'Petrol efficiency experiment; an increase of 20%' blog discussion

charlieheard

Canny_Lad wrote: »

Hi,

appologies if these suggestions are repeated elsewhere on the forum. Below are a couple of tried and tested ways (or so a mechanic mate tells me) to cut driving costs a little.

1) When going down a hill, engage a low gear, to utilise "engine breaking", most effective in diesel's as they have more torque or "grunt". Yes the engine will sound quite noisy as it will have high revs. However, believe it or not, despite this it's only using fuel when the accelerator is pressed. Watch your "current consumption" drop on your fuel computer when you try this, if you don't believe me.

2)Consider having your car engine fitted with a performance enhancing "chip", these not only increase the power by approx 20%, making it nippier, they also enhance the fuel economy by 20 - 40% depending on the driving conditions (better effects in a diesel). The initial cost of £270 - £300 is off set by the savings in fuel economy ( over 6 -8K) & if done properly dosen't damage your engine. *BE CAREFUL* ensure you go to a reputable dealer to carry out the work, it may void your warranty with the manufacturer (some fit there own "Chips" @ twice the price), and you need to check with your insurer. Having said this the chips are easily plugged in and removed. If you have your engine electronically remapped these aren't traceable (get my drift).

1. Most diesels now use turbos, so the relatively small, lower-compression engine is less effective at slowing the car than a naturally aspirated diesel. Formula 1 found their brake wear increased dramaticaly when they switched from naturally aspirated to turbo engines last time round, despite the turbos producing more than 50% more power. Engine braking (Hope you meant "engine braking" - you wouldn't want to break your engine ) will use your engine to slow you down and use no fuel, but as long as you're above idle, modern engines should switch off the fuel altogether whichever gear you're in. I was taught not to use the engine to slow you down, as the torque reversal causes the engine and gearbox to wear differently. "Cheaper to replace brakes than an engine". Not sure how true that is with modern engines, though...

2. I'd love to see independent proof that you can save £300 on fuel after chipping your car. I'm sure the Chipper will claim this, but manufacturers spend millions making their engines more efficient to satisfy consumer demand. Why would they not make their engines as efficient as possible? While you can remap an engine to produce more power, it will come at the expense of fuel economy. The fuel:air ratio for maximum power is significantly different to that for maximum economy. You cannot increase power without adversely affecting economy, unless you up the turbo pressure: however this reduces engine life and you certainly won't be covered by the manufacturer if anything breaks. Many manufacturers now have checks to see if a car's engine mapping has been changed: even if you reinstate the old chip, the change may be flagged, which may well void your warranty...

vax2002

The best way to make a list of weekly journeys and then marry up journeys and see if you can route plan and cut out some trips, like journey home- supermarket instead of home tea, supermarket , less trip = less fuel

crittertog

charlieheard wrote: »

I was taught not to use the engine to slow you down, as the torque reversal causes the engine and gearbox to wear differently. "Cheaper to replace brakes than an engine". Not sure how true that is with modern engines, though...

Current teaching by ADIs, assessment on the driving test (under the non-critical "Eco Driving" section), IAM, and advice from the DSA is to "lift off" the accelerator early, thus using engine compression to slow you down gradually before applying the brakes. I know people who've racked up 200,000m+ on petrol cars from the late '80s driving in this manner without problems ... Obviously, this is not the same as change down and lift off, which is not kind to the gearbox/engine

charlieheard wrote: »

While you can remap an engine to produce more power, it will come at the expense of fuel economy.

For some of the VW diesel engines (yes, I have one, no, mine isn't remapped), I'm aware that once remapped, the fuel economy once remapped is actually increased, as it has much more torque below 2,000rpm (i.e. a more linear and less "peaky" response), so under normal driving conditions, it doesn't get revved as highly, and actually uses less fuel. This is according to people who've actually had it remapped...

Not my "cup of tea", but hey ...

nick1977

Have been experimenting recently with my Skoda Octavia 1.8Tsi. I have a 28 mile trip to work, of which 25 miles is M25 (off peak luckily ) It is astonishing how much difference following some of Martin's techniques makes.
The record I have had for one journey to work is 59.4mpg. Most days it is between 53-57mpg. That is with cruising at about 60-65mph, slowing to 50-55mph in the dreaded roadworks. Careful accelaration, not tailgating, sensible speeds and cruise control all play a part. I still had the climate control on, not sure if I could do better with it off, but there are some things I am prepared to pay a little more for!

I'm pretty impressed for a petrol family car with a 0-60 of less than 8 seconds (not sure I'll ever do that these days with the price of petrol though )

Anyone else got any results that have shocked them?

Nick

twelvebears

nick1977 wrote: »

Anyone else got any results that have shocked them?

Nick

I have a 2011 Skoda Superb 2.0 CR diesel with DSG box. This is a big, heavy luxury car that I came to from a Citreon C4 diesel, so I was expecting a kicking in the wallet.

In practice, by making a deliverate effort to drive economically, I'm getting within 100 miles per tank of the C4 - around 650-680miles from a usual 53-ish liter fill-up.

The in-car computer isn't completely accurate but this morning saw my morning (off-peak) commute at a trip average of 70.1mpg. :T

Basically the biggest factor in how much money you burn is the driver and his right foot. Oh and Cruise Control is fine on the flat and down-hill, but lose it on the up-hill bits....

redux

redux wrote: »

Errrm, a slight mathematical difference about what Martin said:

Going 20% further on a tankful means the rate of consumption, and hence the cost of a fixed length trip or of all fuel bought, drops by 16.7% not 20%

To make the point clearer by stretching things, going 100% further on a tankful is a 50% cost saving

Many countries define fuel consumption in units that are reciprocal to the way we do, e.g. in litres per 100 km, and maybe that's why

I'm a little surprised Martin is still referring back to this article without having corrected this point.

As an example, if someone manages to improve from 50 mpg to 60 mpg, this is a gain of 16.7%, not 20%.

If this doesn't feel intuitively correct, than consider how much fuel is needed to travel 300 miles. To begin with 6 gallons, and the next time 5 gallons. The proportion saved is one sixth not one fifth.

smu95rp

redux wrote: »

I'm a little surprised Martin is still referring back to this article without having corrected this point.

As an example, if someone manages to improve from 50 mpg to 60 mpg, this is a gain of 16.7%, not 20%.

If this doesn't feel intuitively correct, than consider how much fuel is needed to travel 300 miles. To begin with 6 gallons, and the next time 5 gallons. The proportion saved is one sixth not one fifth.

Yes it is a SAVING of 16.7% which is a 20% INCREASE in MPG.

Maybe this will help you with the maths.

If you add 10% to 100 you get 110. If you subtract 10% from 110 you get 99; it is a reciprocal function, as is the difference between MPG and Gallons per mi.

So 1/1.2 (the reciprocal of 120%) is 0.833r which is 1 - 0.166r (or 16.7% less, as you say). If you travel 60 miles for a gallon of fuel, instead of 50 miles, then you are travelling 20% further for that gallon which, if you do the reciprocal calculation, means you save 16.7% of the fuel.

almillar

redux - you're accusing Martin of getting his sums wrong - you're brave! The above explanation should help. You're talking about a DECREASE in the number of GALLONS needed to travel a certain distance, whereas the 10% INCREASE refers to the MILES PER GALLON - a different figure, and in the example that does indeed go FROM 50mpg TO 60mpg, 10mpg more. 10 is 20% of 50, so it IS a 20% increase.

Wheelie-Ross

As I drive a large van, always loaded (cannot do my job without!) and this diesel van will only do 25mpg usually, the ONLY way I can up my mpg is to drive in an eco manner AND IT WORKS! 25mpg if driven like a 'rugby playerr', or 32mpg if driven like a 'ballet dancer' - (examples mean; rugby player charging through the opposition at all cost to get to the try line or ballet dancer being lighter on my feet!)

Hypermiler.co.uk is a good source of information on how to do this and for those 'petrol heads' out there, this driving style often makes me first away from the lights or can cover ground quicker than someone who doesn't apply this technique!

In short, ways to hypermile;
Look ahead, plan ahead, be aware of what/who is around you.
As you approach the traffic lights approx 100mtrs away, they have just gone to red and it is clear up to these lights You saunter up in 2nd gear doing approx 20mph, run over the first 'sensor' at this speed (diamond or parallel black lines - look like camber joiner), slowly slowing, so when you run over the 3rd sensor nearer the lights, the lights should turn green for you to proceed i.e. rolling start! If there is traffic ahead of you, you can still do it, you just need a lower speed. With 2 lanes going straight ahead, its fun, with those who race up to the red light and stop!

By being aware of who/what is around you, if you aren't going to chop someone up, chop your bends, roundabouts, turning right, as small savings equate a BIG saving ultimately!

My van doesn't have 'stop/start' but I can mirror this technology. When a vehcile's engine is up to temperature, if you know you are going to be stopped a long time, like a railway crossing, turn the engine off. You get a good 'warning' ahead that the traffic is going to start moving again, so then re-start.

ALSO in my diesel car, CHEAP DIESEL isn't always best! A modern diesel engine has a 'exhaust recirclation valve' that if blocked, you car will become lumpy and un-responsive at low speeds. This valve can get blocked with continual use of cheap diesel (i.e. supermarket stuff), as carbon deposits build up and when hypermiling. Thus although as I like to save money (not a spendthrift!), if does no harm to your vehicle to drive it hard occassionally, to ensure the carbon deposits don't linger in the exhaust - Google 'How to Kill Your Car'!

Eric_Pisch

Wheelie-Ross wrote: »

As I drive a large van, always loaded (cannot do my job without!) and this diesel van will only do 25mpg usually, the ONLY way I can up my mpg is to drive in an eco manner AND IT WORKS! 25mpg if driven like a 'rugby playerr', or 32mpg if driven like a 'ballet dancer' - (examples mean; rugby player charging through the opposition at all cost to get to the try line or ballet dancer being lighter on my feet!)

Hypermiler.co.uk is a good source of information on how to do this and for those 'petrol heads' out there, this driving style often makes me first away from the lights or can cover ground quicker than someone who doesn't apply this technique!

In short, ways to hypermile;
Look ahead, plan ahead, be aware of what/who is around you.
As you approach the traffic lights approx 100mtrs away, they have just gone to red and it is clear up to these lights You saunter up in 2nd gear doing approx 20mph, run over the first 'sensor' at this speed (diamond or parallel black lines - look like camber joiner), slowly slowing, so when you run over the 3rd sensor nearer the lights, the lights should turn green for you to proceed i.e. rolling start! If there is traffic ahead of you, you can still do it, you just need a lower speed. With 2 lanes going straight ahead, its fun, with those who race up to the red light and stop!

By being aware of who/what is around you, if you aren't going to chop someone up, chop your bends, roundabouts, turning right, as small savings equate a BIG saving ultimately!

My van doesn't have 'stop/start' but I can mirror this technology. When a vehcile's engine is up to temperature, if you know you are going to be stopped a long time, like a railway crossing, turn the engine off. You get a good 'warning' ahead that the traffic is going to start moving again, so then re-start.

ALSO in my diesel car, CHEAP DIESEL isn't always best! A modern diesel engine has a 'exhaust recirclation valve' that if blocked, you car will become lumpy and un-responsive at low speeds. This valve can get blocked with continual use of cheap diesel (i.e. supermarket stuff), as carbon deposits build up and when hypermiling. Thus although as I like to save money (not a spendthrift!), if does no harm to your vehicle to drive it hard occassionally, to ensure the carbon deposits don't linger in the exhaust - Google 'How to Kill Your Car'!

i couldn't be this sad, id rather spend the extra £10 on petrol a week and enjoy driving