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Optimized Urban Emissions: Reduction to Zero with the Prime

Discussion in 'Prime Fuel Economy & EV Range' started by Oniki, Jan 4, 2018.

  1. Oniki

    Oniki Active Member

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    Despite a personal interest in reducing tailpipe emissions for decades, I have only recently learned that close to 100% of SULEV emissions occur in the ~ first 5 minutes of a drive cycle, when the cat converter has not reached optimal operating conditions. To wit, courtesy of the EPA:

    Cold Emissions.png

    This is a fantastic advantage for a 25+ mile PHEV over a simple hybrid or ICE only car, since it allows any interested owner to reduce urban emissions to zero:

    EV driving for urban only;
    EV in the city and HV outside the city for routes longer than a single charge range

    I now follow this routine in my longer trip driving:
    EV from home until out of town, leaving 20% EV for my destination
    HV in my rural part of the drive
    EV leaving my destination after work, then
    HV until home

    Nerdy data
    • A Prime SULEV ICE emits about 100 mg of NOx during it's FTP warm-up cycle. Heavy acceleration when the Cat is below optimal temp leads to transient high emissions, so the warm-up is best done on an easy load part of the drive.
    • A generic T2B5 ICE emits about 1000 mg on NOx during it's warm-up cycle
    • I *suspect* that an ICE temperature below ~ 150F correlates with a Cat temp below optimal.
     
    #1 Oniki, Jan 4, 2018
    Last edited: Jan 4, 2018
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  2. fotomoto

    fotomoto Senior Member

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    FTFY . (y)
     
    #2 fotomoto, Jan 4, 2018
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  3. Oniki

    Oniki Active Member

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    Not any PHEV. The battery has to be big enough to cover urban only drives between charges, and big enough to get out of the city and the destination on longer drives
     
    #3 Oniki, Jan 4, 2018
    Last edited: Jan 4, 2018
  4. Kramah313

    Kramah313 Active Member

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    I suspect this is why the Prius tries to keep engine RPM low during the warmup phase, running mostly off the battery even though the engine is running.
     
    #4 Kramah313, Jan 4, 2018
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  5. Oniki

    Oniki Active Member

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    Yep!
     
    #5 Oniki, Jan 4, 2018
  6. fotomoto

    fotomoto Senior Member

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    Then a volt is superior to a prime, right?

    About 20 years ago, I moved close enough to work so that any PHEV on the market (even a PIP) meets 98% of my local driving needs. (2% is when I fail to (re)charge for the next trip o_O). I made this move to primarily reduce my economic footprint and secondarily to not live in car: hour each way x 5 days x 50 weeks/yr x 20 years= no thank you. My local fuel economy for our ICE vehicles sucked with all the short drives but our overall gas use was WAY down. Years later, a phev reduced that to nearly 0.

    My point is there is no magic number for EV range in a PHEV since it will vary for each driver.
     
    #6 fotomoto, Jan 4, 2018
  7. Oniki

    Oniki Active Member

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    Probably not, for this specific goal of reducing urban emissions. They should both be able to reduce urban emissions to zero for all but really unusual circumstances. That is why I wrote 25+ range PHEV in the OP. Only edge cases remain.

    The idea is to get out of the urban area before the car farts, and to realize that a warm Cat does not release emissions.
     
    #7 Oniki, Jan 4, 2018
    Last edited: Jan 4, 2018
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  8. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Would a BMW i3-REx be superior to both?

    I have a 2014 BMW i3-REx on the driveway and next to it a 2017 Prime. My real world usage is running 50/50 between the two. The more efficient Prime is best for short trips; the three times longer EV BMW for medium around town, and; the highly efficient hybrid mode Prime for trips over 100 miles.

    Bob Wilson
     
    #8 bwilson4web, Jan 4, 2018
  9. wjtracy

    wjtracy Senior Member

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    I would only point out that all of us Prius drivers are driving CARB certified hybrids/plug-ins that strive very hard (expensive cat converters, etc) to minimize start-up emissions. That's why Gen2 for example gets stinky MPG for the first 5-minutes, because Ca. is wanting to focus on low emissions vs. better MPG. That's also why Toyota CARB warranty wording gets so complex, because Toyota is trying to say just because you bought a Ca. certified vehicle does not mean the CARB warranty applies unless you purchased, registered, and drive the vechicle in a CARB state...etc etc. when your state joined CARB alliance...blah blah

    Now if you purchase say a FORD or GM plug-in or hybrid, say in non-CARB Colorado, your emissions are probably higher than a Prius because the cat converters etc are not CARB. FORD/GM do not need fancy warranty words and records about where the car was purchased- your car is either a CARB car or its not based on the hardware design and sticker. You do still have to live in a CARB state. Not sure recent data, but a few years ago a non-CARB FORD Fusion hybrid MPG was better than Prius for MPG during the warm-up phase. We also had some semi-popular DIY electronic hacks for Gen2/3 to get better MPG during the early start-up phases.
     
    #9 wjtracy, Jan 4, 2018
    Last edited: Jan 4, 2018
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  10. Oniki

    Oniki Active Member

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    Does anybody know of a smartphone app that will read OBD Cat temperature ?
     
    #10 Oniki, Jan 4, 2018
  11. Mark57

    Mark57 2021 Tesla Model 3 LR AWD

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    No app needed . . . :p

    ce8d372da59c1b96bfb3a598dfcbd65a.jpg.png [
     
    #11 Mark57, Jan 4, 2018
    Last edited: Jan 4, 2018
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  12. Oniki

    Oniki Active Member

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    Sorry Mark, I cannot see the photo

    Or was that a feline joke ?
     
    #12 Oniki, Jan 4, 2018
  13. Tideland Prius

    Tideland Prius Moderator of the North
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    To supplement this experiment,

    How long does the city driving have to be before the use of an engine block heater to preheat the engine becomes moot? (i.e. the engine cools down before you're able to hit the highway and use HV mode). A warmer engine would help warm the cat up faster, no?
     
    #13 Tideland Prius, Jan 4, 2018
  14. Mark57

    Mark57 2021 Tesla Model 3 LR AWD

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    Look above, was slow to post.
     
    #14 Mark57, Jan 4, 2018
  15. Oniki

    Oniki Active Member

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    That is an interesting question, but it implies that part of your ICE warm-up cycle is in the urban environment.

    Moreover, the pre-drive warm-up is with extra-urban electricity generation which typically has much greater emissions than those associated with a Prime ICE warm-up. So even when considering the wider context of total NOx emissions, I think your idea would end up having higher emissions.
     
    #15 Oniki, Jan 4, 2018
  16. Tideland Prius

    Tideland Prius Moderator of the North
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    Hmm, it doesn't have to be. I was thinking if you could pre-heat the engine with the EBH but still keep the engine off in the urban environment and only fire it up once you hit the on ramp or at least get out of city limits. The active grille shutter will partially help retain the heat but given that the engine is an aluminium block, I suspect the distance you could travel in an urban environment will be small before the engine cools down to ambient and the benefit is lost.

    In my case, the higher emissions may not be from the car but from "wasting" the electricity used to pre-heat engine.
     
    #16 Tideland Prius, Jan 4, 2018
  17. Oniki

    Oniki Active Member

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    Same thought
     
    #17 Oniki, Jan 4, 2018
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  18. Tideland Prius

    Tideland Prius Moderator of the North
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    Ohh oops. :oops:
     
    #18 Tideland Prius, Jan 4, 2018
  19. hill

    hill High Fiber Member

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    wouldn't a nice block heater - even on warm summer mornings . . . regardless of temps - dump emission/warmups?
    .
     
    #19 hill, Mar 10, 2019
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