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[2LV8ETR]

Engine Tuning Stage 1

Exhaust:
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 waste-gate. 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:
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.

Intercooler Upgrade:
The standard R33 SMIC is tiny and before a boost increase I recommend installing a better IC. If you don’t, you'll risk detonation on warm days. The R34 GT-T SMIC is a good cheap upgrade for the R33 and bolts onto the same position as the stock item but some modification is required. The GT-T SMIC is rated up to about 200rwkw and if you plan on going further than this power figure, a GT-R or aftermarket FMIC will be required. Be aware that with FMIC systems new pipe work will be required and you may notice a small decrease in throttle response. 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 GT-T SMIC as it's cheap and you will notice no difference in throttle response.

Boost Increase:
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 too 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 from the system. It is critical to install an aftermarket boost gauge before carrying out this modification as the stock gauge is not accurate enough and is measured in mm/hg not psi or bar. Manual boost controllers are cheap and easy to install but they do have there disadvantages as 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 wastegate actuator. HKS have a actuator with an adjustable arm to help set your desired boost level. I think this is a good option for this level of modification as boost spikes and boost creep are eliminated.

No matter which system you choose, the 2-stage boost control system should be disconnected. After this modification many people have problems with flat spots throughout the rev range this is due to the ECU seeing an increase in airflow and as a safety precaution it enriches the air fuel mixtures. Many people find re-gapping the spark plugs from 1.1mm to 0.8mm and/or using aftermarket coilpacks, fixes this problem but if it doesn't, you'll need to consider the next upgrade.

ECU Edit:
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 driveability. One popular option is the Apexi SAFC (Super Air Flow Converter). 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 by a professional on a dyno. This modification should fix those dreaded flat spots by leaning your air/fuel ratio's at different RPM points.

A better but more expensive option is an aftermarket ECU such as the PowerFC or Wolf3D, which replaces the standard ECU. Many people choose the PowerFC as its less expensive than other aftermarket ECU's, and it plugs straight into your old loom so there is no need to cut any wires. All parameters of your car can be tuned with a PowerFC but once again it should be dyno tuned by a professional. Please note the powerFC cannot be used with an automatic transmission.

Clutch & Fuel Pump:
At this level of modification it’s unlikely that your clutch and/or fuel pump will need upgrading to handle the extra power.

Conclusion:
This completes stage 1 engine tuning for the RB25DET. 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 run 12 second quarter mile passes.

Engine Tuning Stage 2
Stage 2 of tuning is where things start to get expensive as we need to upgrade many of the standard systems. RB engines are known for strength and the RB25 is no exception. With regular maintenance and a safe tune, 270rwkw is easily attainable. Some people push the limits with 300rwkw+ but if you want an engine that will last 270rwkw is a safer limit.

Turbo Selection:
There are many good turbo options available but I recommend a turbo that will bolt onto the standard manifold as this will save time and money in the long run. Many people in Australia have had their standard turbo hi-flowed and these turbos are popular because they use a ball bearing cartridge, and everything bolts back into place. Turbo response is said to be similar to stock and power figures average around 230rwkw or up to 250rwkw with cams. Some people have used larger exhaust housings from the R34 GT-T or the old single turbo 300zx and have achieved 270rwkw+.

HKS in Japan have a range of turbo's for the R33 that come with all the parts needed to bolt on. Suitable Skyline kits that are available from HKS at the moment include the HKS GT-RS known to make 280rwkw and the HKS PRO-S known to make around 300rwkw. The GT-RS is cheaper and also a little more responsive than the PRO-S. Another popular choice since superseded by newer models was the 2535 which is similar to the GT-RS.

Fuel System:
If you haven’t done so already the fuel pump will need to be upgraded. Second hand GT-R pumps are a popular option as are new pumps from Bosch, Walbro, and Tomei. The GT-R and Tomei pumps are a direct fit. You may also install a fuel pressure regulator to increase fuel pressure.

Standard injectors will also need to be upgraded at this stage. You can either have your standard injectors high-flowed, or buy aftermarket ones from Nismo or other performance companies. I recommend you use injectors that are a direct replacement and don’t require any modifications to fit. The JDM spec S15 Silvia injectors are also a popular choice as they flow more and fit without modification.

Airflow Meter:
To improve the tuneability of the engine its a good idea to upgrade your airflow meter this allows for finer tuning which will result in smoother power delivery and make it easier for the tuner to produce a higher peak power output. Popular upgrade choices include the Z32 and the Q45. The Z32 is the cheaper of the 2 but the Q45 will allow more airflow.

ECU:
If you have not done so already the ECU will need to be upgraded as even with an SAFC or similar the stock ECU will not do the job. As stated before the PowerFC is a popular option due to its price, ease of installation, and use. There are plenty of other options that are superior to the PowerFC and allow many other tuning functions like launch control, and the ability to use a MAP sensor instead of the AFM. But the PowerFC is still a popular and is proven to perform.

Head Gasket:
Running boost levels above 1.2bar may require a new metal head gasket to lower compression and improve reliability. Opinions differ on this subject so I think its best to ask your tuner.

Clutch & Flywheel:
The stock clutch will certainly fail quickly at this power level the hardest part is finding a clutch that will handle the power yet not make your car a pig to drive. Exedy, Nismo, and HKS seem to be popular and reliable choices and while you are upgrading your clutch, a lightened flywheel is well worth considering. This will help the car rev quicker but the trade off is your car will loose momentum quicker too.

Cams Or Cam Gears:
At this stage the Skyline will benefit from a set new cams, cam gears, or both. The outright power will be increased but the main reason for installing cams is for a fatter torque and power curve. Upgraded cams can help reduce lag, improve mid and top end power. Popular choice is Tomei poncams as they fit without modification and are proven to give good results.

Conclusion:
Use the above suggestions as a guide only.
If you use one, speak to your tuner for a more in-depth and accurate assessment. Every tuner has a different opinion and will do things differently.