Nissan Skyline
Nissan Skyline


*R32 GTS-T
*R33 GTS25-T
*R34 GT-T
*R32 GTR
*R33 GTR
*R34 GTR
*R34 Z-Tune
*V35 GT350

Tuning Guides
*R32 GTS-T
*R33 GTS25-T
*R34 GT-T



*Project GTS25-T

Tech Resources
*Airflow meters

*Project GTS25T




Home > Skyline GTS25-T Tuning

Nissan Skyline
Nissan Skyline
Nissan Skyline
Nissan Skyline

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 donít 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 itís the ability to run more boost that makes this mod a good one. If you donít 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 turboís 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 donít 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 itís 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 donít 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 itís likely that your clutch and or fuel pump will need upgrading to handing the extra power.

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. takes no responsiblity for any problems you may encounter from following this guide.