41 mpg BMW
 

In this week's episode of "What the Heck is Martin Driving Now?", we find our hero tooling around Southeast Michigan in a European spec BMW 120d. It's a 5 door hatch with a 2.0L turbo-diesel engine.

So why is that relevant to a newsgroup that's focused on hybrid technology? Simply because this one is equipped with BMW's Driving Dynamics package of fuel economy improvement technologies, including Start / Stop.

I've gotten 41.2 mpg over my time driving it. Considering that I've been driving it like I stole it, I think there's 45 mpg potential there. Pravus Prime would cringe if he saw my launch techniques with this little rocket. Definitely the most fun I've ever had in a high fuel economy vehicle.

It took me a couple hours to get used to the Start / Stop operation, but after that it was a piece of cake. The way it works is when you come to a stop, you depress the clutch, shift to neutral, and release the clutch. When you depress the clutch again to shift to 1st, the engine restarts. I'm used to sitting at lights with the clutch depressed, so I had to get used to this procedure. Eventually I recognized that you can shift into neutral and coast to a stop and get a shut-off that way.

So far BMW has only made this package available in manual transmission equipped vehicles. They have a similar setup in the Mini Cooper Diesel with a 1.6L that gets about 65 mpg.


The one I drove looks like the picture below, but with a couple extra doors.

http://www.bmwauto.lv/images/BMW120d_2007.jpg


It's very likely that similar small diesels with Start / Stop will begin to proliferate in Europe. US Emissions standards will likely limit or totally block the availability of this type of vehicle in the US. They can pass 48 state emissions today, but by 2011 they'll have a tough time meeting the tighter specs.

Peace,

Martin

Re: 41 mpg BMW
 

Hi Martin,

You sure get a lot of nice toys to play with:
Although it sounds nice, is there a European testing standard that has been uniformly applied to the BMW 120d and a hybrid? The closest I was able to find were:

http://www.autocar.co.uk/CarReviews/...s-120d/224963/
http://www.autocarmag.com/CarReviews...rid-T3/204492/

BMW 120d / Prius (NHW20) / item
20,160 / 17,932 / price in pounds
7.9 / 10.9 / 0-62 mph seconds
137 / 106 / maximum speed
1415 / 1300 / weight kg
49.6 / 65.7 / combined mpg (1 imperial gallon = 1.2 US gallons)
152 / 104 / CO(2) g/km
1,995 / 1,497 / engine cc
161 / 76 / Max power bhp
251 / 85 / Max torque lb-ft

They don't have similar numbers for the Camry hybrid but we might scale the EPA mileage numbers:

Prius / TCH / item
46 / 34 / USA EPA combined mileage test

So if we take their 65.7 * ( 34/46) = 48 mpg (imperial) scaled Prius->Camry hybrid

Off hand, the Camry hybrid and the BMW 120d look to be fairly close in mileage. However, the Camry hybrid has what drives like a fully automatic transmission. The Camry also uses relatively cheaper gasoline versus what has become more expensive diesel. Still, it is a good effort.

One thing that has me scratchin' my head is to what extent the mileage improvements in the BMW 120d come from:

• 2.0L turbo-diesel
• auto-stop

You mentioned having to learn a new way to come to a stop. If you drive so as to defeat the auto-stop, could you estimate the mpg impact?

Thanks,
Bob Wilson

ps. 49 mpg (imperial) -> 40.8 mpg (USA) Martin reported 41.2 mpg.

Re: 41 mpg BMW
 

"The way it works is when you come to a stop, you depress the clutch, shift to neutral, and release the clutch. When you depress the clutch again to shift to 1st, the engine restarts"

That sounds REALLY easy compared to a Prius :-)

Serious : Does it work with the climate control on?

Re: 41 mpg BMW
 

Comes with the job :D

....

Agreed, but they are two vastly different vehicles. I would never drive a Camry of any configuration the way I drove the 120d. It's the difference between wearing a shirt and slacks and taking a brisk walk (Camry) v putting on the workout gear and gym shoes and going out for an energetic run (120d). Both the Camry and the 120d will get you there with excellent fuel efficiency. For my lifestyle and driving preferences, the 120d will deliver more smiles / mile. I'd be willing to pay some extra for that.

After returning the E2M, I picked up a BMW 520d for a week. Same engine as the 120d, but with an automatic instead of a manual. Since it's an automatic and therefore doesn't have Start/Stop I declined to mention it here. I got 38.5 in that one. That's with a much heavier vehicle and with additional parasitic losses due to the automatic, but balanced by the fact that I wasn't playing boy-racer with it. I picked up the 120d about a week after I returned the 520d.

Comparing the two Bimmers, it appears most of the f/e is inherent in the design of the diesel 2.0 and the fact that diesels can handle higher loads with minimal f/e drop off relative to similar sized or powered gasoline engines.


Typically we use a 2 - 3% improvement factor when considering Start / Stop manual transmission applications. I'd guess you could back that out from the 41.2 I averaged. But I'd still expect to get better than what I got in the 520d which was done with no S/S and with auto-air always on. We were touching 90 degrees the whole time I was driving that one.


Peace,

Martin

Re: 41 mpg BMW
 

I wasn't able to get it shut off with the ac going. Actually, knowing how the system is set up, I didn't expect it to work that way. I spent most of my time with the air off, windows down, and sunroof open. Great for driving experience :shade: , poor for aero / fuel economy impact.

Peace,

Martin

Re: 41 mpg BMW
 

This sounds about right for the auto-stop feature:
This is consistent with the Saturn VUE and other auto-stop systems. Don't get me wrong, any port in a storm. The lean-burn diesel with turbo charger makes a lot of sense.

Just curious, are there any "open" sales figures on the GM two-modes you might point me at?

I'm hoping you' all have a team using the 'lessons learned' to design your next version and hopefully for more 'down scale' vehicles. To replace our vehicle fleet, we need to see larger numbers.

Bob Wilson

Re: 41 mpg BMW
 

I test drove a similar car at an event at my work. Didn't know about the auto-stop when I took off in the car. Needless to say I was VERY surprised at the first light, but after that realized it was natural and thought it was pretty cool.

I was taught to release the clutch rather than holding it in at a light, so from the standpoint of operating ease it's no additional work since you're driving a manual trans and have to shift to neutral anyway, which in effect makes it JUST as easy as the Prius (or my TCH).

Re: 41 mpg BMW
 

Bob - those are the old numbers for the 120D. The current numbers bumps the price, weight, HP, and fuel economy up. Now the 120D is within 10% of the Prius FE and even faster.
http://www.vcacarfueldata.org.uk/sea...s.asp?id=19958

BMW 120d / Prius (NHW20) / item
20,415 / 17,777 / price in pounds
7.6 / 10.9 / 0-62 mph seconds
142 / 106 / maximum speed
1450 / 1300 / weight kg
58.9 / 65.7 / combined mpg (1 imperial gallon = 1.2 US gallons)
128 / 104 / CO(2) g/km
0.186 / 0.010 / NOx g/km << ADDED THIS
1,995 / 1,497 / engine cc
177 / 76 / Max power bhp
258 / 85 / Max torque lb-ft

There is some reasonable detail about what BMW did to reach these numbers on their site. Quoting another article:
http://www.bmw.com/com/en/insights/t...roduction.html

Now if we can only get Europe to focus on NOx emissions as we do in the US. :(

Re: 41 mpg BMW
 

Thanks! I knew there had to be an authority but didn't know how to find them. I wonder if there is an easy way Martin could tell if he has one from the 'old' or the 'new' 120d series? Not a biggie but I was impressed how his number matched the old 'combined' numbers ... not that any of us are trying to follow mileage driving protocols. <grins ... don't look at my signature.>

Bob Wilson

Re: 41 mpg BMW
 

Bob,

I KNOW it's the new spec because it has the Efficient Dynamics package. We had to wait for one to come available. As for my numbers being close to the old spec?

Let's just say less than 10 miles hwy driving out of about 250 miles driven(wanted to get a lot of S/S events) and consistently driving waaay over the speed limit with windows down and sunroof open. Jack rabbit starts....your typical anti-social teenager with first cool car kinda driving. I significantly UNDER performed the MAX f/e that this car could deliver. And enjoyed every minute of it. As I said earlier, I'm sure this car can achieve 45 mpg.

Peace,

Martin