Why some generators require a choke and others do not?

spendlove

New Member
My Sportsman propane generator, which is a complete waste because it produces dirty electricity, requires the use of the choke to get started. The DuroMax generator I've seen online says to NEVER choke when using propane. Anyone have a good idea why the difference?

Thanks!
 

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snoobler

Solar Honey Badger
Moderator
Normally, I'd say carb vs. fuel injection, but it's a total guess. Curious when someone who knows chimes in... :)
 

boondox

Chief Engineer, RedNeckTech Industries
The little Honda I converted to propane needs no choke but does need to be primed with a little puff of propane. There is a little button on the regulator. Since propane is less combustible than gas I guess it needs all the air it can get.
 

Camginger

New Member
Here is some answer to your qst. Taril is a funny guy, I learned SO much about small engines, and I fix all my stuff now. So watch this video and you'll get the answer.

 

Arbee

New Member
The choke restricts air flow into the carburetor to make for a rich gasoline to air mixture of fumes for the engine to, well, explode, as an internal combustion engine does. As the engine warms up the choke can be taken off.

Generators that run on gaseous fuels like propane and natural gas don't need a carburetor as they are already in vapor form: the very thing a carburetor does for gasoline so you get an explosion, as your suppose to, rather than a, well, fire, as occurs when you spark liquid gasoline.
 

Hedges

Photon Sorcerer
Carb needs velocity of air through venturi to create vacuum and pull in fuel. At cranking speed not much, but put your hand (or choke) over inlet and engine vacuum is applied to jets, sucks in fuel.
 

Arbee

New Member
Hedges is correct but I want to be somewhat pedantic and clarify. Carburetor's mix air and, well, nearly universally, liquid fuel to create vapor capable of exploding in a sealed chamber: causing the moving of pistons, etc. through the very venturi process described.

Without the creation of such vapor our liquid fuel would burn more than explode. Fuel injectors do the same thing although they're not likely found in most liquid fuel using generators, rather automobiles.

But use a gaseous fuel like propane or natural gas and there is no need for a fuel injector or carburetion. IMHO these are the best fuels to run a home generator on. Industrial generators, where pollution can be controlled with industrial equipment, given the stability of the fuel and the reliability of such engines are best in mission critical sights like hospitals.

Gasoline has limited shelf life without stabilization (6 months), it can gum up the generator over time, it requires more refills and more storage of fuel (as the gas station down the road also out of power can't help you) and is smelly/dirty.

The downsides to propane and natural gas are that they carry less BTUs per volume that gasoline, but this is usually not an issue at the home generator level of operation.

US Carburetion: whose products I've used and like, but I have no affiliation with, sells kits to convert big box store generators that run on gasoline to run on propane, natural gas or gasoline.

https://www.uscarburetion.com/

Finally, somewhat off topic, but if you plan on being able to crank a self starting generator, put a trickle charger on the battery that cranks it. This can invariable be on an electric line not energized by the generator as most generators charge their crank battery when they run anyway.
 

Ironman

New Member
The little Honda I converted to propane needs no choke but does need to be primed with a little puff of propane. There is a little button on the regulator. Since propane is less combustible than gas I guess it needs all the air it can get.
Actually the combustion zone for propane is narrow compared to gasoline. Gasoline will burn from 7 to 19% with air. This means 19 parts air to 1 part gasoline.

With propane, If the mixture is 2% propane and 98% air, there will not be combustion. If the mixture 10% propane and 90% air, combustion will not occur.
Any percentage of propane in a propane/air mixture between 2.15% and 9.6% will be sufficient for propane to burn.
 
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