HOW TO FIX OR REDUCE THE TRANSITION DIP IN THE 2JZGTE TWIN TURBO SEQUENTIAL OPERATION AFTER HIGH FLOW TURBO'S FITTED.
The Dip between the stages of the sequential can be reduced by slowing the second turbo (rear) from coming on. The idea is to delay the second turbo as much as possible which allows for exhaust manifold pressure to increase creating a “reserve” of back pressure before the #2 turbo is activated. The Dip is caused from the second turbo opening and dumping the needed exhaust pressure to spool up the second turbo so acting as a big wastegate for the first turbo.
NOTE- Carefully study the sequential opertation system
There are several methods to fix the "dip"….
One method is to use a pressure switch which is used for cutting off the signal to the Intake air control
valve VSV so the #2 turbo has a time to build up pressure so when the changeover point between the two turbo’s occurs the “dip” in boost isn’t so prominent.
To wire in, find an accessable wire to the “Intake air control valve” (IACV) vsv and cut it so a wire joining lug can be crimped in. Use two of each male and female joiners and allow for disconnection of the pressure switch and reconnect vsv back to normal if needed. Any wire can be cut that leads to the VSV as any can be switched. Plug these into the two top terminals of the pressure switch. This setup won’t let the VSV activate until the desired boost pressure.
Mount the switch where desired but on the fire wall or out of site is better. Run a boost pressure line that is sourced AFTER rear turbo compressor housing to the pressure switch hose connection.
To adjust while tuning ,locate the tiny allen key adjustment screw on the top of the switch and turn so that the #1 turbo boost to a
bout 13-14 psi before changeover. Although the pressure switch should already be set it should always be checked while tuning.
Another way is to fit an in line pressure ball valve to the air pressure feed line that only allows flow after a set pressure In the line to the IACV Actuator is reached and is not controlled by the factory VSV. This is the same theory as the pressure switch above but a mechanical solution. It is fed boost from the same point or somewhere after the rear compressor but before the IACV the image shows a point that is tapped to the IACV cap. Anywhere along the #2 turbo(rear) outlet bend is fine.