Claims:
Turbo Muffler Delete, a product that if based on the accolades lavished upon it by vendors would seem capable of improving the performance of the Mk7 GTI. A sampling of the claims made follows:
- “Decrease Turbo Lag”
- “maximum airflow”
- “eliminates the restriction and turbulence caused by the OEM part.”
- “additional 10bhp during dyno tests.”
- “Increased throttle response”
- “optimal power and boost response”
- “replaces the restrictive, power-robbing OEM part with a smooth, turbulence free air path exiting the turbo.”
- “increases overall turbine efficiency”
Concept:
How these gains are supposedly achieved is illustrated by a picture from APR:
The slots in the side of the OEM part are shown to allow air to escape out of the pipe resulting in a mixing of the main airflow stream.
The picture doesn’t address how air is escaping out of the OEM tube. The tube sits within a larger housing that is airtight. It has to be airtight otherwise boost pressure would not build. If the Turbo Muffler (TM) is completely enclosed then very little air is going to exit the TM to the space shown in blue. Once that blue space is at the same pressure as the interior of the Turbo Muffler no more air would move into it. Given the very small volume around the TM the time to equalize pressure in the ‘space’ with the air flowing out of the TM would be extremely brief.
This means the condition shown in the picture is a small fraction of the time that pressurized air is flowing through the Turbo Muffler. The majority of the time the airflow through the stock TM is likely to be very similar to that shown for the APR part.
Testing:
Testing of the Integrated Engineering TMD, and now the Neuspeed TMD, have failed to show any increase in airflow by “upgrading” to an aftermarket turbo muffler delete.
The Neuspeed TMD is attached to a charge pipe:
Using a set of eBay charge pipes and an eBay direct fit intercooler for additional components to simulate the vehicle equipment a stock turbo muffler is compared with a Neuspeed turbo muffler. Results of airflow measurements are in the chart below:
Failure of the aftermarket Turbo Muffler Delete to produce any detectable gains in airflow raises the question of Truth In Advertising with regards to the claims multiple vendors make for this product.
Conclusion:
Flow bench test results do not support the claims made by vendors regarding aftermarket turbo mufflers increasing airflow beyond what the stock part is capable of.