RB26 boost control: wastegates, springs and boost creep

RB26 boost is set by the wastegate, its spring and whatever controls it. Here is how a wastegate works, how to choose a spring, why boost creeps, and where internal actuators, external gates and electronic controllers fit. We supply parts; your tuner sets the boost.

• The wastegate lets exhaust bypass the turbine to hold boost.
• The spring sets the lowest boost. A controller can raise boost above it, but not below it.
• Boost creep means the gate can't bypass enough exhaust, and a controller can't fix it.
• Size the gate with your turbo supplier or tuner.

A wastegate is a spring-loaded valve that lets exhaust bypass the turbine. Boost pressure acts on a diaphragm against the spring. When boost reaches the spring pressure, the valve opens and holds turbo speed, and so boost, in check.

An internal wastegate sits in the turbine housing, so its valve is small and its flow is limited, which can cause boost creep at high rpm. An external wastegate is a separate, larger valve.

Turbosmart IWG75 for the RB26

Turbosmart says its RB26DETT IWG75 actuators are for aftermarket bolt-on Garrett and HKS turbos that use the stock turbo position, and are not suitable for the stock ceramic RB26DETT turbos. Turbosmart makes them in 7 psi (TS-0615-6072) and 14 psi (TS-0615-6142).

Turbosmart IWG75, RB26DETT, 7 psi | Turbosmart IWG75, RB26DETT, 14 psi

Turbosmart GenV external wastegates

The number in each GenV name is the valve size in millimetres, from the 38 mm UltraGate38 to the 60 mm PowerGate60. Size the gate with your turbo supplier or tuner. Garrett says the best take-off is at about 45° with a smooth transition. A 90° take-off flows less and can even cause overboost.

GenV UltraGate38, 14 psi | GenV HyperGate45, 7 psi | GenV HyperGate45, 14 psi | GenV HyperGate45HP, 35 psi | GenV Electronic HyperGate45 | GenV ProGate50, 14 psi | GenV PowerGate60, 14 psi

Choose a spring rated near the lowest boost you want to run. A boost controller can raise boost above the spring pressure, but it can't bring boost below it. A spring's rating is a guide, so your tuner checks the real boost on the car.

Boost creep is when boost keeps climbing at high rpm with the wastegate fully open, because the gate can't bypass enough exhaust. A boost controller can't fix it. Garrett says external gates come in larger valve sizes and more than one can be fitted to get the flow you need, and your tuner finds the right fix.

An electronic controller lets your tuner raise boost above the spring pressure. Turbosmart's eBoost2, eBoost3 and eBoost Street are electronic boost controllers, and the 3-port solenoid kit suits the eBoost2 and eBoost Street. If your car runs an aftermarket ECU, ask your tuner whether to control boost through it.

Turbosmart eBoost2 | Turbosmart eBoost3 | Turbosmart eBoost Street | Turbosmart 3-port solenoid kit | Haltech vs Link GT-R ECU guide

See each part page for details, or get in touch to check your build. Many performance parts are for off-road, track and competition use only. Road use can affect the law, your insurance and the MOT.

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