Math whizzes needed...

[scooter]

So the spedo in the Short Bus is 10mph off...
At 55, im goin 65mpg.

Sooooo how can i get a "close" mileage to get a mpg for this sucker????
I recorded the odometer readings at fill up, but i KNOW its not right. I can google map the mileages i guess.
Thanks!!!
Todd S.

 

[cammeddrz]

if it is reading 55, but moving physically 65. that is a 15.4% variation. meaning that you need to multiply the mileage shown on the odometer by .846 to get the actual miles traveled

you would then divide that number by the gallons of fuel used to get the MPG

 

[4.0B2]

if it is reading 55, but moving physically 65. that is a 15.4% variation. meaning that you need to multiply the mileage shown on the odometer by .846 to get the actual miles traveled

you would then divide that number by the gallons of fuel used to get the MPG

shouldn't you multiply it by 1.154 to increase the mileage shown? since the odo is reading lower than acutal?

 

[alwaysFlOoReD]

Assuming 55 is actual mph and 65 is indicated mph then take your indicated mpg and times it by .848
I think that will give you actual mpg

Richard

 

[4.0B2]

but he said at 55 (on the speedo), he's doing 65 actually...
at least that's the way I took it.


regardless, he knows the way to do it now lol

 

[alwaysFlOoReD]

If 65 is actual mph and 55 is indicated mph, then take your indicated mpg and times it by 1.182 for actual mpg.

 

[cammeddrz]

If 65 is actual mph and 55 is indicated mph, then take your indicated mpg and times it by 1.182 for actual mpg.

I got it backwards in my head, he should multiply by 1.182

what I had posted had been for if the reverse was true (i.e. if it said he was going 65, but was actually going 55)

shouldn't you multiply it by 1.154 to increase the mileage shown? since the odo is reading lower than acutal?

allow me to clarify

the same relation can be shown in two different percentages (depending on which one you are comparing the other to)

65 is 18.2% larger than 55. (i.e. 55 X 1.182=65)
55 is 15.4% smaller than 65 (i.e. 65 x .846=55)

 

[scooter]

Changed the rear end gears to 3:77's.

Speedo reads 55 gps, navagaion and phone all say 65mph actually.

THANKS EVERYBODY!!!

 

[cammeddrz]

for that to be true, the rear end gears must've been around a 4.45 before you changed them?

 

[scooter]

for that to be true, the rear end gears must've been around a 4.45 before you changed them?

Not sure on previous ratio.... It was changed right before i bought the bus.

 

[alwaysFlOoReD]

3.2 before change?

edit; cammeddrz is probably correct. A bus would have low gearing.

 

[cammeddrz]

3.2 before change would cause the speedo to read faster than actual.

in order to have the speedo to read slow, he must've been shorter (numerically higher) on the gears before the swap

 

[alwaysFlOoReD]

Ah yes, I was still thinking of the way I first took the meaning of scooters post.
And I'm concentrating on baking oatmeal cookies so my brain isn't on the math so much....

Richard

 

[gw33gp]

While the speedometer may be an indicator of how much the odometer is off, it does not give you a accurate reading on distance. My speedometer can be off 25% at low speed and 3% at high speeds. My odometer is off from 5% to almost right on depending on which tires I have on.

You need to know how much the odometer is off to calculate mpg. When I take a long trip, I zero my trip meter on my Ranger and on my GPS. From that I determine the percent error in my odometer and use that to calculate the actual mpg.

 

[cammeddrz]

^^ I agree.

for the record, GPS can be as inaccurate as anything else.

this is why the people who do distance-precise rallies install magnetic, wheel-driven speedometers. I have one of these in my truck. it is more precise than any gps that I have checked it against for speed (vs laser-radar)

and is super precise on distance too.