A brief guide to the first stages of Silvia S12 Engine modification

[PukkaSilvia]

Here is a brief guide to improving the general engine performance and drive of your s12 Silvia.

PERFORMANCE

The Silvia s12 1.8 turbo comes with a flywheel power of 135bhp. It is a non intercooled 8 valve multipoint injection engine. The Silvia comes with a Garrett T2 turbo as standard which is set at 6-7psi. It is a relatively small turbo but this gives the engine good response and drivability.

The first stages of engine tuning on the s12 usually do not include internal engine work or fuel management. The standard s12 engine and injector system can safely run up to between 200-235bhp. This is a great power increase for relatively small costs for a mere 1.8 litre engine.

To achieve this sort of output the list below contains the modifications which i and many other s12 owners have done in the past.

GENERAL

Free flowing air Filter + cold air feed
NGK BCPR7ES spark plugs set at 0.9mm
Timing between 13-15btdc
C109 OIL FILTER and 10w-50w fully synthetic oil is the general recommendation
97+ RON rated Fuel
A Walbro 255 fuel pump should be considered at BHP figures above 200fbhp.Fuel pumps have been overlooked by many s12 owners in the past but for under £100 it is a modification that is worth it for peace of mind.

EXHAUST SYSTEMS

The standard s12 Exhaust is extremely restrictive.
Usually 2 ½” – 2 ¾” turbo back system with free flow rear silences are custom fitted (If you are on a small budget the std middle silencer can be removed and the rear silencer changed to improve things slightly)

INTERCOOLER SYSTEMS

The S12 was not equipped with an intercooler as standard. By fitting an intercooler kit you can reduce the intake charge temperature which in turn improves power and allows you to increase boost pressure.
(These are DIY) Most common intercooler DIY setups use intercoolers such as the 2wd Cosworth intercooler, Saab 9000 or Volvo intercoolers sourced from the scrapyard. Other options include adapted aftermarket front mount s13 intercooler kits.

TURBO MODIFCATIONS

A reliable Boost gauge should be fitted before any modifications are made on the turbo output. A gauge in single PSI increments up to 20psi should be suitable.

To modify the outputs of stock Turbo Units a boost controller is needed. A mechanical ball+spring valve (MBC VALVE) will work fine, Bleed valves tend to be slightly ‘old hat’ and are prone to giving irregular boost curves. The pov valve located on the back of the inlet manifold needs to be welded up or removed and changed for a 1" bsp blanking plug from a plumbers merchant, this allows the car to run higher boost without the pov valve opening up, This was a safety device fitted by nissan to stop overboosting. As the valves are getting old these can be known to open up at as little as 8/9 psi.

A healthy Standard Garrett t2 turbo will be able to push up to 200bhp at the flywheel at appoximatly 12-14psi. It is recommended that 12psi be the maximum level you run on the t2 turbo to avoid wearing out the turbo excessively fast.

A healthy Standard Garrett t25 turbo most commonly found on a Nissan s13 1.8 turbo is the next turbo up. This is relatively easy to fit to the s12 with only a small amount of fabricating. At 14-15psi this can power up to the maximum power of the engines standard injector System.

Larger Turbos such as hybrid units, Cosworth T3 turbo’ s or T28 turbo’ s can be fitted. These will all have different Powerband characteristics. I have tried a t3 on a standard engine and found it had a bigger power band slightly higher in the rpm range
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