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Jetboil Group Cooking Sytem SPOTLITE REVIEW

The second generation Jetboil stove system - efficient, but speed of heating can vary wildly.

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by Roger Caffin | 2006-06-10 03:00:00-06

Jetboil Group Cooking Sytem SPOTLITE REVIEW

Overview

The genuine claim to fame of the Jetboil system is the efficiency of heating, due they say to their 'FluxRing' heat exchanger on the base of the pot. Jetboil claims the stove is twice as fuel-efficient as conventional canister stoves when used with a FluxRing pot. At the time of the release of the original Jetboil product, the Personal Cooking System (PCS), the company also claimed a boil time of two cups in 90 seconds for the PCS. However the current Jetboil web site now claims 2 minutes for this. While the PCS had a 1 liter/quart tall mug as a pot, the pot on this new release, the Group Cooking System (GCS) system, is larger at 1.5 liter/quart (4 cups) capacity, and is more conventional in shape. This pot should usually be enough to cook for three people. Jetboil claims a boil time of 4 minutes for 4 cups for this pot. Understandably, power and efficiency were subjected to careful testing!

The Jetboil Group Cooking System consists of many items, as shown on the picture. The key items are the burner and the pot.

Jetboil Group Cooking System SPOTLIGHT REVIEW - 1
The Fluxring on the underside of the pot
(picture by Jetboil)

The FluxRing is a ring of fins around the base of the pot, made of concertina'd thin aluminium welded to the base of the pot. The pot has an anodised surface, inside and outside, and the anodising is been done after the FluxRing has been welded on. There are two plastic-coated steel swing-out handles on a large steel bracket. The handles are quite strong, and don't get hot even when the stove is run fairly hard. However, the handles and their support bracket are quite heavy in themselves. There are gradations inside the pot at 0.5 L intervals. In addition, Jetboil provides an orange neoprene cozy (middle of photo) which can be left on the pot without damage while it is cooking. This means the FluxRing on the base of the pot does actually trap a lot of the heat from the flames. I have to add that, in my experience, putting a cozy on a pot for the short time it is heating does very little for fuel efficiency. It might keep the pot warm later, but there are other lighter ways of doing this - I use my hat. Far more critical for efficiency is the use of a lid.

The complex heat exchanger on the underside of the pot does need protecting in your pack, so Jetboil provides a special rugged black plastic cover for the base of the pot. This adds weight of course. Jetboil also provides plastic clip-on lid, which is a bit heavy compared to the shim aluminium lid I use on another pot, but it does seal quite well, and keeps everything inside when packing. Less obvious is the idea that both of these plastic bits can be used as plates, although the bottom cover is a shade flexible even when cold. In addition, the bottom cover has gradations for 2 and 4 cup volumes. This dual use does help with the overall weight.

Jetboil Group Cooking System SPOTLIGHT REVIEW - 2
The Jetboil burner face, pot supports and igniter

The stove itself is made of brass, plastic and steel. Jetboil seem to be seriously concerned about the strength of the connection between the canister and the stove as the hard black plastic surround under the burner has legs which go down almost to the gas canister. What actual use they serve is not clear however, because there is a 0.12 inch (3 mm) gap between the canister and the legs. The author has never had any problem with the strength of the connection between any stove and any gas canister. The burner itself has a face which seems to be made of woven steel mesh in the middle and perforated steel around the edge. The reason for the two different materials eludes me, but the flame produced is quite smooth. This is different from most other stoves where there is a distinct flame from each little hole in the burner head. There is a well-shrouded piezo-igniter built inside the stove, although popular opinion about piezo-igniters does not give them a very long life. The button on this one has to be really fully depressed to make it work.

The actual pot support part can be separated from the burner and the legs folded sideways. They still stick up, but the diameter is reduced a little. It is helpfully labeled 'this side up' in the picture. The whole burner can fit inside the pot with the plastic lid on. The Jetboil product photos show a gas canister fitting inside the pot along with the stove. Be warned that this is a 100 g canister, not the more popular 220 g one which is both more weight-efficient and economical. The 220 g canister does not fit inside the pot. Given the inevitable rattling around which gear does in a pack, the user would be well-advised to put some padding between the canister and the pot when packing, or risk having the anodising scraped off over time.

Finally, Jetboil includes a canister stand with fold-out legs in the kit - this is the triangular spider thing at the left in the top picture. It has notches for both the 100 g and 220 g versions of the canister, and non-slip rubber pads at the tips. To be sure, it is light and can add stability, but does one really need it? I have to confess that while I was at first a bit dismissive of the spider, the lightness of it grew on me over time. I find it can be used instead of a base plate as the downwards radiation from this stove is very small. Base plates are usually a bit heavier.

Jetboil Group Cooking System SPOTLIGHT REVIEW - 3
The Jetboil stove in action at the top of Du Faur Buttress, Blue Mts, Australia (Coleman canister used here)

Testing

Testing was done at 'room conditions' (around 18 C or 64 F), with cold water at about 15 C or 59 F. The standard test volume was 1.0 liter (4 cups). The stove was run flat out with the valve wide open and only the jet limiting the gas flow. Wind protection was used around the stove, although it does not seem to be especially sensitive to wind. Testing was done with two different canisters: a heavily-used Coleman gas canister which contained 70% n-butane / 30% propane when new, and a full Kovea canister which contained 70% isobutane / 30% propane. The used Coleman canister had been used in the cold a fair bit, and it is likely that by the time of this test the propane fraction had dropped significantly, to maybe 15% propane. The significance of this will be explained below. Time to boil for the two different canisters and weight of gas used are listed in the table below.

Analysis of Test Results

CanisterBoil time Fuel used
Coleman 8:20 10 g (0.35 oz)
Kovea 5:10 10 g (0.35 oz)

The difference in boil times is immediately obvious, and quite startling. The slower speed is entirely consistent with the previous Backpacking Light initial tests which showed a boil time of (effectively) 8:30 minutes for 1 liter (4 cups). Tests by other groups have since duplicated these general findings of slow speeds. But the second test showed a remarkable improvement. What is going on here?

The answer lies in the quantity and composition of the gas in the canister. The Coleman canister contained mainly n-butane, and n-butane boils at -0.5 C (31 F). With only a small amount of gas left in the canister, the temperature dropped quite rapidly during the testing, and was only just above the boiling point. The pressure driving the gas through the jet was not high. Contrast this with the full Kovea canister. The isobutane boils at -12 C (10 F), while the propane boils at -42 C (-44 F). Anything near room temperature will be much further above the boiling points of these liquids, and the pressure inside the canister will be much higher. Further, the full tank of gas will cool down much more slowly as it has greater thermal mass. Looking at pressure/temperature curves for the three gases, it seems quite reasonable to say that the pressure in the new Kovea canister may have been nearly double that in the Coleman canister. Double the driving pressure translates to double the gas flow through the fixed-size jet, assuming the valve was wide open in each case. It was. So the Kovea canister could drive the stove at nearly double the power - and this is reflected in the shorter boil time.

Convincing though this explanation may be, it should be noted that original test referred to used a Jetboil canister, not a Coleman one. Since the stove was new at the time it could be assumed that the canister was new with the stove, and therefore full. However, it is more than two years since that test was done, and we don't know what other factors might have affected the result. The current results have been taken under carefully controlled test conditions.

The fuel consumption for both canisters of 10 grams for 1 liter is good. The author normally uses about 15 grams of gas to boil 1 liter of water under similar conditions - without the FluxRing. Jetboil claims their system is twice as efficient as the competition, but the author's figures only make it 50% better. Jetboil claims a fuel efficiency of 75 - 80%, which would make the efficiency of the conventional stoves around 50%. This is consistent with the author's experience and measurements over many other stoves. Jetboil claims the FluxRing is responsible for this improved efficiency, and the author would agree with this. The tests were done with the neoprene cozy in place, and that was not affected by the heat. The gas coming up the side of the pot above the FluxRing was not too hot: the author could hold his hand near the pot quite safely. So the FluxRing-enhanced pot base was certainly absorbing a lot more heat from the flames than an ordinary pot could. However, it does mean that the user is restricted to using just this pot if this sort of fuel efficiency is required.

It is worth noting that Jetboil themselves claim the power output of the stove is about 4,500 BTU/hr, while similar stoves usually claim about 10,000 BTU or more. This is fully consistent with the reduced gas consumption. Regardless of the stove design, the lower power output does mean that using this stove with a non-FluxRing pot is going to give quite slow performance.

Assessment

It seems the performance of this stove is limited by the gas pressure in the canister, while the gas pressure is of course highly dependent on the temperature of the canister. During testing the temperature of the canister fell as the gas evaporated. If the starting temperature of the canister had been, say, 10 C (18 F) higher, even better performance would have been obtained as the internal pressure would have been nearly 50% higher. So the stove should really 'go' on a hot summer day, but using this stove in the snow could prove to be a very slow exercise.

Is this Jetboil Group Cooking System going to be the answer to the lightweight walker's dreams? Probably not. It is well made, it is quite fuel efficient and it is fairly wind-resistant. Under the right test conditions the performance comes close to the claims made by Jetboil, but that requires a new canister of the right sort and quite warm weather. In the author's experience, other stoves seem to be much less sensitive to these factors. Finally, and sadly, both the pot system and the stove are heavier than the competition.

Features and Specifications

  • Stove burner with integrated pot support and piezo ignition: 7.34 oz (208 g)
  • Aluminium pot: 1.5 L (1.5 qt) capacity, 7.87 oz, 223 g
  • Pot dimensions: 180 mm dia x 90 mm high (7" x 3.6")
  • Anodised surface, inside and outside
  • 'FluxRing' heat exchanger on base of pot
  • Protective plastic cover for base of pot: 1.45 oz (41 g)
  • Plastic lid for pot: 1.69 oz (48 g)
  • Neoprene pot cozy: 0.78 oz (22 g)
  • Gas canister stabiliser, plastic: 0.92 oz (26 g)
  • Total weight: claimed: 19 oz (540 g); measured: 20.0 oz (568 g)
  • Boil time for 1 L: claimed: 4:00 minutes; measured: 5:10 minutes
  • MSRP US$109.95 for the full system

Citation

"Jetboil Group Cooking Sytem SPOTLITE REVIEW," by Roger Caffin. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/jetboil_group_cooking_system_spotlite_review.html, 2006-06-10 03:00:00-06.

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