MUST READ!!! MPH to RPM to Time ratios,gas savings!

[eco]

Mph /Rpm /Rpm÷mph /Time to drive 60 miles


45 /1940 /43.111 /1h20m
50 /2150 /43 /1h12m
55 /2360 /42.90 /1h6m
60 /2575 /42.916 /1hour
65 /2770 /42.615 /55minutes
70 /2990 /42.714 /51m
75 /3200 /42.666 /48m
80 /3380 /42.25 /45m
85 /3660 /43.058 /42m
90 /3840 /42.666 /39m


I understand these ratios only stand true for my 1NZ-FE 1.5,but yours are very similar,if not exactly the same.So it looks like your efficiency actually improves slightly at higher MPH's until you hit 85mph,this is shown by dividing the rpm by the mph.
Now on to the time issue,so the car is just as efficient at higher mph's,so you should only be worried about how fast you need to be some where.Please feel free test this yourself,use cruise control at set speeds on flat road,take the average rpm (it was easy for me,I have scangauge,set to update fast),now write that down,use 5mph levels.

[BailOut]

Your data is severely flawed as it omits 3 critical factors:

1) Engine resistance at high RPM
2) Wind resistance
3) Rolling resistance

With those in place fuel efficiency begins to fall off above 55 MPH, drastically so above 65 MPH.

[eco]

That may be ture,I always thought your rpm was the true test of what forces are being put on the car,picture yourself going uphill,higher rpm,even though your trying to stay at a set speed,think about it.If the car was being affected so much,then why dosnt it show in a higher rpm/mph ratio when divided compared to a lower mph.

[eco]

Also,I was not behind any car while testing,but in real world conditions,driving in this area,its hard not to be near a car any where from 55-95 here in Atlanta,and metro Atlanta.So if even minor drafting,lets say wind resistance is dropped by 20-30%,and keep in mind "TIME IS MONEY",its still way better then driving 55mph,you might remeber that song.

[eco]

I guess no one else has any feed back,damn,I can take negative feed back,but I still believe in my numbers.

[SmallCarGuy]

Here's good data to include as well....

Realistically, the force of air resistance from 55+ is crazy.... and it takes much more hp at 65 than 55 to go against the wind resistance of a vehicle... even more so at 75,85, 95, etc....

http://www.racerpartswholesale.com/images/_8387_tabular88.gif

Here's info from a physics dude who worked out for a situation about how much HP is takes to overcome wind drag at certain speeds... (HIGHLY effecting MPG) These are for the drag of a CORVETTE, so our drag is probably MUCH, MUCH more... making these numbers worse...

30 MPH - 1.16 hp
55 MPH - 7.14 hp
65 MPH - 11.8 hp
75 MPH - 17.12 hp
90 MPH - 31.3 hp
120 MPH - 74.2 hp

[SDsurfrider]

maybe there would be more to be said if you explained how you got your data?

[eco]

I have measured many tank fulls of gas,at set speeds aswell,my trips are 95% highway,and I can still get 32-34mpg at 90mph,and I have been able to hit 47mpg at 55mph,this is very hard to achieve.So for a car that is only supposed to get 39 highway,and I can get 32-34 semi-speeding,then its still more efficent time wise to go this speed,because the mpg and the mph do not change at the same ratio.Say I was going 50mph and was able to get a steady 42mpg,so if I was going 100mph and only got 21mpg,it would be the same diffrence compared to time,but I bet I would still get about 30mpg,only losing about 25% in mpg,but going twice as fast.
And if wind resistance affected a car so much after 55mph,you might think you would only get 5mpg at 100mph,thats just plain BS.Remember there was a time when the experts and guinesses thought you would be ripped apart if you went over 50mph,what a crock of shit,so dont forget things that are thought to be true,arnt always true.

[SmallCarGuy]

At 90 MPH, it takes approxamently 31.3 hp just to overcome air resistance on a corvette, I'd say much more on a much less aerodynamic yaris... at 120 mph, is takes approxiamently 74.2 hp to overcome air resistance alone on a corvette... it gets crazy past that...

It's just physics. overcoming air resistance on a yaris past 55 just takes more and more fuel. and the reason why going faster than around 55-65 results in a less efficient consumption of gas, as at a speed like 75, the engine is using at least 15 more hp to maintain speed than at 55, just solely due to air resistance alone, no matter what the RPM of the engine is.

LoL... I'm sure scientists are wrong on all this though... after all, Indy Racers and their fuel consumption isn't important, and the science behind drag, HP, and top speed has nothing to do with Race car design.... (Satire!)

Here's a bit more from my source regarding hp to speed...

It only requires about 7 hp to overcome drag at 55 mph, while it requires almost 12 hp to overcome drag at 65. Fuel consumption is approximately proportional to horsepower expended, so the additional hp required, requires more fuel consumption.

More interesting to the racer is the fact that it takes 145 hp to overcome drag at 150 mph. We know that our Corvette example car has about 240 hp, so about 95 hp must be going into overcoming rolling resistance and the slight braking forces arising from internal friction in the drive train and wheel bearings. Race cars capable of going 200 mph usually have at least 650 hp, about 350 of which goes into overcoming air resistance. It is probably possible to go 200 mph with a car in the 450-500 hp range, but such a car would have very good aerodynamics; expensive, low-friction internal parts; and low rolling resistance tires, which are designed to have the smallest possible contact patch like high performance bicycle tires, and are therefore not good for handling.

[SmallCarGuy]

BTW- IF your curious.... read up...

What I've thrown in is from articles and info tied to, or referring to this document, which is widely recognized as an amazing source of info regarding the physics of racing and race car design.

http://autopedia.com/stuttgart-west/Physics/StuttPhysics01.html

[SDsurfrider]

my trips are 95% highway,and I can still get 32-34mpg at 90mph

I can get 32-34 semi-speeding,then its still more efficent time wise to go this speed

what do you consider speeding if that is only semi speeding? If you are basing this logic on a cost efficiency basis. Wouldn't the impending speeding tickets also come into play?:thumbdown:

[eco]

No because the speed limits in metro atlanta range from 55-70mph,add 10mph to that,because most cops arnt going to pull you over if your doing 80mph in a 70mph zone,now add the extra 5mph that 50% of the drivers here do,so the average speed in some parts is 85mph,so if Im doing 75-85mph in a 70mph zone,then Im semi-speeding reletive to everyone else.

[eco]

Bump,still wondering if anyone has any other thoughts,I also forgot to mention the effect of momentum on air resistance,its not fully defeated,but at a higher speed,momentum is increased aswell.

[swng]

Bump,still wondering if anyone has any other thoughts,I also forgot to mention the effect of momentum on air resistance,its not fully defeated,but at a higher speed,momentum is increased aswell.



Thanks for bringing up this interesting subject! Here is an article about air resistance. Enjoy!

http://www.edmunds.com/advice/fueleconomy/articles/106954/article.html

If you have time, I recommend all the articles about fuel economy the links to which can be found in Post #1716 of the Fuel Economy thread:smile:. I think if you like the subject of fuel economy, you will like them.