I somehow ended up with two of the Primus...
I somehow ended up with two of the Primus 2243. I need to know the fuel burn on 3/4 power. Four guys, six days at moderate temperature and 3,500 feet. As an alternative, maybe my antique Svea would be a better option. Anyone?
It is very hard to determine the exact amount of flow of any stove; there are a lot of variables to account for...Thats why you will usually never see a consumption amount... BTU's will usually be listed, and flow can be determined from this, but only with the addition of several unknown variables, conversions, etc... When I get a new stove, I perform the following experiment to determine the flow or fuel consumption. You must have access to an accurate gram scale (0.1g resolution will be the best). First I weigh a full bottle of fuel, this creates your reference. Then I would burn the amount of fuel you think you will be consuming, i.e. boil enough water for a planned meal... Now reweigh the fuel canister, the difference between your reference and this value will be a good rough guess of how much fuel is consumed by the experiment performed. Ideally you also want to weigh an empty canister to see how much the empty metal can weighs. Most fuel canisters have a fuel amount rating (size of fuel can), i.e. 100g, 220g, 450g, etc... this is the amount of fuel in the canister. So once you know your approximate burn amount (which can become more accurate with a larger sampling, more burns and reweighing), and the weight of the empty canister, you can easily do the math and determine what size/how many canisters you might need. I usually factor in an additional 20% for safety, but its user discretion. Once you have this data for your different stoves and mfg's of canisters, you can use this method for determining how much life is left in that fuel canister used last year; instead of the shake, hold and guess!? Works great and no more waste, rationing, and guessing...
Dean is right about all the variables, but basically, if you're looking for how many canisters to bring, I would think that 3-8oz canisters would be more than enough, although if you really want to be covered, carry one canister per person- plenty of safety margin, and a fair distribution of weight. You don't appear to have absolutely any problems at all with temperature or altitude. I personally prefer MSR IsoPro for the best performance.
That said, here are some specs from REI's lab-
Max burn time on high w/8oz canister- 50:42 (3/4 power should be about 1hr 3 min)
Avg boil time per liter- 3:28
Water boiled per 100g fuel- 6.8L
If you're going to be using a larger pot for group cooking, get yourself a canister footrest.