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Nissan
Skyline R33 GTS25T
Under
the hood (stock 130 to 140rwkw)
The Nissan Skyline R33 GTS25T is a great base for tuning. The GTR's
little brother is 200kg lighter and is equipped with the awesome RB25DET.
The R33 has 187kw at the flywheel and most manuals see 130-140 rear
wheel KW on a dyno. The 2.5 liter six is impressive featuring a twin
cam 24 valve head with Variable valve timing on the intake side only.
Induction is via a Single ball bearing turbo charger which comes onto
boost fast with its ceramic exhaust wheel. To keep inlet temperatures
down the car is equipped with a small side mounted intercooler.
Engine
Tuning Stage 1
Exhaust (around 160rwkw)
The RB25DET is a sweet sounding engine but very quiet in standard form
and as with most factory turbo cars the exhaust causes a huge restriction.
A good free flowing exhaust will have the RB sounding great, turbo lag
will be reduced, and power gained throughout the rev range. The new
exhaust should start from the turbo with a dump pipe either a 3"
open bell mouth or better still a split dump to separate the gases from
the turbine and wastegate. From here a high quality 3" high flow
cat should be used, then 3" all the way to the back of the car
with high flow mufflers.
Intake (160
to 170rwkw)
Now we have the exhaust side of the engine breathing the next step is
to get more air into the engine. Either use a high performance air filter,
or replace the air box with a POD style air filter. If you choose to
go the POD filter route I recommend you fabricate some type of shield
to keep hot air from the engine bay away from your intake. A cold air
intake to the filter from the front of your Skyline will also give you
a performance advantage. 5-10 rwkw is achievable with this mod.
Intercooler
Upgrade (165 to 180rwkw)
The standard R33 intercooler is tiny and before a boost increase I recommend
installing a better cooler if you don’t you risk detonation on warm
days. The R34 GTT intercooler is a good cheap upgrade for the R33 and
bolts onto the same position as the stock item with minimal modification.
The GTT intercooler is rated up to about 200rwkw if you plan on going
further than this power figure a GTR or aftermarket front mount will
be required. Be aware that with these systems new pipe work will be
required and you may notice a small decrease in throttle response. You
may notice a small increase in power with this mod without increasing
boost as airflow will increase and the air will be denser. But it’s
the ability to run more boost that makes this mod a good one. If you
don’t plan on increasing your power level to over 200rwkw I recommend
the GTT intercooler as its cheep and you will notice no difference in
throttle response.
Boost increase
(175 to 185rwkw)
In standard form the R33 runs a two stage boost control system 5psi
to 4500 rpm then 7psi to red line 7000 rpm. As mentioned before the
turbo’s exhaust wheel is ceramic and they tend to fail if to much heat
is generated. The amount of boost you can run with the stock turbo is
debatable but I don’t recommend running more than 10 psi. You have a
few options when choosing to increase the boost either a manual boost
controller, electronic boost controller, or a new wastegate actuator.
A manual controller
is very basic in its operation it bleeds off air causing the wastegate
actuator to open later. The amount of boost run depends on the amount
of air bled form the system. It is critical to install an after market
boost gauge before carrying out this modification as the stock gauge
is not accurate enough and is measured in mmg not psi or bar. Manual
boost controllers are cheep and easy to install but they do have there
disadvantages some can cause boost spikes and boost creep I have also
found boost tends to tail off high in the rev range.
Electronic boost
controllers on the other hand use stepper motors and monitor boost about
every 10th of a second because of this boost spikes and boost creep
are kept to a minimum, and the desired boost level is held to redline.
Electronic boost controllers are expensive and for this level of modification
a manual controller will probably be good enough.
A 3rd option is
to install a different wastgate actuator and the good news is the R32
GTST item is exactly the same as the R33 except the spring inside is
set for 10psi. R32 actuators can be hard to find but I think it’s the
best option for this level of modification as boost spikes and boost
creep are eliminated.
No mater which system
you choose the 2 stage boost control system should be disconnected.
After this mod is carried out many people notice flat spots throughout
the rev range this is due to the ECU seeing an increase in airflow and
as a safety precaution it richens the air fuel mixtures. Many people
find re-gaping the spark plugs from 1.1mm to 0.8mm fixes this problem
but if it does not you need to consider the next upgrade.
ECU (185
to 200+rwkw)
As mentioned before many people have problems with flat spots and rich
air fuel ratios. Even if you don’t have these dreaded flat spots an
aftermarket ECU will give good power gains and improve drivability.
One popular option is the Apexi SAFC (Super air flow computer). The
SAFC is a piggy back to the ECU and works by tricking the ECU into thinking
your engine is getting more or less air than your engine actually is.
Tuning should be done be a professional on a dyno this modification
should fix those dreaded flat spots by leaning you airfuel ratio's at
different RPM points.
A better but more
expensive option is the Apexi Power FC which replaces the standard ECU.
Many people choose the Power FC as its less expensive than other aftermarket
ECU's, and it plugs straight into you old loom so there is no need to
cut any wires. All parameters of your car can be tuned with a Power
FC but once again it should be dyno tuned by a professional. Please
note the power FC cannot be used an automatic transmission.
Clutch and
Fuel Pump
At this level of modification it’s likely that your clutch and or fuel
pump will need upgrading to handing the extra power.
Conclusion
This completes stage 1 engine tuning for the Nissan Skyline R33 GTS25T.
Basically at this stage we are at the limits of the standard turbo and
fuel systems but in terms of car modification this level of tuning is
offers great value for money. Many people with these modifications with
and a well sorted suspension and tyre packages have 12 run second quarter
mile passes.
Continue to Engine Tuning
Stage 2
Please
use this as a guide only I recommend consulting a professonal before
carrying out any of these modifications. Nissanskyline.6te.net takes
no responsiblity for any problems you may encounter from following this
guide.
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