Mk1 to Mk6 600cc standard turbo
This turbo is visually different to the other 2 types and can be identified by the
lack of EGR route below the manifold. Due to the different bolt spacing this is
not a straight swap to a 700 engine.
The exhaust outlet on this turbo is 33mm ID and the stud PCD is 66mm
It is a common fault on the old 600 turbo for cracks to appear in the manifold.
This leads to loss of pressure and escaping waste gas, if this occurs the lambda sensors get confused by the readings and the engine will pulse under normal driving.
The cracks aren't very easy to spot but some can be very obvious as seen below.
There is nothing that can be done to fix the cracks, people have tried welding them closed but the inherent bad design will eventually cause more. Smart did release an updated version of the cast manifold which resists cracking to a greater extent.
Mk7~ & 61bhp Roadster 700cc turbo
The 700cc turbo is identical to the previous 600cc turbo with the exception of
the manifold, which was altered to reduce the likelihood of cracking, as
described above and to add the EGR route.
The inside diameter of the exhaust outlet is 33mm, the manifold stud PCD is 66mm.
The pictures show how the roadster and 700cc turbos are externally identical.
The main visual difference between the 700cc For2 and Roadster turbo can be seen
by looking at the air inlet, as you can see it is straight cut on the inside whereas the Roadster turbo is chamfered on the inside edge.
The above picture shows the air inlet (ID = 25mm, OD = 32mm)
and air outlet (ID = 21mm, OD = 27mm).
The oily residue visible in the pipes is condensed burnt oil vapour which entered the turbo along with the air from the airbox through the TIK pipe. This air/vapour mixture passes through the turbo and the intercooler into the engine where it is burnt by the combustion. The oily deposits occur because the oil vapour cools after leaving the engine.
There are 2 easy ways to differentiate:
#1 - Either take the number stamped near the inlet to smart and get them to check it or measure the size of the exhaust outlet.
#2 - The inner diameter of the outlet (shown below) should be about 40.5mm and the PCD
of the exhaust studs is about 70mm.
The picture below shows the entire underside of the turbo.
The brown cast iron section is the manifold, turbine housing,
wastegate housing and exhaust outlet.
The silver section is the compressor housing.
The rust coloured section between them is the oil chamber.
The black plastic item is the wastegate actuator.
It is also worth noting the wavy cut out in the manifold header, this is the EGR route.
When the engine is cold the EGR valve (exhaust gas recirculation) opens allowing hot exhaust gas to re-enter the engine allowing it to heat up quicker.
The picture below shows the top side of the turbo including the wastegate arm.
Depending on the pressure in the engine, the wastegate actuator opens and
closes to adjust the boost. People adjust this arm to increase boost but it's
not the best method to achieve it.
Below shows the data plate found on all smart turbos.
The opening directly below it is where the air enters the turbo from the TIK pipe.
The air is forced from the outlet shown in the bottom left, this joins to the
intercooler and then the engine.