The Electric Car
in [Design]
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From: Nobody on 2 Aug 2007 02:23 On Wed, 01 Aug 2007 07:16:09 -0700, Jim Thompson wrote: >>> If you shift to a lower gear, 3000 RPM is at a lower speed. If there >>> isn't an issue that is well modeled by a fuel leak, the milage would >>> improve. >> >>Ever consider that transmissions aren't equally efficient in all >>gears and perhaps the over-drive locked-up may be a tad more >>efficient than the lower gears? There is also work done just >>spinning the engine. Me thinks you're wrong. > > Don't both Honda and Toyota have models with CVT (continuously > variable transmission) which keeps engine RPM's in a narrow/optimum > range? It isn't just RPM; load torque is also a factor. Optimum efficiency occurs depends upon both. If there's too little load, increasing the gearing will move the load closer to optimal but the speed away from it, and vice-versa. Engines tend to be designed for optimum efficiency at cruising speeds (~60 MPH, 3000-3500 RPM in 4th/5th gear). This helps counteract the inherent losses from increased drag at that speed, keeping the MPG curve relatively flat.
From: JosephKK on 2 Aug 2007 02:44 MooseFET kensmith(a)rahul.net posted to sci.electronics.design: > On Aug 1, 12:09 pm, Spehro Pefhany > <speffS...(a)interlogDOTyou.knowwhat> wrote: >> On Wed, 01 Aug 2007 20:19:03 +0200, René <rjz~REMO...(a)xs4all.nl> >> wrote: >> >> >> >> >On Wed, 01 Aug 2007 18:44:25 +0100, Eeyore >> ><rabbitsfriendsandrelati...(a)hotmail.com> wrote: >> <snip> >> Don't diesel's have to be heavier to support the higher >> compression ratio? > > They usually are bigger and heavier but that is partly because > when you are designing the engine for a train you don't worry > about > weight. The forces in a high performance gas engine are higher > than in a diesel. Any time you squeeze 100 horsepower (75 kW) out of 1 liter displacement you will have very high stress levels. I have such a vehicle.
From: JosephKK on 2 Aug 2007 02:57 Spehro Pefhany speffSNIP(a)interlogDOTyou.knowwhat posted to sci.electronics.design: > On Wed, 01 Aug 2007 08:26:13 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: > >>On Wed, 01 Aug 2007 07:15:06 -0700, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Wed, 01 Aug 2007 06:22:36 -0700, MooseFET <kensmith(a)rahul.net> >>>wrote: >>> >>>>On Jul 31, 9:12 pm, krw <k...(a)att.bizzzz> wrote: >>>>> In article >>>>> <1185930451.854228.138...(a)x35g2000prf.googlegroups.com>, >>>>> kensm...(a)rahul.net says... >>>>> >>>>> >>>>> >>>>> > On Jul 31, 7:21 am, Jim Thompson >>>>> > <To-Email-Use-The-Envelope-I...(a)My- Web-Site.com> wrote: >>>>> > > On Mon, 30 Jul 2007 20:02:28 -0700, Richard Henry >>>>> >>>>> > > <pomer...(a)hotmail.com> wrote: >>>>> > > >On Jul 30, 7:20 pm, Jim Thompson >>>>> > > ><To-Email-Use-The-Envelope-I...(a)My- Web-Site.com> wrote: >>>>> > > >> On Mon, 30 Jul 2007 19:12:03 -0700, Richard Henry >>>>> >>>>> > > >> <pomer...(a)hotmail.com> wrote: >>>>> > > >> >On Jul 30, 5:48 pm, Jim Thompson >>>>> > > >> ><To-Email-Use-The-Envelope-I...(a)My- Web-Site.com> >>>>> > > >> >wrote: >>>>> > > >> >> On Mon, 30 Jul 2007 17:30:01 -0700, "J.A. Legris" >>>>> >>>>> > > >> >> >- I said fuel consumption will never decrease much >>>>> > > >> >> >unless cars are much lighter, but even radically >>>>> > > >> >> >lighter vehicles are no long-term solution on this >>>>> > > >> >> >overpopulated planet >>>>> >>>>> > > >> >> Amen! I keep telling people that, and they look at >>>>> > > >> >> me like I'm some kind of idiot. >>>>> >>>>> > > >> >You have also told us how you like to drive your big >>>>> > > >> >import illegally fast and tried to rationalize it by >>>>> > > >> >claiming that among the vehicle's luxury features is >>>>> > > >> >that it runs more efficiently at high speed. >>>>> >>>>> > > >> I didn't rationalize anything. However I do agree that >>>>> > > >> leftist weenies should be taxed more heavily to support >>>>> > > >> my excesses ;-) >>>>> >>>>> > > >> And I certainly have no problem with YOU driving a tin >>>>> > > >> can, just NOT my children and grandchildren ;-) >>>>> >>>>> > > >OOHH!. Think of the children... >>>>> >>>>> > > >You sound like a leftist weenie. >>>>> >>>>> > > >Please explain again the more-efficient-at-higher-speed >>>>> > > >feature. >>>>> >>>>> > > I don't ever recall saying >>>>> > > "more-efficient-at-higher-speed". >>>>> >>>>> > > But I guess it WOULD depend on your definition. The >>>>> > > engine is optimized right around 3000RPM (85MPH), but >>>>> > > external drag is higher. >>>>> >>>>> > If you shift to a lower gear, 3000 RPM is at a lower speed. >>>>> > If there isn't an issue that is well modeled by a fuel leak, >>>>> > the milage would improve. >>>>> >>>>> Ever consider that transmissions aren't equally efficient in >>>>> all gears >>>> >>>>Yes but he didn't report he was driving with a faulty one. >>>> >>>>> and perhaps the over-drive locked-up may be a tad more >>>>> efficient than the lower gears? >>>> >>>>A tad but not enough to make the difference. The energy per >>>>mile increases as the square of the speed. >>> >>> >>>Not in this graph: >>> >>>http://www.fueleconomy.gov/feg/driveHabits.shtml >>> >>>I've seen a few other mpg-vs-speed curves, and they all look >>>similar. Looks like aerodynamic drag starts to seriously kick in >>>above 55 MPH. >>> >>>John >> >>You need to look at engine horsepower and torque versus RPM as >>well. >> >>Drag DOES depend on body shape. >> >> ...Jim Thompson > > For a given shape, at automotive speeds, I think there is a square > law relationship between air speed and drag. > > Best regards, > Spehro Pefhany The maximum significant contributing order is 4th power (of speed). Just the same, there are significant contributions from the 3/2 power terms and the 3rd power terms (all of speed). These can and do add up to specific strange maxima and minima in fuel efficiency versus speed. Look at the graph again, the shape dictates a minimum order of 4th power of speed best curve fit.
From: Richard Henry on 2 Aug 2007 03:05 On Aug 1, 11:01 pm, JosephKK <joseph_barr...(a)sbcglobal.net> wrote: > Richard Henry pomer...(a)hotmail.com posted to sci.electronics.design: > > > > > > > On Jul 31, 9:38 pm, JosephKK <joseph_barr...(a)sbcglobal.net> wrote: > >> MooseFET kensm...(a)rahul.net posted to sci.electronics.design: > > >> > On Jul 31, 6:48 am, John Larkin > >> > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> On Mon, 30 Jul 2007 23:31:20 -0700, Richard Henry > > >> >> <pomer...(a)hotmail.com> wrote: > >> >> >On Jul 30, 8:25 pm, krw <k...(a)att.bizzzz> wrote: > >> >> >> In article > >> >> >> <1185850948.051175.139...(a)d30g2000prg.googlegroups.com>, > >> >> >> pomer...(a)hotmail.com says... > > >> >> >> > On Jul 30, 7:20 pm, Jim Thompson > >> >> >> > <To-Email-Use-The-Envelope-I...(a)My- Web-Site.com> wrote: > >> >> >> > > On Mon, 30 Jul 2007 19:12:03 -0700, Richard Henry > > >> >> >> > > <pomer...(a)hotmail.com> wrote: > >> >> >> > > >On Jul 30, 5:48 pm, Jim Thompson > >> >> >> > > ><To-Email-Use-The-Envelope-I...(a)My- Web-Site.com> > >> >> >> > > >wrote: > >> >> >> > > >> On Mon, 30 Jul 2007 17:30:01 -0700, "J.A. Legris" > > >> >> >> > > >> >- I said fuel consumption will never decrease much > >> >> >> > > >> >unless cars are much lighter, but even radically > >> >> >> > > >> >lighter vehicles are no long-term solution on this > >> >> >> > > >> >overpopulated planet > > >> >> >> > > >> Amen! I keep telling people that, and they look at > >> >> >> > > >> me like I'm some kind of idiot. > > >> >> >> > > >You have also told us how you like to drive your big > >> >> >> > > >import illegally fast and tried to rationalize it by > >> >> >> > > >claiming that among the vehicle's luxury features is > >> >> >> > > >that it runs more efficiently at high speed. > > >> >> >> > > I didn't rationalize anything. However I do agree that > >> >> >> > > leftist weenies should be taxed more heavily to support > >> >> >> > > my excesses ;-) > > >> >> >> > > And I certainly have no problem with YOU driving a tin > >> >> >> > > can, just NOT my children and grandchildren ;-) > > >> >> >> > OOHH!. Think of the children... > > >> >> >> > You sound like a leftist weenie. > > >> >> >> Not at all. Not "the" children. *HIS* children. There is > >> >> >> a difference. > > >> >> >> > Please explain again the more-efficient-at-higher-speed > >> >> >> > feature. > > >> >> >> It's entirely possible as was explained at the time. > > >> >> >It was bs then and it's bs now. All fancy gearing and > >> >> >ignition tricks will be overcome by the inevitability of the > >> >> >non-linearity of increase of air resistance with speed. > > >> >> The air resistance is highly nonlinear, cubic power:speed > >> >> roughly, whereas other losses are essentially independent of > >> >> speed. Every car will have an optimum speed for miles/gallon, > >> >> and it won't be zero. > > >> > It also won't be much over about 50MPH. It takes about 15 HP > >> > to push > >> > a modest sized car at 50MPH. The windage losses per mile run > >> > as just about the square of the speed. > > >> Not necessarily. My first new car got about 22 mpg at 55 mph and > >> about 26 mpg at 70 mph. Back then i had plenty of documentation > >> to > >> back it up. Kinda funny, 70 mph occurred right the rmp torque > >> peak. It couldn't be a coincidence could it? > > > Documentation? > > > The first question would be: How did you measure it? > > Quite simply, miles traveled divided by fuel to top up again. With > trip the odometer it was very easy. So you drove 70 mph between fillups?
From: babug62 on 2 Aug 2007 03:33
Why waste your energy with 10 minutes charging and grid failure. We can have battery stations like gas stations with efficient chargers. Just need a removable battery pack on cars and use a fork lift. All done in less than 10 minutes....? |