrary, your first observation about the consensus where you live being
"hp lost is about 11% at 3000 feet" is a great guideline.

I figure most folks who have any Western mountain driving experience know the HP
is going to get worse--but not unmanageable--at the usual driving higher
altitudes. It's better at lower altitudes. So it seems a bit intuitive that HP
variation with altitude is very crudely (but still usefully) linear.

Shoulda figured this from my summer running a little cross-country near Boulder,
Colorado.