Data on effects of weather

[TheEnemy]

bwilson, is the decrease after 85f due to more ac use, or is it something else?

[gone-ot]

...I did similar data collection with my 2009 Vibe while driving to (6AM)/from(6PM) work, and got similar results: (1) AM temps colder than PM temps; (2) AM winds less than PM winds; (3) AM mpg's lower than PM mpgs; (4) AM slope UP-hill and PM slope DOWN-hill (2300' to 2600' over 26 miles).

...however, the BIGGEST change was WIND & DIRECTION. In AM winds were almost always none, but in PM they were always higher, but often in diametric different directions--sometimes WITH my direction, sometimes AGAINST my direction.

[Diesel_Dave]

R^2 is the coefficient of determination. R^2 = 0 means absolutely no correlation. R^2 = 1 means perfet correlation. Basically, it's just higher the R^2 = higher the correlation.

Here the wikipedia definition:
Coefficient of determination - Wikipedia, the free encyclopedia

[Diesel_Dave]

TheEnemy,

The data is ok, but I agree that, theoretically, it doesn't agree with the other data.

To me that just means that there were other factors which canceled out whatever effect winds speed had.

[bwilson4web]

Originally Posted by TheEnemy

bwilson, is the decrease after 85f due to more ac use, or is it something else?

It was AC. When the humidity and temperatures approach each other, there is a serious health risk from a sleepy driver and heat prostration. I can do through the 80s and even 90s if it is dry and no direct sun (aka., I'm on the shady side.) But I don't like to get so hot that I become sluggish and inattentive.

When I have to use AC, I take the higher speed route as this reduces the relative AC contribution. Regardless of speed, the AC uses a fixed amount of power limited by the compressor, power drain. At slow speeds, the AC becomes the predominate load easily equaling the fuel burned to get the car to its destination. The mileage impact can easily double the fuel rate of burn at slow speeds. At higher speeds, the AC becomes a smaller fraction of the load so the mileage more closely approaches the highway mileage. Just make sure you're not going so fast that the engine has to go in especially fuelish power regions.

What I'll do is turnoff the AC compressor when stopped and let the fan recirculate the air and keep it off until I get back to speed. Then I enable the AC to bring the cabin back to tolerable. If coming to a stop, I'll turn off the AC so the ICE can stop while I slow down.

Bob Wilson

[slowmover]

Excellent thread. I was combing your posts after you posted your 1000-miles-per-tank thread to see what the truck spec was as well as relative climate and terrain. Wow, this is waaay beyond what I hoped to find.

I post frequently on CTD boards about FE, and what little interest there is is generally subsumed by "what magic box can I buy (that will painlessly increase my FE)?" The issues of climate & terrain have to factored just as much as truck specification (4WD versus 2WD, manual vs. auto trans, SRW vs DRW) before we ever get to, say, commercial vs. personal use and then finally to questions about driver skill (tire & brake life, for instance).

Just to establish a baseline for a possible comparison a whole buncha stuff has to be eliminated.

Maybe some aero will help. Maybe.

Rolling resistance issues alone (especially coupled to sloppy front end and steering components) are make-or-break on heavy pickup trucks.

So it's great to see clinmate/terrain being addressed. Now I have an idea of how to do it. Thanks!!

.

[slowmover]

Originally Posted by Old Tele man

...

...however, the BIGGEST change was WIND & DIRECTION. In AM winds were almost always none, but in PM they were always higher, but often in diametric different directions--sometimes WITH my direction, sometimes AGAINST my direction.

With the vehicle I drive, and where I live, the wind is also the predominant predictor, the temps can be quite constant. As I am not a commuter (yet another differential between different drivers in re vehicle use) the winds of this area -- much higher than most of the US (we are a wind power producer and wind sailing "destination") -- and the lack of terrain change, it factors highest. Steady 20-30 mph winds with gusts 1.5 to 2X that much will do that.

Question for others: One sees other diesel drivers complain about "winter fuel" (in the areas where necessary) being a factor in reduced FE from October through about May. Based on an above chart (bwilsons long term graph) I have thought for some time it has to do with intake temperature even for a turbodiesel (plus coolant temps).

Is there a "correction" (as with HP production at altitude) for temperatures? I am wondering if one can compare an otherwise given vehicle across differing climates (leaving altitude alone for now)? Or is there too much to take into consideration? My question may be badly put. I am interested in prediction. Thanks.

(And, like unto you, bwilson, I did my science/engineering with "ID Rocks Geology, 401" and "Physics for Non-Physics Majors (+ a touch of stats), 401" as a double-major History & Philosophy student, ha! Keep the innumerate away from formulae beyond parsing language with formal logic!! Gerrhammers E-Z [especially in a society devolving to illiteracy]).

.

[Diesel_Dave]

IMO, in a turbodiesel lower intake temps generally increase engine efficiency. That being said, I think there may be a point where it can go so low that it hurts. You have to keep in mind that temperature affects many things in different ways. It affects your combustion effeciency (both air temp and fuel temp). It affects your heat losses. It affects your frictional losses (both engine and drivetrain). It affects your tires and rolling resistance, and it also affects your aero (cold air is more dense). Keep in mind as well that some of those factors affect you differently depending on your trip. For example, if you have a short trip the time it takes everything to warm up (coolant, oil) is really going to hurt you. If you drive at high speeds the aero effect is going to play a bigger role, etc.

Anyway, I'm still keeping records and I'll try to update eveyone later when I have more data.

[dcb]

Originally Posted by bwilson4web

...there is a serious health risk from a sleepy driver and heat prostration...

Ok, now you are being Satan Nobody has ever tried to paint AC as safety equipment, that is just a little too soft for me. AC is the first thing I disable on my cars (so I can run the defroster fan w/out using the compressor)

[bwilson4web]

Originally Posted by dcb

Ok, now you are being Satan Nobody has ever tried to paint AC as safety equipment, that is just a little too soft for me. AC is the first thing I disable on my cars (so I can run the defroster fan w/out using the compressor)

It is probably just me. Strange factoid, my average body temperature is 97.6 vs 98.6 so it may be something about my biology that makes me relatively heat intolerant.

I grew up in Oklahoma and in summer weather my parents and brothers were fine, I would get sick, throw-up and suffer the symptoms of heat prostration. My wife likes it hot but it brings me to the edge. So at work, I'm known as the guy who has a pedestal fan in his office and uses it.

Bob Wilson