It is widely known that the T25 turbo which is fitted as standard to the Rover T16 engine can be somewhat restrictive when
it comes to trying to realise serious power. It's relatively small size does mean that there is extremely little in the way of
turbo lag, but while it may make for good responsiveness for the average driver, it can mean getting more power a
difficult project. While I have spent a fair bit of time and money reducing the inlet temperatures, a good deal of the heat
produced is due to the actual size of the turbo itself. Even though I may actually be using relatively low boost pressure
levels, the inlet charge is still being compressed enough to produce unwanted heat. One way around this is to prevent the
inlet charge from being compressed so much while still running the same (or higher) boost levels and this can be done by
using a turbo with a larger compressor wheel and housing. This is the step I chose.

The question next was which size turbo to use. I liked the minimal lag that the T25 produced and while a much larger
turbo would be used, I did not want to increase so much lag that the car would not be as responsive in standard form.
The answer was to simply step up a size and use a T28. It was large enough to make a difference while still retaining a
certain amount of responsiveness which I felt would be lost using a T3 or larger.

The next step was to find a suitable unit. One was soon found in the shape of a T28 which was fitted as standard to a
Nissan Pulsar (Sunny) GTi-R. Both the T25 and T28 are manufactured by Garrett which meant a certain commonality of
 parts used which would make fitting of the new unit relatively easy. Despite having a larger compressor wheel and housings,
the centre core of the turbo was essentially the same as was the exhaust housing. This meant that the turbo would bolt up
to the exhaust manifold and the OE turbo outlet elbow which also contained the Lambda sensor could be used. The
compressor wheel housings on both the inlet and outlet sides needed to be adjusted slightly so that they could be lined up
as per OE settings. All that then remained was to connect the water feed and drain as well as the oil feed and drain. While
the water side of things along with the oil drain all utilised the OE pipework, the thread tapped into the centre housing for
the oil feed was found to be different. This meant adapting a union connection from the spares box. A minor problem.
One final difference was on the exhaust housing which bolts up to the exhaust manifold. On the OE T25, the mating surface
is drilled and tapped and 4 studs are inserted. With the Nissan set-up, the studs are inserted into the exhaust manifold. This
was simply overcome by using bolts with 'deformed' nuts. 'Deformed' nuts are used due to the extreme heat generated by the
exhaust. Thread lock is not an option and neither are locking washers as they will quickly lose their 'spring' capabilities.

With everything now bolted up in place, it was time to start the engine. When fitting a new turbo, it is vital to allow oil
pressure to build up so as not to damage the bearings. The easiest way to do this is to disconnect the main ignition lead
and crank the engine over until the oil pressure warning light goes out. I then crank the engine for a further 30 seconds just
to make sure. The lead is then reconnected and the engine started as per normal. The engine is left to idle until normal
normal operating temperature is reached and the entire assembly is checked for any leaks.

The picture above and below compares the T28 (right) and the T25. (All pictures were taken before the inlet and exhaust housings were
adjusted) Note that the mounting holes for the exhaust elbow is identical on both turbos.  It is also obvious that the T28 exhaust
compressor wheel is larger.

The T28 and T28 from the inlet end. The most obvious difference here is the inlet compressor housing. Not only is it considerably
larger on the T28, but is also lacks the recyclable dump valve which is fitted to the T25 unit. The absence of this necessitates the
fitment of a valve elsewhere in the system.

The next two pictures (above and below) show the top and bottom views of the turbos. The difference in size of the exhaust
compressor housing is more evident here. Note the identical size of the casting which bolts onto the exhaust manifold. You can
see that the inlet hosing has a flange. The Nissan uses an alloy pipe which bolts directly onto this - this pipe was also utilised in
the conversion.

The pictures above show the alloy 90 deg elbow which is OE on the Nissan. This was simply bolted onto the turbine housing and 
a thin layer of gasket sealant guards against leakage. A short piece of hose was then used to connect to the pipe which goes to 
the chargecooler. When time allows, I fully intend removing this elbow so that it can be polished smooth.

As you will notice from the pictures above of the turbos, the T28 has a different casting on the inlet side which connects
to the pipe from the air filter. A simple short alloy pipe with a flange is used on the Nissan set-up and, again, this was
carried over to this conversion. The picture above shows this held in place with two bolts and a gasket seals the joint. A
short piece of hose is then used to connect to the air filter pipework.

As the T28 does not have an integral dump valve, a new one was going to have to be installed into the system. A lot
of literature will advise that the best place for a dump valve is as close to the throttle body as possible. Due to the
chargecooler set-up, this was not a viable option. It was decided to mount it in the easiest place possible which was
between the turbo and chargecooler. Once again, I turned to Quest4 and to their range of excellent dump valves (also
know as 'blow off valves here). It is a piston type and sounds very nice. A piece of alloy pipe was welded onto the boost
pipe after a hole was cut out. The dump valve could then be attached using a short piece of hose. The OE hose which
attached to the dump valve on the T25 was retained and simply re-routed. Job done.

A HUGE thank you to Kyrie and Dan at Quest4 for their help with the above. Click on their logo above to visit the Q4 website.