peter@graffiti.UUCP (Peter da Silva) (01/01/70)
> I have come to the same conclusion as Jan, but not because of fancy > calculations, correct though they may be. Quite simply, most cars sold > today in which mileage is a factor are sold on the basis of EPA Mileage > Estimates, which are conducted at 55mph. Thus, the better the mileage > *at 55mph*, the better the stats, and thus the more the mileage works > in favor of a sale. Any smart company would put a lot of effort into > creating an engine which is highly efficient at that speed. The only > people who would design engines more efficient at higher speeds are > people who are selling to people who don't care about mileage, such as > Rolls owners, or who care more about speed, such as sports car > enthusiasts. > > Ken Arnold Actually european cars are likely to be efficient at 100km/h, 70MPH, or as fast as the tires can handle, by this logic, since these are the speed limits in various foreign countries. 100 km/h is the limit in Australia, Canada, and (I think) France. 70 is or was the limit in England at one time, probably still is. On the German Autobahns there is no limit. On the Autostradas the limit is (I believe) 100 MPH. None of these figures are guaranteed, except for the 100 km/h, since they're the result of a conversation with a Pommy car enthusiast which I'm still trying to dredge out of my mind. Anyone have any better info on this?
cwruacm@cwruecmp.UUCP (CWRU Student Chapter ACM) (01/01/70)
> In article <188@cornell.UUCP> prins@cornell.UUCP (Jan Prins) writes: > >In article <492@lasspvax.UUCP> chu@lasspvax.UUCP (Clare Chu) writes: > >> > >> Correct me if I'm wrong but I heard that some of today's cars > >> get better mileage at 70 mph. (16-valve 4 cyl engine???) > >> > >> Clare > >Attractive as this thought is for the anti-55 crusade, I think it's unlikely > >to be correct. > > 3 > >It's the tyranny of air drag: P = 1/2 rho CdA V . ... > > I have come to the same conclusion as Jan, but not because of fancy > calculations, correct though they may be. Quite simply, most cars sold > today in which mileage is a factor are sold on the basis of EPA Mileage > Estimates, which are conducted at 55mph. Thus, the better the mileage > *at 55mph*, the better the stats, and thus the more the mileage works > in favor of a sale. Any smart company would put a lot of effort into > creating an engine which is highly efficient at that speed. The only > people who would design engines more efficient at higher speeds are > people who are selling to people who don't care about mileage, such as > Rolls owners, or who care more about speed, such as sports car > enthusiasts. > > Ken Arnold my '84 Honda Prelude get ~27 highway @ ~60 but close to 32 @ ~80. windows closed, no AC, singe passenger, alternating trials. xoxorich. Of course 55 is safer. The roads were designed for 70+.
mak@t12tst.UUCP (Tm Mak) (01/01/70)
I had driven a VW rabbit with 3 speed automatic (model year 80) and had make it run to full speedo scale. (don't remember whether it's >80mph or >85mph) The car run O.K. for quite a few hours on AZ freeways. Gas mileage is ~25mpg as far as I rememberd. Was I running at redline? (for a few hours?) It is a surprise to know that. I don't own the car. It was a rental. We still keep diving the same car for several months afterward and without problem. TM Mak
prins@cornell.UUCP (Jan Prins) (08/29/85)
In article <492@lasspvax.UUCP> chu@lasspvax.UUCP (Clare Chu) writes: > > Correct me if I'm wrong but I heard that some of today's cars > get better mileage at 70 mph. (16-valve 4 cyl engine???) > > Clare Attractive as this thought is for the anti-55 crusade, I think it's unlikely to be correct. 3 It's the tyranny of air drag: P = 1/2 rho CdA V . Rear wheel power at 70 mph is about twice that at 55 mph. If specific fuel consumption were constant with engine rpm, twice as much fuel would be consumed for 55/70 of the time. Thus fuel economy would be worse. Actually, below peak torque rpm, specific fuel consumption decreases with increasing rpm, but only by a few percent (esp. with fuel injection). That difference is insufficient to make up the original disadvantage. The induction efficiency (4 valve vs. 2 valve) shouldn't have much effect in this case, since the engine will be operating at part load (induction restricted). Although higher speeds use more fuel, the improvements in car aerodynamics and engine efficiency over the last decade completely dominate the fuel saved by the lower speeds. The speed limit is vestigial: a fool economy. jan vax135!cornell!prins prins@cornell (arpa, uucp, csnet)
arnold@ucsfcgl.UUCP (Ken Arnold%CGL) (09/02/85)
In article <188@cornell.UUCP> prins@cornell.UUCP (Jan Prins) writes: >In article <492@lasspvax.UUCP> chu@lasspvax.UUCP (Clare Chu) writes: >> >> Correct me if I'm wrong but I heard that some of today's cars >> get better mileage at 70 mph. (16-valve 4 cyl engine???) >> >> Clare >Attractive as this thought is for the anti-55 crusade, I think it's unlikely >to be correct. > 3 >It's the tyranny of air drag: P = 1/2 rho CdA V . ... I have come to the same conclusion as Jan, but not because of fancy calculations, correct though they may be. Quite simply, most cars sold today in which mileage is a factor are sold on the basis of EPA Mileage Estimates, which are conducted at 55mph. Thus, the better the mileage *at 55mph*, the better the stats, and thus the more the mileage works in favor of a sale. Any smart company would put a lot of effort into creating an engine which is highly efficient at that speed. The only people who would design engines more efficient at higher speeds are people who are selling to people who don't care about mileage, such as Rolls owners, or who care more about speed, such as sports car enthusiasts. Ken Arnold
mikec@petsd.UUCP (Mike Condict) (09/06/85)
Just two minor points to add to Jan's:
(1) If a car's gear ratios are badly chosen, its speed for best gasoline
economy might be almost arbitratily low. It doesn't matter that the
car could theoretically do better with a higher top gear -- it has what
it has, and theory doesn't save you money at the gas pump. A prime
example is the VW rabbit with 3-speed automatic transmission. It
practically red-lines at 75 mph and it cannot thus achieve its theoretical
best fuel economy at that speed. This is why 5th gears have become almost
standard in newer cars.
(2) I had a 6-cylinder 1977 Plymouth Volare (acceleration 0-60mph: 17 secs)
that got 14 mpg over-all economy when driven gingerly. Now I have a
Porsche 944 (acceleration 0-60mph: 8.3 secs) that gets 20 mpg at 100 mph
and 22 mpg over-all. (It has an mpg gauge!) Which is more environmentally
sound?
Michael C. ...!vax135!petsd!mikecbsisrs@rruxe.UUCP (R. Schiraldi) (09/06/85)
Yeh, But you Porsche is a 4 cylinder, not a big ol' 6 cylinder :-).
Rich Schiraldi
rruxe!bsisrs
"Test... Test... Is this thing on????
We begin bombing in....."mr@hou2h.UUCP (M.RINDSBERG) (09/09/85)
> > I have come to the same conclusion as Jan, but not because of fancy > > calculations, correct though they may be. Quite simply, most cars sold > > today in which mileage is a factor are sold on the basis of EPA Mileage > > Estimates, which are conducted at 55mph. Thus, the better the mileage > > *at 55mph*, the better the stats, and thus the more the mileage works > > in favor of a sale. Any smart company would put a lot of effort into > > creating an engine which is highly efficient at that speed. The only > > people who would design engines more efficient at higher speeds are > > people who are selling to people who don't care about mileage, such as > > Rolls owners, or who care more about speed, such as sports car > > enthusiasts. > > > > Ken Arnold > > Actually european cars are likely to be efficient at 100km/h, 70MPH, or 100 KM/H ====== 62.5 MPH Sorry. > as fast as the tires can handle, by this logic, since these are the speed > limits in various foreign countries. 100 km/h is the limit in Australia, > Canada, and (I think) France. 70 is or was the limit in England at one time, > probably still is. On the German Autobahns there is no limit. On the > Autostradas the limit is (I believe) 100 MPH. None of these figures are > guaranteed, except for the 100 km/h, since they're the result of a conversation > with a Pommy car enthusiast which I'm still trying to dredge out of my mind.
gvcormack@watdaisy.UUCP (Gordon V. Cormack) (09/10/85)
> limits in various foreign countries. 100 km/h is the limit in Australia, > Canada, and (I think) France. 70 is or was the limit in England at one time, > > Anyone have any better info on this? Actually, the speed limit in Canada varies from province to province. Most use 100 km/h on divided highways. A couple use 110 km/h. The default speed limit for 2-lane roads varies from 80 km/h to 100 km/h, depending on the province. I have compiled some statistics on the gas mileage of my 85 Honda GL sedan: 100 km/h: 17 km/l 110 km/h: 15 km/l 120 km/h: 14 km/l 130 km/h: 13 km/l in town: 13 km/l Clearly, there is a direct relationship between speed and fuel consumption. As to the speed at which cars are optimal, (a) I would probably get better mileage still at 90 km/h, but have never driven far enough to measure it. (b) I agree that currently cars are optimized to do well in the EPA (or Transport Canada) tests. Unfortunately, this means they are optimized for a particular artificial dyno test, quite possibly increasing the actual fuel consumption. -- Gordon V. Cormack CS Department, University of Waterloo gvcormack@watdaisy.uucp gvcormack%watdaisy@waterloo.csnet
haapanen@watdcsu.UUCP (Tom Haapanen [DCS]) (09/11/85)
In article <162@graffiti.UUCP> peter@graffiti.UUCP (Peter da Silva) writes: > Actually european cars are likely to be efficient at 100km/h, 70MPH, or > as fast as the tires can handle, by this logic, since these are the speed > limits in various foreign countries. 100 km/h is the limit in Australia, > Canada, and (I think) France. 70 is or was the limit in England at one time, > probably still is. On the German Autobahns there is no limit. On the > Autostradas the limit is (I believe) 100 MPH. None of these figures are > guaranteed, except for the 100 km/h, since they're the result of conversation > with a Pommy car enthusiast which I'm still trying to dredge out of my mind. The European fuel economy is tested on the following cycles: 1. City cycle (probably dyno) 2. Steady 90 km/h (55 mph) 3. Steady 120 km/h (75 mph) These are the European Community standards, and they are used all over Western Europe. The highest fuel economy is always (I have seen no exceptions) attained at 90 km/h. Most of the Scandinavian countries have a speed limit of 100 km/h on primary roads, 80 km/h on secondary roads and 120 km/h on divided highways. In Finland a speeding ticket up to 15 km/h over the limit causes a "normal" fine; anything above that, you get a "day-fine" based on your income. For a computer profesional, a 15 km/h might net a fine of $30, and 30 km/h a fine of $300. Sort of discourages speeding, doesn't it? Radar detectors have been very popular in Finland despite exorbitant prices, but these are now being outlawed. \tom haapanen watmath!watdcsu!haapanen Don't cry, don't do anything No lies, back in the government No tears, party time is here again President Gas is up for president (c) Psychedelic Furs, 1982
msb@lsuc.UUCP (Mark Brader) (09/12/85)
> limits in various foreign countries. 100 km/h is the limit in Australia, > Canada, and (I think) France. 70 is or was the limit in England at one time, England is 70 mph on divided highways, 60 on other roads, cities 30. (Not so long ago all roads outside cities were 70 mph; they didn't believe in telling you to slow down to the design speed of the road. Sort of the US 55 mph attitude in reverse. The 60/70 changes are still not signposted, except maybe on main motorways, which I haven't driven on lately.) France allows 130 km/h (81 mph) on toll expressways, 110 (68) on other divided highways, 90 (56) on two-lane rural roads, 60 (37) in cities. (Incidentally, the change to/from urban speed limit is implicit, at the marked city limit.) Many people speed, too. I liked driving in France. Mark Brader
fred@mot.UUCP (Fred Christiansen) (09/13/85)
> 100km/h, 70 MPH
100 km/h is 62 MPH. this detail provided for the benefit of Americans
travelling to Canada et al.
--
<< Generic disclaimer >>
Fred Christiansen ("Canajun, eh?") @ Motorola Microsystems, Tempe, AZ
UUCP: {seismo!terak, trwrb!flkvax, utzoo!mnetor, ihnp4!btlunix}!mot!fred
ARPA: oakhill!mot!fred@ut-sally.ARPA AT&T: 602-438-3472arnold@ucsfcgl.UUCP (Ken Arnold%CGL) (09/16/85)
In article <1306@cwruecmp.UUCP> cwruacm@cwruecmp.UUCP (CWRU Student Chapter ACM) writes: >my '84 Honda Prelude get ~27 highway @ ~60 but close to 32 @ ~80. >windows closed, no AC, singe passenger, alternating trials. > > xoxorich. How did you arrive at this conclusion? No, I'm serious. I do not mean to insult you, nor do I desire you to flame at me for implying you don't know what you're talking about. I would just like to know your experimental method for determining this. Such a report should include how you eliminated such variables as when the last tune-up was, the terrain over which you drove, any strong headwinds, tire pressure, keeping acceleration and decelartion equivalent in some reasonable fashion, or some methods for making these and other considerations irrelevant (such as borrowing the EPA-like test equipment from somebody). I am NOT saying you did not do this. However, several people I know who have made similar statements had no good experimental data, since they did not consider thses problems. I would be interested to know how you *did* take all these into account. Ken Arnold
che@ptsfb.UUCP (Mitch Che ) (09/17/85)
In article <1306@cwruecmp.UUCP> cwruacm@cwruecmp.UUCP (CWRU Student Chapter ACM) writes: > >my '84 Honda Prelude get ~27 highway @ ~60 but close to 32 @ ~80. >windows closed, no AC, singe passenger, alternating trials. > > xoxorich. > >Of course 55 is safer. The roads were designed for 70+. First "xoxorich" posts an article about identifying a radar jammer and reporting the car to the FBI, Highway Patrol, etc. (how did you identify the car? Did it have a big microwave dish on it? Do you travel in a group of cars for triangulation purposes?) Now you say you get better gas mileage at 80 mph than at 60 in a Honda Prelude??? I get it, we're on Candid Camera, right? Look, you've just GOT to start taking that car out of third gear before you get to 70 mph! :-) -- Mitch Che Pacific Bell --------------------------------------- disclaimer, disclaimer, disclaimer, too (415) 823-2438 uucp: {ihnp4,dual}!ptsfa!ptsfb!che