bronto

I told someone that my 928 passed smog without catalytic converters (which I installed to actually get the certificate). I was bragging about how clean it ran. His response was that the bar is set lower for older cars.

Is this true? What are the requirements for my '79 vs a newer car?

nosnow

Your '79 has to meet smog requirements of '79. Give the CA legislature a chance and they'd love to make it meet today's requirements.

That said when I look at the measurements of my 86 against my wife's 02 Outback mine are lower and her car has 2 fewer cylinders.

danglerb

Quebec adopts California's auto emission standards
http://www.reuters.com/article/idUSTRE5BS3SM20091229

dr bob

The standards are based on grams-per-mile at the tailpipe, and equate back to the measurable tailpipe PPM and % values. The tailpipe test has no way to consider total mass of exhaust put out per mile. Your wife's outback probably gets better gas mileage than your 928, so even with a higher tailpipe allowance her car pollutes less.

Consider that the average car easily consumes more than 2x its weight in hydrocarbon fuel every year. We get to adjust the ratios of the various contaminants generated by managing combustion and using catalysts to convert from one pollutant to another, but a pound of fuel mixed with about 14 pounds of air will always make about 15 lbs of exhaust.

jeff spahn

Never thought of it that way.

I always take my wife's Acura MDX to Chicago because I can park in the Electric Car/ULEV parking spaces at McCormick Place. Right next to the handicapped spaces. The thing only gets 19 mpg on the highway yet it's an ULEV? Shouldn't it get better mileage?

Or is it that the 19mpg is a very clean 19mpg?

dr bob

If you consider that CO2 is not a pollutant, ULEV designation makes a lot of sense. If you wear a hat that says "cyclical climate change" on it, it makes a lot of sense. The hydrogen and the carbon in the fuel will always be hydrogen and carbon after thay pass from the tank through to the tailpipe, as will the other elements stay what they are. The bonds are reshaped as part of "combustion", so the compounds exiting the pipe may be different while the core elemental components stay the same. When we hear about a 'carbon tax' on our 'carbon footprint', it an effort to drive home the fact that a pound of carbon going in will always result in a pound of carbon going out. Meanwhile, CO is a poison no worse than CO2, except it's effect on humans is harder for the EMT's to treat.

bronto

This is going off topic but it's interesting...

Am I the only one that finds the idea of "14 lbs of air" difficult to grasp? Of course I understand that air has weight, but exactly how much is 14 lbs in terms of volume at sea level? Does one lb of fuel actually require 14 lbs of air? And how much of that air/fuel mixture get lost in heat? After all, that heat is the thing that makes the wheels of our 3500 lb vehicles and propels them forwards at potentially high speeds.

ptuomov

That's only true if you consider H20 and C02 pollutants. I don't think it's reasonable to consider them pollutants, at least not in this context.

dr bob

Re-read post #6 above. There are a lot of folks who subscribe to 'Global Warming' who definitely consider CO2 a pollutant. I know that the power plants I play wath are all required to measure and report CO2 mass emitted, so there are more than a casual number of people concerned about CO2 generated.

Rob--

The idea of 14 lbs of air with every pound of fuel may be hard to grasp, but it is in fact the case. At wide open throttle, the engine sucks in about 2.5 liters of air every revolution of the crank. At idle, with say 20" of manifold vacuum (1/3 of an atmosphere of manifold pressure) it inhales about a third of that mass. Think about how much comes out the exhaust pipe, and consider that it all had to come from somewhere; only about 7% -by mass- is the from the liquid fuel injected.

dr bob

For the curious, "standard atmosphere" density condition is 1.225kg/M^3. This is at sea level, about 60ºF.

bronto

Like I said I don't doubt that air has weight, just what that means in terms of volume. Which I also realize is a poor measure, since it's volume will be larger coming out of the exhaust (since it's hot) than when it came in. Any idea about the loss to heat used to propel the vehicle?

danglerb

Heat changes the pressure, but not the mass flow, what goes in, goes out.

dr bob

Heat actually changes the density, so hot exhaust is less dense than the cooler intake air. Look at the absolute temp of the intake air vs. the exhaust, and the specific volume (1/density) changes directly with the change in absolute temp. Pressure in the head end of the pipe will go up when the specific volume goes up, and you are still trying to pump/push the same mass flow through the same pipe. (we are leaving the moisture component out of this discussion on purpose, for the purists reading along at home.)

ptuomov

Have our comrades in the central planning committee also classified water as a pollutant?

dr bob

Funny you should ask....

Just a winter or two ago there was s problem in Boston, when the accumulated snow couldn't be shoved out into the harbor for fear that the fresh water would somehow contaminate the ocean water popular in the harbor at that time. OK for river water to go in but not snow, apparently. So just let it melt and run off into the harbor....

A couple seasons after hurricane Katrina hit, the FEMA had been warehousing ICE in strategic locations in advance of another similar situation. But the supplier of the ice had thoughtfully added a "use-by" date to the ice bag, and they were nearing expiration. One warehouse containing refrigerated semi-tralers of ice happened to be within a few miles of a power plant in Florida where I'd done some work. They have a huge cooling pond, where evaporation of the water does the cooling. Could we dump all that 'bad' isce into the pond? NO! Itneeded to be passed on only to legitimate government agencies for one, but the biggest argument was about how the ice would contaminate te pond with fresh water. Oh, and the reason for the use-by date on the bags? Freezer burn on the ice, said the FEMA rep. With either a straight face to hide he embarassment, or that look of blind stupidity that is sometimes confused for a look of confidence. Oh, the final solution? Turn off the refrigeration and let it melt into the storm drain system. Where it isn't a pollutant.