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
-------------------------------------------------------------------------------------------------

[datdrift]

anyone have any recomendations for a decent(cheap) backbox, and will it make much difference to noise/flow fitting a straight thru centre pipe, cos ive got a spare bluey turbo exhaust i could cut up and weld on....
also do you know what model saab 9000 have the big cooler, cos they dont all have it and would a cooler/rad from a volvo 940 turbo be a decent size, cos theres one breaking on ebay....................
thanks for any help

[PukkaSilvia]

Below is a picture of a saab 2.3t intercooler



The standard s12 exhaust is very restrictive. If you look at the design of the rear silencer this will become apparent. The centre box can be removed also and the exhaust will not become excessively loud.

[alundra]

Nice thread...
...but I would recommend you if you can edit your post with brakes (pads, discs, stainless lines) and suspension stuff with web link.

Power isn't an all for our first stages

P.S: I like more and more this forum

[Maximilian]

Actually the thread title says engine mods. I don't know when you'd like to change suspension or brakes, in tuning order that is, but since our cars are old, I'd want to do it asap anyways.

[jakezx]

This has been a big help to see what littel and how cheap you can get more power out the s12 you will have to post stage two tunning up here soon.
great help
Has any one got a good second hand intercooler

[PukkaSilvia]

For greater power than 225bhp the following will have to be installed.


WALBRO 255 FUEL PUMP is a must 100%. If this is not done you will end up putting a hole in your pistons or at the least constantly blowing head gaskets..(I have done a right up on installing one of these in this how-to section)

The exhaust system has to be a custom free flow system of 2 3/4" bore-3" bore with a free flow rear silencer. These systems can not be bought off the shelf but there are custom exhaust companies around along with pipework being readily available from place like demon tweeks. The shape of the s12 exaust is not comlicated and you could make a system yourself if your handy with a welder.

Boost pressure will need to be in excess of 16psi. The standard turbo or a s13 t25 will not be enough. You have a few choices here. Most common upgrades are t28 turbos found on s14 200sx or bought off the shelf. A hybrid t28 with uprated internals i.e 360 degree bearings etc would give you better drivability as the s12 engine will be starting to suffer from lack of immediate response as spool up will take longer. The other option is a t3 turbo from a sierra cosworth. Do not buy an rs turbo t3 as these are different and smaller.
Again a hybrid unit would be nicer but again not essential. I had a std t3 on a std s12 engine and found it great fun at 15/16psi. Anything below this was boring and i would of preferred the standard turbo.

Fueling will need to be modified as the standard 270cc injectors will be flat out already at 225bhp.
You have many options from piggyback ecu's to complete management setups. Complete aftermarket management is far better but cost a fortune.I get the feeling s12 owners dont normally spend this kind of money so for most of you piggy back ecus are the way to go at the moment unless someone works out a way of remapping the std ecu.Piggyback ecu's modify signals between your standard ecu and its sensors and ancilleries. Apexi Safc11 is a common choice.There are other ones out there so shop around.
Fit whatever bigger injectors fit. you can go for s13 injectors very cheaply and these will supply enough fuel for a modified standard internalled engine(270BHP Maximum). The next common size up is 444 injectors from a skyline. They can be distinguised by there mustard yellow colour. There also a common upgrade for s13 owners. Theu are always available on ebay.

Your car should be dynoed and setup correctly and checked for detonation at this stage.
-------------------------------------------------------------------------
In order to fit either turbo mentioned above fittings will need to be modified.
For a t28 you will also need the s14 t28 downpipe and a new oil line to the turbo (companies like hydroquip,pirtec,aeroquip make them)
The t3 will need a t3 flange welded to the bottom of the standard s12 manifold and a custom downpipe made using a downpipe flange from a cosworth breakers. (The flange looks very similar to a s12 exhaust flange but slightly bigger)

[wacomuk]

you can get a bit more out of standard injectors by removing the standard fuel reg and fitting an adjustable type

iv seen 236bhp on standard injectors but this was the max

[s12Rob]

Originally Posted by Pukkasilvia

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

C109 OIL FILTER and 10w-50w fully synthetic oil is the general recommendation


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
-------------------------------------------------------------------------------------------------

where can you get these oil filters from and whats the difference with an oe one. and with the turbos, will the t28 bold on to the std manifold??

[PukkaSilvia]

Halfords or any motorfactors will have those oil filters and the t28 will bolt straight onto the standard manifold