Meths Fuel Efficiency.

Quixoticgeek

Section Hiker
As has been pointed out by many on here in response to me getting an evernew meths stove, it's a thirsty beast. I'm still refining how much fuel I add for the temp of the water. But this got me thinking:

How much fuel do you use with your meths stove to boil a mug of tea?

J
 

Teepee

Thru Hiker
15-20 ml for a 500ml brew. 17ml is reliable with my Fancee Feast and Micro Fancee Feast stoves.

For just coffee hot, 10ml.
 

edh

Thru Hiker
I would guess about the same... although don't do brews. I used Esbit most of last season to complicate things!
 

Quixoticgeek

Section Hiker
What stoves are you all using for these numbers? I've only ever owned two meths stoves. A cat can stove, and the evernew one.

The evernew is much less thirsty than my cat can stove...

Julia
 

Teepee

Thru Hiker
My Cat can stove only becomes highly efficient with a wider pot and larger amount of water.
 

Mole

Thru Hiker
same efficiencies as Teepee

Starlyte

used to use diy zen mini chimney.

in a cone.

Sometimes a big trangia car/base camping. thirstier.

use esbit n hexi too. more efficient than meths weight for weight
 

Beamo

Summit Camper
I had a evernew dx stove and burner for a short time, it was the thirstiest meths stove I've ever had and also unstable when using anything but a small diameter pan.
Much prefer my speedster setup.
 

Teepee

Thru Hiker
Hexy type much more compact too. Reckon I use ~10g of hexy for 500ml. Did it on 7g once but took nearly an hour. :rolleyes:
 

Hedley Heap

Section Hiker
Fuel efficiency is the holy grail of most backpacking cook kit developers.
IME the key to efficiency is matching the components, so they work together in a harmonious manner.
Your evernew burner puts out a lot of btus' so would suit a larger/wider pot or maybe one with a heat exchanger (heat exchanger pots don't usually work with lower output meths burners, too much flame quench) to take advantage of the extra output.
The kit as it's sold is a complete mismatch of parts IMHO.
People don't often appreciate the importance of a windshield, not since a windshield was a piece of canvas held down by two bike spokes, has a windshield just protected the burner from wind.
A proper windshield (in a backpacking situation) shields both the burner and the pan completely from wind, creates a chimney effect and often contributes to holding it all together.
A rough guide to how efficient your set up is, is to check the temperature of the fumes/air coming out of the top of your windscreen, really hot and your pan hasn't absorbed all of the heat out of the flame and your set up is heating the air around you wastefully.
This isn't an absolute measure, as said before flame quench is just as inefficient.
My testing shows a pan twice as wide as it is tall is the most efficient and stable.
So you can spend 10 years developing your kit, measuring fuel usage, exhaust temperatures, stability, temperature differentials etc or you could buy one. ;)
 

Mole

Thru Hiker
Those results fit my 'common sense' thoughts really. And support the idea that an optimally vented cone with the optimal height pot is likely to have a slight efficiency advantage over a plain windscreen at optimal distance to optimal pot - just grabbing that extra bit of heat to the pot before it can disperse upwards.

Significance of that advantage will vary with setup and conditions - with good setups it will be negligible

i.e A matched-to-potn stove Cone or Windscreen/support setup like Hedley's or Flat Cat, builds in all the optimisation , so is always going to be more efficient than a plain foil/plate windscreen unless the user sets up the optimal distance.
 

WilliamC

Thru Hiker
I recently got a Keg-H set-up from Trail Designs. I've also just got hold of some bioethanol so I've been testing them to get some idea what to expect on in the field, using a Starlyte stove. Things went pretty much as expected, averaging a little under 11g to boil 400ml of 15 degree water in around 9 and a half minutes.
Then I remembered a Minibull pot stand I've got lying around and decided to try it with that. It places the pot much higher (about 64mm above the ground rather than 50mm. I found that this increased the fuel use by about half a gram, but knocked a whole 3 minutes off the boil time. It also left some soot on the pot, which hadn't happened before, hence the fall in efficiency. I also tried setting the silicone band to set the pot at the same height as the Minibull stand and got similar results.
A reduction of three minutes in boil time is quite significant for me, the drop in efficiency will add 2-3 grams per day to our fuel needs, which doesn't seem too bad. So now I'm considering punching some extra air holes in the cone to try to increase air intake and eliminate the soot. The problem is, I'm a little reluctant as I don't really understand what is going on and why the drop in boil time is so dramatic. I also worry that there is a danger that there is a risk of the stove running too hot and getting damaged.
Anybody got any thoughts?
 

Shewie

Chief Slackpacker
Staff member
My completely unscientific theory would be that raising the pot places it in a hotter part of the flame? Giving you a shorter boil time because the pot is hotter, maybe an increase in height also allows the fuel to burn hotter, more air flow?
 

WilliamC

Thru Hiker
My completely unscientific theory would be that raising the pot places it in a hotter part of the flame? Giving you a shorter boil time because the pot is hotter, maybe an increase in height also allows the fuel to burn hotter, more air flow?
I was thinking along the same lines. So more air holes to cope with the increased air flow should help with efficiency and get rid of the soot?
 

Mole

Thru Hiker
Agree with the first part of Shewie says.
Doubt the second. No more airflow, but faster burn making it sooty. Add extra airholes one at a time to reduce sooting?
 

WilliamC

Thru Hiker
Agree with the first part of Shewie says.
Doubt the second. No more airflow, but faster burn making it sooty.
I understood Shewie to mean more air flow needed (than the current holes can supply) because burning hotter. Admittedly, he didn't actually write "needed".
Add extra airholes one at a time to reduce sooting?
Great, something to look forward to when we return from the UK:arghh:.
 

Shewie

Chief Slackpacker
Staff member
I've no idea about the sooting, it's not something I've experienced with meths stoves before.
My airflow comment was more about the fuel efficiency dropping, because the pot is higher it's burning hotter and getting through more fuel (&air?)

I've had meths vapourise on the bottom of a pot before in a poorly matched setup, raising the pot usually cured that
 

EM - Tacblades

Ultralighter
On my catboil (fancee feast varient) 20ml of Bio Ethanol makes a seperate large hot drink and a meal, boil in the bag or look what we found meals. Boils in about 4.5mins
 

Teepee

Thru Hiker
Thimblefull.:roflmao:

Good performance though, that's a bit better than my fancee feasts and much quicker.
 
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