The Worst Aerodynamics : A Car Story - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

alohaspirit · 06-14-2009, 08:57 PM

Pulled 26 mpg for my first sg week!

alohaspirit · 06-23-2009, 08:12 PM

Ive read through a lot of posts here which talk about coasting in neutral with an automatic

i can get in lean burn but sometimes the engine (in Drive)
slows me down too much, even on a hill

im really tempted to just shift into neutral but is it really ok?

MazdaMatt · 06-24-2009, 08:08 AM

I think you are confused about what "lean burn" means. If you are talking about the engine cutting fuel when you are off the go pedal, that's "deceleration fuel cut off" or DFCO as it is called on this forum often. Lean burn is a function of.. i think only Honda engines where you are cruising at highway speed and it starts to run a lean fuel mixture (less than the usual fuel/air ratio).

If you are going to have to use your brakes, then coast in gear. If you are able to pop it into neutral, coast a while, then get back into drive to continue on - go that route. So on a hill, you could put it in N, then when your speed gets a little too high, put it in D, if that slows you down too much, put it back in N. The brake pedal is the enemy.

beatr911 · 06-24-2009, 10:35 AM

If you can coast the entire hill safely in neutral then do it. There is an advantage over invoking DFCO then applying throttle to get to where you were by just coasting in the first place.

If you need to use the brakes to slow your coast, instead put it in gear and use engine braking under DFCO engine speeds (probably 1500rpm+) or a combination of DFCO and brakes if you need to shed more speed.

Do I hear 28. 28. 28. 28mpg?

alohaspirit · 06-24-2009, 12:49 PM

yeah, its DFCO

(im still learning the terms)

hopefully my 2wd automatic is able to coast in neutral

because 28 mpg is within sight!

MazdaMatt · 06-24-2009, 12:58 PM

you won't have a problem with coasting in N. The questionable factor with auto's is coasting with the engine off in N. Some require that the engine turns to keep the tranny lubed. Apparently cars that don't have a problem will say in the user's manual that you can "flat tow" the car. Flat towing is what people with RV's do - use a tow bar to drag a car behind on its own wheels, rather than a trailer. If you can do this, then you can coast with the engine off. Not recommended in general for liability reasons

alohaspirit · 06-30-2009, 05:47 PM

28.24 mpg!

All done with DFCO

Next, Neutral Coasting

Then... Aero!

30 mpg, here I come!

i_am_socket · 07-01-2009, 10:17 AM

Coasting in neutral in an automatic is fine. The issue is coasting in neutral in an automatic with the engine off. Some cars don't like that, some don't mind. In my car I neutral coast all the time. Before I changed routes, I even engine off coasted for half a mile at a time at 60+ MPH with no noticeable damage to the trans (big, long bridges).

As an added bonus, neutral coasting is much better for pulse and gliding

alohaspirit · 07-01-2009, 03:55 PM

Thats good to hear.

Although it is a little weird watching the SG. I always thought that 99999 meant that was the best mpg you could get. Of course when I coast in neutral I dont get that.

Hopefully I will pull a bigger number while neutral coasting

beatr911 · 07-01-2009, 06:13 PM

Nice job on the 28+ reading. Keep it up!

You'll get to a point where the additional effort is not worth the gain. There will be a balance point that is comfortable for you. After staying there for a while beware, you just might start looking for a different, more efficient vehicle.

For the freeway commute in the truck, I stopped at 123% of combined epa. The aero is just too horrible to get much more without being a rolling road block. I ride the motorcycle as much as possible.