Understanding the engine terms “rich” and “lean”?

[^TANK^]

Am I right in thinking to rich means to much petrol and not enough two stroke oil and to lean means to much two stroke oil and not enough petrol? I'm finding this quite confusing please can someone explain this to me as I'm new to the mechanical side of things.

[Hoggin]

Rich means not enough air and too much petrol. Lean means too much air and not enough petrol

 

Nothing to do with the oil, just the ratio of petrol to air.

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Edited October 14, 2012 by Hoggin

[Rich2484]

Yep rich is too much fuel to air ratio.

 

Lean is too much air to fuel ratio.

[^TANK^]

Thank you.

[TimberCutterDartmoor]

In general terms "rich" means fuel-rich from stoichiometric or lambda-1 or in laymans terms more fuel than required for calculated complete combustion in regards to air / fuel ratio. Lean thus means more air and less fuel in relation to a/f ratio - and these ratios are different between fuel and engine types; from memnory a 4-stroke gasoline engine is circa 14:1 i.e. 14 parts air to one part fuel. Overfuelling (rich) not only wastes fuel, but fouls the plug, produces more UHC in the exhaust and so on; engine will run cooler too. Running too lean engine will run hotter and more likely to experience temperature problems. In a 2 stroke, some refer to lean as too much oil in the mixture meaning the mix is thus fuel lean - not to be confused with a/f ratio. Not sure that helps much.

[MATTMOSS]

Am I right in thinking to rich means to much petrol and not enough two stroke oil and to lean means to much two stroke oil and not enough petrol? I'm finding this quite confusing please can someone explain this to me as I'm new to the mechanical side of things.

 

The terms rich and lean refer to the mixture of fuel and air running through the carburettor.

When a saw is running LEAN there is too much AIR and not enough fuel, which leads to serious engine damage.

When a saw is running RICH there is too much FUEL and not enough air, which also causes damage to the engine over time and running problems.

Lots of explanations on the tinternet. Enjoy

[MATTMOSS]

In general terms "rich" means fuel-rich from stoichiometric or lambda-1 or in laymans terms more fuel than required for calculated complete combustion in regards to air / fuel ratio. Lean thus means more air and less fuel in relation to a/f ratio - and these ratios are different between fuel and engine types; from memnory a 4-stroke gasoline engine is circa 14:1 i.e. 14 parts air to one part fuel. Overfuelling (rich) not only wastes fuel, but fouls the plug, produces more UHC in the exhaust and so on; engine will run cooler too. Running too lean engine will run hotter and more likely to experience temperature problems. In a 2 stroke, rich might mean too much oil in the mixture meaning the mix is thus fuel lean - not to be confused with a/f ratio. Not sure that helps much.

 

bloody hell thats hard to understand, even if you know what youre talkin about..

[TimberCutterDartmoor]

Oh and a diesel is inherently lean-burn - much higher vol of air to fuel. A diesel can run rich or lean dependant on injector spray pattern, air cleaner fouling, injection pump advance etc. Much less significant issue than in a gasoline engine tho.

[TimberCutterDartmoor]

bloody hell thats hard to understand, even if you know what youre talkin about..

 

Oh no done it again

[Rich2484]

TCD you need to go to bed mate. Think it's a bit late in the day for all that. :lol: