Interesting MPG experiment

I see a lot of them too. I've taught my kids to watch for this special kind of moron and give them space. Most of them seem to think they're still playing a rally game on their X-Box.

-John O

And most of them would not last very long in the "real world" of rallying, either. Posers and wannabees. AKA aggressive drivers, AKA idiots.

** Posted from **

Not so. At peak torque the engine is using a great deal of fuel. I have an

04 STi. At 4000 RPM (its peak torque) it is burning fuel at 60 litres/hr at 100% load, and 20 litres/hr at light loading. Its best gas mileage is at about 80 km/hr where it burns 7.2 litres/hr. That works out to about 31 MPG (imperial gallons). I have hooked up the monitor to my wife's Forester as well. Although the differences are not as great, her car still gets it best mileage at around 80-85 km/hr.

The engine produces maximum hp/hr per lb of fuel at maximum torque rpm. This is a well known proven fact. Now running it at full load at this speed is a different story all together. The gearing is not necessarily set up to provide maximum fuel economy at this speed on the road - onn an STi I can almost guantee it is not - it is geared for PERFORMANCE.

** Posted from **

My 2000 OBW usually gets shifted to 5th when I reach about 80kph (50mph), until then 4th is the gear I can sustain it at. It really doesn't matter when you shift into 5th or 4th, as long as you stay below a certain RPM, you're doing fine. I usually use 3000RPM as my rule of thumb. On my OBW @ 100kph (60mph), it reaches exactly 3000RPM in 5th. This seems to be the sweet spot right now.

Yousuf Khan

I think you want a CVT.

Yousuf Khan

Wind is a full load for any vehicle, and without considering it the numbers are meaningless. Take a test drive and try it...my OBW does about 30 mpg if I drive at 64 mph on a trip....as slow as I can safely drive on the highways here. At 70 mph, I get about 27 mpg. At 80, about 23. All cars have the about the same curve, even your STi.

The *only* way you get better mileage at 80 mph is if you drive a torpedo-shaped car, which has no wind resistance, and the STi doesn't qualify. That's a proven fact, too. :-)

-John O

I've tried it - many times . It works. The 1975 Celica did over 50MPG in fifth gear at about 80MPH, which had the engine at it's torque peak. At 60 it would not do 40MPG, in any gear. In 1976 they changed the gear ratio, and 50MPG was impossible. Otherwise, the vehicle was virtually identical. The aerodynamics on the GT fastback were pretty good. No Soob has aerodynamics - particularly the ones with the boy-racer scoops and tails.

** Posted from **

You're saying that you violate the laws of thermodynamics, and you just can't do that.

-John O

I agree. By 80 MPH a very high proportion of the work done by the engine is lost to drag in any car.

It is not a proven fact. You are thinking of thermal efficiency. You are completely disregarding drag which is a very much more significant factor. The thermal efficiency of a modern gas engine is between 25% and 30%. To put that in layman's terms, every 100 gals you burn, only 25-30 is actually converted to work. The rest is lost to heat. So, yes, it has its best thermal efficiency at peak torque. However, the efficiency does not drop significantly unless the engine is chugging at the lower end (incomplete fuel burn) or pinging at the other end (predetonation). Everywhere else, drag is the most important factor for the fuel economy of a car. At low speed, most of the work the engine is doing is translated into movement of the car. As speed increases, drag increases exponentially, and so does the percentage of work used to overcome drag. At 40 MPH, about 10% of the work the engine is doing is to overcome drag. By 55 MPH about 30% the work the engine is doing is to overcome the drag. By 80 MPH, its more like 65%. by

100 MPH, it is like 90%.

An STi, at peak torque in 6th gear, is doing nearly 100 MPH. At that speed gas mileage would seriously suck.