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Exhaust gas emissions

Vlad,

I agree with many of your points regarding our dependence on oil and the connection to the Middle East. However, there are a few things that need a bit of clarification regarding exhaust gas emissions.

CO2 emissions are directly related to the gas mileage a vehicle gets. A Ford Explorer getting 19 mpg will emit about twice as much CO2 as the Honda Civic getting 38 mpg for a similar distance traveled. This is a definite plus for motorcyclists.

However, this relationship does not follow for other pollutants like CO, NOx and HCs. The 38 mpg Civic is held to the same emission standards at the 25 mpg Cadillac sedan. Each engine meets the requirements with a combination of electronic engine management systems, oxygen sensors, mass air flow sensors, catalytic converters and the like. By design, the Civic might be less polluting than the Cadillac, though maybe not. It certainly has nothing to do with the fact that the Civic has a 1.6 liter engine while the Caddy has a 4.6 liter motor. Certainly, the Civic is not 25/38ths less ‘polluting’ than the Caddy. Trucks are also held to certain standard (less strict than cars, but still reasonably strict). Motorcycles, on the other hand, are held to an even lesser standard than both cars and trucks. As a result, they are pretty stinky. The new CARB regulations are designed to address that (though seemingly at the expense of not allowing exhaust pipe mods) sometime in the near future.

Just because I could, I borrowed a photo-ionization detector (calibrated for gasoline range hydrocarbons, which I will abbreviate as HC) from work and did a little emission tests. My 1999 VFR emitted about 100 ppm HC at idle when warmed up and spiked to 200-300 ppm when the throttle was blipped. A 2002 VFR emitted 25-50 ppm HC at idle (warm) and not much more when the throttle was blipped. That bike conforms with the CARB 2008 (I think…) motorcycle emission regulations. I then tested the 2001 Ford Ranger (4 liter V6) work truck I was borrowing. From cold start, the truck was emitting over 700ppm HC. Within 30 seconds, however, the Ranger’s catalytic converter had warmed up to the point that HC emissions dropped to 0 (below the detection limit of the PID, which is 0.1ppm). Revving the engine still got a 0 result. Same story for my girlfriends CR-V. Of course, this was a very unscientific test as anyone who knows about PIDs can attest to, but should be a good approximation of relative ‘stinkiness’ with regard to HC emissions.

The bottom line is that bikes are a good solution to our dependence on foreign oil (or domestic oil, for that matter). However, in current form, they are in general greater polluters than the SUV herd is.

Jon (VFRGeo)
 

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Re: Exhaust gas emissions

Vlad,

Unfortunately, engines are not created equal. Essentially, every engine is just a big air pump with the sole purpose of pulling in as much air as it can, mixing it with some gas, burning the mixture and pushing out the remains. CO2 emissions are going to scale more or less linearly with gas mileage as it is a natural product of this process. The 40 mpg VFR is going to emit roughly 62.5% of the CO2 that the Caddy does. On the other hand, HC, NOx and CO are products that form when combustion is incomplete. The PID measuring the amount of unburned HCs in the exhaust gas stream did not take into account the total volume of exhaust gasses being emitted from each vehicle, only the gasses the built in air pump could grab. So, at best, the comparisons were qualitative.

What one really needs to do is to magically collect all of the gasses that a VFR and a Caddy emit while they travel the same distance at the same speed. Then take each bag of gas and measure the TOTAL VOLUME of unburned HCs. You will find that the VFR has emitted significantly more HCs (and probably more NOx) than the Caddy. This occurs because the engine management and control systems on the Caddy are vastly more advanced then on the VFR. The Norstar motor in the Cadillac burns fuel much more completely at all RPM ranges and throttle positions then the VFR could ever hope to, and hence is a much ‘cleaner’ vehicle. Late model cars and trucks burn gasoline much more completely than motorcycles do simply because motorcycles lack sophisticated engine management and control systems.

The absolute figure is important, but I wasn’t measuring absolutes out of each vehicle.

Jon
 
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