gallons per inch

[robertglines1]

Russel; Glad to see your getting running. On my MCI 8 I usually could plan on around 6.4 mpg running 65 mph in our part of the country. The inch thing is a little of a personal thing of how you place stick in tank each time (angle -how far etc) Best way is fill it up to you see fuel in neck take a trip keep record of mileage. then refill to same place. Then if you want to build stick you can do it.  If you have a hudometer  (sp) that will record your trip distance for you. Garmin will give you distance also. Or like other suggested take a stick to station with you put  mark on it put 20 in put another mark put another 20 in  or your choice of gallons differant.   Bob

[Scott Crosby]

What's the temperature of the fuel?     Volume changes with temperature. The expansion/contraction ratio for diesel is approximately 1% for every 22oF (-6oC) change in temperature.   Figure that into your equation   (I found that figure online so I don't know if it's 100% correct, but I do know it changes)

I would just fill it up... for all I know I have 8-9 gallons of water in my tank anyway.     

[rcbeam]

Bob:  glad to hear from you.  Yes, she runs fine and most of the mechanicals are in good order now, so my plan is to drive it every 3-4 weeks.  Besides I simply enjoy driving her around.  The inside is still a shell at this point.  The past 18 months or so have been a financial challenge to say the least, so maybe next year will be better and I can begin to put the inside back together.

I quickly learned that the 'dip' process is not always accurate.  I have to dip the same way and be careful not to get the wire bent or crooked and also the results changes depending on how level the coach is.

At any rate, thanks to everyone that took the time to reply.  Happy motoring everyone.

Russell

[buswarrior]

It is quite easy to have a reliable dipstick, for those who want one.

You need a dipstick that will remain straight when inserted into the tank, and be able to maintain its structural integrity when stored.

It has to be able to reach the bottom at whatever angle the filler neck and the bodywork will allow. Or, it has to have a stop on it to rest on the edge of the filler neck, if the bottom is unobtainable.

The angle at which measurements take place must remain constant, wedging it either up or down against the filler neck to accomplish this consistency is appropriate.

Having a second dipstick to use as your template for transferring the marking to your final good one is handy.

Start with a fairly empty tank, remember, you can add more marks to the bottom of the stick as you gain experience with your set-up. And most of our bus tanks are fairly consistent in shape in the lower regions, so you may simply add marks yourself based on your experience up higher in the tank.

Find a quiet fuel pump where you aren't holding up the world with your experiments...

Dip the tank, and make a mark on the stick where the fuel level is.

Choose a unit of measure, perhaps 10 gallon increments? Once you start marking the stick, you'll decide soon enough what number of gallons gives you the spacing you want to have.

So, put 10 gallons of fuel into the tank, and then dip and mark the stick.

Repeat until full.

Depending on the shape of the fuel tank, the distance between the 10 gallon marks will change. In an MCI 7/8/9/early 102 the last couple of marks will be further apart, as the tank is much narrower towards the top and 10 gallons will have more height, if you know what I mean.

I will echo the post already made:

Always fill the tank right to the brim, and record your fuel and mileage. Right to the brim reduces the margin for error in how the coach is sitting, or in the shut off of various pumps. Full to the brim is a fairly consistent fill, from fill to fill.

Remember, a US gallon is 231 cubic inches. So for instance, in a 2' x 5' tank, an inch of fuel is over 6 gallons. That will really screw up a typical busnut's fuel mileage calculations...

You have to wait a few seconds for the foaming to die down when filling a fairly empty tank, but if you are going to bandy about your fuel economy numbers, best to be as accurate as you can be, eh?

happy coaching!
buswarrior

[rcbeam]

Buswarrior:  a thorough and thought out explanation as usual.  Thx for the additional info.  I will give it a try.

Russell

[mikelutestanski]

Hello:   Measure your tank.   Length x width. and height.   FIgure the tank is a rectangle and measure to where the tank starts to slope.  Take that number  say 20 inches wide by 60 inches long..   20 x 60 is 1200 now the height is 12 inches.   1200 x 12 is 14400.   OK now fuel is approximately 231 inches per gallon.so divide 1400 by 231 to get 62.33  gallons which is not exact but close enough for your needs.    SO 62 gallons divided by 12 inches of height equals 5 + gallons per inch  That it for the rectangular part.  You need to figure the rest of the tank and come to a height and a figure per inch.  You can average the value or figure  the total number depending on the inch reading of the tank.
 The mci 7 tank is rectangular with a hump in the front. I figured 6  gallons per inch and calibrated the fuel gage by dipping the sender in a column of fuel and reading the value of the tank and the gage together.  I wrote the figures down and now I know fairly accurately what the fillup will be when I pull into the station.
      update to this post:::
   I looked up the calculations for the mci 7 tank and this is what I came up with:
     66 x21 x 1 inch equals 1386  divided by 231  equals 6 gals    times 23 inches of height equals 138 gallons.. the federal stamp is 136 so the calculation is close enough... FWIW.   this does not answer the posters questions but is a method to find out the answer.   Regards   mike
   

     
   

[gmcbuffalo]

what federal law is this?  I people with buses carriing well over 200 gals.

[belfert]

what federal law is this?  I people with buses carriing well over 200 gals.

The "law" has nothing to do with maximum fuel allowed.  It has to do with not completely filling the fuel tank to allow for expansion.

[gumpy]

At this point I have no idea what my fuel mileage is and I would like to begin to get a handle on that for planning purposes.  The bus starts easily, does not smoke at all, and runs great. Having mileage in line with norms would just further indicate that the engine and drive train is in fact running properly.  Knowing somewhat what my mileage is would help in planning costs for future trips.

Knowing the quantity of fuel in the tank is not necessary to check fuel mileage. You simply need to be consistent when filling the tank. Always fill to the same level, whether you use the dip stick, or the bottom of the fill tube. Then you know exactly how much fuel you burned in a given number of miles and can easily calculate the rate of burn. With that, and knowing what your total usable capacity is (120 gallons), you then know what your maximum range is and can plan accordingly. 

If you really want to know per inch, then level your coach when the tank is nearly empty, empty the tank of all fuel using a siphon or pump, and fill the tank in increments of 10 gallons, dipping and marking your dipstick with each increment. This will be very time consuming, but will be the only reliable way to get an accurate dipstick, and it will be accurate only when the coach is level (not very often).

An alternative is to calibrate the dipstick for mileage. Fill to your known full point (e.g. the bottom of the fill neck). Run a specific number of miles (e.g. 50 miles). Dip the tank and mark the dipstick. Do this for 800 miles, dipping every 50 miles. Now you have a mileage calibrated dipstick, rather than a gallon calibrated dipstick. And isn't that really what you want to know? How many miles can I go on what's left in the tank? 

Incidentally, if you fill the bottom of the fill neck, you will often find that as the fuel expands in the tank you may see dripping out of the fill cap. This is especially true if you park on the curb where the fill side is slightly down hill.