Fuel consumption in a Brabus (Sorry for the lame question, but it's killing me!) - 451 smart fortwo

Hi Guy, The smart has a stee…

2009-09-08T21:21:55.300Z

Hi Guy,

The smart has a steering wheel position sensor for the ABS and ESP. Evilution mention it on: http://www.evilution.co.uk/index.php?id=521

It would be nice if the transmission was linked to the steering wheel position to better control downshifts... maybe the ESP already has that input for braking control but is not it using for applying power, just limiting it.

Manual shifting with the paddles is so much more fun than using full Auto. Using full pedal down to force a downshift causes a delay and lurch on my car... a flick of the left paddle is a lot quicker and smoother.

Hi Ian, Most interesting. Th…

2009-09-08T12:23:24.961Z

Hi Ian,

Most interesting. The ECU definitely has a funny way of downshifting and I am definitely using manual mode much more these days for super smooth driving including taking turns and speeding up the downshifting so that I have more control coming out of the turn (instead of the gearbox hunting for the best gear to be in).

Maybe as time goes by and ECUs become more intelligent, they'll take into consideration steering angle, and predict that you are turning, or even better it will be ready to downshift if you use your indicators and start to turn the wheel in that direction :)

I think I'm going to have the guys at the dealership take a look at the excessive consumption thing, it could be a faulty sensor on my side too, although no other symptoms are displayed.

Hi Guy, The crankshaft positi…

2009-09-07T23:22:41.557Z

Hi Guy,
The crankshaft positioning sensor was replaced last Friday.
Did the Cairns to Townsville round trip yesterday - 707 km total. Average speed 74 kph, max legal speed 100 kph... it's not a good highway!

Fuel consumption with Shell Premium 95 RON was 5.8 lhk, both ways. That's a lot more stable than previous trips that bounced up to 6.5 lhk. I'll switch back to Shell V-Power 98 RON and perhaps see the consumption drop to 5.5 lhk.

The car is now sticking in 5th in Auto, more than it used to. At 100 kph, it's doing about 3,000 rpm - just under the max torque output. Turbo around 80 kpa. That's a bit sluggish on downchange for hills, so I still prefer manual shifts. Turbo boost drops when in 4th doing 100 kph.

Hypothesis: if the crankshaft positioning sensor is not quite right, the whole fuel mix is affected and fuel consumption can be high.

On a road dominated by Toyota Prados, it takes a while before they give up trying to push me as we leave each town / slow section of the road. I need a rear facing camera to catch some of the expressions.

Hi Guy, The wastegate is disc…

2009-08-30T22:32:39.292Z

Hi Guy,
The wastegate is discussed on Evilution. One the things to remember is the small size of the engine and turbo... the wastegate generally is not an issue on the smart.
If you check the power and torque figures for the turbos vs the na the biggest difference is in the torque, not the power. Max torque for the na is 92 Nm @ 4,500 rpm. My turbo is rated 120 Nm @ 3,250. Your Xclusive is: 140 Nm @ 3,500. To me this indicates that the turbos boost torque and move it down the rpm scall compared to the non-turbos. This should mean we have more grunt in 5th than the na and this is where the turbo is working a bit more. Start doing over 4,000 rpm in 4th and the turbo phases out (?)
Yep.. the quirk in manual shifting is to flick the paddle down one or two gears before pulling hard on the steering wheel on a 90 degree residential corner... or suffer the "where the heck is that paddle" syndrome.

Hi Ian, Good to know it all…

2009-08-30T19:53:13.950Z

Hi Ian,

Good to know it all went ok!

The higher boost pressure could sound like "boost creep" to me. It occurs on some turbo cars when you get into in longer gears.. It's usually when the wastegate can't bypass enough exhaust gases and the turbo's boost pressure increases.

Cars are usually tuned from the factory to understand small rises in boost pressure a little bit beyond the norm, in case things like this happen.

On the other hand, if the boost pressure is electronically controlled with a solenoid or something, it could be that the car's ECU gives some more boost in 5th to keep the car accelerating at a healthy pace..

I've been driving the car in manual mode, and it's pretty cool (only "quirk" is that it can get caught off guard on corners, but now i just blip it down right before entering the corner).
I can also get the shifts super smooth now, with a quick lift off the gas pedal and a smooth stepping back on.

Unfortunately I did a lot of highway driving and that will affect my mileage figures, but as of the next refill, I will see if there are any noticeable improvements.

Hi Guy, I did the round trip…

2009-08-30T07:38:04.073Z

Hi Guy,
I did the round trip ok... just a bit of a worry getting the smart to cold start on both mornings.
Managed to attain 5.5 lhk driving south, then 6.1 lhk coming back. Really inexplicable differences in fuel consumption that I'm hoping is caused by the crankshaft positioning sensor being flaky. The ScanGauge shows varying fuel consumption (second by second) when steady cruising at 100 kph. MAP (Manifold Absolute Pressure) stays constant, but the mixture is obviously changing from around 5 lhk to almost 7 lhk at the same speed and load.
Turbo boost (MAP) seems to be greater in 5th gear than in 4th at 100 kph... maybe the turbo is producing more torque at the lower rpm in 5th. In 4th the rpm are higher and the power is more in the brake horse curve. (?)
The only way I reproduce your heavy consumption would be by sustained uphill drives... with no fuel saving by returning downhill.
I hope the replacement sensor arrives this week...
One reason for the fist bar on the fuel gauge lingering is that the gauge measures the level in the fuel tank.. it does not try to guess how much is in the filler pipe so until that is used and the tank starts to drain, the gauge stays on full.

Ian, 100% of all my fills we…

2009-08-30T01:38:56.720Z

Ian,

100% of all my fills were made at the same station, at the same pump (there aren't many 100octane pumps here). It's the same place that I fill my other cars.

The 31.45 was me coming back from a long trip on literally fumes. The fuel gauge in the car read 0.5 liters!! It was that I really wanted to go to that pump specifically. I left another town 70kms away and the car flashed low fuel and said 5 liters left just as I turned onto the highway.. I risked it, babied it with A/C off for most of the trip. I was really curious to see what kind of mileage it would get.

I would probably trust the pump more than the car's gauge. The car's gauge shows 8 bars when full, and stays on the first bar for at least 60kms, about 40-50kms on the second bar and then races through the last 6 bars. It is somewhat accurate at below 5 liters when it gets into the details.

By a boost gauge, I meant finding an aftermarket gauge that resembles the colors of the Brabus clock, and replacing the clock with a boost gauge, just for fun.

Guy, One thing that stands ou…

2009-08-28T21:39:41.981Z

Guy,
One thing that stands out is a fill of 31.45 litres. The smarts have a maximum tank capacity of 33 litres (5 of which shows up as reserve / finer scale fuel gauge readout).
You seem to have been fillig up at a variety of pumps. That is an unpreidcatble variable. I know my local service stations well and at one I know that one pump will deliver precise quantities (according to ScanGauage), whil another pump on a different aisle will deliver about 2 litres more than expected. Pump one is less sun exposed to pump two. The cross fall on the hardstand is different. Pumps are a much bigger variable than we may expect.
Always use the same pump at the same time of day - preferably early morning when the fuel is coolest and densest, when trying to get consumption figures.
How do you do know the turbo boost? Xclusive has a gauge?
I'm using the ScanGauge to monitor MAP in kpa. Anything over 100 kpa is obvious boost. Don't see it much in normal cruising.
Have to lead foot around town to get worse than 6.5 lhk. Your figures really are too high a consumption.
I'm off for an 800 km round trip with a dicky CKP sensor... my lhk figures may be a bit abnormal for this trip due to drifting ignition timing and mix... an adventure beckons.

Here's my summary, if you're…

2009-08-28T15:46:21.490Z

Here's my summary, if you're interested:

A/C pretty much on all the time, usually only one person in the car (me), only I drive the car, Using Auto Mode. Average air temps are between 28 degrees (night) to 35-40 in the days. Mostly driven during the day. Mix of in-town and highway driving about 50/50.

27.53 liters (98 Oct)
319.3 km
8.6 l/100km
Notes: First fill ever, definitely Zero Boost, totally babied it, varied revs really gently, never went past 1/4 throttle.

28.89 liters (98 Octane)
312.1 km
9.3 l/100km
Notes: Breaking in the engine

30.29 liters (filled it with 100oct)
274.5 km
11 l/100km
Notes: Driving up to 4,000rpm no full throttle, but was going on boost

25.44 liters (100 oct)
222.8 km
11.4 l/100km
Notes: Driving up to 4,000rpm no full throttle, but was going on boost

31.45 liters (100 oct)
368.0 km
8.5 l/100
Notes: Mostly highway driving. I drove some 70km on about 5 liters of fuel, no A/C, keeping the revs really low as an experiment on the highway. Those are unrealistic driving conditions. This is probably the best efficiency this car will ever do.

20.38 liters (100 oct)
182.7 km
11.2 l/100
Notes: Some more "normal" driving now that it's past the babying stage

19 AUG 2009
28.89 liters (100 oct)
274.0 km
10.5 l/100
Notes: Usual, mix of highway and in-town

My '09 fortwo PURE is now get…

2009-08-28T12:12:48.878Z

My '09 fortwo PURE is now getting 49.6 UK MPG. That's with about 2400 kilometres on the odometer. My overall mileage for the 2 months I've had the car is over 45 UK MPG. This has been with air-conditioning on 75-90% of the time and a mix of highway and city. Different car, but just as a guide. I've explained each of my fill-ups here. (http://fuelthesmart.blogspot.com/)