Pulse & Glide / EOC: Anyone rated their gallons per hour @ 0mph?
 

So I just started trying out pulse and glide on my 93 Civic DX hatchback and haven't done the final fill to see what my MPG has changed to, but it got me thinking on exactly how much gas my car burns when sitting idle. I travel 35 miles to work in just about 35 minutes and get about 39mpg, so by those numbers I'm going about a mile a minute and use .89 gallons per trip. That makes it roughly .0255 gallons I burn per minute. So it takes my car just barely over 39 minutes to burn a gallon of gas while doing 95% freeway driving and the rest city driving.

So if I leave the car idling for 15 minutes, I could find out roughly how much gas I could save per minute by having the engine not running at its minimum strain. Even going as far as wiring a stop watch to a starter kill to give me minutes I'm in motion and not running to get a good idea of how much gas I'm saving.

Are people already doing this sort of thing?

On my 1.6 L I burn .3 GPH at idle in "N" and on the 2.0 L it was the same. In "D" it increased to .4 GPH. I should of put the SG on LPH to get a better resolution.

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P&G or EOC?
 

My car's engine burns 0.5 litres per hour, fully warmed up @ idle, according to the ScanGauge. That's for a 1.0 L, 3-cyl.

You could extrapolate an estimate for your engine from those figures - though it doesn't scale exactly with displacement & number of cylinders. But it'll get you in the ballpark until a Honda person speaks up.

That said - a question about your technique (to clarify what we're talking about)...

If you're talking about turning the engine OFF where you were previously left it ON while not under load (such as idling while coasting with the clutch in, or the tranny in neutral down an off ramp, for example), that's probably not quite the same thing as pulse & glide.

I'd call that engine-off coasting (EOC).

EOC will save you fuel for sure, but not to the same extent as P&G.

I'm guessing that I probably burn a gallon an hour :D probably more. JK, but if it were true it wouldn't surprise me.

I have a question. My Jeep either shifts into neutral when I let off the gas, or shifts into the highest gear possible without lugging the engine (so that I could be doing Idle engine speed at 40 mph). But Whenever I shift manually into neutral, the rpm's go up from 750 to about 1300 (at around 30) and slowly go down as speed decends. So would letting the tranny do what it's supposed to do be better than neutral to a stop? I think that once I stop at a red light I should shift into neutral to save fuel, but when coasting to a stop, I should leave it in Drive? I also coast farther in drive because my Jeep can Idle after coming from at around 20mph. (it's that 4 Liter I tell ya)

I'm new to this, so I'm not quite sure what I'm doing. Here in the coastal regions of California, it's all valleys. So you can find yourself pulsing up a hill and gliding down it, where they lineup pretty well for pulsing and gliding. To be pulse and gliding here with only regard for your target speed will find you downshifting and wasting gas to make it up a hill. There's few stretches on my commute that remain level for any sizable distance. As far as gliding down an off ramp, it's a crap shoot here - city planners in San Diego decided to go for variety. There's many places where ramps alternate as overpasses and underpasses like clockwork, some of those are a straight shot and some have you do a 180, and many have a signal just to get on at heavy traffic times (halting you where you would have gained from the overpass on ramp slope). That was a bit of information, my point was that an offramp underpass is the least significant place to coast on my commute.

Anyway, my current trial into this P&G/EOC world has me targeting 70mph. I'm hitting about 80 and letting it go down to about 60. I know going slower would be more beneficial, but I'll check out that trade off as I go.* I'm not religiously maintaining the target speed due to all the constant changes in elevation and traffic speeds, so I guess I'm just opportunistically EOC and trying to P&G where I find it safe and logical to do so.


*Another argument for the higher speed is that it's hard to retain any constant motion in the slower lanes at peak traffic times, where you can easily pulse to the fast lane and just merge to the right once or twice as you glide (we're five lanes wide nearly the whole stretch). If you were doing this in the slower lanes, you'd come to nearly a stop (if not a complete stop) very often. Luckily I go the opposite direction of heavy traffic, so coming to a stop on the fast lane only happens when there's an accident.

Well, I did a fill up last night just a few tenths short of traveling 150mi according to the trip odometer. I had hardly used a third of the tank and the suspense was killing me to find out what my recent driving habits had gained me. So here's what I got...

149.6 mi
/
2.677 gallons
----------
55.88mpg

That's a bit shocking over the 39mpg I steadily have gotten in the past. Also, I didn't start experimenting with the engine off coasting until I had rolled past 65 miles on the trip, so only 56% of that fillup benefitted from my changed driving habits. This still seems abnormally high, so I'm reserving my enthusiasm and am doubting that I actually topped off the tank completely (it's just too good to be true). Still, there had to be some gain - and I'm excited to verify that my habits are really paying off.

From your description, you're doing genuine P&G. And based on that, I'm not at all surprised to see 55.9 mpg vs. 39.

When I compared engine-off coasting vs. "normal" conservative driving in my car on an urban loop, I saw a 12.9% gain. My fuel economy went from 50 mpg to 63 mpg.

Knowing what I do now, had I repeated that test loop a third time using dedicated P&G rather than just "opportunity coasting" EOC, I would have seen numbers in the 75-90 mpg range.

Normally I would question the effectiveness of P&G at the very high freeway speeds you cite (80-60 mph), and I'd want to see the results on instrumentation at the time rather than just at the pump. That said, if there are hills involved, and if you're benefitting from the "corridor effect" of air movement within a stream of traffic, those speeds may just be working for you.

MetroMPG:
Thanks for the info! I really appreciate all the help and knowledge you lend. It's good to get clarification on the vocabulary of what I'm actually doing. As a newbie I'll throw the word "drafting" out to loosely describe following an SUV about 200-300 feet off, and not realize the true meaning/practice. As for investing in the instantaneous instrumentation, I'll move on to after I've seen what I can do with what the factory gave me and see what eccentric cravings I have afterwards :)
(there's also the consideration of whether I can get better milage in the geo 'vert or the civic hatchback, which will decide which should be my daily driver and warrant the extra investments and labor)



Well, the New Years vacation break hit since my last post. My wife and I got out of town for the weekend and I didn't get to practice my new driving habits much on the trip. We were pressed on time to make it from San Diego to Modesto to visit family, traveling over 430 miles in about 6 hours (while taking the hit of LA traffic in between). Tssk me as you like, but when a 91 year old widowed Great Aunt is waiting up late for you on the other side with a meal prepared - you put your foot in it. I did get in some engine off coasting over the Grapevine (AKA the Tejon Pass, a 4000 foot mountain range that separates LA from the San Joaquin Valley). On the way down I got a surprise when my brakes lost power. Since then I have learned what a vacuum booster is and how it temporarily provides power to the brakes when the engine is shut off. Between the Grapevine and the 7,000 foot climb/descent to the Sequoia National Forest, I had some extreme examples of coasting that gave me time for experimentation to figure out just how much power the brake booster will provide.

Now that I've been back in town and back to normal driving, I've refilled and I'm out to see just how high a milage I can do on one tank. The needle has hardly gone below the F (full) point on my gas dial and I've already put just over 100 miles on the tank. I have been noticing that I can do far more coasting heading home from work than I do heading to work. I'm going to borrow my Dad's old altimeter (from his old piloting days) to see exactly what the elevation change is and see if that instant knowledge can help me in planning my coasting. What goes up, must come down... and if I can guesstimate my potential energy when traveling through less familiar valleys - it may help me in planning my EOCs by knowing just how much I gained. Fun stuff! I definitely have been noticing when I take repetitive and familiar routes in my car I can be very accurate in my EOC and P&G timing, where I have a whole lot of practice to do to get such accuracy on unfamiliar roads.

Did the vacuum go away because you were tapping the brakes here and there, or did it lose it over time with no braking?

I hope you also learned that you can still stop without assis - you just need to put your leg into it much harder. I'd recommend trying that sometime too - purposefully depleting the vac reserve on an empty road/lot and doing a couple of rapid stops. Just FYI.

Woo! That's the spirit. :)

Just like a race car driver will have lower lap times on a familiar track. Knowing the road helps immensely.

It is satisfying, with some practice in this style of driving, how you can develop the ability to look down a grade or a stretch of road towards a stop and are able to judge just when to get off the power to coast to a stop at the right spot.

It was tapping here and there, the grapevine is quite a massive slope with many turn offs for overheating uphill and many truck runaway ramps going down. I get about two hard brakings in before the vacuum needs to be recharged by the engine. I'm no stranger to braking without the assist of power through different vehicles I've driven over the years, so I didn't panic - but it did certainly get me nervous on something as treacherous as the descent of the Grapevine. Once the initial shock wore off, I turned back on the engine and realized the correlation to something that gave me braking power being charged when the engine was running (and read up to find the name of that something when I got home). I'm interested in seeing if there's a cheap way of putting a pressure meter in place to give me a good idea of what braking power I have.

According to my VAGCOM, my TDi burns .5 liters per hour @ idle when cold. Never checked it hot. That's for a 1.9 liter, 4 cylinder turbocharged, direct injection diesel.

The manual that came with the 8-cyl Cat 3208 in my motor home (1300 lbs and 610 cubic inches of the finest Detroit cast iron... :p) says it burns 1 gallon per hour at idle. :thumbup:

a vacuum gauge behind the vacuum check ball would allow you to see how much assist is left. While slightly more dangerous, you could pull your parking brake to stop(or slow) at times. dangerous part is 1. just using your rear brakes(which is what the parking brake engages) means that the rear of the car may lock up and get away from you and 2. forgetting to release the button may be suprising.

About a thousand years ago my Dad had a 1970 SAAB 96, and one thing about it that always drove him crazy was the freewheeling clutch - it would keep popping between settings and that made it hard to drive.

But most significantly, that thing would've been the owl's howl for P&G - tap the gas to go, let up to coast. Is anyone making a slipper clutch that could be bolted into a modern app? Like an '87 Toyota truck? :D

what are the savings for highway pulse and glide without EOC as compared to normal conservative highway driving?

i like the idea of P&G but on the highway at 60mph turning the engine on and off becomes very frequent and annoying. surely putting the clutch in is just as good? ideling losses are not that much?

i would really like an answer to this :)

I can't tell you what he differences are on your Corsa,
But,
In my wifes Avalon, fully warmed up, with its automatic transmission, according to the SG;
.33 GPH in neutral, coasting or sitting,
.49 GPH in D. sitting (Thats 50% more fuel)
.00 Gph in D. coasting over 47 MPH (decel fuel cutoff)
1.5 GPH in D. and dropping coasting under 46 MPH
So when I am on the highway I coast in D until we break the threshold of 46 MPH then put it in N until I need more speed again.

My Metro has no High Tech readout, it is too old for SG, and I don't feel confident enough to build a Guino.
But I have been told by those who have one that the Metro burns ~.25 GPH at idle, (and I cut my idle down to 500 rpm for further savings)
So at 60 MPH that would work out to 240 MPG coasting at idle engine on.
Not as good as EOC, but this is what I do in heavy traffic. (which is most of the time here)
Hope this helps,
Schultz

This shouldn't be too difficult to figure out if you have a gauge that reads mpg.

When you are coasting in neutral read the mpg figure and note the speed at the same time. Because you now know 1) miles per hour and 2) miles per gallon and 3) your engine is at idle, it should be easy to calculate gallons per hour at idle.

It's late now but I'll work out a formula tomorrow.

i think pulse and glide is only benificial for big muscle cars and trucks. i tried it in my 1L econobox and it actually lowered the mpg. probably this is because my 1L engine is already well sized for highway driving. the engine needs to be on full load just to reach motorway speeds.

I experimented today on the way to work with just doing EOC when the opportunity arose and no Pulse and Glide. Yesterday I did Pulse and Glide when ever I could along with EOC. This is the same 32.3 miles route both days.

My findings:

EOC only without Pulse and Glide= 50.2 mpg
EOC and Pulse and Glide =52.8 (it was raining and cooler this day)

My route to work is always better then going home. The best on the way home was also with EOC and Pulse and Glide and was 41.3 mpg. Without Pulse and Glide its just 36-38 mpg.

My homework now is to just dial in the correct acceleration needed to regain my top target speed.

Sadly, it's pretty dangerous to do this in most of those bigger cars - no power steering and brakes are fine on a small car, but on a big car... it can be a beast. Most of the people who freak out about EOC have experienced trying to steer a heavy car with no power steering - you can't swerve quickly if needed in them.
I actually tore up the steering shaft joint (rag joint) in my mustang from turning the wheel too much while the car was off.

That will be quite a savings in a years time.

This is why people need to work out at the gym. Buncha pansies that can't steer a 4,000+ lb vehicle without power steering. :rolleyes:

Why back in my day, we used rope tied to the front wheels instead of a fancy steering wheel, and power steering was something that happened when the spark plug wires shot off the engine and caught you in the leg. :D

For comparison. My Jeep warmed up at idle burns around .70 gallons per hour. So I try not to stop at all.

Sorry to bring back an old thread, but I think it's still relevant. From what FastPlastic gave as a fuel consumption, I guess my worst fears are confirmed. I probably do burn about a full gallon per hour at idle (extrapolated). No wonder Jeeps get crappy city MPG...

I burn .6 gph at idle with the a/c on in a hot day with the tranny in gear, so I'm now feeling lucky!

Can you back the idle down a bit? I managed to back mine down to ~600 rpms which trimmed down the idle consumption rate to ~.45-.48 gph according to the SG. Before it was about .55 gph. But if i kick on the AC or steer or cause the fan to turn on, the idle jumps up to close to 1k rpms.

On my (now sold) Insight CVT, I coasted in neutral until the instant fuel economy bar dropped below 150 MPG. The reading was consistently 16 MPH, so I just use 16/150 for idle fuel consumption.

Works out to just under .12 GPH at idle.

I think but cant prove the VX is very close to that becasue it idles at about 450 RPM, lowest idle speed of any car I have owned except my 37 Ford flathead V8 which idled at 350 RPM.

The Insight will average 40 mph on the same fuel an average V8 consumes idling with no electrical accessory loads.

I once tried to measure idle consumption on my brothers 90 Civic, with a DVOM on the fuel tank sending unit. When the tank level actually read that it had INCREASED, I realized that the heat conducted by the fuel and the ambient temperature increase had made the fuel in the tank expand, which was the cause of his magic Honda that made fuel while running ;).

regards
Mech

The Jeep only idles at about 650 rpm anyway, and it can only be adjusted via the computer. It doesn't raise the idle at all under load, just throttles up a little to maintain speed. My fuel use at idle is simply the product of having a 5.9 liter V8 under the hood. Not a whole lot I can do for it, except minimize idling. In gear with A/C on, 1.2 gph wouldn't surprise me at all.

Maybe the engine jumps to 1000 rpms because that's what the A/C compressor needs and can't function at a slower speed?

Here's some more idle talk:
How's your idle? (Just some idle blabbing)