Speed vs. Semi

[RandomFact314]

Originally Posted by PaleMelanesian

It's possible, but much harder, with an auto. I find the best results with an auto come from keeping steady speed, losing a bit on the uphills and gaining on the downhills, and some strategic engine-on coasting. Find a good speed that gives you just enough power to stay in top gear without downshifting, and don't go much faster than that.

So if I'm going down the highway at 50 at night, do you recommend I just keep on going 50 with cruise control or should I do P&G my way? P&G @ 60,neutral,50,drive (Repeat)?

[basjoos]

Originally Posted by RandomFact314

Oh wow, I never even thought about the fact that worst cds would get more of an advantage but I see that obviously makes tons of since.... You taught me something today (or at least made me realized the should-be-obvious)

The mpg benefit you get from drafting is definitely related to the Cd of your vehicle. The Cd on my car is so low I get almost no benefit from drafting.

The mpg you get while drafting is a quick and dirty way to estimate your car's aeromodding potential since the only thing that changes while drafting is the airspeed (and hence the wind load) experienced by your vehicle. Engine rpm's and rolling loads remain the same.

[wagonman76]

As far as shifting in and out with the automatic, it depends on the vehicle. Mine for one does not like to go back into gear at anything above 25 mph. Anything above that it pretty much has to run itself through the gears again and then takes a bit for the TCC to re-engage. So it's not worth it to P&G for me. Even trying to lose speed, then regain speed.. doesn't amount to any gains either. Your mileage may vary.

[PaleMelanesian]

Some autos are quick to release the transmission and go into a semi-neutral mode when you let off the gas - GM models in particular. Others, like Hondas, are very strong on holding it in gear, giving you heavy engine braking whenever you let off the gas. Clearly, in the 2nd case it's more advantageous to shift to N, while in the first case you really don't need to, since it's already doing it for you.

I would hold speed at 50-55 mph. Cruise control is good on flat ground, but as hills come in, you'll do better with manual control. CC is a reactionary device, whereas you can anticipate. CC will overreact and floor the gas, causing a downshift. In the same locations, you can hold it in top gear yourself.

[Christ]

Originally Posted by RandomFact314

JACK MY OWN THREAD******OK I have an important question for everyone, will P&G give me better MPG if I'm in an auto that cant be flat towed, so I would basically be going up to say_ 60 mph, then putting it in neutral, going down to 50, putting it in drive, (repeat) since I would not be turning off the engine and all that mess? I have been wondering for a long time******

PSS: How old is everyone here? Just wondering, Im 19, turning 20 on July 25th

Yes, P&G still works in an auto that you can't EOC in. 60 to 50 might not necessarily be the best choice of speeds, though.

BTW - still 24.

Oh - I didn't really document it, but I did some P&G in Granny for awhile... didn't really amount to anything, but that was varying speeds from 60-45, 65-45, 55-40, etc... trying different things, but I didn't get any real results that I could safely attribute to anything. In Granny, it was better to just leave her in gear, since the tranny basically goes into neutral on it's own.

[RandomFact314]

Originally Posted by Christ

Yes, P&G still works in an auto that you can't EOC in. 60 to 50 might not necessarily be the best choice of speeds, though.

Yeah Crist I know it does not alert the subscribers when I do things like that, I just would not like to make thread after thread after thread and seem like a d-bag to answer simple questions. Like in some of my threads I have asked one thing, and when its answered iv asked about how much change will I get removing my antenna, which I don't think people would like if I made a thread over something so easy to answer...

[Christ]

No, what I was suggesting is that you ask the question later in the thread, but still edit your original post if you please. Asking later in the thread will bump it up the list for a new reply, and that will alert people to check it.