truth about AVEO5
 

I love this car, but it is SERIOUSLY aerodynamically challenged!!! I bought this 2009 AVEO 5 hatchback with 17k miles about 5 months ago. It has a 5 speed manual transmission, cruise control, and air conditioning. Of all the different driving techniques I've tried, none is as near a significant factor as the difference between cruising at 55mph vs. 75 mph. It's literally the difference between 31 mpg and 38 mpg.

the engine doesn't need the mods on this car, the powertrain engineers did just fine. it's the aerodynamics that are killing it . . . i need a boat tail. anyone want to start a company with me that makes boat tails for aveos and sonics?

A kamm back would probably do you quite well. However, you could easily start with a grill block and bellypan.

Welcome to EcoModder!

Aerodynamic drag is always an issue, no matter which vehicle you are concerned with. Drag goes up with the square of the speed, so the proportion is 3025 vs 5625; which is almost double the drag at 75mph vs 55mph.

I think with hatchbacks though, and especially one like the aveo 5 that has such a blunt backside, the drag is a much more significant factor. I'm sure the gearing is a factor as well, but the difference in gas mileage in my 2002 impala at 55mph vs 75mph is less than 2 mpg as opposed to the difference of 7 mpg in the aveo. The back end of the impala allows the air separated by the cross section of the car to flow back together much more smoothly than the aveo. With the backside of the aveo the air is basically separated by the full cross section of the vehicle, and then tries to flow back together all at once which causes signifcant vortices that induce a TON of drag.

I drive a Scion xA, with a stock Cd of 0.31. So it is pretty average to decent. All vehicles have drag and the drag always goes up with the square of the speed.

What percentage is the 2MPG on the Impala, and the 7MPG for the Aveo? How do their Cd's compare?

My aero mods have helped a lot -- I am averaging ~50% above the 30MPG EPA Combined year round, and at least half of that is aero improvements. So, I think aero drag is critical on all and any vehicles.

I have the same car ('09 Aveo5) except mine is an automatic. I get 37 MPG at 65 MPH with the A/C on. But at speeds of under 45 the MPG is terrible - only 22 MPG, thanks to the way the A/T is programmed.

The belly pan and grille block I added had no effect aerodynamically. The removable upper grille block may have some benefit in winter in helping the engine reach operating temp faster. But you can't leave it on when the temperatures are above freezing.

I don't think the aerodynamics are the source of most of the problem with FE on the Aveo5. But then again, ours is rarely driven at even 55 MPH, let alone 75 MPH.