We talk about and hear a lot about the hybrids that are being offered on the automotive market, we also discuss fully EV models as well, but there’s a classification of vehicle that we don’t discuss much at all and seem to forget is part of the equation when it comes to cutting emissions when we drive. These vehicles are called Partial Zero-Emissions Vehicles (PZEV) and they are made to reduce the emissions by a great deal without you having to add a plug or worry about regenerative braking to keep the electric motors operating and the hybrid parts working.
Currently every Honda Civic, every Mazda6 and most Subarus are sold with this PZEV label on the back, but many times dealers don’t explain exactly what that means and automakers aren’t making a big fuss over these vehicles. That certainly puts PZEV in a category we must discuss and find out why these are the vehicles we want to drive when we don’t want to look to a typical hybrid or EV model.
The PZEV categorization came from the California Air Resources Board (CARB) in 1998 to classify these specially made vehicles. This was well before hybrid and EV models became what they are today and vehicles that are built with PZEV technology inside emit nearly eighty percent less pollutants than typical vehicles. The beauty of these vehicles is the fact they use the same engine and transmission as a traditional model which means they don’t require the same design changes that a hybrid or EV model need.
For all PZEV model there are three unique parts to the fuel system and one in the exhaust to give it the PZEV classification:
Anti-Permeation Fuel System Liners – These liners are made of layers of polymers that block the gasoline vapors from escaping. Typically when a vehicle sits for any length of time the gasoline vapor leaks through some of the outer surfaces of the gas line, but with PZEV vehicles this doesn’t happen.
Carbon Canister Scrubbers – In many PZEV models there are two of these under the hood. The purpose it to capture the gasoline which can evaporate with temperature changes from day to night. The first one captures most of the vapor in the activated carbon and the second one finished the job ensuring at least 95 percent of the vapor is trapped which is then routed into the combustion chamber to be burned off and used.
Carbon Air Intake Trap – This is a trap to capture the vapor that remains in your combustion chamber and intake manifold after you shut off your engine. This trap keeps the vapor from making it into the air and uses a metal honeycomb filter with zeolite or other porous filter minerals to keep this vapor from emitting.
Close-Coupled Catalytic Converters – PZEV models add two of these catalytic converters closer to the engine to be able to reach operating temperatures more quickly. These additional catalytic converters help to convert most of the pollution gasses into less harmful gas before passing into the third catalytic converter near the end of the exhaust pipe.
Why are these vehicles not spoken about more and why aren’t all vehicles PZEV equipped?
To answer the first part of the question we must understand the PZEV hardware is in place to help reduce emissions which cause smog, but these vehicles sill contribute to the greenhouse effect by emitting greenhouse gasses. Because this features only eliminates the potential of smog it’s not as widely necessary a feature as some of the other technologies.
The second part of this question can be answered by one word; cost. Subaru charges its customers $300 more to have PZEV equipment on the vehicle and the fact that it only reduces the emissions and doesn’t add any value to the greenhouse effect might be a reason for many customers to look at EV or hybrid models. Since 1998 more states have adopted the CARB regulations which make it much easier to sell these vehicles all over the country and after 2017 the PZEV classification will go away as every vehicle will carry the features necessary to reduce emissions and be a PZEV vehicle. By 2025 we will have only PZEV models sold in the US, which will certainly reduce emissions greatly across the entire nation.
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