EPA and saws

[drkptt]

You guys keep mentioning CO2 and that the EPA says it is a greenhouse gas and wondering where it is on these tests. It's not a greenhouse gas, and they never said it was. People breath out CO2 and it is basically harmless. CO is what they are referring to, which is a greenhouse gas and is emitted any time you burn pretty much anything regardless of how "clean" your fuel source and ignition area (in this case engines) are.

You've got that mixed up. CO2 is a greenhouse gas, it and water are the only products of perfect combustion of a hydrocarbon fuel. CO is a poisonous gas that is a product of incomplete combustion. Unlike the other regulated emissions (NOx, HC, particulates) CO can kill immediately. CO2 is not yet a regulated emission (other than indirectly regulated by fuel-economy standards).

 

[drkptt]

I wonder why they lump HC and NOx together, being as they are two entirely different emissions.
You're gonna have a lot of hydrocarbons with an air cooled 2stroke because it depends on excess fuel for cooling but the oxides of nitrogen should not be that high since they are formed at high temps.
Am I missing something here or is this a non issue?

2-strokes have high HC, low NOx. 4-strokes have low HC, high NOx. If the EPA specified an individual limit for each gas they would have had to set both high, otherwise they would have eliminated one engine technology for the other. By making the assumption that HC and NOx are equally harmful (they both promote the formation of smog) they set limits for their sum total. This allows manufacturers to make legal 2-strokes or 4-strokes, as they choose. That's the way it is for small si engines and outboard motors.

 

[joecool85]

You've got that mixed up. CO2 is a greenhouse gas, it and water are the only products of perfect combustion of a hydrocarbon fuel. CO is a poisonous gas that is a product of incomplete combustion. Unlike the other regulated emissions (NOx, HC, particulates) CO can kill immediately. CO2 is not yet a regulated emission (other than indirectly regulated by fuel-economy standards).

Yeah, I think you're right. Regardless though, I'm more worried about CO than CO2, since CO is dangerous.

That said, the EPA needs to stop worrying about CO2 for now and focus on NOX and HC. Carbon output is only dropped by using less fuel. Right now we have some pretty fuel efficient engines out there, we just need to get them to burn a little more clean and release less NOX and HC.