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11-17-2021, 07:11 PM - 2 Likes   #2536
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QuoteOriginally posted by bogwalker Quote
Nice. I'm a nerdy engineer, so I also have a spreadsheet of all my fill-ups (computerized since 2006, on paper before that).
I didn't even know you could still buy a 1.2 liter engine car in the U.S!
I ran some experiments on my commute to see how temperature affected mpg. I had a Scangauge that plugged into the OBD-II port, so I could get the mpg for the trip (my new car displays that on the screen, but it wasn't a thing in 2006). Nothing like driving in 0'F weather without using the heater, just to get a new datapoint in my graph
I used to use a bluetooth OBDII dongle and smartphone app on my Metro to do the same thing. It was amazing how much real-time data you could get from a car made in 1996! Also addicting, to keep track of all those data points to try and see how you could get just a little bit more efficiency out of it. I've calmed down a bit since then. The Mirage doesn't have anything colorful or animated to monitor efficiency like many other cars now, but it does have a basic cumulative MPG display on the trip meter. It's only off by about 5% compared to the real mileage-to-gas-pump calculations (some other car's efficiency displays are wildly optimistic). I still enjoy trying to keep that number up on road trips.

My mileage on summer trips is always better than in the winter, in spite of the air conditioning. Something to do with the density of the air? I always get more mileage at higher elevations, too, even with the lower-octane gas they sell there.


QuoteOriginally posted by MarkJerling Quote
That's pretty impressive specs. I bet I cost more than that per mile on my bicycle!
Oh, given how much you can spend on a bike, I believe it!

The bike I'm riding to work now has a spreadsheet, too. I built it last year from the frame up, and kept track of where I bought each part, how much I paid, and when. It was $1,040.63 total. After 1,896 miles on the bike as of tonight, if I compare and include the car's purchase price and insurance, the bike is about a quarter of the cost per mile so far. But that's not a very fair comparison when the car has so few miles on it yet.



11-17-2021, 08:08 PM   #2537
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QuoteOriginally posted by scratchpaddy Quote
The bike I'm riding to work now has a spreadsheet, too.


Why am I not surprised!
11-17-2021, 10:20 PM - 3 Likes   #2538
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QuoteOriginally posted by scratchpaddy Quote
given how much you can spend on a bike
The cost of the bike is cheaper when you use paint left over from the car's hub caps.
11-18-2021, 04:16 AM   #2539
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QuoteOriginally posted by Mooncatt Quote
That's a negative. The compressor has a clutch that fully disengages the compressor when you turn the a.c. off.
But the pulley has mass, and the belt has friction where it runs in the sheaves. So even when the clutch is disengaged, there is still a parasitic load.

Also, even with the air conditioning switched off, the system still cycles on and off to circulate the refrigerant and compressor lubricant. A compressor wouldn't last very long otherwise.


The only way to do a true comparison would be to remove the belt when running with the air conditioning off and the windows down.

11-18-2021, 04:25 AM   #2540
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QuoteOriginally posted by Racer X 69 Quote
But the pulley has mass, and the belt has friction where it runs in the sheaves. So even when the clutch is disengaged, there is still a parasitic load.



Also, even with the air conditioning switched off, the system still cycles on and off to circulate the refrigerant and compressor lubricant. A compressor wouldn't last very long otherwise.





The only way to do a true comparison would be to remove the belt when running with the air conditioning off and the windows down.
Pretty sure my compressor only runs when AC is on. It is generally recommended to run the AC once a month or so for lubrication. The belt on mine also runs the alternator and the power steering.

11-18-2021, 04:37 AM - 1 Like   #2541
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QuoteOriginally posted by scratchpaddy Quote
I used to use a bluetooth OBDII dongle and smartphone app on my Metro to do the same thing. It was amazing how much real-time data you could get from a car made in 1996! Also addicting, to keep track of all those data points to try and see how you could get just a little bit more efficiency out of it. I've calmed down a bit since then. The Mirage doesn't have anything colorful or animated to monitor efficiency like many other cars now, but it does have a basic cumulative MPG display on the trip meter. It's only off by about 5% compared to the real mileage-to-gas-pump calculations (some other car's efficiency displays are wildly optimistic). I still enjoy trying to keep that number up on road trips.

My mileage on summer trips is always better than in the winter, in spite of the air conditioning. Something to do with the density of the air? I always get more mileage at higher elevations, too, even with the lower-octane gas they sell there.
Cars have had electronic control modules since the late 1970s. Sure they were stand alone "dumb" systems, but data could be extracted real time if a person wanted to go to the trouble.

Today the fuel economy numbers are extracted from the pulse width modulation of the fuel injectors. The ecm calculates how much fuel passes, compares that to vehicle speed, distance traveled, throttle position, and engine load (calculated by either the mass airflow sensor, a manifold absolute pressure sensor, or a barometric pressure sensor depending on the configuration).

When calculating fuel economy manually, even then there will be error, as one cannot always refill the tank with exactly to same amount each fill-up.

When I worked at PACCAR doing product test and development, we ran fuel economy testing on heavy trucks. A calibrated fuel tank was used, the fuel was weighed before and after each phase of the test, atmospheric conditions were monitored, recorded and factored into the fuel consumption. The trucks were outfitted with calibrated speedometers and odometers (in addition to a wide array of other testing and recording instrumentation), and the route was carefully planned and every effort was made to duplicate the conditions.

We even weighed the truck, trailer and load before and after each test.
11-18-2021, 04:37 AM   #2542
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I never turn my aircon off.

I once got in a car where the owner had never run his aircon (to save money !).

I got straight out.....it smelled of old socks.

11-18-2021, 04:40 AM   #2543
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QuoteOriginally posted by slartibartfast01 Quote
Pretty sure my compressor only runs when AC is on. It is generally recommended to run the AC once a month or so for lubrication. The belt on mine also runs the alternator and the power steering.
Start the car, open the hood (bonnet), and observe the compressor clutch with the air conditioning switched off.

If the clutch doesn't cycle on and off every 30 to 60 seconds, something is not right. A low refrigerant charge, or a malfunctioning valve in the system can cause this.
11-18-2021, 06:02 AM   #2544
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Spend money on lenses, not cars.

I helped select a tiny, blue 2013 Toyota Prius C for my son. Since he is a pipeline welder's helper, he travels all over the country, and I figured the gas mileage would be great for him. The mileage was/is great, but the other pipeline welders and helpers ridiculed him severely for driving a Prius even to the point of questioning his manhood. Not wishing him to have to continue enduring such taunting, I gave him my full-sized pickup and took the Prius for myself. We bought it used at around 30,000 miles, and now it is up to 98,000. The little car is comfortable, maneuverable, parkable, economical, reliable, and not too bad to look at, although some people driving big SUVs and pickup trucks do tend to look down on me, physically as well as figuratively. It is the perfect little car for in-town trips, but for two people I have found it both comfortable and economical to drive out of town as well. Mileage is fantastic, from 42 mpg up to 65mpg, mainly depending upon the route and distance driven. Storage for this hatchback is quite enough for grocery shopping and more. You can carry a fairly large camera collection in the hatchback luggage area. For large items, the back seats fold down, and I have hauled stacks of garden trellises, garden mulch, fertilizer, etc. Reliable? No repairs of any kind since I got the car, only replacement of soft parts--wipers and brake pads only. The light weight of the car means that tires seem to last forever. Body style is great--it does not have the nerdy "woke" look of its larger siblings nor its cousins from Honda. The vehicle has a 99 hp engine so does not accelerate with alacrity and is way slower than the Corvette and other "boy racer" vehicles. However, I have only found the modest acceleration annoying when starting off when headed up hill. You know, of course, that folks tend to adjust their driving habits based upon how rapidly their vehicle accelerates. I tend to wait for longer breaks in the traffic than folks with more powerful cars. The only bad thing is that the avaricious Ohio politicians have begun charging a $100/year surcharge on license tags to reclaim a part of the state's lost tax revenue on gasoline, a bit unfair I think because the surcharge does not apply to high mpg cars that are not hybrids. If you are of a thrifty and practical tendency, you will love this little car, and I heartily recommend it to you. At the age of 81, I suspect this little car will carry me all the way on out.
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11-18-2021, 08:08 AM   #2545
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QuoteOriginally posted by Racer X 69 Quote
Start the car, open the hood (bonnet), and observe the compressor clutch with the air conditioning switched off.

If the clutch doesn't cycle on and off every 30 to 60 seconds, something is not right. A low refrigerant charge, or a malfunctioning valve in the system can cause this.
Not sure what kind of cars you've driven, but I've never had a car that operated this way. Not even when brand new. The only exception is if running the defroster, but that's because the purpose of that is to quickly clear fog from a window. Yes, there is a small parasitic loss when the clutch is disengaged, but it's very minimal and unlikely something you can calculate.
11-18-2021, 09:36 AM - 1 Like   #2546
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QuoteOriginally posted by Mooncatt Quote
Not sure what kind of cars you've driven, but I've never had a car that operated this way. Not even when brand new. The only exception is if running the defroster, but that's because the purpose of that is to quickly clear fog from a window. Yes, there is a small parasitic loss when the clutch is disengaged, but it's very minimal and unlikely something you can calculate.
Every vehicle I have owned with air conditioning does this, for the reasons I explained.

Oh, and I am a journeyman mechanic, with over 30 years of experience, and many certifications, including air conditioning.
11-18-2021, 09:39 AM - 2 Likes   #2547
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QuoteOriginally posted by ivanvernon Quote
I helped select a tiny, blue 2013 Toyota Prius C for my son. Since he is a pipeline welder's helper, he travels all over the country, and I figured the gas mileage would be great for him. The mileage was/is great, but the other pipeline welders and helpers ridiculed him severely for driving a Prius even to the point of questioning his manhood. Not wishing him to have to continue enduring such taunting, I gave him my full-sized pickup and took the Prius for myself. We bought it used at around 30,000 miles, and now it is up to 98,000. The little car is comfortable, maneuverable, parkable, economical, reliable, and not too bad to look at, although some people driving big SUVs and pickup trucks do tend to look down on me, physically as well as figuratively. It is the perfect little car for in-town trips, but for two people I have found it both comfortable and economical to drive out of town as well. Mileage is fantastic, from 42 mpg up to 65mpg, mainly depending upon the route and distance driven. Storage for this hatchback is quite enough for grocery shopping and more. You can carry a fairly large camera collection in the hatchback luggage area. For large items, the back seats fold down, and I have hauled stacks of garden trellises, garden mulch, fertilizer, etc. Reliable? No repairs of any kind since I got the car, only replacement of soft parts--wipers and brake pads only. The light weight of the car means that tires seem to last forever. Body style is great--it does not have the nerdy "woke" look of its larger siblings nor its cousins from Honda. The vehicle has a 99 hp engine so does not accelerate with alacrity and is way slower than the Corvette and other "boy racer" vehicles. However, I have only found the modest acceleration annoying when starting off when headed up hill. You know, of course, that folks tend to adjust their driving habits based upon how rapidly their vehicle accelerates. I tend to wait for longer breaks in the traffic than folks with more powerful cars. The only bad thing is that the avaricious Ohio politicians have begun charging a $100/year surcharge on license tags to reclaim a part of the state's lost tax revenue on gasoline, a bit unfair I think because the surcharge does not apply to high mpg cars that are not hybrids. If you are of a thrifty and practical tendency, you will love this little car, and I heartily recommend it to you. At the age of 81, I suspect this little car will carry me all the way on out.
Put a decal on the back window like this Ivan, it should garner acceptance from the jacked up truck redneck crowd.
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11-18-2021, 10:01 AM   #2548
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QuoteOriginally posted by Racer X 69 Quote
Every vehicle I have owned with air conditioning does this, for the reasons I explained.

Oh, and I am a journeyman mechanic, with over 30 years of experience, and many certifications, including air conditioning.
So your argument is basically "Everything you've experienced is wrong, and trust me because I say so."

You'll need to provide some documentation on this, because you are literally the only person I've seen mention this, and many others saying the opposite. If the a.c. keeps cycling, why have the option in the first place?

Since you also claim to have worked at PACCAR, I'll also add that I have been trucking 15 years. None of those cycled the a.c. when turned off either.
11-18-2021, 10:24 AM   #2549
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QuoteOriginally posted by scratchpaddy Quote
My mileage on summer trips is always better than in the winter, in spite of the air conditioning. Something to do with the density of the air? I always get more mileage at higher elevations, too, even with the lower-octane gas they sell there.
Here are my guesses:
1. Tire pressure will drop with temperature, so if you don't adjust it seasonally, it'll be lower in winter.
2. Winter is tough on electrical systems. I'd rank this idea higher if you were in Chicago and commuting. The car would start cold, which takes more out of the battery. Then it would have to run lights, rear window defroster, high blower speed once it warms up, twice a day because sunset is so early. The battery is less efficient too.
3. Snowbirds.
11-18-2021, 12:20 PM - 1 Like   #2550
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QuoteOriginally posted by Racer X 69 Quote
But the pulley has mass, and the belt has friction where it runs in the sheaves. So even when the clutch is disengaged, there is still a parasitic load.

Also, even with the air conditioning switched off, the system still cycles on and off to circulate the refrigerant and compressor lubricant. A compressor wouldn't last very long otherwise.


The only way to do a true comparison would be to remove the belt when running with the air conditioning off and the windows down.
I probably shouldn't get caught up in this fray, but my Prius didn't do that. This was a special case for Toyota hybrids - because the engine could be off when using the A/C, it was electrically powered, not off the belt. Since it wasn't a common item, it was pretty expensive when I had to replace it after about 10 years of driving. a little more expensive than getting a refurbished battery pack (about $900) at the 13-year mark. Those were my 2 big items in the 15 years I owned it.

Here's another chart, this time for my Mazda 3i. Still the same 7.5 mile evening commute. Driving speeds were 30-45 mph.


---------- Post added 11-18-21 at 01:29 PM ----------

QuoteOriginally posted by Just1MoreDave Quote
Here are my guesses:
1. Tire pressure will drop with temperature, so if you don't adjust it seasonally, it'll be lower in winter.
2. Winter is tough on electrical systems. I'd rank this idea higher if you were in Chicago and commuting. The car would start cold, which takes more out of the battery. Then it would have to run lights, rear window defroster, high blower speed once it warms up, twice a day because sunset is so early. The battery is less efficient too.
3. Snowbirds.
I'd agree.I would add cold oil giving more resistance to the moving parts, maybe colder lubricant in the axles too.
Also, many areas have different gasoline blends in the winter to reduce emissions that tend to build up more then.

I've heard the "dense air" theory before, but what I'm reading is that high/low pressure weather systems have more effect than seasons on air pressure.In any case, that difference would only be a few percent.
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