Stove Test – Pot Base Diameter vs Boil Speed

[bradmacmt]

So it’s a windy, grey day in SW Montana and since I wasn’t outside thought I’d do a few stove tests I’ve had in mind for a while. Specifically, how does the base diameter of a pot influence boil time.

What got me thinking about this was all the love for the MSR Pocket Rocket Deluxe. I got one when they were first available, used it on one trip, and was underwhelmed compared to the Jetboil Ti I usually use. As a result it’s languished on a shelf unused.

What influenced this test was the nagging idea that the diameter of the pot I’d originally used might not be up to allowing the PRD (Pocket Rocket Deluxe) to achieve its full potential. The pot was a Snow Peak Mini Solo Ti. It’s got a base diameter of 3.75″. That’s essentially the base diameter of a Jetboil, but in the field with wind it didn’t seem to come close to the Jetboil’s boil time.

So here’s the test:

16oz ‘s of H2O @ 44*F (69*F Room Temperature) in each test pot on the MSR PRD brought to a full boil.  Each test I opened the valve 1-1/2 turn to the same position.

The results:

3.75” base Snow Peak Mini Solo 850ml boil @ 2 min 52 sec:

5.15” base Snow Peak Trek Ti 1400ml boil @ 2 min 22 sec:

4.50” base Olicamp XTS 950ml boil @ 1 min 58 sec:

Jetboil Sol Ti (modified cozy) 2 min 12 sec:

Jetboil Sol Al 2 min 15 sec:

The Jetboils were thrown in for comparison’s sake, but the big surprise was how well the Olicamp pot with heat transfer fins did with the MSR Pocket Rocket Deluxe. Of course, my original idea that the base diameter of a pot to be used with any stand-alone stove does matter (especially with one of the Pocket Rocket Deluxe’s power), and it’s clear the larger diameter pot (Snow Peak 1400) beat the smaller diameter pot (Snow Peak Solo 850) by 30 seconds ( a not insignificant amount). BUT the smaller dimension Olicamp with heat exchanger beat the wider SP 1400 by an additional 22 seconds, and the SP solo by 52 seconds (nearly a full minute). The two Jetboils were in a statistical tie.

So, all this leads me to believe if we could get our hands on the new Jetboil Stash pot (apart from the Stash stove) and modify it with three relief grooves to allow the PRD to sit closer to its bottom, we might just have an ideal stove/pot combo for wind and boil speed… maybe :)

 

[Michael B]

This seems in line with physics as well as other tests I’ve seen. You will see even better results if you “dam” the heat in with a windscreen, whether that be with an alcohol stove setup, a remote setup, or a “dam” which involves wrapping the lower half of the pan somehow in way such that the dam is about 1” lower than the bottom surface of the pot. This will force the heat to dwell longer along the bottom pot surface rather than just rising and being carried away.

[Jon Fong / Flat Cat Gear]

Is there any chance that you measured the amount of fuel used?  I was think of running a similar experiment comparing an Evernew pasta pot with an Evernew 1.3 liter pot.  I was going to do the test at different burn rates.

I have been following some conversations over on Trek-Lite and some people are using a BRS 3000t and need 12 grams to boil 500 ml.  They seem to be boiling hot and fast (less than 3 minutes).   When I test it, I use only 6 grams to boil 2 cups (473 ml).   But I also get boil times of 5-7 minutes. I suspect the difference is the burn rate.  My 2 cents.

[Roger Caffin]

I suspect the difference is the burn rate.
Definitely. High rate => low efficiency.
I agree with your figures btw.

three relief grooves to allow the PRD to sit closer to its bottom,
Thereby significantly increasing the CO emission rate, but probably not improving the boil time.

Cheers

[James Marco]

Yup. Note that there are instances where bigger is not better, for example a pie tin (10″dia or 25.4cm) set over a small diameter burner (like a BRS-3000.) Air mixing can occur at a high rate with the center quite hot(2000c) and the edges barely warm (<100c) depending on the amount of heat generated at the center.
With a heat shield/wind screen, you will find the wider pots do very well. I get about 4.5g/500ml boiled (~99c) from 1c(ice water) in 7min with a FMS-300T and a 130mm(5.125″) grease pot. I do this consistently, in the field, though at unknown starting temps. Not the best, but overall, darn good. Larger and/or thicker pots sink, ie soak up, too much heat getting started…basically wasted.

[bradmacmt]

Is there any chance that you measured the amount of fuel used?  I was think of running a similar experiment comparing an Evernew pasta pot with an Evernew 1.3 liter pot.  I was going to do the test at different burn rates.

I have been following some conversations over on Trek-Lite and some people are using a BRS 3000t and need 12 grams to boil 500 ml.  They seem to be boiling hot and fast (less than 3 minutes).   When I test it, I use only 6 grams to boil 2 cups (473 ml).   But I also get boil times of 5-7 minutes. I suspect the difference is the burn rate.  My 2 cents.

You make some very good points. I did weigh the canisters before and after each burn. And indeed, the fuel consumption at turbo was something like the 12 gm’s you mention. My goal was not to find fuel consumption but to measure boil times with various pots at the same (turbo) temp.

However, thinking it over I can see that my efforts may have been a bit of a “false positive.”  I think re-doing the test, running the stoves at a medium heat and turbo and logging fuel consumption as well as boil times for each will probably be the more enlightening test…

Thanks all for sharing your input.

[Michael B]

Was your fuel burn the same for all your test samples, regardless of burn time?

[bradmacmt]

Was your fuel burn the same for all your test samples, regardless of burn time?

With the MSR, the longer the boil, the more fuel consumption. But the Jetboils used less fuel than any of the three MSR boils. Probably doesn’t operate quite as hot at max output, and the heat exchangers DO work. On a long trip I’ve always mused the Jetboil will outperform any canister stove without a heat exchanger, despite a slightly heavier base weight. I suspect this is true, but would have to do more and thorough empirical testing to know for certain, as well as using a fan with a known, consistent airspeed to mimic wind conditions.

[Mark Verber]

In the early 2000s (when the snowpeak gigapower stove ruled) I did a slightly a related fuel efficiency vs pot dimension test. First observation same as roger’s high rate ==> lower efficiency. Saw that larger diameter pots were more efficient. Of the pots I tried, the champs were the evenew “short & wide” pots. In particular the 1.3L was 20% more fuel efficient than the next closest pot I tried.

[Michael B]

With the MSR, the longer the boil, the more fuel consumption. But the Jetboils used less fuel than any of the three MSR boils. Probably doesn’t operate quite as hot at max output, and the heat exchangers DO work.

For some reason, I missed the fact that you used the full jetboil systems, rather than just the pots with the MSR for the test.

The big idea of fuel efficiency is capturing as much heat as possible – boil time improvements are just a way to extend that efficiency, as you are effectively reducing the time allowed for the system to give off its heat. Jetboil accomplishes this with a)heat exchanger to maximize the heat transfer and b)an integrated cozy to insulate the system. You might be onto something, stating that the Jetboil system might not get as hot, i.e. the mfr might have designed the max heating output of their burner such that it is not possible for the user to input more heat into the cook system than the cook system can theoretically absorb, both with the bottom of the pot and the heat exchanger surface area.

I believe you may be right about Jetboil systems being universally better performing. I’d be inclined to reason this is because they designed the entire system so that it is idiot (me) proof, preventing me from trying  to crank up the heat to make it go faster. Most non-integrated systems rely on the user to find a setting that works to their satisfaction; max-BTUs is a selling point for most people, so non-integrated systems mfrs work to maximize the performance metrics they think will convince people to buy their product. Weight and power are usually the metrics people look for.

It would be interesting to take the MSR stove, note its BTU rating, and design a HX system around it that was sized properly to effectively make use of the heat output in a similar manner to the Jetboil.

I just looked up specs for the Sol and the PRD, Sol burner is rated at 4500BTU, PRD is rated at 10400, quite the opportunity to waste more fuel in the name of boil time.

 

 

 

[David Gardner]

“You will see even better results if you “dam” the heat in with a windscreen, whether that be with an alcohol stove setup, a remote setup, or a “dam” which involves wrapping the lower half of the pan somehow in way such that the dam is about 1” lower than the bottom surface of the pot.”

As has been noted before in many places, when using any kind of windscreen with a canister stove: it can be very dangerous very quickly, even when the windscreen does not enclose the canister or sit lower than an inch or so below the pot.

I suspect Jon Fong and I have had similar experience with windscreens that hang about 1″ below the pot, although he focuses on efficiency and runs at low throttle so the effect may not have been as noticeable or a problem for him.

Even without in any way enclosing the canister, and no part of the windscreen lower than an inch below the burner, I was shocked how much heat was reflected back down to the canister, even though it was 3+” below the bottom edge of the windscreen, and even though the windscreen was spaced away from the pot to allow hot gasses to rise.

Perhaps coincidentally, we both have come up with rigs that also include some kind of metal plate below the burner and above the canister. Jon has at least one separate thread here at BPL on his windscreens for canister stoves. This is one of mine:

Partly it seals the whole assembly off from the wind more effectively, but it also helps keep the heat from getting down to the canister. Even with that, when running the rig pictured above at full throttle the canister got too hot very quickly. So I also include an additional, separate heat shield that sits loosely on the canister. Below is an early version. I have since enlarged the hole so that it’s big enough to sit below the standard crimped ridge around every canister Lindal valve:

On the other hand, if I remember correctly, Dan Y.’s canister stove windscreen with folds that space it away from the pot and also act like HX fins, does not include a low heat shield, presumably because it is not needed for his particular design.

Just saying be very careful and test any such design at full throttle and specifically monitor the canister temperature for safety.

[Roger Caffin]

I have been using full-height windscreens (ground to 1/2 way up the pot) on upright stoves for decades, with few problems. But those windscreens were usually no more than a 3/4 surround. I always left room for access to the the valve and for touching the canister.

The reflectors have been around for decades too. Some vendors include them with older stoves. My impression is that few use them as they are fiddly to carry and to set up. After trying them for a few months, I dropped them.

The photo of the white Kovea canister above really worries me. There is a serious restriction on the oxygen inflow to the flames, and that spells serious CO emission to me. CO is toxic and can be fatal.

On the other hand, I fervently support the recommendation to monitor the canister temperature for safety. You are playing with fire and a container of explosive: don’t be stupid.

Cheers

[David Gardner]

Roger, agreed about the Kovea rig. That was an earlier prototype, not meant specifically to show a “right” way to do it, so probably not the best picture I could have used. Current version looks more like Swiss cheese.

When you say fiddly I assume you are referring to reflectors that sit at or near the burner, versus the heat shield sitting on the canister that requires essentially zero fiddling.

[Roger Caffin]

Current version looks more like Swiss cheese.
Air holes: essential. Good.

When you say fiddly
Well, mostly.
Actually, arguably (imho) the biggest problem with the Al reflectors which used to be included was the fact that after folding and unfolding a few times, great cracks at the folds started to appear. That was a right pain!
Perhaps those reflectors were just too big?

Cheers

[David Gardner]

Like on the way, way back MSR GK all-liquid-fuels stove? Maybe the same with MSR liquid fuel stoves today. The folding aluminum windscreen and reflector. I don’t remember seeing those for canister stoves, but it would make sense. The ones in my pictures are Ti or SS, sized just big enough to cover the diameter of the canister and fit into my pots. 2-3 grams of major safety improvement. Also functions as a base sheet for small alcohol/esbit kits.

[Bonzo]

Like on the way, way back MSR GK all-liquid-fuels stove?

Pretty sure I have one of those underneath that most-hated of stoves – the Whisperlite – on my Shelf of Hated Gear, right now.  I would go look, but it would just absolutely ruin my mood.

[Rex Sanders]

MSR still sells those much … loved windscreens separately:

https://www.msrgear.com/stoves/stove-accessories/solid-heat-reflector-with-windscreen/11812.html

Haven’t (ab)used one in decades, but when I did, cracks in the thick aluminum were common. Didn’t notice those flaws affecting the blowtorch-like performance of early MSR gasoline-powered stoves.

And yes, I frequently burned “regular” gasoline straight from gas station pumps. And lived to tell more tales. Somehow.

— Rex

[Bonzo]

Didn’t notice those flaws affecting the blowtorch-like performance of early MSR gasoline-powered stoves.

If all you wanted to do was burn water, they worked great.

[bradmacmt]

I believe you may be right about Jetboil systems being universally better performing.

Michael B, while its fashionable to disdain the Jetboil, I’ve still never found a stove that better combines a quick boil time and miserly fuel consumption, while allowing me to have a compact, fully integrated cooking system that’s as fiddle-free as possible and does an ok job of shedding wind.

I still think it was a fine innovation that could be refined further to shed another couple ounces, though my Ti version is good enough, and far better than any canister stove/pot combo I’ve yet used from almost any perspective (except actual cooking)… :)

[bradmacmt]

All this discussion leads me to wanting to do more testing with simulated wind conditions, and a detailed logging of fuel consumption.

As to “daming heat”… yeah, that can be a somewhat dangerous practice depending on the burner design and how the windscreen integrates with it.

Here’s a windscreen I made for the Gigapower. It’s a Snow Peak Ti bowl. Works great, but the burner style of the Giga really allows for mounting the screen nicely. With a moderate diameter pot it never overheated and worked very nicely. Probably need to test it for boil times, fuel consumption w/ and w/out wind too :)

[obx hiker]

far better than any canister stove/pot combo I’ve yet used from almost any perspective (except actual cooking)… :)

You mean like simmering? Anything? other than water. ;)

I guess it would be thread drift to discuss tactics for use with something that requires some time to cook? Like rice or some pastas. Cold soak along the trail then add hot water at camp. Soak with hot water along the trail on a break (for a little tea Roger) then add some more hot water to re-heat at camp. Oh well. It’s a quandary.

 

[Michael B]

Brad, it is interesting you created that windscreen for that Snow Peak stove when Snow Peak created one almost identical but made from stainless. I have and use that stove still with the stainless windscreen. I am not concerned about the weight penalty as it continues to meet my pack volume requirements and my base is still only around 13lb including a camp chair.

When I recommended putting a “dam” around the bottom, I was assuming that since the discussion was about stoves, that the people in the discussion already are aware of the types of risks associated with chasing thermal efficiency on these types of stoves. I appreciate that it was mentioned, however.

[David Gardner]

while its fashionable to disdain the Jetboil, I’ve still never found a stove that better combines a quick boil time and miserly fuel consumption, while allowing me to have a compact, fully integrated cooking system that’s as fiddle-free as possible and does an ok job of shedding wind.

I don’t know the exact weight or price comparison, but the MSR Windburner is almost invulnerable to wind.

Hikin’ Jim did a real world side-by-side comparison with a Jetboil, putting them on a desert ridge in very breezy conditions. The MSR used more fuel and took a bit longer than it did in calm conditions but still boiled the water. The Jetboil never did.

Don’t mean to endorse or dis- either one, or compare them in any other respect.

 

[Michael B]

With any system, I would bring along something to block wind. Even my food bag can do double duty if needed.

When comparing things to Jetboil, it is easy to forget that there are different BTU ratings for different systems. Flash is 9000 BTU, while the new Stash system is only 4500 BTU, a not insignificant amount. It is good to make sure we are comparing apples to apples here. The Hikin Jim compared a 7000BTU stove system (windburner) to a 4500BTU system (Sol). It would be pretty obvious to me who would win a battle in the wind. It is just a good thing to note when trying to decide what system to buy/use. I bet both work fine when properly protected.

[James Marco]

I believe a lot of the JetBoil disdain is because of the weight. It is relatively easy to design a super efficient system for boiling water/cooking. However, when you consider the weight, you find that efficiency comes at a weight penalty. An alky stove at 1/2oz, a windscreen at 1/2oz and a pot/lid at 3.25oz with a concentric ring heat exchanger gives you a fairly efficient system for boiling water and other light cooking chores. So, 11oz vs 4.5oz not counting fuel containers.The roughly 6oz will go a LONG ways towards efficiency when the difference is only 4gm…about 3 weeks. Nobody really cares about the time, after all, it is all camping out.

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