Gas dynamics: How to calculate the pressure distribution before and after the turbine in an AGT-Delta engine?

Hello,

When tuning a gasoline engine, the exhaust gas temperature (EGT) in the exhaust manifold is a fairly important factor.
The MED9.1 for 2.0L TFSIs calculates the air-fuel ratio (AGR) based on data from hundreds of models and the specific operating conditions of the engine (load, lambda, etc.), and provides this data as diagnostic information for various points in the exhaust system: in the exhaust manifold, before the catalytic converter, inside the catalytic converter, etc.
The WOT (Wide Open Throttle) diagnostic data delta between the exhaust manifold and the pre-catalytic converter typically averages around 140-150 kPa. Unfortunately, the diagnostic scale for the crumb temperature ends at 999°C.

A friend wants to tune his CDL (presumably a diesel engine control unit) to its "maximum stable" performance and has installed a probe at the entrance of the downpipe as an AGT (Air Gap Temperature) control point. Initial highway tests with software calibrated for approximately 330 horsepower showed a maximum temperature of 850°C at that location. Adding the aforementioned 140-150K delta for the manifold temperature, this results in approximately 1000°C. However, the exhaust gas temperature in the diagnostic readings rises so quickly to 999°C that I would suspect even more – IF you can even trust the diagnostic data from an engine that is operating beyond the limits of the original equipment manufacturer (OEM) software.

Therefore, I would like to estimate the crushing temperature using a different method, namely by calculating the power required to drive the crusher.
The compressor performance can be calculated based on the mass flow rate, the air density at the intake, and the boost pressure. Dividing by the compressor and turbine efficiencies should, in my opinion, give you the required drive power. You may need to add a bit to account for friction losses in the bearing system.

The exhaust mass flow is, according to my estimation, roughly "air mass + 8%" (including internal cooling due to a lambda value of 0.. Can we use the gas laws to calculate the necessary cooling of the exhaust flow, which would allow the turbine to achieve the pre-calculated required power output? Then, you would only need to add this cooling value to the probe reading behind the turbine, and you would have a (hopefully) well-founded calculated value for the blade temperature... ?

Hi,

Why doesn't he install the temperature probe before the turbocharger?

Best regards, Rainer.

Hi Rainer,

because drilling and welding the (cast) manifold is more complicated than simply removing the metal downpipe and installing the port there .
The K04-064 turbocharger is also "a part included." Exhaust manifold.

I don't want to be mean, but it would have been even simpler to put the exhaust temperature sensor in the tailpipe and estimate the temperature before the turbocharger from there.

"+/- 40°C within that temperature range can mean either a good or a bad result... I'm skeptical that it can be estimated accurately enough based on air mass, pressure, etc."

A user on this forum once drove an Audi A2 1.4 TDI with over 150 horsepower. In the process, a connection on the four-cylinder exhaust manifold was cut off and welded.
Mechanically, it looked quite clean, and you can practice on scrap loaders/crushers.

Best regards, Rainer.

@ulf: if you absolutely want to calculate something ->

EDIT: but be careful - it's at the university/technical college level http://www.springer.com/de/book/9783642289897