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Smart Fortwo Passion CDI by Tunit

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Tunit customer Nathan has quite a passion for Smarts – no pun intended – and has almost lost count of how many he’s owned. We certainly had, by the time he’d told us about imported LHD diesels, a hot Brabus, and any number of different variants of the original Smart, before it became the new model fortwo; then there was a Smart Roadster, a forfour hatchback, and a petrol fortwo, before his latest steed, a fortwo Passion cdi

The vital statistics of the fortwo cdi don’t sound that promising, with a mere 45bhp pushing the admittedly light (770kg) rear wheel drive two-seater, backed up by 81lb ft of torque. Compactness and economy are its prime virtues, with an 88g/km CO2 emission figure promising EC Combined economy of over 85mpg – a figure that rates as a world best, but one that few will manage to match in real world driving.

But the little 799cc cdi turbo unit, with its two-phase injection and six hole injectors, is a very willing engine and we agreed with Nathan when he told us that the factory figures of 0-62mph in 19.8 seconds and an 85mph top speed, are pessimistic. He hasn’t reached any vastly illegal speedometer figures though, no doubt on account of being a responsible, law-abiding guy, who earns his daily bread in the unenviable world of road traffic law enforcement!

Nathan’s car had actually been converted at Tunit headquarters in Chorley the previous week – a job of literally a few minutes, since midthe necessary plugs to install the harness of the Tunit are easily accessible under the engine cover that doubles as the Smart’s boot floor.

“The final count was 60.2bhp at a still very modest 3,775rpm, and 104.8lb ft of torque at 2,740rpm, up by 22 and 17 per cent respectively.”

So the return trip was to find out what before and after power and torque figures came up on our rolling road, and maybe tweak the base Tunit settings which were originally capped at a fairly modest level. Dan Johnston, Tunit’s Sales Manager, soon had his head buried in the rear end of the Smart and, after one abortive dynamometer test run, established that a certain fuse needed pulling to disable the ESP system that would prevent full power runs.

ESP disabled and the Tunit temporarily removed, a couple of test runs produced some credible, (better than specification) figures for the standard engine’s power and torque. Dan then refitted the Tunit and spent another 30 minutes running further tests and refining the tune level, to eke a more macho, threefigure torque output from the Smart. The final count was 60.2bhp at a still modest 3,775rpm, and 104.8lb ft of torque at 2,740rpm, up by 22 and 17 per cent respectively, and both at virtually the same engine speeds as standard.

The output curves of both the standard and Tunit converted engine are impressive in their smoothness, and the width of the power and torque bands accounts for the feeling that the car is even nippier than the figures suggest. We rode shotgun with Nathan on a short motorway run with some mixed suburban motoring, and he was seriously impressed with the transformation.

Having visited Tunit previously (it’s amazing how many customers return as soon as they get a new motor) he knew what to expect, and certainly wasn’t disappointed. The fortwo cdi doesn’t offer any computer generated economy figures, but Nathan was planning to do some brim-to-brim fuel range checks in the next week or two. When we checked in with Nathan later, we weren’t surprised to find him thrilled to bits after further road experience of the Tunit Smart cdi. “The torque is just brilliant – in third gear it just pulls endlessly. There’s so much mid range grunt now.” Previously, he told us that he couldn’t get out of the slow lane and over 60mph on the long climb up into the moors on the M62 motorway, but that’s “Just no longer an issue.” He then told us that his first tank of diesel – just 28 litres and mostly consumed during 70mph motorway cruising, took him as far as 430 miles – that’s a figure of 69.8mpg!

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