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# CICO and calorie counting explained by analogy

Posts: 7,122 Member
Pretend you have a car. Okay probably you do have a car but pretend you have a rather unique car. This car has two tanks, a normal tank that you can pump fuel into and another reserve tank that the car can draw from if the main tank is empty. The main tank is rather unique in that it can take a huge variety of different fuels…gasoline, bioethanol, butane, propane…you name it. In fact it requires that you use different fuel types all at once. The reserve tank only accepts gasoline but your car can convert whatever fuel you put into the main tank into gasoline to top off the reserves, it can even grow the size of the reserve tank if needed. If you use up all of your fuel in the main tank it will start to pull from the reserve tank.

Lets say you want to find out how much fuel you’d need to have in your main tank to drive 300 miles without having to pull from your reserve tank. If this was a normal car that took only gasoline you could just divide the 300 miles by the miles per gallon your car gets to calculate the number of gallons you need. Unfortunately, this is not a normal car since you can put multiple fuel types in your tank and the different fuel types don't all have the same energy per volume. Therefore it doesn’t make sense to track volume, you want to track energy instead because that is what is related to how far you can go. There are lots of units for energy just like there are lots of units for distance: there are joules, BTUs, kilowatt-hours and calories. It doesn’t really matter what unit you choose to use so lets choose calories then. So you need to figure out how many calories you need to go 300 miles and then put that many calories into your tank. But how do you figure that out?

Well your car weighs a certain amount and you can find that in your owners manual…here it is, 1000 kilograms, and you want it to go over a certain distance, 300 miles. So you could try to calculate the amount of work (energy) it would take to move 1000 kilograms by 300 miles. Lets call that the calorie output or CO. Now, of course, whatever you end up calculating by that method would be wildly off because that is the bare minimum energy required and it doesn’t account for everything like friction between the wheels and the ground, the friction of the moving parts in the car, the generated heat, the noise generated, the amount of time you are idling versus moving etc etc. So what do you do? Well luckily there are lots of studies out there of cars and how much energy they require in calories to go a certain distance in miles. Sure, they aren't exactly all the same car but if you put in your make and model and year you can get a decent estimate of how many calories you need to go a certain distance. So now you have a ballpark number now for CO.

So if you know the calories you need to output you know the calories you need to input, or CI. You can look up the calories per gallon of the various fuel types you have on hand and you can count them up and put together a fuel plan to hit your target. So that is it right? Not quite. You see the calories per gallon of the fuel is the amount of calories you would get from that amount of fuel if your engine was 100% efficient. Your engine, however, is not 100% efficient. In fact, it isn’t even the same efficient for the different fuel types. Not only that but you look in your manual and there isn’t any info at all about how efficient your engine is and even if there was your specific engine might have quirks that other engines of the same make and model don't. So your calculated CI is the total amount of calories your engine COULD get out of the fuel if it was 100% efficient, but it is actually going to be less than that...but by how much?

So are we stuck then? I mean if you had the ability to exactly calculate the CO and exactly calculate the CI then it would be easy to balance the two…CI=CO to figure out how much fuel for 300 miles. But you don't have that ability, so what do you do? Well perhaps the situation isn't as dire as it looks. Since the value you got for CO was based on averages from similar cars and how many calories they required to go a certain distance that value already actually took into account the average efficiencies of those cars engines both for CO for mileage and for CI for fuel energy efficiency. Since there are millions of cars out there that have roughly the same make, model and year as yours those estimates aren't too far off the mark. As it turns out those studies have shown that there isn’t all that much variation between engine efficiencies no matter what kind of car you have and it has allowed for the creation of calculators that adjust CO based on how much your average car gets out of your average fuel mix and gives you a rough approximation of what CI you need regardless of the actual efficiency of your engine. So now you can look it up with a calculator that if you are driving a 1000 kilogram 1979 car 300 miles you are going to need 30,000 calories and you can load up on a mix of 30,000 calories worth of fuel and hit the road.

So you started with what the calculators told you which was a rough approximation and found it wasn’t quite right for you. So you diligently track the amount of calories you put in your fuel tank (CI) and the amount of miles that you travel (CO) and how much fuel is left in your reserve tank and after a few months of tracking you learn how to adjust those initial estimates so that you know pretty much exactly how much fuel you need to go a particular distance for your particular car no matter what types of fuel are available to you.

Later you run into someone who asks you how you keep only spending exactly what you need to get somewhere and you tell them you track your calories. They scoff and say that they tried to track calories and it didn’t work for them at all. They were super diligent about tracking but if they put 30,000 calories of 80% butane and 20% propane in their car they were able to go 290 miles but if they put the exact same number of calories of 20% propane and 80% butane into their car they only went 250 miles so clearly CICO is wrong. Another person overhears and pipes in their own opinion arguing that no matter what car you drive 30,000 calories of any type of fuel will allow you to travel exactly 280 miles no matter what and anyone who is off by even a mile is clearly just measuring wrong. You just smile and check your log to see how much you need to get to the next town.

The truth is CICO is just is concept referring to the fact that if you know how much energy you are expending you know how much energy you need to balance that, whether you want to end up with more, less or the same energy. It is just a fact of math and nature. Trying to get accurate estimates of CI and CO though isn't exact, it is based on assumptions and population averages that don't always apply. That doesn't make it wrong though, or even a poor method...frankly only math itself is 100% accurate and everything that is a real world application has this sort of error. That said if you count your calories consistently and track your reserve tank you can correct for any quirks that your car might have relative to the average. With some diligence and accurate honest tracking you will end up with a tailored model for you that will get you exactly where you need to go.
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## Replies

• Posts: 3,565 Member
rkayg2845 wrote: »
Aaron_K123 wrote: »
Pretend you have a car. Okay probably you do have a car but pretend you have a rather unique car. This car has two tanks, a normal tank that you can pump fuel into and another reserve tank that the car can draw from if the main tank is empty. The main tank is rather unique in that it can take a huge variety of different fuels…gasoline, bioethanol, butane, propane…you name it. In fact it requires that you use different fuel types all at once. The reserve tank only accepts gasoline but your car can convert whatever fuel you put into the main tank into gasoline to top off the reserves, it can even grow the size of the reserve tank if needed. If you use up all of your fuel in the main tank it will start to pull from the reserve tank.

Lets say you want to find out how much fuel you’d need to have in your main tank to drive 300 miles without having to pull from your reserve tank. If this was a normal car that took only gasoline you could just divide the 300 miles by the miles per gallon your car gets to calculate the number of gallons you need. Unfortunately, this is not a normal car since you can put multiple fuel types in your tank and the different fuel types don't all have the same energy per volume. Therefore it doesn’t make sense to track volume, you want to track energy instead because that is what is related to how far you can go. There are lots of units for energy just like there are lots of units for distance: there are joules, BTUs, kilowatt-hours and calories. It doesn’t really matter what unit you choose to use so lets choose calories then. So you need to figure out how many calories you need to go 300 miles and then put that many calories into your tank. But how do you figure that out?

Well your car weighs a certain amount and you can find that in your owners manual…here it is, 1000 kilograms, and you want it to go over a certain distance, 300 miles. So you could try to calculate the amount of work (energy) it would take to move 1000 kilograms by 300 miles. Lets call that the calorie output or CO. Now, of course, whatever you end up calculating by that method would be wildly off because that is the bare minimum energy required and it doesn’t account for everything like friction between the wheels and the ground, the friction of the moving parts in the car, the generated heat, the noise generated, the amount of time you are idling versus moving etc etc. So what do you do? Well luckily there are lots of studies out there of cars and how much energy they require in calories to go a certain distance in miles. Sure, they aren't exactly all the same car but if you put in your make and model and year you can get a decent estimate of how many calories you need to go a certain distance. So now you have a ballpark number now for CO.

So if you know the calories you need to output you know the calories you need to input, or CI. You can look up the calories per gallon of the various fuel types you have on hand and you can count them up and put together a fuel plan to hit your target. So that is it right? Not quite. You see the calories per gallon of the fuel is the amount of calories you would get from that amount of fuel if your engine was 100% efficient. Your engine, however, is not 100% efficient. In fact, it isn’t even the same efficient for the different fuel types. Not only that but you look in your manual and there isn’t any info at all about how efficient your engine is and even if there was your specific engine might have quirks that other engines of the same make and model don't. So your calculated CI is the total amount of calories your engine COULD get out of the fuel if it was 100% efficient, but it is actually going to be less than that...but by how much?

So are we stuck then? I mean if you had the ability to exactly calculate the CO and exactly calculate the CI then it would be easy to balance the two…CI=CO to figure out how much fuel for 300 miles. But you don't have that ability, so what do you do? Well perhaps the situation isn't as dire as it looks. Since the value you got for CO was based on averages from similar cars and how many calories they required to go a certain distance that value already actually took into account the average efficiencies of those cars engines both for CO for mileage and for CI for fuel energy efficiency. Since there are millions of cars out there that have roughly the same make, model and year as yours those estimates aren't too far off the mark. As it turns out those studies have shown that there isn’t all that much variation between engine efficiencies no matter what kind of car you have and it has allowed for the creation of calculators that adjust CO based on how much your average car gets out of your average fuel mix and gives you a rough approximation of what CI you need regardless of the actual efficiency of your engine. So now you can look it up with a calculator that if you are driving a 1000 kilogram 1979 car 300 miles you are going to need 30,000 calories and you can load up on a mix of 30,000 calories worth of fuel and hit the road.

So you started with what the calculators told you which was a rough approximation and found it wasn’t quite right for you. So you diligently track the amount of calories you put in your fuel tank (CI) and the amount of miles that you travel (CO) and how much fuel is left in your reserve tank and after a few months of tracking you learn how to adjust those initial estimates so that you know pretty much exactly how much fuel you need to go a particular distance for your particular car no matter what types of fuel are available to you.

Later you run into someone who asks you how you keep only spending exactly what you need to get somewhere and you tell them you track your calories. They scoff and say that they tried to track calories and it didn’t work for them at all. They were super diligent about tracking but if they put 30,000 calories of 80% butane and 20% propane in their car they were able to go 290 miles but if they put the exact same number of calories of 20% propane and 80% butane into their car they only went 250 miles so clearly CICO is wrong. Another person overhears and pipes in their own opinion arguing that no matter what car you drive 30,000 calories of any type of fuel will allow you to travel exactly 280 miles no matter what and anyone who is off by even a mile is clearly just measuring wrong. You just smile and check your log to see how much you need to get to the next town.

The truth is CICO is just is concept referring to the fact that if you know how much energy you are expending you know how much energy you need to balance that, whether you want to end up with more, less or the same energy. It is just a fact of math and nature. Trying to get accurate estimates of CI and CO though isn't exact, it is based on assumptions and population averages that don't always apply. That doesn't make it wrong though, or even a poor method...frankly only math itself is 100% accurate and everything that is a real world application has this sort of error. That said if you count your calories consistently and track your reserve tank you can correct for any quirks that your car might have relative to the average. With some diligence and accurate honest tracking you will end up with a tailored model for you that will get you exactly where you need to go.

What happened to your other thread like this? BTW, this is very informative?

Ah, thanks! I thought I had left a comment on this, and then suspected I might be losing my mind a little

This is excellent! Thanks for taking the time to lay it out so clearly.
• Posts: 5,864 Member
Great post!

Many thanks for putting in the time to do it
• Posts: 4,080 Member
Brilliant analogy. Sadly the people who really need to read and UNDERSTAND it aren't going to read it. If they do read it, they probably aren't going to understand it.