Pulse and Glide: Geo Metro - Fuel Economy, Hypermiling, EcoModding News and Forum

MadisonMPG · 08-09-2009, 10:16 PM

I hear that P&G is one of the BEST ways to improve MPG's. I've read up on it, I still don't understand exactly how to accelerate. I have read and I feel that this is the "correct" way to do it...

Drive up to 50mph, coast down to 30mph (takes 15 seconds), drive back up to 50mph in a manner that takes 15 seconds. Is this right? Or do I want to coast down to 30mph and then accel @ WOT to 50mph.*** Someone tell me please.

***All mph and times are made up.

SVOboy · 08-09-2009, 10:20 PM

I generally accelerate at about 60% throttle, but I don't use it unless the average speed is something like 35 or less

Christ · 08-09-2009, 10:37 PM

Since aerodynamics start really taking effect at 40-ish MPH, trying to keep a speed that requires more top speed than like 45 isn't going to yield the results you're looking for, unless you're already a horribly inefficient driver.

You've got the basic concept, but I believe that most people accelerate at ~60-70% throttle, since WOT usually puts you in open loop mode, but low throttle angles (as you already know) are horribly inefficient, due to the restriction. Slightly off topic, I wonder how that really works in a diesel format?

Back on topic, once again - you've got the concept. It's more a matter of finding your "sweet spot" to get the best gains from it. It does work great in the city, though, especially when you can time lights and coast through long distances with relatively short pulses.

MadisonMPG · 08-09-2009, 10:42 PM

Christ, could you reword (or further explain) that first sentence. I've been up for 20+ hours and it's confusing me.

SVOboy · 08-09-2009, 10:46 PM

P&G is bet done where aerodynamics is less of a factor, so try to keep the speed down as much as possible

MadisonMPG · 08-09-2009, 10:53 PM

Quote:

Originally Posted by SVOboy

P&G is bet done where aerodynamics is less of a factor, so try to keep the speed down as much as possible

So would a 40-30-40 coast be better? Because like I can't go much slower than that, unless it's in a neighborhood.

SVOboy · 08-09-2009, 10:57 PM

Yeah, I don't really P&G ever because of that. It's too much on the bubble to be worth the effort at higher speeds for me

MadisonMPG · 08-09-2009, 11:04 PM

Alright then, thanks.

Christ · 08-09-2009, 11:25 PM

Quote:

Originally Posted by MadisonMPG

So would a 40-30-40 coast be better? Because like I can't go much slower than that, unless it's in a neighborhood.

You got it. Sorry I didn't get back to you on that as quickly as normal, I was feeding my Son.

Basically, what I said:

Aerodynamics really become a concern over 40 MPH, so if your upper limit (pulse limit) exceeds that, you're not going to get what you bargained for, unless you were already the crappiest driver in the world. You seem somewhat knowledgeable, so I would tend to doubt the latter.

40-30-40 seems to be ideal. The median average is still 35, although the mean average won't be. (It depends on time spent accelerating/decelerating, so the mean average will vary on a per-scenario basis.)

skyl4rk · 08-10-2009, 01:04 PM

I find that a slow acceleration works best. Fast acceleration does not give me as high mpg according to SG.

Opportunistic P&G is more practical than aggressive P&G. If no one is behind you, do a few 30-40mph pulses. If someone is behind you and there is a good opportunity to pass, do a glide to give them a chance to pass.

If there is a hill coming up and you know it has a good long coast on the other side, arrange your pulse to start at the bottom of the hill and peak at the top. If you don't know what is on the other side of the hill, arrange your pulse so that you barely make it over the hill.