Turbo V8 Micro
In 2000 I made my first stove, Roy Robbinson's Cat Stove. At that time I had been using gas stoves and expected a stove to heat as fast as one and simmer on call. The only stove that could do that was the Cat, and it does it like a champ. But in 2001 I accepted the challenge to scientifically test the stove to see how truly efficient the stove was. The challenge was to see if it could really boil water, and do so as efficiently as a canister stove. In this comparison, efficiency was measured in starting weight.
AYCE really opened my eyes on that test. A stove like the Cat may heat like a rocket, but in regards to weight, alcohol fuel needs a lot of volume to achieve true boil. Propane and Butane have about twice the BTUs per ounce that alcohol has. So in that regard, the propane/butane stoves have the advantage. But because a canister stove weighs at a minimum about 3 ounces, and needs a heave pressure cartridge, the start weight is very close.
So at that point I started looking to make my stove lighter and more fuel efficient. I wanted a stove that could get the maximum performance from the BTUs in alcohol and do so with as little weight and parts as possible. There are some good designs on the internet, but most are aimed at making light and small stoves, they haven't really looked for efficiency. But I must caveat this by saying one really efficient performer is out there - the Trangia, it just isn't the lightest.
So I do a little research. Science has already figured out a lot of the facts for us, all we need to do is search and ask question. First thing I looked up is how many BTUs are in Alcohol.
Methyl Alcohol has 10,200 BTUs per pound and is made from wood grains. It is also the type of alcohol that causes blindness and death if ingested. Methyl Alcohol is sold as HEET fuel line dryer and also comprises 80% of what is sold as denatured alcohol in the 32 ounce cans at Wal-Mart.
Ethyl Alcohol has 12,550 BTUs per pound and is made from grains. It's what you drink in beer, tequila, etc. You can get it as Everclear (90% pure) or in denatured alcohol from Wal-Mart because it makes up the other 20% of that formula.
Compared to Propane/Butane or gas with about 21,000 BTUs per pound, you can see what the problem could be with alcohol.
So the next thing I had to figure out is what the exact definition of a BTU is. Well, a BTU is the amount of energy required to raise the temperature of a pound of water by one degree. A 60 degree pint of water needs about 152 BTUs of energy to achieve boil. SO if a pound of methyl alcohol has about 10,200 BTUs what does that mean?
A pound of alcohol is approximately 19.5 fluid ounces, which equals 577 ml. A ml of alcohol has 17.6 BTUs - so it would take about 9 ml of fuel to boil the 60 degree pint of water in a stove that is 100% efficient. Since no stove is 100% efficient, we will accept aim to make it as efficient as possible.
Something I should point out at this point is that a canister stove should only need .096 ounces of fuel to boil if it was 100% efficient, but based on tests from AYCEs www.thru-hiker.com, they need about 3 times that. That would make this stove type only about 30% efficient.
So now I have an idea of how much fuel is needed that is scientifically arrived at. But I also know that even a stove as well designed as the SnowPeak is only 30% efficient. What efficiency should I am for? I started at 50% efficiency, which would mean about 18ml of fuel. I started working on my Turbo V8 stove and with some tweaks, I achieved this. And it performed that way consistently and still maintained some good boil times. I was also able to make a soda can stove do the same thing with the ability to simmer.
But not only was I able to do this, but Aaron Rosenbloom of Brasslite did it too with his amazing little stoves the Solo and Duo. But where I used air + fuel = fire, he got it done with a cool system that develops pressure to get rapid heating with good fuel efficiency. Based on the Brasslite design, and my V8 stove, I thought I had hit the limit of performance.
Then I got a Trangia to test. The thing was even more efficient than anything I tested before. It boiled water very consistently on 15 ml of fuel, making it 60% efficient. But it is way to heavy to be weight efficient overall. I wanted to make a lighter stove just as efficient, so I played around with a new design and even made a smaller version of AYCEs V8 stove again. I actually hit 12 ml of fuel to boil which is 75% efficiency, but it was never consistent, and the design was so finicky you would put it out if you removed the pot and then put it back on the stove.
Finally I decided to try making a smaller Turbo V8 and changing the burner holes, nothing to lose. Guess what? It worked! I originally was going to call the stove the Turbo V8 Micro, but the new stove isn't made from V8 cans, but grape juice, and the stove really has little in common anymore with the original V8 that AYCE has on his site. The stove is a double wall alcohol stove that uses fiberglass wicking material to improve cold weather performance. It primes in it's own filling hole, uses a built in stove stand, and uses a burner pattern to control the burning of the fuel.
On AT Forums, Early Riser compared the design to the NASA Ion Drive which uses a highly weight efficient low power drive to produce speeds that could not be re-produced by chemical rockets, but the engine takes a long time to reach those speeds. I like that analogy, so I decided to name the stove after the Ion drive.
O.K. now for the numbers.
Weight: .3 ounce stove, .3 ounces windscreen. Total = 0.6 ounces.
2 cups of water at room temperature – 70 degrees.
Pot used is a Snow Peak 720ml titanium pot.
3. Stove tested using the windscreen and lid.
Alcohol was tested in 6 ml increments, starting at 6 ml
Each amount was double checked using a scale. The weight of one fluid
ounce of alcohol is .82 avoirdupois ounces.
Each Test was repeated three times, the average was used.
Starting time was when the stove was lit.
Stoves were allowed to completely cool between tests.
Barometric pressure here was 30.15, the boiling point was determined to
be 212.43 degrees.
Altitude is 90 meters above
Temperature was measured using a thermocouple and digital multimeter .
Air temperature was 70 degrees with the stove fan running to simulate a
13. Scale used was a
13. Scale used was a Royal EX3.
Something interesting (at least to me) was the performance curve. Normally in a non-pressurized stove, I get a pretty straight progression of lower times to each temperature with lower fuel amounts. But for some reason this stove doesn't do that. It operates very strangely at 6 ml (more below) and has a weird curve where it takes a long time to boil at 12ml then at 18 ml and above it acts like I expected.
So far I'm happy with this stove. Besides being smaller and lighter it also does the following:
1. It reaches true boil with only 12ml fuel and can do it consistently, at least under kitchen conditions. This makes it 75% efficient, better than I thought I could ever get.
2. It maintains temperatures over 175˚ for a long time. With a 2:45 time over 175˚, many dishes are done cooking by the time the fuel burns out.
3. A cool feature I didn't count on was this stove can simmer! When I did the 6 ml test (one cap full of alcohol) the stove stayed lit for over 22 minutes with a low flame. It never got hot, but stayed hot enough to maintain cooking temperature on a pot of food already warm. Apparently the insulation in the sides holds the fuel so that it never gets enough going hot, but also keeps it warm enough to stay lit. The key is to let the stove burn out, then cool off, your food won't go cold while waiting - it only takes about 2-5 minutes. Then add 6 ml (one cap full) fuel and light it up.
4. I decided to conduct the 30ml test for cold performance since there wouldn't be a normal need to use this much fuel. To test the cold weather performance of this stove, I cooled the pot, lid, stove, and fuel to 26.5˚ then filled the pot with 16.7 ounces of ice. the room temperature was still at 70˚, but all the components were so cold it effectively lowered the temperature at the test site. While not a true simulation of winter conditions, it certainly taxed the stove's ability to boil. It took a long time for the flame to transfer to the burner jets But the stove still was able to melt then boil the entire pint of water on only .83 ounces (weight) of fuel.
Because it is shorter than my original Turbo V8, it is also more stable. Overall height is only 1.25", so this means the pot gets better stability, and the windscreen can also be shorter.
Something that should also be mentioned because it may pertain to other stove types. After about 10 stove test, performance dropped off badly. I couldn't get the stove to boil at all. I found that the jets were somehow clogged on the inside, so using a paperclip I opened them back up all the way to the bottom, then the stove burned great. Because of this I cut a small piece of wire and added it to the stove and it's parts. As a general rule I clean out the jet holes before use.
Red = Worst performer
Yellow = #3 performer
Blue = #2 performer
Green = Best performer
**Note. For purposes of this illustration I am considering my fuel bottle a 24 ounce soda bottle weighing 1.0 ounces.
The stoves are listed from left to right - heaviest to lightest over time hiked.
Standard is 14 days hiking, although if you go on a shorter hike, the average weight per day will go down. The chart assumes you will make 2 hot meals a day requiring a full boil.
Stove Weight = empty stove weight.
Fuel per boil is the volume of fuel needed to boil water (true boil).
Fuel per boil (weight) is the actual weight on the fuel needed in ounces.
Average Weight/day is what you will carry on average in weight over a 14 day hike without re-supply.
Total over 14 days shows the weight you carry if you total every days weight over the 14 days.
Trail days are computed from day out (14) to last day (day 1) If you decided to do 5 days between re-supply, then day 5 weight would be the start weight for your trip.
Total fuel needed in ounces gives you an idea of what sized fuel container is needed
This part is not yet complete because I still need some trail testing.