and tweaks supplied by
|The cheapest way to get more power from your Nissan
Silvia S12 is by using a bleed-off valve fitted between the turbo
and it's actuator. You will need to use silicone hose as the heat
from the turbo will melt other types of hose. An 8mm diameter
plastic tee will also do the trick. Routing the pipe from the turbo
through the straight part of the tee to bleed off, and coming from
the tee at 90 degrees to the actuator gives the best results. A
valve can be fitted to the bleed-off pipe to regulate the amount of
boost. An up-rated actuator will do the job more efficiently without
spiking, but they can be quite expensive. Other work is necessary
before you attempt anything of this nature.
||On top of the inlet manifold and towards the rear
of the engine is a safety valve. This is fitted to protect the
engine from being boosted too high. It was designed to vent to
atmosphere at 14 psi, but with age it can operate as low as 10 psi
This valve can be removed and the head of a bolt welded inside the
fitting, or a cap from the plumbers merchants fitted in place. The
T2 turbo will not deliver much above 14 psi, so the safety valve is
|You will need to fit a colder
spark plug than the NGK BCPR6ES and this is the NGK BCPR7ES. The
standard plug gap is also too large as boost pressures above standard
blow the spark away whilst it is trying to jump the gap. In imperial the
reduced plug gap is 25 thousandths of an inch. The timing can be
adjusted from the standard 15 degrees before top dead centre to 17.5
degrees to liven things up more.
|A less restrictive exhaust system and air intake
are also recommended. These alone should provide an extra 20 BHP.
Modifying the air filter housing is easy and costs very little. The
mesh is already there under the lid. All you have to do is remove
the mesh and the sound deadening material and cut around the lid.
Spot weld or glue the mesh back in, put a bit of paint on and plonk
a Nissan badge on top. The exhaust is harder to make especially if
you increase the diameter. There is not much space over the top of
the rear cross-member. Usually the front silencer is removed and a
straight-through silencer is fitted to the rear.
To set the boost level a separate boost gauge is recommended. If you
are still running the standard T2 turbo, your engine has been well
maintained and your turbo is good then you may proceed. Wind the boost
up to 10 psi and run the car for a while making sure that no detonation
noise can be heard. If all is fine increase the boost to 12 psi and test
again. If you are using the bleed off method don't go higher as you will
get a 2 psi spike above your 12 psi. It is more than double what it is
supposed to do including the spike!
Remember that you probably are near if not above 200 BHP now! The
turbo is thrashing your oil and your engine is working the oil harder,
so change it even more frequently than Nissan's recommended 3,000 miles.
Reliability should not be any less if you bear this in mind