Audi 2.5 TDI: Boost Issues When Downshifting.

Good day.

I have an Audi A6 C4 Quattro TDI Avant with the engine code: AEL.

My question to all drivers of these turbocharged engines with boost gauges is:

What boost pressure, for example, do you typically see on the highway when coasting in 5th or 6th gear?

Mine still shows a good half bar before the speed drops low enough.

The only explanation I have is the high airflow through the turbine.
But without accelerating?
Otherwise, the display works perfectly fine.

Best regards, Stephan.

Good day to you too.

It's perfectly normal; the turbine doesn't stop immediately after the gas supply is cut off .
The pistons continue to move, and there is still a mass flow through the intake and exhaust passages of the engine.
You don't have a throttle valve like in a gasoline engine, otherwise the gauge would go into the vacuum range.
So, the airflow doesn't stop, and the turbocharger is still generating "some" boost pressure.

Aq301 wrote:

The only explanation I have is the high airflow through the turbine. But without accelerating? Otherwise, the display works perfectly fine.

...and in doing so, you've already given yourself the correct answer.

Regards, Mpire.