Finally, the truth about speed bumps and low speed limits

[henk4]

Originally Posted by Matra et Alpine

THe companies running the cameras make lots and lots of profits

good for the economy...

[Fleet 500]

Originally Posted by henk4

If you want to ignore speed bumps buy a big Citroen

Big?

Is it true that an automatic car will use more fuel doing a steady 20 mph than when doing 30?

Yes. Some do. And some don't. Some even get better mileage at 40 mph than at 30 mph. Here is an example:


---------------------------- MPG @ 30 mph- @ 40 mph--- @ 50 mph
'68 AMC Javelin (290-cu-in)------ 24.5----------- 23.5------- 20.5
'68 Ford Mustang (289)---------- 23.5----------- 24.0------- 21.5
'68 Dodge Charger R/T (440)----- 18.0----------- 18.0------- 16.5
'68 Buick Riviera (430)----------- 19.0----------- 19.0------- 17.5
'68 Ford Thunderbird (429)------- 18.5----------- 18.0------- 17.0

'68 Mercedes 250 (152-cu-in)---- 23.5----------- 22.0------- 21.0
'68 Rover 2000 (121)------------ 34.5------------ 31.5------- 28.0
'68 Peugeot (99)---------------- 33.0------------ 31.5------- 29.0
'68 Volvo 144 (109)------------- 31.5------------ 31.0------- 27.0

'68 Ford Galaxie (302-cu-in)----------- 21.0------------ 21.5------- 20.0
'68 Pontiac Catalina (400)------- 19.5------------ 21.5------- 22.0
'68 Dodge Polara (318)---------- 23.5------------ 23.0------- 22.5
'68 Chevrolet Impala (307)------ 21.0------------- 19.5------- 19.5
'68 AMC Ambassador DPL (290)-- 22.5------------- 21.5------- 19.5

Note: the Pontiac had a very high (2.29:1) rear axle ratio which is why it got better mileage at 50 mph than at 30 mph.

[henk4]

thank you very much, in the mean time we have reached 2008, and technology has moved on, also that of autoboxes....

[Fleet 500]

Originally Posted by henk4

thank you very much, in the mean time we have reached 2008, and technology has moved on, also that of autoboxes....

I went back to 1968 cars because I don't think the modern magazines have mpg figures for steady 30, 40 and 50 mph speeds.

[henk4]

Originally Posted by Fleet 500

I went back to 1968 cars because I don't think the modern magazines have mpg figures for steady 30, 40 and 50 mph speeds.

yep, but you might have considered that they could be of very little relevance. Do you think I would have asked the question if modern magazines would produce such figures?

[Fleet 500]

Originally Posted by henk4

yep, but you might have considered that they could be of very little relevance. Do you think I would have asked the question if modern magazines would produce such figures?

I figured that the figures for those 1960s cars were better than no figures at all.
Besides, it should apply to modern cars, too.

[henk4]

Originally Posted by Fleet 500

.
Besides, it should apply to modern cars, too.

why???modern cars have 5-6 speed computer controlled autoboxes, and not 2 or 3 speed torque converters....

[Fleet 500]

Originally Posted by henk4

why???modern cars have 5-6 speed computer controlled autoboxes, and not 2 or 3 speed torque converters....

Because the most efficient speed for most cars, old and new, is 30-40 mph.

[henk4]

Originally Posted by Fleet 500

Because the most efficient speed for most cars, old and new, is 30-40 mph.

bullshit...

[crisis]

Originally Posted by henk4

replace "defensive" with "effective" and you will see much more progress....

I know what you mean but I am referring to the type of course that teaches you what to do in an emergency, where to look and how to steer and brake. Driver training should be more than assing in the road rule questions and being able to park (which everyone forgets after passing the test).

Originally Posted by Matra et Alpine

Watch out their next phase is to then deploy cameras to monitor these new speeds -- and to fine everyone caught.
THe companies running the cameras make lots and lots of profits and nothing happens to the injury/death rate !

Fear not Matra! We have plenty of cameras. They spend more on that technology than on building better roads I rekon. And place them in 50kph zones at the end of 60kph ones or 100kph zones at the end of 110kph ones. I wonder why that is?

[crisis]

Originally Posted by Fleet 500

Because the most efficient speed for most cars, old and new, is 30-40 mph.

It has more to do with the engine revs and effective torque range than the actual speed.

[Fleet 500]

Originally Posted by henk4

bull...

Then post some cars which get better fuel mileage at over 40 mph compared to 30-40.

[Fleet 500]

Wait a minute... alllow me to make a correction. There are some cars that get better mileage at 50 mph than at 30 or 40 mph. Like the Pontiac I posted before:

'68 Pontiac Catalina (400-cu-in engine, 290 hp, 2.29:1 axle ratio, 4,133 lbs curb weight)

MPG @ steady:

30 mph------------ 19.5
40 mph------------ 21.5
50 mph------------ 22.0
60 mph------------ 19.0
70 mph------------ 17.5

[Ferrer]

Originally Posted by Fleet 500

Then post some cars which get better fuel mileage at over 40 mph compared to 30-40.

This isn't highly scientific but the trip computer in the BMW seems to get the best numbers (regarding range, so aplicable to fuel consumption) at about either around 80km/h (~50mph) in fifth or around 110km/h (~68mph) in sixth. However if you decrease the speed the range decreases too. And the same happens if you increase the speed.

[henk4]

Originally Posted by Ferrer

This isn't highly scientific but the trip computer in the BMW seems to get the best numbers (regarding range, so aplicable to fuel consumption) at about either around 80km/h (~50mph) in fifth or around 110km/h (~68mph) in sixth. However if you decrease the speed the range decreases too. And the same happens if you increase the speed.

I'll do some experiments with my trip computer today. And not looking at the range, but looking at the actual fuel consumption at a given speed in a given gear. (like running idle in the lower three gears)