Mitsubishi Outlander PHEV Forum

It is currently Fri Nov 24, 2017 5:56 am

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 33 posts ]  Go to page 1, 2, 3, 4  Next
Author Message
 Post subject: Effect of gradient on fuel consumption...
PostPosted: Mon Jan 18, 2016 1:56 am 
Offline

Joined: Fri Jul 18, 2014 4:46 am
Posts: 2789
... OK - clearly there will be one, but I was watching the numbers yesterday and I was surprised at how great it is - has implications for assessing performance...

I was driving back from the coast (Southampton) to our home (north of London) - the starting point was just a few metres above sea level. Following some of the discussions going on here, I was keeping an eye on fuel consumption. I knew that I had about a hundred miles in front of me - almost all motorway - so I was running in Save mode with about 75% battery charge. Ambient temperature was between 3C and 5C all the way and I had the heater on at 21C.

A few miles up the motorway (probably 10 miles from the start of the trip) I was surprised to see the fuel consumption showing 27mpg. I've done this trip many times and know that I generally get around 42mpg on it. I wondered if I had pulled the figure down very low in the first couple of miles, with a cold car in city traffic, so I reset the fuel consumption meter and it settled back on 27mpg within a couple of miles. I assumed that this was a symptom of the cold temperature and carried on.

About 30 miles into my trip, the fuel consumption suddenly dropped to 41mpg - and stayed at that figure more or less until I got home. I've just been checking on Google Earth and the break point in fuel consumption is just past the top of the South Downs. The altitude of the M3 motorway tops out at about 150m just past Micheldelver and the rest of my trip home is broadly flat - slightly down hill overall since my house is about 80m ASL.

So, a climb of 150m over a distance of 25 miles seems to be enough to increase fuel consumption by as much as 25% - that surprised me!


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Mon Jan 18, 2016 9:54 am 
Offline

Joined: Fri Nov 20, 2015 2:35 am
Posts: 260
Location: Poole Dorset
Weird!
Mine does the same. I think all the readouts talk bollox! I don't trust any of them!
I am just starting a full to full (petrol) test to see what the REAL overall consumption is. Together with diarising each charge with cost.
My leccy is 13.1p per Kw X5 hours X2.7Kw =£1.70.. but screen shows last charge from flat cost £1.18. So it obviously took less than 5hours, or I got the 2.7Kws incorrect

_________________
2015 Glacier Blue. PHEV Gx4h. Osram Nightbreakers, Dashcam.Cherished Plate. Image

All contentious comments should be taken with a pinch of salt!


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Mon Jan 18, 2016 10:04 am 
Offline

Joined: Mon Dec 16, 2013 1:18 pm
Posts: 3222
Location: Netherlands
Charging is not linear, it decreases as the battery approaches its maximum charge, so it is not a simple multiplication.

_________________
www.jaapvphotography.eu
www.l-camera-forum.com

Posts in bold green are made as a moderator. All other posts are just my private opinion as a member.

Instyle+ 2013
Titanium Grey
Off-white leather
Body kit
Protection kit
Sidebars
TPMS
Skidplates


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Mon Jan 18, 2016 10:08 am 
Offline

Joined: Thu May 07, 2015 4:24 am
Posts: 469
Location: Doncaster, South Yorks
Carnut wrote:
Weird!
Mine does the same. I think all the readouts talk bollox! I don't trust any of them!
I am just starting a full to full (petrol) test to see what the REAL overall consumption is. Together with diarising each charge with cost.
My leccy is 13.1p per Kw X5 hours X2.7Kw =£1.70.. but screen shows last charge from flat cost £1.18. So it obviously took less than 5hours, or I got the 2.7Kws incorrect


The battery will only take about 8.4kw from 30% full and will trickle charge towards the end so will not be drawing as much power as you think! even with conversion losses. If you assume 8.4 kW + about 9 - 10% for losses @ 13p per kW, the car is telling you fairly accurately what it has cost. Beware that any FREE rapid charging or charging at work will also be reflected in the overall monthly figure. I have found mine to be very accurate.

_________________
Pearlescent White GX4HS from 30 April 2015


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Mon Jan 18, 2016 10:52 am 
Offline

Joined: Mon Dec 01, 2014 11:30 am
Posts: 2598
Location: Netherlands, Utrecht area
WRT the gradient: Of course climbing comes at a cost. But do not underestimate the effect of a (really) cold engine. My previous car (Outlander Diesel) needed at least 40 km befor the fuel consumption would settle down. There is a good reason for me wanting to prevent cold starts as much as possible.


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Mon Jan 18, 2016 2:25 pm 
Offline

Joined: Fri Nov 13, 2015 3:05 am
Posts: 82
maby wrote:
... OK - clearly there will be one, but I was watching the numbers yesterday and I was surprised at how great it is - has implications for assessing performance...


You know, I was able to push my old 1.8 tonne car on flat ground. Surprisingly, I can't bench or dead lift more than 100kg. Gravity, hey?

You know that to overcome wind resistance and frictional resistance for most cars at 60km/h is in the single digit kilowatt range? But a decent hill climb on a 1.8 tonne car can push you over 100kw just to maintain speed.

Put into that perspective, maybe it should be surprising that hills only cost 25% more.


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Mon Jan 18, 2016 2:41 pm 
Offline

Joined: Sat Dec 12, 2015 4:02 pm
Posts: 13
Clearly gradient has a big effect on energy consumption...potential energy (m.g.h) is changing with height, then there is the energy expended in overcoming drag. I suspect that much of the variation in fuel consumption is due to differing wind strength, which can either assist or oppose the car motion depending on direction. I'm currently logging my phev's fuel consumption for my daily work commute, and I'm noting wind strength and direction (roughly) to assess the effect, as well as outside air temperature. Time will tell!


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Mon Jan 18, 2016 10:03 pm 
Offline

Joined: Mon Dec 01, 2014 11:30 am
Posts: 2598
Location: Netherlands, Utrecht area
Sunder wrote:
maby wrote:
... OK - clearly there will be one, but I was watching the numbers yesterday and I was surprised at how great it is - has implications for assessing performance...


You know, I was able to push my old 1.8 tonne car on flat ground. Surprisingly, I can't bench or dead lift more than 100kg. Gravity, hey?

You know that to overcome wind resistance and frictional resistance for most cars at 60km/h is in the single digit kilowatt range? But a decent hill climb on a 1.8 tonne car can push you over 100kw just to maintain speed.

Put into that perspective, maybe it should be surprising that hills only cost 25% more.

We are talking about 150 m over 25 miles. That is roughly a 1:250 ratio, which will add 7 kg gravitational force, or something like that? Sure you can push your car up a 1:250 ratio.

EDIT: To lift 1800 kg up 150 m you need 1800 kg * 9,81 m/s2 (at least where I live) * 150 m = 2648700 Joule. This is the equivalent of approx. 0.74 kWh. Lets say a liter of petrol contains about 9.7 kWh of energy and burns at an efficiency of 25% (which is a negative estimation), then you need about 300 cc of petrol to concur gravity. Normally, 25 miles will take about 3 liters or so? So, an additional 10% to 'get up there'?


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Tue Jan 19, 2016 1:29 am 
Offline

Joined: Fri Jul 18, 2014 4:46 am
Posts: 2789
anko wrote:
Sunder wrote:
maby wrote:
... OK - clearly there will be one, but I was watching the numbers yesterday and I was surprised at how great it is - has implications for assessing performance...


You know, I was able to push my old 1.8 tonne car on flat ground. Surprisingly, I can't bench or dead lift more than 100kg. Gravity, hey?

You know that to overcome wind resistance and frictional resistance for most cars at 60km/h is in the single digit kilowatt range? But a decent hill climb on a 1.8 tonne car can push you over 100kw just to maintain speed.

Put into that perspective, maybe it should be surprising that hills only cost 25% more.

We are talking about 150 m over 25 miles. That is roughly a 1:250 ratio, which will add 7 kg gravitational force, or something like that? Sure you can push your car up a 1:250 ratio.

EDIT: To lift 1800 kg up 150 m you need 1800 kg * 9,81 m/s2 (at least where I live) * 150 m = 2648700 Joule. This is the equivalent of approx. 0.74 kWh. Lets say a liter of petrol contains about 9.7 kWh of energy and burns at an efficiency of 25% (which is a negative estimation), then you need about 300 cc of petrol to concur gravity. Normally, 25 miles will take about 3 liters or so? So, an additional 10% to 'get up there'?


That is an interesting calculation which puts it in context - allowing for inaccuracies in my observations, in the car's instruments and other variables, my apparent 25% impact on fuel economy is not out of the question. Naively I would have thought that the effect of such a small gradient would be lost in the noise!


Top
 Profile  
 
 Post subject: Re: Effect of gradient on fuel consumption...
PostPosted: Tue Jan 19, 2016 1:31 am 
Offline

Joined: Fri Nov 13, 2015 3:05 am
Posts: 82
Quote:
We are talking about 150 m over 25 miles. That is roughly a 1:250 ratio, which will add 7 kg gravitational force, or something like that? Sure you can push your car up a 1:250 ratio.

EDIT: To lift 1800 kg up 150 m you need 1800 kg * 9,81 m/s2 (at least where I live) * 150 m = 2648700 Joule. This is the equivalent of approx. 0.74 kWh. Lets say a liter of petrol contains about 9.7 kWh of energy and burns at an efficiency of 25% (which is a negative estimation), then you need about 300 cc of petrol to concur gravity. Normally, 25 miles will take about 3 liters or so? So, an additional 10% to 'get up there'?


That assumes a straight lift. I doubt you'd get 25 miles of road that is perfectly and uniformly 1:250. Most likely it would rise and fall many times over that 25 miles.

It reminds me of a running joke in one of the world's toughest marathons. Winners tend to finish in the low 3h mark, rather than the typical low 2h mark. Yet it's marketed as:

Quote:
The course climbs a total of 1,528m and drops a total 1,788m giving a net drop of 260m (it's a downhill course !!)


http://www.sixfoot.com/index.php/the-co ... se-details


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 33 posts ]  Go to page 1, 2, 3, 4  Next

All times are UTC - 8 hours [ DST ]


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
© Mitsubishi Outlander PHEV Forum - part of the MyElectricCarForums.com Group