2007 NAIAS Recap
UNSW Smashes Record for Solar-Powered Trip from Perth to Sydney

BMW Introduces New, More Fuel-Efficient 1 Series; Fuel Consumption Improves By Up to 24%

The new 1 Series.

BMW is introducing its new 1 Series—which includes the 118d, the most fuel-efficient production vehicle yet from BMW—in Europe with a range of fuel-saving technologies.

Brake Energy Regeneration (earlier post), an Automatic Start-Stop function and Electric Power Steering are combined with lower rolling resistance tires and a gearshift change indicator to encourage economical driving. These are in addition to the use of variable valve technologies and High-Precision Direct Injection engines on some 1 Series models that boost power output but cut fuel consumption and emissions.

The BMW 118d, BMW’s most economical car with fuel consumption of 4.7 liters/100km (50 mpg US), combines the new technology with the use of further lightweight engineering. The car now has an aluminium crankcase to save weight. Aside from the BMW Hydrogen 7, the BMW 118d also posts the lowest ever CO2 emissions of any BMW: 123 g/km.

Other engines in the new 1 Series range record economy improvements of up to 24% compared to the previous model, while emissions have also been cut by up to 21, while power outputs have increased by up to 20 hp.

Brake Energy Regeneration (iGR) uses an Intelligent Alternator Control (IAC) and an absorbent glass mat battery to reduce drag on the engine by only engaging when required to charge the battery, whereas a traditional alternator is always pulling power from the engine. Additionally, the energy generated by the engine on over-run (under braking or descending a hill) was previously wasted. Now this previously lost energy is utilized by the IAC to charge the battery. iGR alone is responsible for a three per cent improvement in fuel economy. (At NAIAS, BMW announced that iGR would be applied in the new 5 Series as well. Earlier post.)

The new 1 Series comes with an Automatic Start-Stop function to cut fuel consumption. Standard on all manual transmission models (except 130i), the system automatically switches the engine off when the vehicle is stationary and the driver puts the car into neutral. To restart the driver only need engage the clutch again before pulling away in the normal manner. The driver can choose to disable Automatic Start-Stop.

The use of Electric Power Steering results in a 90% energy saving compared to a conventional mechanical hydraulic steering system. Power assistance is now provided by an electric motor that works only when required, such as turning a corner. Other fuel saving enhancements have been made courtesy of various ancillary devices, such as the air-conditioning power supply being disconnected from the drivetrain when not in use. Even flaps behind the kidney grille improve economy, closing up for improved aerodynamic efficiency should the engine require less airflow. The feature also improves cold starting times.

Select new members of the 1 Series engine line-up include:

  • 120i: New four-cylinder gasoline engine with High-Precision Direct Injection (gasoline direct injection) and Bi-VANOS technology. Output is 170 hp / 127 kW (up 20 hp) while peak torque is now 210 Nm / 155 lb-ft (up 10 Nm). Combined fuel consumption is 6.6 l/100km (37 mpg US) (improves by 17%), CO2 emissions are 152 g/km (down 16%).

  • 118i: New four-cylinder gasoline engine with High-Precision Direct Injection and Bi-VANOS technology. Output is 143 hp / 107 kW (up 14 hp) while peak torque is now 190 Nm / 140 lb-ft (up 10 Nm). Combined fuel consumption is 5.9 l/100km (40 mpg US) (improves by 24%), CO2 emissions are 140 g/km (down 20.5%).

  • 120d: Second generation common-rail diesel engine with aluminium crankcase with output of 177 hp / 132 kW (up 14 hp) while peak torque is 350 Nm / 258 lb-ft (up 10 Nm). Combined fuel consumption is 4.9 l/100km (48 mpg US) (improves by 16%) and CO2 emissions are 129 g/km (down 15.1%).

  • 118d: Second generation common-rail diesel engine with aluminium crankcase achieves with output of 143 hp / 107 kW (up 21 hp) while peak torque is 300 Nm / 221 lb-ft (up 20 Nm). Combined fuel consumption is 4.7 l/100km (improves by 19%) and CO2 emissions are 123 g/km (down 18%).

Since its launch in September 2004, the BMW 1 Series has sold more than 200,000 units worldwide. The new three- and five-door BMW 1 Series models will be on display at the Geneva Motor Show in March.



Too bad "worldwide" never includes the US as far as the 1 series is concerned.

I'd love to get a 118i (even if they make the 118d 50 state legal I like a lighter machine).

Rafael Seidl

All that tinkering really does add up, doesn't it? Cleverly, they do not market the way they manage the electric power as a micro-hybrid. Instead of endlessly explaining themselves to the press and hybrid purists, they focus on what their package of enhancements means to the customer: good fuel economy/low climate footprint with the superior handling of RWD.

Note that the relative improvements were about the same for both engine types. Of course, the gap is narrowing in absolute terms. If history is any guide, the refinements introduced here will eventually trickle down to the engine partnership with PSA, where unit volumes are much higher.

Mind you, BMW has not been known for fuel economy in the past, so perhaps they had more room for improvement than others. As one of the signatories to ACEA's voluntary commitment to achieve industry fleet average emissions of 140 g/km CO2 by MY 2008, fuel economy has obviously become a priority new - lest the EU regulate CO2 emissions by law, after all. Germany's carmakers tend to rely on more powerful engines than their French and Italian competitors.

Note: the ACEA commitment actually entails a 25% reduction in CO2 relative to 1995 levels, for those models for which a predecessor existed back then. It does NOT mean every individual manufacturer's new vehicle fleet sales have to average to the same absolute CO2 emission rate.


Please note these are Uk gallons. 1.25 x a US gallon.

But well done BMW. Keep 'em coming.

It will be interesting to see these engines in the 3 series (if they are not ther already) [ I'm not an expert on BMs ]

H. Myers

I sold my BMW and purchased an Audi A3; BMW has nothing in its US lineup that offers 30+ mpg. I average between 30 amd 32 mpg with the A3.


Interesting that the 118s have similar power and that the 120d slightly more power than the 120i. Is that correct?

Bill Siuru

Always amazed at the potential of the IC engine. We can enjoy the driving pleasure a RWD BMW even if the CAFE reaches mpg.


I just wanted to point out that 4.7 liters/100 km DOES work out to be about 50 miles per AMERICAN gallons:

(100 km/4.7 L)*(1 mile/1.609 Km)*(3.785 L/gallon)= 50.051 miles/gallon.
The quote of 1 UK gallon = 1.25 US gallons is irrelevant.


The 1 Series are compact hatchbacks. If you can afford to, you may be able to get it imported, into US, if you live in non-CARB states. Perhaps there is a niche market waiting to be exploited (Tier2Bin8 or "45 state diesel"), by importing Euro diesel models that meet the standards, but where the automakers are not keen on tackling the task of marketing/selling them, until their Tier2Bin5 diesels come out (2009-2011).


You can bring a 1 series to the US, for off road use only and most likely for only a one year registration until you have it changed over to US spec.


Good progress. It seems they can do more about the air conditioning. They can have a slightly bigger battery and run the AC with battery. Only charge the battery when needed like in over-drive conditions.


These new engines, with similar sizes and power ratings, dramatically demonstrate the superior economy of the clean diesel. Also demonstrated is the efficacy of cylinder enlargement and unit reduction (larger and fewer cylinders) with a diesel. BMW should have lopped off a cylinder from the larger diesel engine instead of producing a separate smaller engine. The 3 cylinder engine would have saved money, and would have achieved similar performance with much higher fuel economy.

Rafael Seidl

Mahonj -

the numbers quoted are indeed in US gallons. These engines are all inline fours, the 3 series uses inline sixes. However, it is fair to expect that all BMW models will take advantage of these refinements when they are next revised. Second-gen GDI was first introduced on the 335i with twin turbos last year.

cidi -

the turbocharged 120d has a little more rated power than the naturally aspirated 120i. The numbers for the smaller 118 variant are identical. If the gasoline engines were turbocharged as well, they would obviously blow the diesels out of the water becuase they can rev so much higher.

JC -

it is common for manufacturers to offer the same base engine in a narrow band of displacements, so their sales & marketing teams can offer more price/performance options. Displacement can be varied by changing bore or stroke.

Three-cylinder engines are not the panacea you suggest: there are free mass moments of the first order, making a compensation shaft necessary. Inline fours have free mass forces of the second order, so the additional expense of compensation shafts lets them run much smoother.

Also, an engine with three larger cylinders cannot rev as high as one with four smaller ones. If what you care about most is smooth rated power, fewer cylinders is not the way to go. Also, the difference in aggregate internal friction is not as great as you suggest.

Thomas Pedersen

Unfortunately, the 1 series is butt-ugly (no need for rebuttal - just my personal opinion) and quite cramped, I've heard.

It will be interesting to see what mileage these engines will get in the 3 series. Maybe 5-10% less?

Now we finally see that diesels have overtanken gas engines in hp/litre (for normal cars).

Rafael, good point about their marketing! Also nice to see BMW deliver what has been promised (more or less) earlier on this site.


Where does it indicate "Clean Diesel"? "Clean Diesel" means it should be, at a minimum, equal to current gasoline engine requriements for emissions. Even better if it can be equivalent to ULEV, SULEV or PZEV emissions.


Despite producing more power and torque than the 1.9 TDI in the jetta, the engines don't achieve better fuel economy. I always get at least 49 MPG in my 03 jetta.



I was assuming that the BMW diesels had different displacements. However, they probably have the same displacement, but with different turbos and timing. Therefore, my statement of implied demonstration is probably not here shown. But I still believe that diesels benefit from larger cylinder sizes as opposed to having more cylinders.

As to balance shafts, these all have them I believe, so what's the point you're making? I know that some BMW owners may get an occasional thrill from revving their engines to redline. But for the average user, in either part or full throttle applications, the engine very rarely runs at or near redline. So again, what's the point of having a redline which is a little bit higher?

I said that that BMW 1 series diesel would have been better as a 3 cylinder than as a 4 cylinder. I didn't mention anything about the ICE as being a panacea - please.

Diesel technology is rapidly improving. I'm suggesting that manufacturers should seriously look at 3 cylinder turbo-diesel engines for their upcoming micro-hybrid cars. The cost savings on the engine will significantly help offset the added cost of the hybridization. Drag strip acceleration numbers aside, real world performance should be similar; but CO2 output would be significantly lower. I believe that this is the next step forward while we wait for the price/size/weight of batteries to come down.

Rafael Seidl

Patrick -

no mention of "clean diesel" aka T2B5 emissions because the BMW 1 series isn't even sold in the US.

JC -

my panacea comment referred to inline threes vs. inline fours. The merits or otherwise of ICEs vs. other forms of power plants were not at issue.

In a passenger car, engine size, weight and dynamic response demands are different so the optimum displacement range per cylinder is 350-600cc, with most coming in at 450-500cc. This happens to be true for diesels as well as gasoline engines. The price for using e.g. 4x450cc instead of 3x600cc is perhaps 1-2% thermodynamic efficiency, which is not nothing but not as much as you seem to think, either.

Three-banger diesels are in fact used in European compact cars, for displacements of 800cc (old smart fortwo) to 1500cc (Merc A-class). One advantage is that they respond very well to resonance boosting when naturally aspirated. Another is that they can make do with a single scroll turbo, if one is used. The main reason inline threes are not used more often is that you practically have to add a compensation shaft to deal with the free inertial moments of the first order. Also, the crankshaft is not flat and therefore more expensive to produce.

Note: in theory, you could build an inline three in which the central cylinder has twice the displacement of each of the outer ones and the crankshaft is flat. The outer cylinders would fire at the same time, yielding firing intervals of 360 CAD (cp. two-cylinder engine) vs. 240 for a regular inline three and 180 for an inline four. The larger the interval, the larger the torsional vibrations.

Your point about redlining is valid, as rated power is indeed rarely used in normal passenger cars (as opposed to HDVs and race cars). Modern boosted engine designs often focus more on achieving 90+% of rated torque at very low RPM, ~1500 RPM for many modern diesels. Indeed, their torque curve is often artificially flattened by the engine controller over a wide speed range to keep the mechanical stresses tolerable. High torque at low RPM permits long gearing for fuel economy plus reduced NVH.



I'm waiting for JC to show me how these are clean diesels. He mentioned these engines dramatically show the superiority of fuel economy of the "clean diesel" which these are not. 25% improvement in fuel economy but the actual improvement in CO2 emissions is 13.8% coupled with the higher emissions of pollutants. If they achieved the same fuel economy while having the same levels of emissions as a gasoline engine then I would be impressed.

Rafael Seidl

Patrick -

the 1 series diesel engines are not designed to meet US emissions specs.

For the 118 engines, the diesel produces 123 g/km = 88% of the CO2 the gasoline variant does, based on the NEDC. The 120d comes out a 85% of the 120i. I'm not sure where you get either the 25% or the 13.8% number from. However, you are right to point out that fuel consumption figures in l/100km or fuel economy in MPG should not be compared naively when the fuel composition is different. CO2 emissions provide a more useful basis for comparison, in addition to their direct relevance to the global warming debate.

These new diesel engines come standard with wall-flow DPFs. If BMW decided it wanted to introduce the 1 series to the US after all, it would have to add an expensive NOx aftertreatment system for the diesels. For engines of this size, NOx store catalysts are cheaper than SCR systems. Using ULSD only, expect fuel consumption to increase by about 4%. Ergo, a clean diesel should indeed emit less CO2 than a gasoline engine rated at similar power. However, the difference may shrink to less than 10%.

A recent ADAC study in Germany of TCO over the first 4 years after initial purchase suggested that for many (not all!) mid-sized and larger vehicles, diesel delivered 15-20% savings when driven at least 12,000 miles per year. Substituting US fuel prices for the German ones and accounting for the additional cost of NOx aftertreatment, I concluded that about half of that benefit was due to superior thermodynamics. If you drive a lot, choosing a clean diesel when they become available should save you 7-10% in TCO per mile driven.

For vehicles that are driven less far but spend more time in stop-and-go traffic, gasoline hybrid technology probably makes better financial sense.


Nah, you are right. I took the wrong denominator.

I used 17/123 (but since we are talking about improvement over the 140 number I should have used 17/140 for a 12.1% improvement).


I'm not sure why JC thinks it would be cheaper to make a new 3 cyl engine rather than reducing the bore or stroke of and existing 4 cyl?


Can someone say more about importing a diesel not sold in this country? I'm military, and if I could bring one back with me from Germany, I would BEG for that assignment. What is necessary to bring it in to alignment with US regulations? I'm assuming the difficulty isn't in importing it, but in registering. Thanks! Tell me how to do it, and I'll bring one back for you, too!

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