spikez513

Can somebody explain what running lean versus running rich is?? Does running rich mean that the air/fuel ratio is greater than the air/fuel ratio when running lean??.... Please explain in depth... I tried searching for this question but the thread did no seem to fully go into it enough... explain which would cause greater temperatures and why? Thanks a lot....

yuchen

Correct me guys if I am wrong. Spike - I believe that rich means more fuel to air ... and lean is just the reverse. Running lean would generate higher temperatures and more power ... but runnign rich keeps the engine cooler .. but at the expense of more petrol and power.

jguerdat

Running lean doesn't necessarily mean more power but running as close to the stoichiometric ratio does. You want the proper combination for best efficiency (efficiency is what it's all about). That said, lean running can cause so much heat that holes in the tops of pistons can occur. Rich can cause raw gas to wash oil off the cylinder walls and pollute the oil in the system. Best gas mileage can occur by twiddling with spark advance and lean running but it still is centered around the stoichiometric aim point of 14.7:1 (air:fuel).

Economy cars will be tuned to a lean burn and emission control tuned to deal with the increase in NOx. Performance cars will be tuned for a rich mixture and again tuned to handle the increase in unburned hydrocarbons. Since we're driving street cars, the computer can be programmed to achieve a good balance - lean when at a steady state and rich under high loads and RPMs. That's one reason the S can be rated as LEV with the extreme levels of power it can produce.

cjb80

Regarding forced induction applications, you want to run more rich. The higher the number is "14.7:1" (for example) means it is more lean, and richer means the number is lower. For a turbo application, running 12:1 is agressive while still being safe. Some run it up to 12.5:1 but any higher is on the edge.

Running richer can also act as a coolant inside the cylinder, so running rich during various cycles of the engine can help (decelerating for example.) Running lean will cause heat, and will increase EGT temps, and potentially melt components of the engine. Running hotter also leads to uncontrolled fuel burns (detonation.)

Chris

spikez513

i had it backwords before. With the way i thought rich and lean meant, it didn't make sense to me how lean would cause higher temperatures... Thanks a lot guys... Oh and correct me if i'm wrong but for forced induction applications u want to run rich because your trying to compensate for all that air that's coming in??.... But wouldn't it not be running richer than? wouldn't that keep the same ratios if u are adding more more fuel in with bigger injectors?? Okay i might not be making sense.. Please correct my babbling....