What makes the Coleman 533 have double the BTU of the Coleman 502?

Two things for 2 cents each. Simmer is an interesting term. Looking up the the word I found simmer is anything under boiling. So there is three types of simmer, I gather, high, medium, and low. So the 502, the 576, the first generation cousins to the 576 and the double burners can do low simmer. The later 508s, 4XX, and the 533 can do high and medium simmer.

Why the later single burners have higher output? My guess that there is less fuel going through the generator tube of the 502. From the air/fuel tube it goes through a restricted line, like the 500. Where as the generator for later single burners, based on the 576 has the fuel go directly to the jet with no restrictions. More fuel, higher outputs. Again just my 2 cents each

 

The solution to increasing the power to the 502 then could be just to replace that thin brass tube with a thicker one!
I'll likely give this a go at some point, when i get my hands on a 502, unless someone beats me to it.

But another thought...will increasing the 502's overall power proportionally increase the low simmer, so it won't be a low simmer anymore but a medium simmer? Well that wouldn't be any good.

 

The 508, 400, 576, 533, & 500 all share the same gas tip. Thus, they all put out the same amount of heat. The 500, however, cannot deliver as much heat to the pot as the other large single burners because the flame is too far away from the pot. The restrictions in the f/a tube are irrelevant as the gas tip is a far larger restriction.

The 502 has a smaller gas tip, leading to decreased output.

Simmering is controlled by the tip cleaner. The large single burners all simmer well, with the exception of the 533. The reason for this is because the generator is not hot enough, and thus flaring occurs.

 

my 533 will turn down but then fades to nothing Have to keep increasing the fuel to hold a simmer.

 

Of course, we don't drink alcohol before or while hiking. Don't know where you may have gotten that idea.

We do one-night backpacking trips; our main thing. We use classic stoves to cook real meals. We bring a baguette, steaks, and various side dishes for dinner. And red wine. Hike in is done. Camp is set up. Campfire is going. Then comes a good dinner....

 

You might need to pump more. I often do upwards of 200 pumps with the 533.

No. The gas tip needs to be larger, and the U-tube intake geometry needs to be adjusted to allow more intake air.

 

Having fabricated many generators for my stoves, let me first correct the phrase about 533 simmering incapability. No, it just simmers very well, so well that you can't see blue flames in the daytime. I keep my tank well pressurized, and operate on the knob for simmering. You can go from HIGH to LOW or from OFF to LOW whaftever you want. Both do the same thing. Sometimes the stove may project yellow flames occasionally, however if you keep the tank well pressurized and the jet clean (turn ON turn OFF a few times) then the stove simmers perfectly.
The BTU values are directly proportional to the combustible amount that enters into burning head. That depends on the jet's orifice. The bigger the orifice the more gases enters into combustion. Also 502 has smaller burning head than 533. I own a 400A, a 533 and a 425F stoves, technically speaking one burner stove's generator's systems are equal even 400A has 2 controls and 533 has only one. Both controls the gas flow by inserting a thin steel wire through the jet. 400A controls this tip cleaner piece with a second lever, 533 controls it through the main valve and a long wire, that is it. There is no gas flow control mechanism similar to propane stoves.

 

I love @Ed Winskill 's approach to backpacking!

 

Fjfj765 has it exactly right. You can only get out of a burner what you put into it fuel wise. It's ALL about the gas tip size. Period end of story. All gas appliances are btu rated by the amount of fuel they consume and the energy available in that fuel. You can easily push enough fuel through that thin supply tube on a 502 to heat a house. But only for about 4 or 5 minutes. The choke point that everything else is sized and engineered for is the gas tip. It's not rocket science, but it's not too far off. You can give an engineer a gas tip size and he can tell you with great accuracy how many BTU it will produce. Home appliances like ranges and furnaces often come with a natural gas to propane conversion kit. The only thing in that kit is a smaller jet for each burner and a set of instructions. Because propane has more energy that the same volume of natural gas.

You could easily drill out the jet on a 502 and get a huge sick flame that out drives the burner. You could add more burner rings, but then it would burn rich. So you'd need to drill out the bunsen to allow more air and wow! You got a heat producing monster, but then the cleaning/regulating needle would no longer be able to throttle the gas tip sufficiently to attain a low flame, so you'd need a fatter cleaning needle. Then you would also have the problem of insufficient back pressure on high to keep the generator and tank pressure at equilibrium and it would probably pulse like hell.

Bottom line: It's fun to play with and experiment, but Coleman engineers knew their stuff. Everything is sized for a reason. You have to be able to get the right balance of fuel, air, velocities, burner output cross section to get that nice blue with sea green tongues from each burner ring corrugation.
You can reinvent the wheels that Coleman produced long ago if you like. And it may be fun. But it may be dangerous too. If you don't understand the theory of what makes these run the way they do, you probably shouldn't be playing with fire, so to speak.