The 2jzgte Sequential system explained


Supra Specialists Ireland
The fist image here, is the vacumm layout for the varous components used on the engine. The left handside area relates to the System components used in the Sequential operation. Jspec car do not have the EGR system


The next pic is the actual Sequential system layout and components


What it all means..

There are four VSV/actuator assemblies that control the sequential turbo operation:
Intake Air Control Valve (IACV)
Exhaust Gas Control Valve (EGCV)
Exhaust Gas Bypass Valve (EGBV)

VSVs switch manifold pressure (boost) to and away from actuators. The actuators open/shut valve butterfly flaps.

When this switches, boost generated by #2 turbo is allowed to join the intake stream
When it isn't switched, there is a small flap in the IACV assembly that allows any boost generated by #2 turbo as it prespools to join the intake stream, preventing turbo stall.

This allows exhaust gas to flow through #2 turbo, causing it to spin up. When it's shut, there is no gas flow through the impeller of #2 turbo and therefore it doesn't spin.

This allows some exhaust gas to bypass the EGCV and join the output of the first turbo. It serves two purposes - one, it prespools the second turbo by allowing some exhaust gas flow through it. Two, it controls the amount of exhaust gas going through the first turbo in much the same way as a wastegate - therefore controlling the maximum boost pressure generated by #1 turbo.

This bypasses exhaust gas from the first turbo, lowering the overall amount of exhaust gas going through *both* turbos and controlling the maximum boost pressure generated by both turbos in parallel.

So how it all comes togather :-
You get 0.7bar of boost on turbo 1, a slight dip in power between 3500 and 4000rpm, and then 0.8bar of boost with both turbos online. This should be a smooth and linear power delivery.

When modified with a boost controller/decat, you'll see an increase in boost after 4000rpm when the second turbo comes online. You may also get 0.8bar of boost on the first turbo with a decat. You'll feel the same power dip at 3500rpm but then a noticeable surge in power at 4000rpm when the second turbo comes online and hits over 1 bar of boost. Full boost is acheived before 4500rpm.