Mileage versus travelling Speed ?? Is there truely exists something like fuel economy Speed? 1

[ninjaz]

I am just curious to know the theory behind vehicle speed versus mileage.
My mechanic advised that vehicle should be driven at optimum speed to get the maximum mileage.Low speed or High speed may result in over fuel consumption.

Is it true?
How low speed consume more fuel.
How high speed consume more fuel.

 

[Tmoose]

Some Prius owners have posted reviews over on Tire Rack. At least one claims to have lost several mspg switching to normal tires I was looking at. I forget which tire brand and model

 

[pickler]

Actually the Prius can operate at bsfc sweet spot while cruising on the highway at ~65mph. This translates to 15kw of power. I would worry more about factors like terrain, driving witg load and witgout bramea than operating at lowest bsfc. Read this:

http://techno-fandom.org/~hobbit/cars/sweet/refl.html

"you're now thinking "gee, if I lock it in at 15+ kW and burn 1.3 gallons in an hour and travel 68 miles at best, that's only 52 miles per gallon!" -- while true on paper, real life driving presents enough opportunities to glide that it generally winds up a good deal higher than that."

 

[pickler]

Without brakes*

 

[GregLocock]

That's an interesting graph, the subtext is that the Prius engine is relatively low powered for that size of vehicle, because any deficit in transient performance is covered by the electric motor. So when cruising it is working at a higher %age of its maximum than in a normal car.


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Tmoose]

Factory Studebaker data ca: 1959

S= six cylinder
V = V8 engine (which V8, and which equipment unknown)

http://i132.photobucket.com/albums/q8/LHSJR/59SGasolinemileagechart.jpg

Unfortunately Stanwood W. Sparrow died in 1952. If he had been behind the above testing, with his NACA and SAE credentials it would have borne even more weight.

 

[ninjaz]

That sounds really intersting. Thanks for the data ..

 

[hydroman247]

That is exactly what I was thinking. What is lowest possible speed in highest gear? I can sit in top gear with the car lurching around trying to maintain minimum operating RPM and be anywhere from there upwards.

 

[IRstuff]

Not "lowest" but "lowest possible," which means that if you are going 60 mph, it's whatever rpm that gets you that speed in the highest gear you have.

TTFN
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[JayMaechtlen]

That Stude info is interesting - it seems to show that the best V8 economy was exactly the same as the best I6 economy!


Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[IRstuff]

It kind of makes sense, though. At the end of the day, the beat mileage should be where the frictional and other losses are overcome. Anything above that just allows you to get there faster, but incurs thermal and other frictional losses.

TTFN
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[Lou Scannon]

That Stude info is interesting - it seems to show that the best V8 economy was exactly the same as the best I6 economy!

That's not surprising, actually. I'm no expert on Studebaker engines, but I do know that the high compression (for the time) OHV V8 was introduced in 1951, while the inline 6 was a pre-war, L-head design.
Oldsmobiles of the time, with their relatively large displacement but high-compression V8 engines were noted for good fuel economy relative to their market position. When comparing automatic transmission equipped vehicles, the Hydramatic transmission was also part of the equation for good fuel economy.


"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[Tmoose]

Studebaker info " seems to show that the best V8 economy was exactly the same as the best I6 economy!"


I think some of the Studebaker ads of around that time talked about the V8 and 6 being best in their classes, but intentionally did not compare the 6s and 8s.
Not sure of the year, but I think Studebaker converted the flathead 6 to OHV around 59/60.