BMW 1-Series Forum (F20) 135i - 1Addicts.com > Second Generation 1 Series Forum > 2012 BMW 1-Series Sporthatch (F20) Discussion > why i like my 116d (non ED) - the economy
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      01-11-2013, 11:57 AM   #23
HighlandPete
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Originally Posted by orcomma View Post
I dont work and live off a sliproad you know lol

70mph on the motorway, plus several miles at 30mph and 20mph! at either end
Average speeds do have a lot to do with the economy we achieve. True the mix of driving is important, but had a 'feel' for what you are doing, to get to the high figure, from your first post.

BTW, you are showing the OBC figures. Do you know how accurate it is from proving with brim to brim testing?

I also note you say 65 - 70mph, is that speedometer, or true speed?

The above two factors are important, particularly when others can get mpg envy.

On OBC figures, a reading of say 63mpg +/- 10% gives us a spread of 56.7mpg to 69.3mpg. Not uncommon to have that sort of tolerance band across OBC readouts, even in BMW cars.

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      01-11-2013, 12:42 PM   #24
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cold starts arent the only thing that affects economy in the winter - the denser air requires the ECU to inject more fuel to keep the same fuel/air ratio. The result is worse economy but (theoretically) slightly more power!
Here's a thought... If there was more power it would move the car faster, and we'd lift off the throttle. Also remember air to fuel ratio is not fixed in the diesel, it can lean out to something like 60:1 in normal use.

There is another factor which often gets left out when we discuss diesel engines in the cold, that is IAT, it can be too low for complete combustion. The cylinders just don't heat enough for optimum efficiency, and can take much longer to achieve that state.

When running the VW TDI engines, it was clear when driving for maximum economy, (in the 50 - 60mpg range), very little boost was necessary and therefore the intercooler was over efficient in colder weather.

At least 3 of us experimented with our engines and kept data. We all found that peak mpg was attained in the 12 - 16C ambient temperature range. Below and above that range, efficiency dropped off. Mike Fishwick (long term VW enthusiast and often published in Volkswagen Driver) kept more data and experimented with blocking off his intercooler at lower ambient temperatures. He was still covering part of the intercooler in his Golf PD TDI at ambient temperatures towards 12 - 15C, to get peak mpg.

He found he could increase the efficiency window which was best between 12 and 20C in those engines, (I second that temperature range). In fact he claimed to improve his mpg by up to 5mpg when using the cardboard to block off the intercooler at the lower temperatures. The only change was warmer air entering the engine.

To clarify, these comments apply when driving light, particularly driving at constant speed. If you drive harder, then the boost required will heat the air and the intercooler cooler will be less critical to the above comments.

But in sub-zero temperatures even a harder worked engine can suffer from AIT chilling, hence the AIT heaters that get used on diesel engines in some industries and on HGV rigs running in cold climates.

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      01-11-2013, 01:41 PM   #25
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Quote:
Originally Posted by orcomma View Post
cold starts arent the only thing that affects economy in the winter - the denser air requires the ECU to inject more fuel to keep the same fuel/air ratio. The result is worse economy but (theoretically) slightly more power!
But since it has slightly more power, you can use slightly less throttle, so that brings the consumption back down again. The winter wheels are often lighter, and the winter tyres sometimes narrower, also adding to the equation. So for me, the lowest consumption I get, is on long journeys on cold winter days.
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      01-11-2013, 03:29 PM   #26
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All fuel economy will improve in the summer - mine was about 10% better last summer. How many miles has your ED done?
I've had it since October with 4000 miles on the clock and its at 8765 miles now, so only driven in the winter
! Well rain really!! I do find a huge difference going 65mph compared to 85 mph and when my boss is in the passenger seat it goes down by about 15 mpg, he's a big lad with an A8 so won't be on here
I do a fair bit of town driving and generally stay in comfort or sport as nothing demists in Eco, my tank average last time was 51.6mpg however I am pretty hard on the right foot so am pretty pleased with that seeing as my 320d only did 32mpg in town.
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      01-11-2013, 04:26 PM   #27
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Some interesting comments.

I can say I've had some economical specials and cars with supposed good figures but by far the easiest to get good figures was again the 1.9Tdi 110 engine in an Octavia.
I think that engine was a one that will not be repeated, you didn't have to drive any differently and it would easily get in the 60's mpg.

The current crop of cars with efficient dynamics and bluemotion and ecomotion and ecotec and greentec etc, etc just con the EU test. They don't add much to real world economy in my experience..

As a real world example when I bought my Passat 2.0TDi it was sold with or without bluemotion tech, the bluemotion versions were 1.5k more.
I bought the standard model with a combined 48mpg figure, the bluemotion version was 60mpg.
On my motorway commute I get 50mpg to 55mpg depending on temperature. I once had a bluemotion version for a week and the economy was no different what so ever.

The 116i we have has economy figures within 1mpg of my Passat but that's due to the efficient dynamics screwing the figures. In reality it's about 10mpg less on a run. The petrol is a lot closer around town from cold though.

The heat for diesels is another interesting comment. I had a Jeep Cherokee with the 2.8 CRD VM Motori engine and that had a viscous heater that engaged at low temperatures to ensure the engine warmed up quickly and stayed at optimum temperature. Probably only really needed in Canada where it was also sold but never come across it before.

Cheers
Lee
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      01-11-2013, 05:17 PM   #28
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Originally Posted by logiclee View Post
....The current crop of cars with efficient dynamics and bluemotion and ecomotion and ecotec and greentec etc, etc just con the EU test. They don't add much to real world economy in my experience..

As a real world example when I bought my Passat 2.0TDi it was sold with or without bluemotion tech, the bluemotion versions were 1.5k more.
I bought the standard model with a combined 48mpg figure, the bluemotion version was 60mpg.
On my motorway commute I get 50mpg to 55mpg depending on temperature. I once had a bluemotion version for a week and the economy was no different what so ever.
You make a very relevant observation, something that got my interest as an "mpg anorak", as ECO technologies came along. Mpg shortfall is increasing with these eco models, some suggesting that real world averages now showing over a 20% shortfall.

DieselCar recently posted observations of a standard Golf 140 TDi, against the Bluemotion model with the same 2.0 TDI engine. Driven as we do in normal day to day driving mpg was very similar, only when driving with economy in mind did the Bluemotion show its 'eco' credentials.

So guys who drive in ECO-PRO mode and 'reset the mind' to driving, as much as economy drivers do already, will see the benefits.

We've lost the slack we used to have against the official mpg figures. The manufacturers have used it up, so now very hard to get good looking mpg against the official combined figure.

Take my E39 540i, I could improve on the combined figure by over 25% long term, without using economy driving techniques. Current F11 535i, will never make the combined figure as an average, driving as I did in the 540i. The extra 10 or so mpg "on paper" is not a real world reality.

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