• Dec 10th 2009 at 3:09PM
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Deciphering the new vocabulary of the green car movement can sometimes be a real head scratcher. To alleviate as much confusion as possible, we would like to present our readers with a list of common acronyms and what they mean, with plenty of links for more information. If you have some TLAs (that's three-letter acronyms) that you'd like us to add to our glossary, just let us know in the comments.

B5 (also: B20, B99) – Petroleum diesel fuel mixed with biodiesel. The number is the percentage of biodiesel in the liquid, so B5 is 95 percent petroleum and five percent biodiesel.

BEV – Battery electric vehicle. That is, an electric vehicle without a range extender, like an engine or a hydrogen fuel cell, of any type.

CAFE – Corporate Average Fuel Economy standards. A system used in the United States to define the mileage requirements of new vehicles. More details here.

CARB – The California Air Resources Board. It's mission is, "To promote and protect public health, welfare and ecological resources through the effective and efficient reduction of air pollutants while recognizing and considering the effects on the economy of the state."

CVT – Continuously variable transmission. A type of transmission with an effectively infinite number of gear ratios that provides improved fuel economy because the engine can run at its most efficient revolutions per minute independent of vehicle speed. Wiki here.

DCT – Dual-clutch transmission. A single housing that contains two separate transmissions and clutches. Can improve fuel economy. Wiki here and a video showing how it works is available here.

DI – Direct injection. A type of fuel injection in a gasoline engine that uses high pressure to inject the fuel directly into the combustion chamber. This can provide better fuel efficiency and lowered emissions in some situations. Wiki here.

DSG – Direct shift gearbox. Another name for dual-clutch transmission.

E85 (also: E10, E15) – Petroleum gasoline mixed with ethanol. The number is the percentage of ethanol in the liquid, so E85 is 15 percent petroleum and 85 percent ethanol.

EDTAElectric Drive Transportation Association. Puts on the annual EDTA conference and is self-described as "dedicated to advancing electric drive as a core technology on the road to sustainable mobility. As an advocate for the adoption of electric drive technologies, EDTA serves as the unified voice for the industry and is the primary source of information and education related to electric drive. Our membership includes a diverse representation of vehicle and equipment manufacturers, energy providers, component suppliers and end users."

ER-EV – Extended range electric vehicle. A vehicle that is driven by an electric powertrain but includes a powerplant that can recharge the batteries on the go, through a fuel cell or a liquid-fueled engine. This is GM's preferred term for the Chevy Volt's powertrain.

GTDI – Gasoline turbocharged direct-injection. Gasoline-powere engines that use higher compression ratios and inject fuel just before ignition. Ford's EcoBoost engines use GTDI. Explained in full here and here.

H2 – Hydrogen.

HCCI – Homogeneous charge compression ignition. A gasoline engine that uses high temperatures generated by compressing the intake stream to ignite the fuel. Explained here.

HHO – Hydrogen-on-demand. A way to make hydrogen in a vehicle and use it in the engine. Not commonly accepted as an effective fuel-saving technology.

ICE – Internal combustion engine.

Li-ion – Lithium-ion. A type of battery chemistry commonly used in advanced automobile batteries to provide more power with less weight. Wiki here.

MPGe – Miles per gallon equivalent. A way to calculate the longstanding miles per gallon rating used with liquid fuel-powered vehicles in a vehicle where some of the energy comes from another source, like the electric grid. See more here.

NEV – Neighborhood electric vehicle. Low-speed electric cars that may or may not look like golf carts. Explained in detail here.

NiMH – Nickel-metal hydride. A type of battery chemistry that is used in most of the hybrid vehicles on the road today. Wiki here.

PHEV – Plug in hybrid vehicle. A vehicle with two power sources, one of which is a battery that draws power from an outlet.

PZEV – Partial zero emission vehicle. One of the categories defined by the California Air Resources Board for emissions standards. Wiki here.

SAE – This acronym, which used to stand for the Society of Automotive Engineers, is now just the name of that group and related organizations. Official page here.

SULEV – Super ultra low emission vehicle. One of the categories defined by the California Air Resources Board for emissions standards. Specifics listed here and in this PDF.

SVO – Straight vegetable oil. Liquid fuel that can be used in diesel engines with some modifications. More details here and here.

TDI – Turbocharged direct injection. A name for the modern diesel engines from the Volkswagen group. Wiki here.

TSI – Turbo stratified injection. An engine that uses direct injection with a turbocharger (and sometimes a supercharger) to get more power from the same amount of fuel. More here.

ULEV – Ultra low emission vehicle. One of the categories defined by the California Air Resources Board for emissions standards. Specifics listed here and in this PDF..

VMT – Vehicle miles traveled. The number of miles that all vehicles in a national fleet travel in a given year. More here.

VVT – Variable valve timing. A system that allows the engine computer to change the lift, duration or timing of the intake and/or exhaust valves while in operation. Wiki here.

WVO – Waste vegetable oil. Similar to straight vegetable oil, but describes oil that has been used at least once for another application (e.g., cooking).

ZEV – Zero emission vehicle. One of the categories defined by the California Air Resources Board for emissions standards. Details available here.

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    • 1 Second Ago
      • 5 Years Ago
      So you prefer PHEV to ER-EV. Whichever, as long as we know what we're talking about. Thanks for the vocabulary lesson.
        • 5 Years Ago
        E-REV is a term created by GM specifically for the Volt, likely so they wouldn't have to call it a hybrid and have it get lumped in with the likes of the Prius.

        • 5 Years Ago
        Hmm. ER-EV was in the original list, don't know why it disappeared. Will add it back in.
        • 5 Years Ago
        ""Serial and Parallel is the difference between PHEV and ER-EV."
        No. A PHEV can be either serial or parallel. Same for an ER-EV."

        Correct. And further, a series hybrid can be a PHEV (if it plugs in) or just a HEV (if it does not).
        • 8 Months Ago
        Wait a minute Good Cheer, I do not concur with a ER-HEV (Toyota) being serial. Their are no predominantly serial ER-HEV (Toyota's) in production today. Sooner or later a ER-HEV (Toyota) must be parallel same with a ER-PHEV (Toyota). It can be serial only for a very short time. Predominantly parallel.

        A RE-EVH or ER-EVH (Volt) is serial and never is parallel. The engine never directly drives the wheels.

        Yes anything with a electric ICE combination is a ER-HEV or ER-PHEV but their damn well better be a separate name for the Volt set up because it is never parallel and always serial.

        The above makes reference to mass manufacturing about to begin and already being produced.
        License and title not included, mileage base on EPA estimates your mileage may vary.
        • 5 Years Ago
        Personally, I consider PHEVs and ER-EVs to be different things. A PHEV being mainly driven by an ICE (when it's on) and ER EV, or a serial hybrid, being directly driven by the electric motor.
        • 5 Years Ago
        "Serial and Parallel is the difference between PHEV and ER-EV."

        No. A PHEV can be either serial or parallel. Same for an ER-EV.




        • 5 Years Ago
        Exactly the reason why the term was invented. GM wanted all the green cred of an "electric car," but didn't want to be associated with hybrids like the Prius.
        • 5 Years Ago
        What is the difference between a TSI and GTDI?

        Sounds like HHO is on the down low.

        I want to run some WVO in my SHO.

        Serial and Parallel is the difference between PHEV and ER-EV.

        What's up y'all, yea you know me, I'm down with OPB! Not sure what OPB stands for but it was a song in the late 80's or earlie 90's. Oregon Public Broadcasting?

        Any one know where I can score some B5 man? B5 must be what Tri-met runs in there buses here in P town OR.

        Sorry, just trying to have some fun with it.
        • 8 Months Ago
        "What is the difference between a TSI and GTDI?"

        None. Though there might have been a car that actually did utilize stratified charge. But I might as well confuse it with TFSI.
        (Both is marketing gibberish by VW/Audi.)
        • 5 Years Ago
        OK, not so easy to make a parallel ER-EV. Probably won't see many of those...
      • 5 Years Ago
      Very useful glossary! I would make a correction on the EREV entry - since the Volt does not recharge its batteries.
        • 8 Months Ago
        Good point. It just keeps them in charge sustaining mode.
      • 5 Years Ago
      Suggested addition: PZEV
        • 8 Months Ago
        • 8 Months Ago
        Excellent! +++1
        • 8 Months Ago
        Being a purist EV fan I thought PZEV stood for Pure Zero EV. Partial Zero is more accurate. Unless charging off renew-ables but then pollution was most likely created when the solar panels, wind mill or Dam was built so Partial would still be right.
      • 5 Years Ago
      It would be nice to have this or something like it as a clearly labeled permanent link on the site that would be easily accessible.
        • 8 Months Ago
        We're working on it.
      • 6 Months Ago

      Here is one that should be in the common canon:
      PST: Power Split Transmission.  This is the type of transmission found in most hybrids including the Prius, Ford hybrids, Volt.  It's in just about every non-very mild hybrid apart from Nissan.  It is planetary gearset connecting one engine to two electric motors.
      Instead this transmission is often called an CVT or eCVT.  This is very misleading because it is nothing like the other variable drives, most belt driven.

      Not Rappaport
      • 6 Months Ago

      PZEV is the one that drives me crazy. Because despite the California Air Resources Board's apparent ignorance of basic mathematics, there is no such thing as partial zero. Either it's zero, or it's not.

      • 5 Years Ago
      OMG, IMHO UR 2 Gr8!!!! ROTFL AFAIK
      • 5 Years Ago
      Don't forget the VW TDI ALH has a VNT .
      • 5 Years Ago
      I'm a little disappointed you haven't listed my personal acronym for my EV/Solar Garage combo -

      SSEV - Solar Sourced Electric Vehicle
      • 5 Years Ago
      OMG! I've been looking for a list like this since Y2K. TY!
      • 5 Years Ago
      A very useful glossary, that helps first time reader and when confusion arises.
      Your effort to help the community is laudable and worthy.
      Engineering community can make use of this site and add further the new terms.
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