The great intake debate!

[fmicle]

I feel like giving up. If you don't understand that 20% is the same as 20% I can't debate you anymore.

20% of 1,000,000 = 200,000 and not 20 ppm. I have a math degree and your statements make me shake my head in disbelief.

The smog checks percentage of pollutants in exhaust, so unless the percentage changes, the smog results are the same, no matter how much are you're pushing through the engine.

To make it easy for you to understand: about 20% of air is oxygen, alright? Whether it's a room full of air or a small bag, it's still 20%. Just because a room has more air it doesn't mean the air is cleaner than in a smaller space!

Here is how the smog check is done - I honestly don't understand how you can even argue with me when you don't know how the smog test is done. You're telling me I am wrong and at the same time you say you don't know how the smog is done! How ridiculous is that?

3. Emissions Test:
So what exactly is the sniffer measuring?

HCs are essentially unburned fuel. When you hear about octane it's often a reference to the anti-knock index at the pump (87 etc) but it is also a reference to the chemical composition of fuel, part of which is made from C8H18 (eight carbon atoms and 18 hydrogen atoms; hence octane). HC is measured in parts per million (ppm) by the sniffer.

When fuel (HC) and air (O2 + N2) are combusted the ideal product would be energy and water vapor (H20). Because the combustion process is imperfect, CO is one of the byproducts produced. CO is measured as a percentage of the exhaust gas. It is a colorless odorless gas and if you breath it, it will combine with the hemoglobin in your blood and make you sick or kill you in larger doses. Running your engine in the garage is a great way to pass out and possibly die.

CO is also used as an indicator of fuel mixture ratio. An ideal percentage of excess CO would be zero. In practice the %CO measured is a few percentage points: a fuel ratio the VW engine can burn efficiently in all climates, temperatures and conditions. For example, 1-2% would be a relatively lean fuel ratio for a VW especially fuel injected models; 10% very rich (so much so that you can smell the unburned fuel from the exhaust pipe).

NOx is produced when combustion chamber temperatures are high. It was once viewed as the #1 enemy and responsible for the smog in the LA basin. At that time emission reducing devices were geared towards reducing it at the expense of other emissions. That was 20 years ago and since then scientists have come to understand that all the emissions are destructive especially CO2 (a harmful greenhouse gas).

Unfortunately on a VW there is no simple way to minimize all three emissions at once like a modern car is able to do. Lower the HC and CO by leaning out the engine and you produce too much NOx and vice versa. Plus, the catalytic converter (which few models are equipped with) can only do its job at the near perfect fuel ratio (theoretically ideal) which isn't the best ratio for long life of an air-cooled engine.