Lowering your car in order to increase fuel economy

[Matt Timion]

Originally Posted by SVOboy

But how much is a matter of guesswork?

I'm unsure what you mean by this. Perhaps you didn't read this part above.

Originally Posted by Matt Timion

It was significant to .002, which means that there is only a .2% chance that the drop did NOT affect fuel economy.

[krousdb]

Originally Posted by Matt Timion

In other words, lowering the car works in krousdb's case.

See the Del Sol aerodynamics thread for highway mileage info.

[SVOboy]

I'm unsure what you mean by this. Perhaps you didn't read this part above.

I meant the amount by which is was affected.

[krousdb]

Originally Posted by Matt Timion

Temperature: Temperature correlated to MPG (Pearson's Correlation) at .254. This means that the significance was .30. This essentially means that the temperature has no significant impact on MPG (in your case at least).

Dropping the car: This yielded the most interesting results. Comparing the MPG of the pre-drop and post-drop group yielded a significant result. It was significant to .002, which means that there is only a .2% chance that the drop did NOT affect fuel economy.

In other words, lowering the car works in krousdb's case.

I am not going to argue with your results because I am not a statistician. But there are many reasons why FE should increase with temp. Faster warmup, (engine and drivetrain) and less dense air to displace as you move through it would be the major contributors. I am surprised that you found no correlation between FE and temp.

[Matt Timion]

Originally Posted by krousdb

I am not going to argue with your results because I am not a statistician. But there are many reasons why FE should increase with temp. Faster warmup, (engine and drivetrain) and less dense air to displace as you move through it would be the major contributors. I am surprised that you found no correlation between FE and temp.

Like I said, there was a correlation, just not a statistically significant one. I do believe that if you had a wider range of temperatures it would be a different story. Just looking at your data it's no surprise that no correlation was found. you often achieved higher FE with lower temps.

It can also be pointed out that once the engine is at normal operating temperature the effect of air temp is probably minimal. This has been demonstrated by non-hybrid drivers with HAI installed. Since most of these cars do not have a "lean burn" mode it is no surprise to find out that hot air has no real effect on FE after the engine is warmed up. See MetroMPG's experiment thread about the WAI for his results.

[rh77]

Originally Posted by Matt Timion

This has been demonstrated by non-hybrid drivers with HAI installed. Since most of these cars do not have a "lean burn" mode it is no surprise to find out that hot air has no real effect on FE after the engine is warmed up. See MetroMPG's experiment thread about the WAI for his results.

Balls! That stinks -- or might not be true in all applications. I need at least 3 independent tests to be convinced. I'd like to participate, since the weather is still cool, I could give it a try when I get back from Calgary on Monday (Vacation, woo hoo!). Depends on my schedule, but getting scientific numbers with this car is tough. I could give it a shot...

RH77

[GasSavers_Ryland]

If you lower your car, remember to get an alinement done as well, or your missalinement will cause even more drage.
I think it was a Nisson that is coming out, that lowers it's self at highway speeds as well, and because of how long it is, it's CD is almost exactly the same as the insight while at highway speeds, at lower speeds, when it has more clearance, it's two points higher, so if done right, like making sure that the front and back are both lowered the same amount, or lowering the front just a little more, and that you have wheels that are properly alined, then is should for sure help, less air under the car, is less drage, that is why the HF, and the VX hondas have the extra air dams, to reduce the air going under the car.

[SVOboy]

Dan has checked his alignment I am sure, we talked about it somewhere. When I smack my car to the ground I will do my own alignment and then have it checked by the computer when I have my 9 pound 13" vx alloys put on. That'll prolly wait until I can buy my new aftermarket shocks though and get them installed, don't want to go too low on stock shocks after all.

[krousdb]

Yes, I checked camber and toe in. The camber is out of spec (top tilted in, bottom tilted out)by a bit but the cornering is much improved. The toe-in is a little more than spec but my FE has nit suffered and the car still tracks straight. I have about 1200 miles on it since the drop and I do not see any unusual tire wear. I am monitoring it though.

[thisisntjared]

i might have missed this little tid bit earlier so forgive me if im wrong, but havent you guys considered that an increase in camber decreases rolling resistance as less of the tire is touching the pavement when driving without body roll. this is especially true when the tires are filled to the maximum psi.

also i think there are three real gains in aerodynamics for lowering the car. the decrease of frontal area for the tires is decrease. the upper half of the wheel(the part thats moving twice as fast into the wind) is tucked further into your wheelwell. by further i mean because of camber and because of ride height. and finally there is less 'free room' in your wheel well for turbulent air to flow around.