I started my journey with artifical engine sound systems from Sound Actuator for the cabin and eventually managed to buy this one from a friend.

Audi Active Exhaust contains of one or two steel “stewpots” connected to the car’s exhaust pipes. The system adds rumble and loudness to the original exhaust sound with bass speakers inside the “pots”: it is the only way to seriously change the sound of diesel engines while keeping ecology in place. Audi defaults the system to TDIs only – they appeared on two generations of the A6 / A7 and SQ5, the latest SQ7 / SQ8. Retrofit kits were also available for A4 8K, A5 8T, A6 4G, and A3 8V.

Golf GTD, Kodiaq RS, Porsche, and many German non-VAG cars also use the same “pots” – they all are identical and produced by Eberspächer.

Speakers are controlled by the sound generation module / signal amplifier produced by KUHNKE company. The module is visible in the CAN network as a SAS-GEN 2 AGA device with index C0. Switching sound profiles is linked with Drive Select modes, and their presence is mandatory.

GEN 2 part numbers:

4G0 907 160 B
4M0 907 160
8R0 907 160 / 8R0 907 160 A / 8R0 907 160 C
8W0 907 160 A
5G0 907 160
565 907 160 / 565 907 160 A
4G0 071 953 / 4G0 071 953 A / 4G0 071 953 D
8T0 071 953 A
8V0 071 953

Newer modules with the Kendrion logo and the H11 hardware are installed on the MLB-Evo platform. Their device name is SAS-GEN2.5AGA, firmware is different from GEN 2.

4K0 907 160 A
4M0 907 160 A
80A 907 160 A

Several third-party CAN boxes exist that cheat the original module to work on other VAG- and even non-VAG cars. They also scale RPM graphs from diesel to petrol range, have their sound profile editing software, add buttons to turn on/off, and change profiles without Drive Select.

Many people buy complete active exhaust kits from those manufacturers (of magic boxes) without going into details of part numbers. The web is full of examples of VAG components working on BMWs, Mercedes, etc.

I got the complete kit from Kufatec, including an Eberspacher pot, 4G0 907 160 B unit, wire splitter with button, and Kufatec add-on unit (first version with miniUSB port and without Bluetooth). You could collect your set piece by piece on eBay, Allegro, buying only a Kufatec box with a splitter, or kits from other manufacturers such as MaxhausT, InsidePerfomance, Thor, Panthera, Cargraphic. They all have very similar functionality.

Condition of used Eberspacher pots and pipes geometry can vary greatly, be careful when purchasing. On bigger Audis, pipes are welded to the exhaust, but it’s unnecessary for the sound. The speakers are more vulnerable to heat and diesel soot in a closed system. But a pot hooked independently to the chassis is more likely to get water and debris. The choice is up to you and your exhaust configuration.

Here is a detailed post about the internals and repair of the speakers, the author did awesome work! Please, do not drill a hole for water drainage – it will make things worse! And do not turn the pot upside down too!

Original Retrofit Kits

8T0 071 901 B retrofit kit was available for the 2008 Audi A4 TDI. It appears to be the first of an Eberspacher active exhausts for Audis. They did everything thoroughly – together with the pots, they were selling half the exhaust system. Several retrofit reports on D2: 1, 2, and 3.

A6 kit is very similar to the previous one, but there are practically no mentions of it on the web.

A retrofit kit for the Audi A3 8V appeared in 2017. The pot is mounted under the chassis on the right side, with no connection to the exhaust. The kit didn’t last long (as someone explained on the motor-talk.de) – TÜV banned the sales in 2018 because of the new neighborhood noise restrictions.

The pot in the kit is stamped with the whole kit’s part number – 8V0 071 901, control unit – 8V0 071 953. Neither the first one nor the second was sold separately. Surprisingly, the same pot without a pipe, but with a whistle and three mounts, is used in the Skoda Kodiaq RS. Its part number is 565 253 903 B; the control unit is 565 907 160.

Connection

The connection diagram for all cars is identical. In the case of additional boxes, they cut into the CAN bus between the original unit (J943) and the gateway (J533).

I tied a sandwich of boxes under the dashboard, next to the fusebox; dragged the strip of CAN-drivetrain to the gateway and connected the power to a random Kl.15 fuse with this adapter; made a wire (~5 meters) running to the rear bumper with 4F0 973 702 connector at the end.

I also checked the Kufatec splitter for my future experiments – CAN-bus comes to the 17/18 pins (Low / High) and runs out of it from 15/16 pins.

My car is already the third one on which this pot was retrofitted – we had to cut out the old fasteners again and weld in new ones. The factory mounting point is on the right side (regarding motor-talk.de). There is no room to do so next to exhaust tips on the left – Sportback is too short.

Here is the most detailed description of a similar retrofit: parts 1, 2, 3, 4, and 5.

Controls

Kufatec module allows switching six sound profiles by an external (ugly) button. I cut it out and started native look-n-feel integration to the central “piano” console. I bought one more donor panel with three blanks (the cheapest one) to get spare parts and used this tutorial to disassemble both.

I replaced a fixed white blank with a clickable black switch and brought the board to a friend to solder the button mechanism and the diode to the only empty space. We also had to add a 2k Ohm SMD 1206 resistor to the backside of the board. The switch track goes on the 9th pin. Mass is the 11th pin.

I found a company that does laser engraving on any item and gave them a donor panel for experiments to find the right beam parameters. We used Porsche icon: PNG24 with alpha channel, vector CDR.

The final version with 10mm width turned out like this:

How Does This Sound?

The most interesting part.

When connected to a laptop, Kufatec software allows you to edit volume graphs linked to RPM, car speed or pedal position, add bracing (irregularity, gurgling) to the exhaust sound, etc. Kufatec’s site has a detailed description of all the features.

You can enable “engine start sound” with peaked revs when you press the button; you may hear it in the first video. And the answer to the most popular question is: there are no pops-n-bangs in GEN2 factory firmwares and Kufatec profiles.

I disabled 2 out of 6 profiles. The accelerator pedal controls the volume of the first profile; the rest depend only on RPMs.

I read that the original AGA system reduces the volume on a highway and found this limitation in the Kufatec configurator too, but with a reasonable explanation: a risk of breaking the speaker suspension after 3000 RPM at 100% volume. It can’t bounce so fast. Starting from these revs, Kufatec draws a red zone from 60% and warns that the sound will be lowered after 30 seconds of operation, regardless of the settings.

In addition to the external button, most cars can have profile switching with the cruise control lever. You can also return the classic control through Drive Select.

The Kufatec device responds to the engine mode changes, not the “Engine Sound” profiles in the gateway dataset. It’s a little awkward and can be confusing.

There are many more videos on their YouTube channel.

Stay tuned …