Pulse 'n' Glide style of driving

[no_akira]

This is probably old news but came across this term for a style of driving that is popular with Prius owners in the States "Pulse 'n' Glide". Its especially suited for long, rolling interstate journeys (motorways) to increase their tank range. Its a sort of game they call "hypermiling".

Basically you gun up the hill sections 70+ and then roll / coast down the rolling section, speed slowly dropping back to 58 / 60+. Its been proven that you use less fuel than if you drove at a constant speed over the same section.

Another reason the Prius owners do it is when they drop the clutch the engine cuts out totally so they coast with the engine on zero revs and it doesn't effect the steering or breaking as it would with traditional motors. Obviously disclaimer here that its illegal in the UK blah blah blah........

Its funny because i've been driving this way (dropping clutch, engine to idle revs) on my weekly commute up the M1 for about the last 3 years but finally found a name for it. Dislaimer again its always late at night and only when on the quiet sections.

You will have noticed I haven't used the dreaded 'C' word..........

I've got a 130bp tdi which is a low reving engine so when I'm introducing the clutch back to the engine its only doing 800 idle revs. I've done 100K miles in this car, its currently on 220K, still possibly on the original clutch (hydraulic diesel industrial strength build). It might not suit higher reving petrol engine.:geek:

I mainly do this as a sort of game to while away the 3 hour journey.

[Wideboy]

i was taught to do this on a eco friendly driving coarse i was sent to for work but the lecturer didn't seem to understand that it was against the law to coast

we didnt see any massive effects on mpg when it was put to the test

[Bluefish]

I've always stuck it in neutral when going down a steep straight hill, obviouse it uses less fuel.

[B1k3R]

I did not realise this was illegal.

That said, If I did this I could possibly see my MPG rising on my dash giving about 6MPG more over a 42 mile return commute.

[Milky Bar Kid]

Since when has it been against the law to coast? It's an instant test fail but I am pretty confident there is nothing in the RTA saying its an offence.

Apparently though, this isn't a good way to save fuel in newer style vehicles or so my boss told me the other day but he may be talking rubbish. I wasn't really listening to him so I can't actually remember his reasoning for it!

[Wideboy]

its classed has not being in control of your vehicle, like riding with one hand ect

[Bluepete]

I am lead to believe that with many modern engines, when the road speed is above the engine speed, the injectors turn off.

In other words, on downhills, just take your foot off the gas, leave the engine engaged and the fuel stops flowing. This gives higher mpg than coasting as the engine needs fuel to idle whilst coasting.

Pete ;)

[Milky Bar Kid]

I am lead to believe that with many modern engines, when the road speed is above the engine speed, the injectors turn off.

In other words, on downhills, just take your foot off the gas, leave the engine engaged and the fuel stops flowing. This gives higher mpg than coasting as the engine needs fuel to idle whilst coasting.

Pete ;)

That's what my boss told me!!

Gav...how the hell would we be able to prove someone was coasting???

[B1k3R]

..............Apparently though, this isn't a good way to save fuel in newer style vehicles or so my boss told me the other day but he may be talking rubbish. I wasn't really listening to him so I can't actually remember his reasoning for it!

I have a '09 merc and it makes a big difference especially on a run. You can see the MPG rising on the dash. Allegedly of course. Just in case.

[MisterTommyH]

I am lead to believe that with many modern engines, when the road speed is above the engine speed, the injectors turn off.

In other words, on downhills, just take your foot off the gas, leave the engine engaged and the fuel stops flowing. This gives higher mpg than coasting as the engine needs fuel to idle whilst coasting.

Pete ;)

+1 - Top gear fuel challenge a few years ago said you actually use less fuel leaving it in gear and engine braking at lights than either coasting or using the brake.

Although, they do talk some carp so could have been having us on.

[Wideboy]

That's what my boss told me!!

Gav...how the hell would we be able to prove someone was coasting???
no idea, i was always told i'd be booked for it

i still do it

[Bluefish]

+1 - Top gear fuel challenge a few years ago said you actually use less fuel leaving it in gear and engine braking at lights than either coasting or using the brake.

Although, they do talk some carp so could have been having us on.

Agree when wanting to slow down at lights etc, leave it in gear and coast up to them, but when going downhill if you leave it in gear of course you will use more fuel cos of the gears slowing you down, so neutral and when you get to a speed you think slow enough blip of the throttle into gear and away again, simples.

[Nobbylad]

no idea, i was always told i'd be booked for it

i still do it

lol...that could be used in so many responses ;)

[Ed]

What if the car's automatic:confused: It's a while since I had a manual car. I don't like 'driving' in neutral as the brake servo don't work.

[yorkie_chris]

That's what my boss told me!!

Gav...how the hell would we be able to prove someone was coasting???

Same way you manage to prove a couple mph over the limit is dangerous driving :smt082

What if the car's automatic:confused: It's a while since I had a manual car. I don't like 'driving' in neutral as the brake servo don't work.

That could probably be disabled but I'm not sure what else you could do other than general eco mileage driving style. Or not buying an auto because they're naturally thirsty.

[punyXpress]

I am lead to believe that with many modern engines, when the road speed is above the engine speed, the injectors turn off.

In other words, on downhills, just take your foot off the gas, leave the engine engaged and the fuel stops flowing. This gives higher mpg than coasting as the engine needs fuel to idle whilst coasting.

Pete ;)

But wouldn't you get engine braking?

[embee]

A few issues here (as usual ;) )

As far as I was aware, the Prius is a CVT and I didn't think it had a clutch you could "dip" (I'm pretty sure the one I tried was a 2 pedal jobbie), may be wrong.

Yes, FI engines have "overrun fuel cut-off" above a certain RPM (around 1500rpm typically) so on overrun don't use fuel, but the engine braking means you slow down and then have to use fuel again. If you truly coast, yes the engine is idling, but the car will run as far as the kinetic energy will take it and if it's more than a couple of percent downhill gradient it'll keep on going, aerodynamic drag permitting. Coasting sensibly will give better fuel economy than overrun in gear. Out of interest, a typical car engine will use around 0.2L/hr per litre swept volume at idle.

On those economy run competitions they are strictly not allowed to squirt and coast.

Brake systems do work with the engine idling, as long as it doesn't actually stall. Not quite sure how ABS systems are designed to work if the engine stalls, I would have thought as long as the ignition is on it'll still work, it's electric. Even vac servo systems will usually give you one or 2 brake applications after the engine stops before you lose all assistance.

Once upon a time some Saabs did indeed have freewheels when they had 2-stroke engines as long periods of overrun starved them of oil. See Wiki (http://en.wikipedia.org/wiki/Freewheel)

I'm a bit surprised with modern control systems that there isn't a freewheel system in use, it could be done on a part open throttle (trailing) so if you took your foot right off it would re-engage engine braking, but under the right conditions you could gain the benefit of freewheeling.

[DarrenSV650S]

I'm so glad my car doesn't have a mpg gauge. I think if it did I'd put a sticker over it

Just thrash it, you'll get there quicker! :D

[no_akira]

embee - I haven't got or driven a Prius but there are videos of "zany" Americans on utube explaining it....

You talk about flywheels to extend that coasting range an extra few hundred meters which is a cool idea

Idea 1 ....How about "frictionless electro magnetic super conducting wheel bearings" on on four wheels ? Roll all the way down the M1 !

Idea 2 ...Electic motor wrapped / mounted on the drive shaft with push & squirt button on the steering wheel for when your coasting again to extend the range linked to a 24 volt battery that is triggle charge by the engine. Or a capictor type battery with like a green power gauge. After five minutes of driving the green leds indicate full. Then on the next roll/coast you press on the button to sustain the coast.

Fiat and I think the new sporty/eco Honda CR are doing electric engine wrapped around the drive shaft type thing.

As I said 3 hours drives is a long time to think about these types of crazy ideas.

[embee]

OK, just watched a clip. They are using the hybrid function that stops the petrol engine on trailing throttle but doesn't apply regenerative (electric) braking until you take your foot off the throttle altogether (see the note in my earlier post about potential for freewheel on trailing throttle).

In his Prius the engine only shuts down if you do it below about 40mph, above this it remains idling, presumably purely for driveability reasons, so benefits are less.

It's worth noting that they were saying the method gives useful mpg gains below 30mph average compared to steady speed driving, he was accelerating up to 37mph and coasting down to about 20mph. Not sure that would be much fun on the open road and would seriosly pi$$ other road users off in traffic. He said above 30mph the gains were insignificant.

It reminds me of when I was in the Alps in my Yaris, which has a quite accurate mpg readout. I drove about 30mls up 2000m or so into the mountains and stopped at a cafe, getting about 35mpg I think. I then drove back, about 20mls on overrun without touching the throttle, and got 999mpg (as high as it would read).

[-Ralph-]

I used to drive most of my way to work in 6th gear with just a tiny bit of throttle and the fuel computer reading anything above a couple of hundred MPG. I lived at about 1000 feet and worked 15 miles of straight motorway away at about 300 ft. Thing is I couldn't get more than 35 or 40mpg on the way home when I had to climb the same hill, so overall 50-60mpg was my best average. I could get just the same with the cruise control set to 75mph on a 350 mile journey from Scotland to Birmingham, which is up and down over Dumfries and Galloway and the Lake District, with every motorway gradient in between, so I don't think it really makes much difference. It all averages out.

Wouldn't you coast further in neutral than with the clutch down? The wheels are not having to spin the driven side of the gearbox and the clutch plate.

I am lead to believe that with many modern engines, when the road speed is above the engine speed, the injectors turn off.

In other words, on downhills, just take your foot off the gas, leave the engine engaged and the fuel stops flowing. This gives higher mpg than coasting as the engine needs fuel to idle whilst coasting.

Pete ;)

But wouldn't you get engine braking?

Correct, these guys want to coast as far as possible, so engine braking is not desirable.

What if the car's automatic:confused: It's a while since I had a manual car. I don't like 'driving' in neutral as the brake servo don't work.

Just plan ahead and avoid your brakes. You burn fuel to generate speed, then when you brake you take that kinetic energy and turn it into heat. Even in an automatic, if it's modern FI, a closed throttle will shut off the injectors.

When you hit the 1/2 mile sign exiting a motorway, move over to lane 1 gradually loosing speed with your foot light on the throttle, when you see the 300 yd sign, foot off the throttle completely, and let the car slow down naturally. You'll be down to 50 mph or so by the time you hit the slip road and usually down to 15-20mph by the end of the slip don't touch the brakes unless you have to stop at the end.

With the likes of roundabouts and junctions, throttle off as soon as you see it, earlier if it's downhill, and let your car slow gradually, just the same as above. If you can watch the traffic and anticipate ahead as you approach the roundabout or junction, you can try and time it so that you don't have to brake at all, you arrive just as there is a gap in the traffic flow, and you accelerate gently away again.

Your average MPG is also directly related to how far down your foot is on the accelerator pedal, go for a 'light touch' approach with your foot, only using just as much throttle as you need, and you'll use less fuel.

Another trick with an auto box is if your feel it's holding a gear for too long when accelerating, lift your foot slightly as though you were up to the desired speed, and it'll change up a gear, then reapply throttle gently to get back up to the speed you really wanted, but not hard enough to make the box kick down again.

It'll all drive the people behind you nuts, but who cares if you are saving money.

[punyXpress]

With the likes of roundabouts and junctions, throttle off as soon as you see it, earlier if it's downhill, and let your car slow gradually, just the same as above. If you can watch the traffic and anticipate ahead as you approach the roundabout or junction, you can try and time it so that you don't have to brake at all, you arrive just as there is a gap in the traffic flow, and you accelerate gently away again.
BUT - there will ALWAYS be a car in front of you that will STOP, look both ways, select gear, back into neutral, look both ways . . . ad infinitum!
Why do they do that, and what traffic ( apart from bluepete chasing scrotes ) comes from the left on a roundabout?

[Quedos]

When you hit the 1/2 mile sign exiting a motorway, move over to lane 1 gradually loosing speed with your foot light on the throttle, when you see the 300 yd sign, foot off the throttle completely, and let the car slow down naturally. You'll be down to 50 mph or so by the time you hit the slip road and usually down to 15-20mph by the end of the slip don't touch the brakes unless you have to stop at the end.

With the likes of roundabouts and junctions, throttle off as soon as you see it, earlier if it's downhill, and let your car slow gradually, just the same as above. If you can watch the traffic and anticipate ahead as you approach the roundabout or junction, you can try and time it so that you don't have to brake at all, you arrive just as there is a gap in the traffic flow, and you accelerate gently away again.
.

Classic IAM talk - you fancy your pipe and slippers now!

though i'd find you infuriating on a motorway if you done that - that's why its called a de-acceleration lane! ;)

[Quedos]

BUT - there will ALWAYS be a car in front of you that will STOP, look both ways, select gear, back into neutral, look both ways . . . ad infinitum!
Why do they do that, and what traffic ( apart from bluepete chasing scrotes ) comes from the left on a roundabout?

That made me laugh!!! and its always when you have managed to apply the law of Ralph!

[Daimo]

Its right, when coasting in gear, the engine is still being turned over, it doesn't need fuel so no fuel is injected. The driveshafts spinning keep the engine going.

Take it out of gear, no natural spinning, hence fuel is needed to be put in to keep it turned over.

As for Priuses, no, no clutch, boss has one and I drive it often. Front heavy awful handling car. No all that great on fuel either as its no more economical than any other 1.6 engine, and at motorway speeds it only does 40mpg odd. Where it excels is slow speed, town running. But the motor is terrible and to pull away just using electric is stupid. I'd say just using the motor, so free running, is 0-40mph in about 20 seconds. so you have to use the engine as well, knocking the economy down. He gets about 45mpg average, which is what a normal derv runs at. I've had it over 100mpg though pottering around. Dash/dials are good, but materials are terrible (recycled).

Technology on the braking kinetic power return is a good idea, but needs to be made more mainstream and available on other more powerful cars, with bigger/better brakes to return more charge to the motor.

[-Ralph-]

what traffic ( apart from bluepete chasing scrotes ) comes from the left on a roundabout?

:confused: You've lost me. Why do you ask? Did I say somewhere there would be traffic from the left?

[metalangel]

BUT - there will ALWAYS be a car in front of you that will STOP, look both ways, select gear, back into neutral, look both ways . . . ad infinitum!

I was behind a guy in a brand new Jag once. Every time he came to rest at a red light, his brakelights would flash.

Just before he pulled away when the lights changed, the brakelights flashed again.

He was putting it in Park every time he stopped!

[yorkie_chris]

He's on about the idiots who can't plan ahead who get in the way when you are trying to drive smoothly

[-Ralph-]

He's on about the idiots who can't plan ahead who get in the way when you are trying to drive smoothly

I'm with you, he's on about people who sit there at roundabouts and look right AND LEFT. Yes, morons!

[punyXpress]

:confused: You've lost me. Why do you ask? Did I say somewhere there would be traffic from the left?
No, I did - post #22
Yorkie Chris has explained it.
Why oh why do people stop at a roundabout when there's nowt coming?

[Sir Trev]

When you hit the 1/2 mile sign exiting a motorway, move over to lane 1 gradually loosing speed with your foot light on the throttle, when you see the 300 yd sign, foot off the throttle completely, and let the car slow down naturally. You'll be down to 50 mph or so by the time you hit the slip road and usually down to 15-20mph by the end of the slip don't touch the brakes unless you have to stop at the end.

Have you ever driven on the M4 around Reading at peak times???

Sensible advice but gits in Idon'tcare company cars, nutters in scrap-yard-dodgers, clueless old duffers who should not be on the road at that time of day and other assorted imbeciles will cut you up, get in your way and harass you terribly. I've tried to be fuel efficient in this way but it doesn't work if the traffic volume is heavy.

I've also found that a sensible speed, at quieter times, held steady by the cruise control gives the best results.

[Daimo]

Cruise control is the WORST thing for fuel saving. Its ruddy awful. Can't cope economical wise with hills and such. When you approach a car, you roll off, traction control = brakes. Braking on motorway is bad driving. Cruise control is not good for economy. Tried the experiment many many times with the work cars. On a 200 mile motorway trip, i'd loose on average at LEAST 1-2mpg

[Luckypants]

Well I agree with Sir Trev, cruise control on a long motorway stint is more efficient in my experience.

[Sir Trev]

Cruise control is the WORST thing for fuel saving. Its ruddy awful. Can't cope economical wise with hills and such. When you approach a car, you roll off, traction control = brakes. Braking on motorway is bad driving. Cruise control is not good for economy. Tried the experiment many many times with the work cars. On a 200 mile motorway trip, i'd loose on average at LEAST 1-2mpg

Heavy acceleration is where you burn most fuel so if you avoid it by lots of small throttle tweaks you should (in theory) use less fuel. And CC does exactly this with your throttle. Several magazine reports on the web suggest CC can be more economical , but it's always going to depend on the gradients, traffic levels and speed. I've driven many thousands of miles in my Mundaneo on CC and have not noticed much difference to be honest.

[carelesschucca]

Cruise control is the WORST thing for fuel saving. Its ruddy awful. Can't cope economical wise with hills and such. When you approach a car, you roll off, traction control = brakes. Braking on motorway is bad driving. Cruise control is not good for economy. Tried the experiment many many times with the work cars. On a 200 mile motorway trip, i'd loose on average at LEAST 1-2mpg

If someone is struggling with cruise control it means your not using it properly or its a poor system. Speed can be adjusted with cruise control (if its decent) and can be switched off without having to use the brakes. What I find is cruise control shows the inabilty of most average drivers to keep a constant speed I had days where I've past people 4 or 5 times in a 50 mile journey (so they've also gone past me 4 or 5 times)

[-Ralph-]

Have you ever driven on the M4 around Reading at peak times???

Sensible advice but gits in Idon'tcare company cars, nutters in scrap-yard-dodgers, clueless old duffers who should not be on the road at that time of day and other assorted imbeciles will cut you up, get in your way and harass you terribly. I've tried to be fuel efficient in this way but it doesn't work if the traffic volume is heavy.

I've also found that a sensible speed, at quieter times, held steady by the cruise control gives the best results.

If your'e slowing down, people don't tend to get in the way, they tend to want past and away in front. If they cut you up they cut you up, don't worry about it, and if they harass you smile sweetly and ignore them.

I do drive the M4 at rush hour, including every other motorway at rush hour from the M62 down to the M20, depending upon where I am on any particular day.

It is possible to drive calmly, smoothly and economically in any traffic conditions, so long as you keep your cool. I drive too many miles to allow myself to get stressed by driving, traffic and other peoples driving. If I added to the stress I do have to deal with, with stress that I don't, I'd have a nervous breakdown.

Well I agree with Sir Trev, cruise control on a long motorway stint is more efficient in my experience.

+1

[Daimo]

Yeah, I know about the speed controls, but tap tap tap tap tap tap to loose 10+mph gets tedious. Also when applying the speed to increase. Your driving is dictacted by the gradients around you and the car doesn't know when its going uphill.

We'll have to agree to disagree. I too have done substantial miles, but have always found cruise control to be more fuel guzzling. And I actually drive my cars with economy in mind when doing distance driving. Almost like a game, something to do whilst doing the driving.

I.E when i've had the VAG derv machines, i've had over 800 miles from a tank. Never ever got over 722 miles using CC. (not predicated, actual mileage). I guess it depends how good you are with throttle control and forward planning.