Greetings to all from the Czech Republic ...

I'm thinking about the function of the secondary turbo and its functioning ...

The secondary turbo turns on from 2400 rpm, right ?!

And when the speed drops below 2400 rpm, does it turn off ?!

My main question is ....

WHAT HAPPENS TO A SECONDARY TURBO WHEN I DRIVE SLOWLY? THAT I DON'T GET OVER 2400 RPM? OR FOR EXAMPLE DRIVING A HIGHWAY WHEN DOES THE ENGINE RUN LONG UNDER 2400RPM?

("If the engine idles for more than 3 minutes, the secondary turbocharger is actuated to
keep the turbocharger shaft rotating, to prevent oil from leaking into the turbine
housing. This is achieved by periodically opening the turbine shut-off valve to operate
the turbocharger.")

IS THERE ANY PROTECTION FOR A SECONDARY TURBO WHEN THE CAR DRIVES IN MONO MODE?

("A pipe on the center housing of the turbocharger provides for the connection of a bleed
air pipe from the charge air duct connection with the electric throttle. The bleed air is
used to pressurize the seals of the compressor stage to prevent oil leaking into the
compressor housing when the turbocharger is not running.")

IS THIS THE ANSWER TO PROTECTING THE SECONDARY TURBO WHEN IS IS NOT WORKING?

(When the engine operating parameters approach the limits (approximately 2800 rev
/min under load) of the primary turbocharger, the ECM begins the switch to parallel biturbocharger
operation. The secondary turbocharger is brought into operation by the
opening of the turbine shut-off valve which allows exhaust gasses to flow through the
turbine. Fresh air is then drawn through the left air cleaner and the MAFT (mass air
flow and temperature) sensor to the secondary turbocharger compressor.
Initially, the secondary turbocharger does not produce a charge air pressure to equal
that of the primary turbocharger. Therefore, the charge air from the secondary
turbocharger is fed via the recirculation solenoid into the clean air duct of the primary
turbocharger.)

AND HOW DO I UNDERSTAND THIS? WHY 2800? I UNDERSTAND IT AS ANY INTERFACE BEFORE BI-TURBO MODE?


I will be happy for any opinion, or I apologize if it is in some way a stupid question ... L405 2013 Vogue 4.4 SDV8 339.000km/211.000miles

You have answered your questions on the protection of the second turbo, as to the why.

There are two turbos, one is a low pressure unit which gives extra power at low rpm, below 2800rpm.
Then when you need it there is a bigger turbo that kicks in for maximum performance.

If you’ve ever driven an 80’s turbo car you’ll know of this -
Foot down, 1000rpm nothing, 1500rpm nothing, 2000rpm nothing, 2500 rpm nothing, 3000rpm holy until about 5000rpm.
The twin turbo means you get instant low down power and then the full power later on.