Featured Nissan claims it's made a more thermally efficient gas engine, but there's a catch

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by Tideland Prius, Feb 27, 2021.

  1. Trollbait

    Trollbait It's a D&D thing

    Feb 7, 2006
    eastern Pennsylvania
    Other Non-Hybrid
    Those are commercial trucks. Generally, anything over 5 tons gross vehicle weight rating is a commercial vehicle.

    A large scale test of trucks of varying weights being driven over a test road was done in the 1950's. This is where the fourth power function per axle load came from. It also tied a damage unit to the axle load for use during road design. A 9 ton single axle load was equal to 1 damage unit. Because of that four-power rule, the damage unit increases faster than the weight of the load. 5 ton is 0.1, and 10 ton is 1.5 for example. https://epd.wisc.edu/tic/wp-content/uploads/sites/3/2019/12/Bltn_002_Vehicle_Load.pdf

    Many cars, ICE, SUV, and BEV are under 1 ton per axle. "Test results show that an automobile axle weighing 2,000 pounds would have to pass over an interstate highway 7,550 times to have the same impact as 20,000 pounds concentrated on a single truck axle." - http://archive.gao.gov/f0302/109884.pdf

    "“The damage due to cars, for practical purposes, when we are designing pavements, is basically zero. It’s not actually zero, but it’s so much smaller -- orders of magnitude smaller -- that we don’t even bother with them,” said Karim Chatti, a civil engineer from Michigan State University in East Lansing." - How Much Damage Do Heavy Trucks Do to Our Roads? | Inside Science
    Or people making armor for tanks aren't concerned with a 9mm pistol chipping the paint.

    If a BEV is truly 1000 pounds heavier than a comparable car, that is 500 pounds to the axle load. A quarter ton in a design formula that sets 9 tons to 1. As mentioned in the quote, the difference isn't zero damage, but it's less than what weather likely accounts for.

    When the difference between the weight of personal cars is brought up for road wear and damage, it's usually just a BS excuse for raises fees on some group. So an old Ranger, a true compact pick up truck, pays a higher registration fee in PA for being a truck. Meanwhile, a Tahoe pulling a 5000 pound trailer pays the lower car fee for being a station wagon. If road damage is truly a problem, the solution is to enforce load limits on commercial trucks.
    austingreen, Prodigyplace and fuzzy1 like this.
  2. Prodigyplace

    Prodigyplace Senior Member

    Nov 1, 2016
    Central Virginia
    2017 Prius
    So they need to raise road diesel fuel taxes and blaming efficient hybrids is just FUD.
    austingreen and Trollbait like this.
  3. austingreen

    austingreen Senior Member

    Nov 3, 2009
    Austin, TX, USA
    2018 Tesla Model 3
    Nissan described the 50% efficient version as having heat recovery systems. From Nissan racing both super gt and a special technology formula one car heat recovery in these sports is done via a turbocharger (e-turbo in winning F1 car). I assume that the 50% efficient version has a turbo like the 50% efficient f1 car and runs the miller cycle in its most efficient mode. None of this has been mentioned by Nissan, but they also have not mentioned another method for heat recovery, and do mention high compression and lambda of 2. This lean of a mixture would only make sense in a blown environment.

    Now I don't actually think they will use a turbo charged 50% efficient version of e-power any time soon. If they really can get a normally aspirated version up to 46% efficient then I don't know why they would spend and charge the extra money for a turbo version. Then again if the battery in e-power stays small, they may turbocharge to save weight and engine size and keep the engine a rather small 3-cylinder 1.2L model while increasing power enough for better acceleration. If they really are only running it in the most efficient range then they may get by with a very inexpensive turbo sized for that power and rpm. A US version might use a different turbo or native compression to keep NOx levels low enough for epa emissions at the expense of a little efficiency.

    I had a chance to review more of the video. It really acts like they are not using turbulent jet ignition (tji) but don't really show the spark plug as part of the cylinder. If it is a stratified charge, my guess is rpm will be kept low so that the flame front can actually fully combust (a problem with stratified charge for lean burn solved by tji). TJI really acts like stratified charge with the benefit of distributing the combusting material. This results in lower NOx and particulates with the penalty of additional mechanical complications.
    vvillovv and Trollbait like this.