I'm new... don't flame me! Crown Victoria

Discussion in 'Fuel Economy' started by 73VWTodd, Mar 30, 2013.

  1. some_other_dave

    some_other_dave Well-Known Member

    But for most engines, peak BSFC in any gear will almost always mean the car is accelerating. And if you're doing it right, you do very little acceleration--so that becomes even less important.

    For steady-state cruise, use the tallest gear you have, and go as slow as you can stand in that gear.

  2. phoebeisis

    phoebeisis Well-Known Member

    Yeah-tall gear means max throttle opening for that load(pumping losses lowest)
    and lowest RPMs for that load(speed) meaning lowest friction-
    friction is frequently something accelerating oil or other lube out of its way.
    Faster you accel that oil or lube-more power it takes
    Load in this sense -is speed more or less-
    Now lugging limits how tall a gear you can use-especially since folks want acceleration-which mean low effective flywheel mass-
    One reason the prius does so well HY-when it shouldn't-
    is probably because the electric motors allow the ICE to spin 1400 or fewer RPMS without lugging at 60 mph
    Normally a little 1.5 lt 4 3000 lbs would need to spin 1800 RPMs or so at 60 mph to not lug
    PS- that is my guess on one reason the Prius gets such good hy mpg-despite the penalty its forced mech-elect -mech energy transfer should exact.(whole purpose of GM two mode was to not pay that HY penalty)-Toyota pretty clever.
  3. RedylC94

    RedylC94 Well-Known Member

    Mostly OK, but the author fails to understand the difference between BSFC and the more general term SFC, or the difference between power and energy. For example, the statement "It’s the amount of fuel consumed, divided by the power being produced," ain't exactly true. (Should be fuel consumed divided by energy produced, or equivalently fuel consumed per unit time divided by power being produced.)

    The part-load BSFC plots under the "Real World" heading are a step in the right direction, but need to have lines of equal power superimposed, to make it easier to spot the speed-torque combination needed to hit the best possible efficiency at various power levels. Toyota obviously made use of that data to, as he says, to keep the Prius "engine working as much as possible in the area of low SFC (red line)."
    Last edited: Apr 2, 2013
  4. some_other_dave

    some_other_dave Well-Known Member

    Oh, sorry, I forgot one thing:

    *grabs pitchfork and torch*

    OK, now:



  5. pickler

    pickler Well-Known Member

    Well its not all about gearing. I get better fuel economy with my subaru and 4.11 final drive cruising at 70mph and 3000rpm vs my moms acura tl at 1800rpm. Both cars have same power to weight ratio and similar aerodynamics (subaru is slightly less aerodynamic but has 0.5sq ft smaller frontal area and subaru is 4wd). Now this is not to say shorter final drive is better, because its not. Im just sayig there are other factors. For example my subaru's variable vlave Lift keeps the throttle plate completely open during highway cruising which reduces vacuum and pumping losses. The acura completly relies on increasing engine load by operating at lower rpm, an old trick. Finally to get 35mpg in your CV you gotta slow down and do some pulse and glide. You have a v8 in there and so probably the friction levels are tremendous as RPM levels rise. So try and keep RPMs as low as possible while increasing engine load during acceleration. Buy a scangauge.
  6. jcp123

    jcp123 Caliente!

    No flames here. I like Crown Vics. They are also relitively simple to maximise the MPG with careful driving.
  7. phoebeisis

    phoebeisis Well-Known Member

    Yes-Gearing isn't everything.
    My 2004 Nissan Titan 5.6 modern 4 valve V-8 would not quite reach 20 mpg at 60 mph-
    Despite turning just 1520 rpms at 60 mph
    My 98 Suburban gets 21 mpg 5.7 pushrods 2 valve-despite turning 1720 RPMs at 60 mph
    On the other hand my 2001 Tundra 4.7 4 valve-got just 18 mpg at 60 mph-2000 rpms
  8. jcp123

    jcp123 Caliente!

    I was able to pull about 28mpg in a rental CV last year. It's tempting to dip into all that torque, which makes it hard. But it does respond reasonably well to gliding. It's also not the kind of car you really want to hustle in, much more at home in a relaxed cruise which also helps your mental state when trying to peg some more MPG out of it.
  9. 08EscapeHybrid

    08EscapeHybrid Moderator

    Oh yeah. I can better concentrate on my mileage when I'm comfortable too.
  10. jcp123

    jcp123 Caliente!

    They sure are nice cars to drive though. Very smooth, very quiet and confident. Wish more cars packed such a torquey wallop with a smooth ride. I could nitpick, but I won't, because I really do enjoy them.
  11. 08EscapeHybrid

    08EscapeHybrid Moderator

    There's a reason cops and cab drivers love them. If you have to sit in that driver's seat 12 hours/day, you want to be comfortable.
  12. herm

    herm Well-Known Member

    they are also reliable, rugged and dirt cheap to fix
  13. 08EscapeHybrid

    08EscapeHybrid Moderator

    Yeah, that too...
  14. jcp123

    jcp123 Caliente!

    Cop and livery suspension lacks the real smoothness that the "civilian" models do, though, they tend to crash over bumps and such. I think the choice has more to do with V8 punchiness and rear-drive for the cops, and the overbuilt frame and suspension for taxis, plus Ford offered plenty of heavy-duty service options for livery and law enforcement.
  15. phoebeisis

    phoebeisis Well-Known Member

    Around here-NOLA-
    A fair number of airport to downtown taxis were older Suburbans
    for the same reasons
    Cheap to buy
    Cheap to fix
    Sturdy frame steering-rwd
    Downside is obvious-fuel use-but if you have 5- passengers per load-not bad.

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