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This fortwo started its life as a 2000 registered imported mk4 Passion. The car was bought looking very sorry for itself and in the real world the car would have been broken for spares. However the decision was made to buy it and give this classic shaped City-Coupé a new lease of life.

The engine was at the end of its life with nearly 90,000 miles on the clock and with a massive list of problems. this list grew under closer inspection:

  • Turbo's manifold was badly cracked in several places.
  • A dump valve had thrown oil all over the engine's ECU and wiring.
  • Piston rings were needing replacement.
  • Input shaft seal was leaking.
  • Both driveshaft seals were gone.
  • The clutch plate was contaminated with gearbox fluid.
  • Rocker cover had a severe leak.
  • Dipstick guide was leaking from the bottom of the block.
  • Both breather pipes had perished.
  • One breather valve had failed totally.

To add to the major things wrong with the car, the exterior had this pretty heavy list of issues which needed addressing:

  • Smashed N/S rear quarter.
  • Numeric Blue N/S front quarter.
  • Headlight mounts were snapped both sides.
  • Exhaust pipe was broken along the lower weld.
  • Fog lights didn't work.
  • Wiper arm capping was missing.
  • N/S rear brake cylinder was leaking.

The original plan was to rebuild the engine that was already in the car but as you can see it just wasn't viable, especially with the turbo in such a state.

A 2003 Roadster engine was bought as a replacement using the experience gained from building the old project car (599cc to 698cc). We knew this setup worked very well on the older management system and gearbox.

The old engine was pulled from the car on the rear subframe and the swap began. It's worth noting that anyone planning on doing this conversion should bear in mind a few differences that could cost you a lot of time if you are not aware of them.

Upto mk4:

  • Water housing - There is a coolant flange on the back on the head that needs to be transferred off the older engine as the newer models have three outlets rather than the older two.
  • Cycle valve and wastegate need to be transferred to the new engine.
  • When mounting the turbo ensure you have the new 'bigger' 7mm studs and nuts along with the newer manifold gasket.
  • If changing the exhaust for a later one like us, ensure you have something to block the second lambda sensor hole.
  • The EGR (exhaust gas recirculation) valve needs to be blocked off at source as it's not fitted on the older engines.
  • Alternator - Use the old unit as it is earthed back through itself rather than having a dedicated lead on the loom like the later models. (see the picture below to compare the two units).


  • When mounting the turbo ensure you have the new 'bigger' 7mm studs and nuts along with the newer manifold gasket.
  • The EGR (exhaust gas recirculation) valve needs to be blocked off at source as it's not fitted on the older engines.

The engine itself is a direct swap if just fitting the block and head, following the changes listed above.

The standard 45kW gearbox needed to re-fitted to ensure correct operation with the car's standard management system. This is true even with the addition of a Roadster clutch and flywheel assembly to aid the spoil up and gear changes.

If you are doing this conversion you will need a newer style turbo, but ensure you make the right choice for your own personal needs as it's an expensive bit of kit to be spending money on.

45kW - A standard fortwo exhaust fits with no modification along with the Brabus SB1 version and many aftermarket suppliers.

60/74kW - Brabus G2 or an aftermarket exhaust needs to be fitted to match the bigger outlet and stud pattern.

We fitted a standard G2 45kW unit in place of the 60kW Roadster charger to allow us to fit a standard 45kW fortwo exhaust.

Below you will see the differences in charger inlet sizes. Again you will be faced with a choice of TIK (turbo to airbox pipe).

They are available in the aftermarket in several different makes and sizes; however they are also available direct from smart in three sizes to match their three turbo sizes.

Below are two pictures of the turbo chargers inlets, starting with the bigger 60kW turbo.

This is the EGR system we talked about earlier. It quite simply needs to be discarded as it doesn't fit the older, pre-2003 models.

The car was reassembled with its new engine, filled with oil, the cooling system bled, along with the brakes and wheel cylinder replacement.

It fired up without problems.

We have driven the car for over 1,000 miles now on a daily basis and it is a pleasure to drive compared with the older 599cc engine. This fortwo now has bottom end grunt that the 599cc always lacked.

The body work was replaced and sprayed to match the yellow colour scheme and fitted with countless new trim clips that had got lost over the years. The headlights fitted with new beam benders and cleaned thoroughly to produce a very good example of the older 'classic' shaped City-Coupé.