Calling all mental giants for math question

cyclepro101 · #1 05-30-2009, 10:38 PM

Can anyone tell me the answer to this question and how they worked it out?

How much fuel do I need to add to 1 litre of 1:20 mix to make up to 1:30?

Steve

matt167 · #2 05-30-2009, 10:53 PM

well 20:1 is 50ml and 30:1 is 33.3ml and with a diffrence of 16.7ml..... so unless my math is wrong, if you add 16.7ml of fuel to your litre of mix, you will end up with 30:1

Creative Engineering · #3 05-30-2009, 10:56 PM

Quote:

Originally Posted by cyclepro101

Can anyone tell me the answer to this question and how they worked it out?

How much fuel do I need to add to 1 litre of 1:20 mix to make up to 1:30?

Steve

Did you intend to ask:

How much fuel should I add to an existing 20:1 fuel/oil ratio mix, in order to achieve a 30:1 fuel/oil ratio mix?

If so...the answer is 50% more, or 1/2 litre.

Jim

wheelbender6 · #4 05-30-2009, 11:32 PM

You are bringing back bad memories of freshman algebra.

cyclepro101 · #5 05-30-2009, 11:52 PM

So I needed to divide by 21 parts, so the answer is 476mls.

Cabinfever1977 · #6 05-31-2009, 04:41 PM

if you are still in breakin i would stick with the 20:1 unless you want to burn up your engine. but if you do kill it they have engine kits with free shipping at zoombicycles.

cyclepro101 · #7 06-01-2009, 12:04 AM

I have done 450km's now so I guess it is broken in?

Steve

HoughMade · #8 06-01-2009, 11:20 AM

Jim (Creative Engineering) is about right- about 1/2 liter.

Here are the numbers:

1 liter of gas/oil mix at 20:1 (that is, not one liter of gas plus oil, but one liter total of gas and oil) contains:

.04762 liters of oil (47.62ml)
.95238 liters of gas (952.38 ml)

If you have the same amount of oil, 47.62 ml, the how much gas do you add?

Multiply .04762 liters by 30 = 1.4286 liters.

Subtract how much gas there was from how much you need:

1.4286 - .95238 = .47622 liters of gas to add.

It will vary a bit depending on rounding and how many decimals you carry it to.

So, about 1/2 liter, but a little under. If you had 1 liter of gas plus oil at 20:1 (50 ml), you would add exactly 1/2 liter.

Cabinfever1977 · #9 06-01-2009, 02:51 PM

i would guess its broken in,but i wouldnt go to 30:1,but maybe 25:1 instead.

HoughMade · #10 06-01-2009, 03:08 PM

Whether you go with 25:1 or 30:1 or whatever, truth be told, this is a useless mathmatical exercise (though it's fun to do simple algebra). Just use up what's left in the can and start with you new mix with the next can you mix up. There's really not an advantage that I can see to going through the hassle of changing the mix of what's in the can. If you expect some sort of noticeable speed increase- you will be diappointed.