First test drive: Smart Fortwo diesel cabriolet - saw 67 mpg US (100% city)

[MetroMPG]

For a while, I recall some company was importing them to the States.

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I forgot to mention: the owner of this car was getting it "upgraded" somehow. He says the next time I see it, it will have almost twice the horsepower than when I drove it before.

[Xist]

What is the rule of thumb for horsepower versus fuel economy?

[houseofdiesel]

I love these little cars, so incredible efficient. I have a 2006 that we bought new in late 2007, pure cabrio, only has 26000kms to date.

99% of the people who are considering one are better served in a VW tdi (early models like 1996-2003), they are slightly less efficient in the city but as good on the highway and have no long term engine issues. The smart is challenged that way unless you REALLY baby it and take exception care of it. Most have a lifter failure in the valve train (of the engine I have seen that were dead locally). Few change the oil properly and leave sludge/residue behind, it has to be sucked out when HOT and even pour a bit of clean and keep sucking to get it all, of the engines I have seen apart-they were filthy inside with large chunks of carbon everywhere on the timing chain side and goo everywhere (dealer serviced that one). High quality fuel is extremely important, the common rail injectors do not like anything else and are not serviceable (dead injectors are common, they just plain wear out and only deliver half the required fuel when worn or worse so hard starting is common). Wiring harness issues are another problem from either water and salt getting in or from the engine vibration (it rocks a lot), the protective sleeve on the harness will chew right through the wires.

I have a lifetime average of 3.1L/100kms on mine (75 mpg US), if I have to go long distance on the highway it gets worse very fast, going 100-105km/h even drafting nets 4-5L range (47-59 mpg). Keeping it at 80-90 nets 3 (78 mpg). City running does not really bother the fuel consumption if you are careful, it is so light. I do sometimes coast and use other techniques but never engine off. These poor little cars work hard and I wouldn't want to coke the oil in the turbo or have other problems.

Chipping it is fine if you are careful with it, otherwise a recipe for disaster. You can get 60hp and 100 torque with a tune, most of them need the waste gate adjusted to prevent overboost and limp mode once chipped. As mentioned, these engine work really hard and are easily overstressed they only hold 2.5L of oil, it gets hot. I have some long term goals to increase my sump and add a bypass oil filter, then maybe chip it!

[Ptero]

I just want to share the belly laugh I got from "the uncalibrated Scangauge" mileage report. You guys with your Scangauges are hilarious.

If you want an accurate measure of mileage, top off your tank, note your odometer reading, drive the tank down, fill up at the same pump, then divide the gallons into the mileage.

If you want more precision, make a little dipstick for the tank.

The main thing I use my UltraGauge for is realtime MPG. I figure no matter how far its off, just tellin' me I'm doing better or worse is just what I need.

[MetroMPG]

Ptero, did you read the post? I had the car for probably 30 minutes. So it was an uncalibrated reading or nothing.

Of course doing the calcs from tank to tank is best.

Though I suspect houseofdiesel can probably say how accurate a ScanGauge on its default settings is in a Smart.

[Ptero]

If someone wants to tell me how their Scangauge stood up to a tank test, I'd be interested. If we get enough replies, I bet it's all over the map.

[houseofdiesel]

I find the scangauge is very acurate in the smart, less then 5%. On my automatic VW tdi it is out by 35-40%. On my Mercedes R class cdi 8-10%-but adding roof racks/boxes and towing move it around a bit.

[MetroMPG]

Originally Posted by houseofdiesel

The smart is challenged that way unless you REALLY baby it and take exception care of it.

Thanks for the run-down on maintenance/durability. That confirms the impression I got from a couple of sources.

I have a lifetime average of 3.1L/100kms on mine (75 mpg US), if I have to go long distance on the highway it gets worse very fast

Impressive lifetime number - congrats!

If you're in the Kemptville area, I bet your typical usage is pretty fuel economy-friendly like mine: mostly country road / secondary highway driving? Trips to Ottawa going along scenic River Road instead of blasting up the 416/417? Not a lot of stop & go driving anyway.

Chipping it is fine if you are careful with it, otherwise a recipe for disaster. You can get 60hp and 100 torque with a tune, most of them need the waste gate adjusted to prevent overboost

Yeah, he was talking about "almost doubling" the car's HP. I may get a chance to drive the car again soon. What does chipping it do to the fuel consumption when driven gently?

[houseofdiesel]

I stay off the major highways with it, it consumes way too much at 100+. Mostly a back roads discovery car, going to work the long way, going out on weekends and such. Hardly ever get the chance to use it.

The reflash has no effect on FE under the same conditions, unless it removes emissions features such as EGR, then it will take a tiny bit more (longer warm up)

Also a known problem on them is the oil pump chain drive gears wear out fast on certain engines, no idea the cause as it is not universal to all engines. I am guessing lack of proper oil changes. When I wrenched on them it was common to see them horrible over due for service (twice the factory km interval). People who bought them were not generally car types and over drove them and under serviced them. The poor little engine works hard, anytime I go up to the Laurentians with mine it is near full throttle on several hill climbs not by choice, but to make it over!

[HHOTDI]

I too have always wanted to play with one. i'd like to yank the little motor and stuff it in a road bike!! "Smart-Dieselson" of sorts.
:{)