hypermiling

Steve

E92 wrote: »

No, because you only live once and because I enjoy driving, I acquired it so I could have something that puts a smile on my face when I go driving and loves to be revved.

+1

That's what it's all about for me as well.

JHMEG

Well there goes another thread killed by the flat earth society. And here I thought we were going to have a bit of an interesting discussion, and not a lecture on the dangers of being different.

@stratos, the poeple on the cleanmpg forums are cool. If you'd like to know more etc that's the place to go.

That's me done with this thread.

Steve

JHMEG wrote: »

Well there goes another thread killed by the flat earth society. And here I thought we were going to have a bit of an interesting discussion, and not a lecture on the dangers of being different.

@stratos, the poeple on the cleanmpg forums are cool. If you'd like to know more etc that's the place to go.

That's me done with this thread.

Who's lecturing - there's two sides to every discussion.

Please don't stop now, I am interested in this.

Matt Simis

My cars get pretty bad MPG. One of the things I was trying out was flooring it at the bottom of a steep hill (a brief blip to 75mph) then coasting the entire way up the hill. To clarify the hill is about 70m long, quite steep and noone around me.

I havent checked all the numbers, but it would be interesting if a burst of acceleration and terrible MPG offsets maintaining say 50mph up the hill. Also of interest was the fact the 2 cars decelerate strangely different:

2.6ton Phaeton goes from 75 to 49mph at the peak (Tiptronic)
1.7ton Allroad goes from 75 to less than 40mph just before peak (Tiptronic)

I would have thought the heavier car would slow down faster.. unless its inertia keeps it moving longer?


EDIT- In the interest of true Hypermilling topics, another HM tactic is to cruise in the "wake" of a large truck, staying as close as possible (although over 1car length away). This is to allow the truck to face wind resistance and punch a hole you follow in (ie drafting). I dont actually think this is as dangerous as it sounds as you read over it it, its basically driving slowly behind a slow large vehicle.

Steve

Matt Simis wrote: »

I would have thought the heavier car would slow down faster.. unless its inertia keeps it moving longer?

The heavier car has greater moment of inertia = it will take longer to slow down.
It also takes more energy to accelerate it.

force = mass * acceleration

peasant

Matt Simis wrote: »

My cars get pretty bad MPG. One of the things I was trying out was flooring it at the bottom of a steep hill (a brief blip to 75mph) then coasting the entire way up the hill.

The trick is not to coast (certainly not uphill) but to carry enough momentum so that you can maintain speed (or close enough) while keeping a feathered foot on the accelerator. Ideally you want to do this at the revs where your engine has maximum torque to get the most out of very little pressure on the gas.

I have to push my yoke up a very steep hill every day on the way home.
I start the hill in second (no choice, there is a crossroads before it) and keep the acceleration very light at the point where the turbo is at full blow but the accelerator is only down one third or so until there is a slight dip, shift into third there and again with very light pressure on the gas make it to the top where I finally shift into fourth.

I could whip the car up there, getting into fourth before the brow ...but you can actually hear the fuel gurgle trhough when you do that

Whipping the car before you hit the hill would have a similar effect.

JHMEG

SteveC wrote: »

Who's lecturing - there's two sides to every discussion.

There are several on this thread.

Matt, Steve C's maths are pretty much correct. In your case there's no such thing as a free lunch. Altho when you're coming back down that hill you could coast and recover a lot of energy.

Drafting, or draughting I think on this side of the Atlantic, is actually very effective from my own experience. I did it just once, in the Integra (which never did more than 30mpg, even on a run), from Dundalk to the M50 and managed to get 60mpg! I was shocked! It's not that dangerous as big lorries can't stop that quicky, but it didn't stop me from bricking it anyway. If I had hit him iirc it would have been his back wheels, as the Integra was fairly low

peasant

Matt Simis wrote: »

EDIT- In the interest of true Hypermilling topics, another HM tactic is to cruise in the "wake" of a large truck, staying as close as possible (although over 1car length away). This is to allow the truck to face wind resistance and punch a hole you follow in (ie drafting). I dont actually think this is as dangerous as it sounds as you read over it it, its basically driving slowly behind a slow large vehicle.

I used to do that with my old, tragically slow camper (50hp diesel) on long motorway trips ...that is I tried it a few times.

DON'T DO IT ! It is ridiculously dangerous !

Travelling at 80-90 km/h (average truck speed) with a distance of a mere 5- 7 meters is suicidal. Those trucks have pretty good brakes and you're travelling totally blind behind them. If the trucker has to throw anchor, you will hit the truck before you're even able to hit the brakes.

80 km'h may feel slow ...but believe me it's way too fast to keep such a small distance. I learned that lesson after being about 5cm away from making contact with the back of an articulated lorry. Thankfully he only tapped the brakes hard and then sped up again ...otherwise I probably wouldn't be here to write this.

Matt Simis

Cool stuff, Ill try the less dramatic feathering next.

On the maths, I dont question force = mass * acceleration and a re-read of mass vs weight on Wikipedia answered my own question.

PS: I dont do any actual Hypermilling other than laying off the brakes, definately not drafting as I hate not to be able to see the road ahead.

JHMEG

Sound. I actually don't do any really either, apart from trying a few things out now and again, and have never done any of it in the Civic IMA. Hence I'm looking forward to trying!

Steve

On the subject of 'draughting' or slipstreaming, I've read that it's just as effective to hang close behind a large truck in the other lane on a motorway/ DC. This solves the braking distance / view ahead problem.

Be polite and move in if you get traffic behind though.

caesar

E92 wrote:

I didn't acquire a not at all CO2 friendly petrol straight 6 with RWD so that I could save a couple of polar bears.

Something for my sig

Matt Simis wrote: »

On the maths, I dont question force = mass * acceleration

ROFL....you'd have some explaining to do if you did!!


Anyway I heard some guy on the last word a few weeks back, he was some world champion for this thing. I listened to it out of curiosity but I couldn't listen to him again, talk about removing all of the the enjoyment from driving. I think they should use that as some sort of definition for the term hypermiling .

Mr Benevolent

I'd actually like to know why some people think that's dangerous when it's done on the open road with good visibility etc

One more point about engine-off coasting - when the engine is off the airbags and pre-tensioners won't fire in a crash.

Steve

Confab wrote: »

One more point about engine-off coasting - when the engine is off the airbags and pre-tensioners won't fire in a crash.

I asked that earlier - I'm not sure what you say is true.
When the ignition is on, they're probably active.
It they weren't then an accident caused by stalling would cause them not to deploy - I find that hard to believe.

E92

Matt Simis wrote: »

EDIT- In the interest of true Hypermilling topics, another HM tactic is to cruise in the "wake" of a large truck, staying as close as possible (although over 1car length away). This is to allow the truck to face wind resistance and punch a hole you follow in (ie drafting). I dont actually think this is as dangerous as it sounds as you read over it it, its basically driving slowly behind a slow large vehicle.

I think it is extremely dangerous. What if the car behind you wants to overtake on a single carriageway road?

There should always be enough of a gap so that if the car behind you decides to overtake and for some reason they need to pull in just in front of you, where are they supposed to go?

Oh and being that close to the truck means you won't be adhering to the most important rule of all for road safety : the 2 second rule.

Matt Simis

E92 wrote: »

I think it is extremely dangerous. What if the car behind you wants to overtake on a single carriageway road?

There should always be enough of a gap so that if the car behind you decides to overtake and for some reason they need to pull in just in front of you, where are they supposed to go?

Oh and being that close to the truck means you won't be adhering to the most important rule of all for road safety : the 2 second rule.

Hey, Im not advocating it, just repeating stuff from a list of 14 or so Hypermilling "skills"!

JHMEG

Matt Simis wrote: »

Hey, Im not advocating it, just repeating stuff from a list of 14 or so Hypermilling "skills"!

The hypermiling guys appreciate drafting, but don't advocate it on safety grounds.

JHMEG

SteveC wrote: »

I asked that earlier - I'm not sure what you say is true.
When the ignition is on, they're probably active.
It they weren't then an accident caused by stalling would cause them not to deploy - I find that hard to believe.

I'd be inclined to take it a bit further.. when the Vehicle Speed Sensor is registering a speed above which the airbags will fire on an impact I'd say the computer will fire them, engine/ignition on or off. Why would a safety feature be turned off just because the ignition is.