why is lean hotter?

[cjridert1]

Searched for a while and couldnt find much. If v. rich, I understand why egts are high, but not why lean mixtures melt pistons. Maybe gas having a higher specific heat than air to absorb more heat/energy?

 

[turbodsm_125]

i think i know what you are asking, i will try me best...Leaner conditions result for a lack of fuel obviously. Fuek is used to cool the combustion chamber. when that fuel is not present the temps of the pistion and heads increases. THus melting internal parts.

 

[baldur]

leaner mixtures burn faster and hotter. Surplus oxygen in the combustion is able to oxidize and combust matter like pistons.

 

[TunaTalon]

Here's a couple of good references from my research on the StrokeOrNot document.

Everything you ever wanted to know about gasoline and the combustion process from the performance engine builders viewpoint.
http://www.jcmmachine.com/PDF files/JCM Tech Report ch 4 to 9.pdf

Normal and abnormal combustion. What really goes wrong to cause those holes in your piston?
http://www.jcmmachine.com/PDF files/JCM Tech Report ch3.pdf

 

[spectr019]

^ ^ ^ ^ ^

Yep yep!!! As much as we may want to lean out our mixtures, each different engine needs a CERTAIN amount of gasoline in it (this is why everybody could have the same exact car but could have different afc settings, for example) to keep the mixture from knocking. When there is a drastic insufficiency of a cooling factor in an engine, that's when engines are 'grenaded.'

Ben

 

[c5chris]

You can lean your mixture out but you gotta replace the extra gasoline used for cooling with methanol or water injection. Keeps the temps lower and takes care of your pistons.

 

[gixxerdrew]

simplified explanation:

Combustion chamber is hot, fuel is cold. You put something cold into something hot and it heats up by absorbing heat that was already in there. If it ignites it makes even more heat if it doesnt it has only absorbed heat and then gets pumped right back out the exhaust. Make sense? Cold only means an absence of heat. The particles of fuel that are cold will get energy from the particles that are already hot in the chamber.

The richer you run the more fuel particles dont absorb enough heat to reach ignition temperature and you increase the number of unburned but now heated fuel particles escaping to the exhaust. Thats why you can smell gas from the tailpipe on a rich burn or it can even ignite in the exhaust and spit flames.