Modify Gas Stove for Wok Cooking

I do a lot of wok cooking, using the 14 inch carbon steel wok I bought 40 years ago when I was still in high school. I have a gas stove, supposedly good for wok cooking, but it was never really hot enough. Looking around the internet various people have found various solutions, but a lot only work outdoors, or require a dedicated stove, or they cost a lot.

I just bought a new stove, the hottest burner on my old stove was rated at 12,000 btu, the new is rated at 17,000 btu. I thought it would be a lot better, but it was only slightly better. So I tried a bunch of stuff. It turns out the stove I bought is easy to modify to a wok stove. The burner is now so powerful I usually don't use full power, and when I do I have to completely speed up my cooking technique to handle the heat.

The modification didn't work on my old stove which has an older burner design.

You want burners where you can see the gas orifice from above the cooktop. To see what you have:

1. Remove the burner plate (round cast iron disk)
2. If you have the good type the cast aluminum burner with the ports cast in lifts off as well, and you can see the gas orifice in a little box. In this type the venturi and the primary gas mixing is all done in the cast aluminum burner (more on that later).

If your cast aluminum burner with the ports isn't removable and you see a hole in the middle that doesn't have the gas orifice visible the mod doesn't work. That is how my old stove worked, and the gas mixture coming out of the hole was flowing too slow, and gas velocity is what makes the modification work.

Gas burners use the venturi effect to pre-mix gas with "primary air". The venturi uses the flow from the gas orifice to draw in the right amount of air so it can be delivered to the gas ports where it is burned by the surrounding air (called "secondary air") The primary air mixture in is important. Too little air and you get a yellow flame, soot on your pans and carbon monoxide in your kitchen. Too much air and the mixture can ignite before it on its way to the burner ports, or the flame will blow away from the ports. There are various rules about venturi throat diameter and port area, a well engineered burner has a blue flame and has a high "turndown ratio" (adjustable from a low simmer to high). If you are interested here is a great download.

https://pdhonline.com/courses/m367/m367content.pdf

The picture here is a lot like my old stove. The gas orifice and venturi are under the cooktop and the primary mixture is delivered through several inches of tube.

My new stove is a Samsung NX58R5601SS, $900 from Lowes or Home Depot. I don't think there is anything special about it, other stoves I saw at the store had both types. Fortunately it is easy to check at the store if you are buying a new stove. Burner type doesn't correlate to price. I saw really expensive ranges with supposedly superior "open" (rather than sealed) 25,000 btu burners that would not work as well for wok cooking.

If you remove the cast iron burner plate on the new style burners the gas orifice shoots gas straight up through the hole in the cast aluminum burner, and that gas has enough velocity that when it hits the wok or the grille it acts like a blowtorch. No gentle silent flame here, it sounds like a bunsen burner. The jet draws in plenty of air, and it keeps that gas flames moving across the wok, and that makes all the difference for heat transfer.

The flame is concentrated in the center of the wok, you can see how it boils water.

Yeah, take off the burner plate and it makes that much difference. Compare the boils. Time to boil later in the article.

Not to worry, the flame will be great when it hits the wok. I cut off the fingers of my grille to see the difference. It works about equally.

I tested both cast iron and stamped. The stamped ring came with my wok, I bought the cast ring from Amazon for $24. The cast ring is better, again, air flow. The stamped ring holds the air under the wok, sealing it and reducing gas velocity. The stamped ring with the stock burner is truly terrible, remove the cast iron burner plate and the stamped ring is still worse, but not terrible.

Well, yes. My range came with an orifice kit in case I want to convert it to LP gas. With extra orifices in hand I decided to see what would happen if I drilled one out. The Samsung stove regulates natural gas to 5 inches of H2O. I used a gas orifice chart and did a few calculations. The existing orifice was 1.92mm and the chart predicted 17,300 btu, and the burner is specified as 17,000 so the chart checked out. I decided on a #44 drill (2.18mm) that calculated to 22,400 btu. Works perfectly. I didn't want to make too great a change because I still want a working burner for non-wok cooking. It had no downside. Turndown, flame color, everything just fine. Could I have gone larger still? Maybe, but I don't need to, I already have all the power I want.

After reading about gas burner design I decided to increase the port size in the cast aluminum burner about 25% because I had increased gas flow. ("port loading") It made no difference.

I'm an engineer, and I want quantified results, and that's what you get here. I ran a series of tests timing the time needed to bring a quart of water from 54°F to a full boil:

11 minutes. Stock setup. Cast iron burner plate in place. Stamped wok ring.

6 minutes 20 seconds. Cast iron burner plate in place. Cast wok ring is much a lot better on a stock burner.

Both stock setups were not only slow, but the wok was heated in a ring leaving a cold bottom. That is not how woks are supposed to work! The standard ring of flames is great for flat bottom pans, but not for works.

Now the good results with the cast iron burner plate removed:

4 minutes 40 seconds. Stamped wok ring.

3 minutes 50 seconds. Cast iron wok ring. Fierce boil.

Wow, 11 minutes to under 4.

If you have the burner type with the gas orifice blowing straight up into a removable cast aluminum burner you are in luck. Remove the round cast iron burner plate and the jet blows straight up onto the bottom of the wok for way more speed and a concentrated flame at the bottom of the wok.

• The auto igniter won't work
• You don't get a lot of turndown, about to medium and then you get yellow luminous flames which you don't want. But wok cooking is not about low heat, it is about power. When you want to simmer put the burner plate back on.
• Cast iron wok rings are better than stamped steel. It might seem like the stamped rings trap the heat, but the real effect is to trap the air and slow the gas speed against the wok. A stamped ring is OK with the burner plate removed (that gas jet blowing straight at the wok really helps), but on a stock burner it is terrible.
• Increasing the orifice can work, water boiled in about 80% of the time, and the burner otherwise works fine. Proceed with caution, the stock burner will stop working at some point (yellow flame, blowback, poor turndown ratio). I drilled out an spare orifice so I can revert anytime I want.