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Author Topic: Fuel mileage?  (Read 5186 times)

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Jessechop

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Fuel mileage?
« on: February 11, 2016, 09:28:24 PM »
Odd question. Do any of you keep track of fuel mileage on your bikes? Rather, it takes xxx to make a full run at Loring (including the return)

I am working on a small displacement (400 cc) twin cylinder bike and my purposed tank is going to have a capacity of right around 1/3 of a gallon. 43 ounces....

Ricer math tells me when I rode the bike on the street I was getting, on average, 50 mpg. Call it 1/2 that because of the racing nature equals 25 mpg. 1.5 miles down and 1.5 back plus shut down, staging, etc so to be safe call it 5 miles total. No way I will be using long shut down.

So 25/.333 = 8.33 miles per tank...according to ricer math.

Anyone care to chime in there findings? I have no idea how much fuel my other bikes were using.

Offline hotrod

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Re: Fuel mileage?
« Reply #1 on: February 11, 2016, 09:47:36 PM »
Do you know the expected power output?

Rule of thumb is takes .5 pounds of gasoline to make one hp for one hour.

Jessechop

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Re: Fuel mileage?
« Reply #2 on: February 11, 2016, 09:53:11 PM »
Do you know the expected power output?

Rule of thumb is takes .5 pounds of gasoline to make one hp for one hour.

I did not know that. Stock power was 27...so 22? LOL Call it 30 I guess to be safe.

30*.5=15 lbs per hour. /6.5 lbs per gallon =  2.3 gallons per hour

Now to convert that further......

Offline RidgeRunner

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Re: Fuel mileage?
« Reply #3 on: February 11, 2016, 10:21:04 PM »
Something to consider beyond mileage when designing a fuel system is the potential for air in the fuel/frothing.  Problems with that are more likely in an injected system but they can occur with carb bowls and floats as well.

                Ed

Offline wobblywalrus

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Re: Fuel mileage?
« Reply #4 on: February 11, 2016, 11:03:51 PM »
Fuel in the tank provides the pressure to move the gas into the float bowl.  It is a good idea to lower your floats a quarter inch and determine the flow into the float bowls on each carb with both carbs flowing fuel.  A graduated bottle under each carb and a stopwatch are the basic tools.  The goal is to get a bit more flow than the .5 pounds per horsepower per hour.  Try this test with various fuel levels in your tank.  The flow rate drops as the tank empties.  There is less fuel pushing down when the fuel level is closer to the carb level.

Some bikes with stretched and low frames do not have a lot of vertical drop and a long nearly horizontal fuel line between the tank and carb.  Sometimes it is necessary to have a gallon or so in the tank just for pushing.  My Triumph is like this.  I like to keel at least a gallon in the tank at all times so I am certain to get all the fuel pressure I need at the carbs.

Jessechop

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Re: Fuel mileage?
« Reply #5 on: February 12, 2016, 05:04:04 PM »
Thanks for all of the insight. Exploring options right now. I really want to run a backbone tank like the old drag bikes but it might not be feasible.

Jessechop

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Re: Fuel mileage?
« Reply #6 on: February 13, 2016, 04:07:41 PM »
After a little more measuring I can stay the style I want and have .68 gallon capacity. That gives me a bit more comfort

Offline Truckedup

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Re: Fuel mileage?
« Reply #7 on: March 14, 2016, 04:51:50 PM »
 My 650 MPG Triumph used about 3/4-1 gallon to do four runs and pit running/riding at Loring. 55 rear wheel HP on the dyno...The bike tank is  larger than the 1.3 gallon rule for the class, SCTA and ECTA....I don't know if you guys follow the exact same rules?
« Last Edit: March 14, 2016, 04:53:22 PM by Truckedup »
Triumph 650 LTA MPG record holder  133.1 MPH...

Jessechop

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Re: Fuel mileage?
« Reply #8 on: March 14, 2016, 05:05:18 PM »
Thanks for the info. All said and done I ended up at a gallon.

It is an A class bike so no tank limits

Offline dresda

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Re: Fuel mileage?
« Reply #9 on: May 24, 2016, 10:19:21 PM »
My 55 supercharged Triumph on Methanol will get me down the 11/2 mile and back to the pits on a gallon my tank only holds 1.3 gallon, guess I need a bigger tank for Bonneville.
Ray.