Wikipedia confusion

Discussion in 'Start Your Journey Here' started by Sharpy, Aug 14, 2007.

  1. Sharpy

    Sharpy New Member

    Hello everyone. I'm a new user from Socal. I drive a 93 Camry v6. I've been trying to save money on gas lately and stumbled on this site. Been driving mostly highways at 55-65. Usually manage to get about 23-24mpg.
    Theres somethingthat confuses me. Wikipedia says on hypermiling that while accelerating, you should keep the engine at the peak of the torque curve and that slow acceleration is less efficient.

    Anyone wanna clear it up for me?

    Side question: Is it possible to pulse and glide w/ a nonhybrid automatic?

    Thanks.
     
  2. desdemona

    desdemona Well-Known Member

    Hi,

    I am sort of a newbie at this, but just want to encourage you on this. I'm not sure that the minimum acceleration is necessarily true.

    Get yourself a Scan Gauge (www.scangauge.com) will help you see everything in real time and what you do and how it effects gas mileage. But if this idea were true wouldn't 2nd gear be terrible for gas mileage. As a matter of fact, it isn't. I tried climbing a hill today, otoh it drove me nuts and I didn't like the sound of it. (Scan gauge said I was getting 76 mpg! Too bad I was only going 10 mph!)

    You can pulse and glide in automatic (without a hybrid). There is an excellent and clear explanation of how to do it here: http://www.cleanmpg.com/forums/fuel...sting-why-illegal-some-places-page2-5780.html

    There is also a nice explanation of driving up hills here:
    http://www.cleanmpg.com/forums/fuel...ow-more-about-driving-with-load-dwl-5809.html


    These answers were helpful to me.

    HTH,

    --des


     
  3. worthywads

    worthywads Don't Feel Like Satan, I am to AAA

    With my truck I've tried many different combinations of throttle and shift points and consistantly found slower acceleration was better. My torque peak is at 3800, but if I shift there my FE plummets, even more if I actually would try to maintain 3800, I get best FE if I'm shifting so that my rpms bottom at 1400-1500 at each shift.

    With automatics and cvt that may be different.
     
  4. igor2

    igor2 Active Member

    it is simple really - at peak torque the engine needs to make the least effort to propel your car with the same acceleration - less effort than at any other point of the rpm spectrum available (0 to red line)

    This means you get the same result of momentum (motion), but the engine is working less.

    The point of the piece over at Wiki is that if you keep the Rev's extremely low, and your engine has very little torque down low you are actually making your engine work hard (and use a lot of gas) even though the Revs (conventionally believed to be correlated with fuel consumption) are low.

    The Torque curve (torque levels at different rpm's) varies from engine to engine - so you have to find the one for yours.

    For example I have a 2.3l I4 in my Mazda3. the Peak torque is 145 ft.lf - at 3500rpms. However, 90% of the torque is available between 2500rpm and 4500rpm - meaning that my engine probably operated the most efficiently at 2500-3000rpm's

    That said - it seems there is a TYPO or mis-explanation in the Wiki piece - because the key is not the actual acceleration - slower is always better - but rpm's (rev's) - where lower is better, but only to a point (the point where your torque starts dropping).

    Igor
     
  5. Pravus Prime

    Pravus Prime Banned

    Hello, and welcome to the site.

    A few little things, a Scangauge won't help you, since it's a 93 and the OBDII port that the SG plugs into isn't on your model, sorry. (It's '96 and newer.)

    Igor2 pretty much hit the nail on the head. In laymans terms, get up to speed, don't push it, don't dilly dally. By keeping the engine working moderately hard to get up to speed, you're far better off than not pushing it at all, in which case it's out of it's element by providing lots of low end power, and keep from flooring it and demanding far more than needed. With every vehicle it's different. For example, in the FEH, you want to keep your RPM's around 2K, as that is a good amount of power and fuel efficiency and is the best point on a torque curve chart in terms of dead stop accelerating.
     
  6. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Sharpy:

    ___Do not believe everything you see on Wiki. Half that stuff is BS given those that wrote it haven’t a clue as to what they are doing or writing about wrt Hypermiling. I wish I had better news but we practice what we preach here on a daily basis vs. the wannabe’s that screw the Wiki site def’s up on a daily basis :( I simply cannot control the non-sense like I should :ccry:

    ___If you are not P&G’ing, a slow and steady accel up to a semi steady state speed is usually the best practice. For P&G, a high load but low R shift point before the Glide to make up for the burn works for me. The two accel methods are completely different.

    ___Good Luck

    ___Wayne
     
  7. Sharpy

    Sharpy New Member

    Thanks for the replies everyone. Ok so let me get this straight...
    Super slow acceleration up to speed isnt necessary and neither is keeping it at the peak torque? Just a nice steady acceleration up to speed?

    Thanks for the reading desdemona. Ill try it out tomorrow. A little afraid of putting it in neutral and back in gear at high speeds. Especially the bit about reving the engine a bit before putting it back to drive. Sounds a bit like that neutral bomb thing.

    I'll try these out on the next tank and see how it goes. =)
     
  8. tbaleno

    tbaleno Well-Known Member

    Disregard everything before what Xcel said. He has the numbers to back it up, so what he says has the most authority.
     
  9. nash

    nash Well-Known Member

    Correct, you want to accelerate at a moderate rate, preferably keeping the engine rpms near the bottom of the torque curve. Google found a curve for the 3VZFE 3.0 engine and it shows a fairly flat curve from about 2300 to 3500 rpm. But I'd say you would likely do well to keep rpms close to 2300 as long as you are accelerating at a reasonable rate.

    [​IMG]

    The "reving the engine a bit" before putting it back in drive is just matching the engine rpm to minimize the driveline jerk as the tranny goes back into drive. Ideally you will not feel the tranny engage if the engine rpm matches the tranny.
     
  10. Sharpy

    Sharpy New Member

    Yea, I've seen that dyno for the 3VZ. That particular camry had a few intake and exhaust mods at the time but the curve should still be fairly close right? I'll try it out around 2300, thanks.

    As for rev matching thing... I've heard of it for manuals, just never heard it practiced on automatics before. Thats why I'm a little afraid :eek: I don't really feel any drive train shock when I drop it back into neutral w/o rev matching. But I'll try it out with it and see if its any smoother.

    I think the big thing for me is going to be DWL over hills. Lots of them from here to school. Ill go buy some fuel injector cleaner later. =D
     

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