Latest News

Feb 23, 2013

RB26DETT Vacuum and Wastegate Diagram and Operation for Nissan Skyline GT-R

Updated for 2019. D.S. noticed I had two lines on this crossed. RB26dett Wastegate control

Updated for 2019. It only took 6 or 10 years for anyone to realize that I swapped two of the lines around. D.S found out I had did it wrong.

The forward hard line under the collector has the restrictor in it. It also is the supply from the back of the collector.  The rear hard line goes back into the inlet of the rear turbo.

 As far as 1980s-1990's engines go, the RB26 is pretty simple. Still there are a few vacuum lines that get people confused. This causes either minimum or maximum boost, so its a good idea to check everything out. Also under the collector is a bit of a tough place to work, so a leak may never be noticed.

JUN collector with Q45 throttle body. Stock collector. The smallest rear fitting is for boost source

The boost supply to the factory wastegate solenoid comes from the back of the plenum/collector. The last nipple under the plenum supplies the wastegate solenoid, and directly to the wastegate actuators.

Boost pressure presses on the wastegate actuators to open them, against base spring pressure.

RB26 bolt on turbochargers

The way that boost is raised is by venting some of this pressure back to the inlet side of the rear turbo. The more pressure bled off, the higher the boost pressure will be.

The factory solenoid line has a restrictor in it. The restrictor is marked by a yellow ring on the boost line. This restrictor limits the amount of bleed off from the wastegate solenoid. The more pressure you bleed , the higher your boost pressure.

Fuse box, factory boost solenoid, and battery

The problem with the stock boost control setup is the stock turbos. If you run the boost pressure too high, you will lose a ceramic exhaust wheel. Normally aspirated Skyline GT-R's - ones that lose a turbocharger exhaust wheel- are slow. If you plan on running more than about 14 psi on the stock turbos, have a spare set on standby.

Rear of balance tube. This gives you a nice stable vacuum/boost signal. We normally pull the tube, drill and tap it

Tapping rear of balance tube

Rear of balance tube drilled and AN fitting put in. We use this to run the boost sensor. 

How to test for boost leaks - DIY Boost Leak Tester

Buy US legal Nissan Skyline GT-R from

No comments: