Pulse and Glide: Geo Metro
 

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.

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

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.

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

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.

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

Alright then, thanks.

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.)

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.

I do what most would call aggressive P&G. I do it constantly pretty much everywhere I go. General rule I use is 5 mph over the limit to 5 mph under the limit. When my car was in near stock form this got me in the high 50s for mileage, or roughly 200% EPA.

For metering acceleration, I use LOD on the scangauge and keep it around 75%. This translates to very low throttle input at low rpms.

Same for me as Daox. I regularly P&G on the freeway with a 5-7 MPH window, ideally behind a truck to get some drafting effects and not have someone riding my bumper. With a consistent average speed, the cars behind me dont seem to be too affected by my changes as long as they keep a steady speed themselves. When Im behind a truck, people seem to expect slower speeds and maybe some more dramtic speed changes or just go around as soon as they can.

As long as you arent doing big changes in speed, P&G is effective even at highway speeds. Its most effective if you are adding in engine off coasting at lower speeds with little to no traffic.

I've found that at highway speeds, even when P&G can be effective, DWL is more so. This is just anecdotal however, has anyone tried to do a decent comparison?

ESmooth and Daox sum up what I have done. I am very new to this also and I don't have an opportunity to drive under 40mph as I drive mostly highway. My bests results were slow lane, drafting, killing the ignition on long hills (when no one is following closely), keeping the air off, and never exceeding 65mph.

My results are far better with P&G than with DWL, even at painfully slow speeds on the freeway that i found to be almost dangerous. With the combination of accelerating at known optimal BSFC levels and high tire pressures/aero mods/drafting for improved glides I am easily able to beat 40MPG on trips where DWL was in the mid-high 30s at best. My personal best was 54mpg on a trip while P&G drafting a truck at 50-55mph.

I suppose I should also note that my experiences with P&G are different because of honda's lean-burn technology, which to a certain degree makes a constant state of driving in lean-burn very advantageous for fuel economy when compared to the fuel spent during the pulse portion of P&G. I should try it out at higher speeds in another vehicle sometime...

Very true, I dont have lean burn in my EX so I cant take advantage of that feature making P&G the better choice.

MadisonMPG - the slower the speeds at which you P&G, the more advantageous that technique is, vs. driving with load (DWL).

I'll echo what others have said: P&G gives better results than DWL. But I don't do P&G much any more in normal highway driving (a repeated P&G routine, that is) because it's kind of a pain in the butt (to me), and it makes sense to me that it's harder on the car.

Skylark: you're right that pulsing briskly will show worse instant MPG than pulsing slowly. But the brisk, low MPG pulse is more efficient when it operates the engine in its best BSFC zone. You'll end up using less fuel to reach a given target pulse speed because you spend less time accelerating.

Of course, this mostly applies to cars with manual transmissions, where the driver has more control over engine load (through gear choice, no torque converter).

Thats the theory that I had heard as well, but on long, comparable runs, I could achieve better mpg with a very light acceleration compared to a moderately brisk acceleration. My Versa has an odd engine, a Renault design, I believe. It seems to like higher rpms and light acceleration.