MPG ?   I think it is nicer to know how much fuel it takes to drive one mile. My car takes .68 liters to go 10 kilometers

Quote from: redhow does that come into an mpg conversation.

good one.

americans are doing 55 on the freeway when they are calculating their mpg.

europeans are doing more like 70 when calculatin their mpg.

its fact that the faster you are going, the more drag you get, the more fuel you use, the less economy, etc etc blah blah.

Matt

yeah but your dig about fighting for something you know is wrong.

tbh im not desputing that as the airs viscosity has more of an impact at higher speeds. thats why teh veyron needs 1001 bhp to get up to 250 mph+ speeds.

Quote from: bytejunkieits fact that the faster you are going, the more drag you get, the more fuel you use, the less economy, etc etc blah blah.

Matt

No its not a simple as that.

Sure if you are going at 90 or something silly you will burn of fuel at a quicker rate, thats simple becuase of the higher revs you constantly have your engine at (depending on you car / gearing ratios.).

Your car will be most efficent at a constant 60-70 MPH.  Its how hard your engine is working and how long it is staying at a constant speed, rather than stop start 30 mph town driving is the most inefficent way of your engine using fuel.

Air resistance has only part to do with it, the engine has to work harder to get up to that speed regardless of resistance forces in the first place.

56mph is supposed to be the most economic speed, which is why the US ended up with 55mph speed limit.

I love it on the news where all parties involved from porduction to sale of petrol are acting like school kids going

"was not me, I didnt do it"

Quote from: Serious56mph is supposed to be the most economic speed, which is why the US ended up with 55mph speed limit.

sounds criminally slow to me, id never get anywhere at that sort of speed

Quote from: neXusI love it on the news where all parties involved from porduction to sale of petrol are acting like school kids going

"was not me, I didnt do it"

yeah its like they are making out the cars all broke down by coincidence

Quote from: Binary Shadow

Quote from: Serious56mph is supposed to be the most economic speed, which is why the US ended up with 55mph speed limit.

sounds criminally slow to me, id never get anywhere at that sort of speed

Thats what all the American motorists said when it was introduced. TBH I think they are all right! Their government eventually dropped it and they can go at up to 80 on the freeway IIRC

/waits to be burned by maxi...

Quote from: Binary Shadow

Quote from: Serious56mph is supposed to be the most economic speed, which is why the US ended up with 55mph speed limit.

sounds criminally slow to me, id never get anywhere at that sort of speed

its not that bad, if i am doing long distances on the DC/Mway i just get to 60 and wack the cruise control on.

i get near 65mpg doing that, goes down to 50~ at 70

ah so thats why theres always 60or less mph on the inside lane and 110+mph on the outside and surprisingly 80 in the middle with patches of 60.. why can no one actually do the speed limit on the motorway?

Quote from: Cypherthe engine has to work harder to get up to that speed regardless of resistance forces in the first place.

why? if there are NO resistance forces, then the engine wont have to work to get to that speed. if we could eliminate all resistance forces, wed not need energy to create motion.

say what you mean cos that doesnt make any sense.

Quote from: Serious56mph is supposed to be the most economic speed, which is why the US ended up with 55mph speed limit.

all depends on the total drag coefficient of the car.

Quotewhy? if there are NO resistance forces, then the engine wont have to work to get to that speed. if we could eliminate all resistance forces, wed not need energy to create motion.

say what you mean cos that doesnt make any sense.

He means air resistance.

If there was no resistance the electric system would leak all the power away and if it did manage anything it would be to fall to bits. Sometimes the English language is just too loose.

Even without that issue a car engine suffers significantly greater stress as speed increases. It still has to shift mass and components have to change direction