Fuel mix Ltr's VS Kg's

[barry]

Hey all,

Ive been talking with some older fly boys about mixing fuel and they where saying to get a true fuel mix you should weigh your fuel rather than measure it by the ml. So rather than making a Ltr of fuel you make a kg. Just wanted to no how guys out there are mixing there concoctions

 

[jetpack]

Fuels are always mixed by volume, sold in volume, used in volume. Recommended by volume.

To properly mix by weight you need to measure your liquid components using a hydrometer to find its exact density...then convert and adjust your percentages per base readings to volume standards. It is a tail chase.

The only advantage to weighing your components is to determine its puritey to correct your percentages to volume mixing.

 

[Rick Doane]

Barry:

You can do that since 1 gram = 1 mL. You will need a nice set of scales that measure to 3 decimal places. However, it is a lot simpler to get a graduated cylinder and measure the components accurately. I do not believe that you will notice the difference in performance especially in heat racing, using either procedure. If you plan to get the most from your set up for SAW, then you may see a small increase. As you know, anything you can do to make increases in the 1-3% range is a plus for this event.

Regards...........Rick

 

[barry]

To properly mix by weight you need to measure your liquid components using a hydrometer to find its exact density...then convert and adjust your percentages per base readings to volume standards.

I agree and I have always mixed by volume ml. These guys are in there 70's and have been involved in RC for 50yrs ++ so I respect there opinion They do use the method you have stated. I suppose my question should be, is this method more accurate. They say it is but to me either formula is as accurate as each other.

 

[piper_chuck]

Barry:
You can do that since 1 gram = 1 mL.

Yes, for pure water at 4 degrees C... Other liquids will have different values.

 

[barry]

Barry:
You can do that since 1 gram = 1 mL. You will need a nice set of scales that measure to 3 decimal places. However, it is a lot simpler to get a graduated cylinder and measure the components accurately. I do not believe that you will notice the difference in performance especially in heat racing, using either procedure. If you plan to get the most from your set up for SAW, then you may see a small increase. As you know, anything you can do to make increases in the 1-3% range is a plus for this event.

Regards...........Rick

Sorry rick I hate to say it but 1 ml of oil is heavier than 1 ml of Nitro. The method needed is as jetpack stated. Klotz for example sell differant weights of oil just like Penzoil does for your car. Next time your at your local auto store pick up a container of 2 stroke oil then pick up the same size engine oil.

 

[Terry Keeley]

I've been doing exactly that for a long time now, funny, thought I was the only one. :lol:

I have a postal scale that measures in 5g increments which is much more accurate than looking at a level in a beaker or whatever.

I mix 4 liters at a time (which completely fills a US gal. can). My standard race mix is 60% nitro, 25% alcohol, 12% oil and 3% PO. Four litres is 4000ml, so I need:

0.6 x 4000 = 2400ml nitro

0.25 x 4000 = 1000ml alky

0.12 x 4000 = 480ml oil

0.03 x 4000 = 120ml PO

To get the weight of each component you need to multiply by the specific gravity (SG), so:

2400 x 1.13 = 2712g nitro

1000 x 0.79 = 790g alchy

480 x 1.0 = 480g oil (I checked the oil I use with a hydrometer and it's pretty close to 1.0, or you could ask the mfg)

120 x 0.82 = 98g PO

I round to the nearest 5g to suit my scale, also it's prolly a good idea to check with a measuring cup or watever the first time you try this. Doing it this way I can measure ingredients to 5g which for the nitro works out to 5.6ml (about a teaspoon), I'd never see that looking at a line on a beaker or whatever... :blink:

Ahhhh, details, details...

 

[barry]

Thanks Terry, was starting to think I was a fool for starting the post. Is there a noticable differance between mixing by weight compaired to mixing by the ml

 

[Terry Keeley]

Thanks Terry, was starting to think I was a fool for starting the post. Is there a noticable differance between mixing by weight compaired to mixing by the ml

Actually you're still mixing by volume (which is the standard), but measuring those volumes by weight, which is more accurate. :blink:

 

[Rick Doane]

Barry:
You can do that since 1 gram = 1 mL. You will need a nice set of scales that measure to 3 decimal places. However, it is a lot simpler to get a graduated cylinder and measure the components accurately. I do not believe that you will notice the difference in performance especially in heat racing, using either procedure. If you plan to get the most from your set up for SAW, then you may see a small increase. As you know, anything you can do to make increases in the 1-3% range is a plus for this event.

Regards...........Rick

Sorry rick I hate to say it but 1 ml of oil is heavier than 1 ml of Nitro. The method needed is as jetpack stated. Klotz for example sell differant weights of oil just like Penzoil does for your car. Next time your at your local auto store pick up a container of 2 stroke oil then pick up the same size engine oil.

You are correct.....I left out the density.

Rick

 

[Preston_Hall]

If measurements are critical then a hydrometer must be used. I have not seen where a splash extra makes a difference in this sport. Of course that excludes propelyne oxide.

 

[barry]

I use a 500ml Laboratory Glass measuring Cylinder with 1ml graduations and are more than happy with the accuracy. I am quite aware with the method required to messure by weight. Until latley I had not heard of people in the hobby using this method until I ran into a few old timers who swear by the weight method & Terry has just confirmed that this method is still used.

 

[Terry Keeley]

And it really is simpler, you can put your can on the scale and just add ingredients til yur done.