Project Audi S4: Chip & Exhaust

Faithful AudiWorld readers know that a great deal of time has passed since the last Project Audi S4 update. Too much time. Although the upgrades to the vehicle have continued, they have yet to be documented online. In this installment we'll be covering two performance-enhancing upgrades: chip and exhaust.

For the purpose of refreshing everybody's memory it's worth going over the initial goals that were set out for this project car. While we acknowledged that the stock S4 is a great starting choice for building a track monster, the objective with our S4 was to enhance the various systems (whether performance, cosmetic or otherwise) while retaining an "everyday driver" look and feel. This, of course, ruled out any major engine work or mind-numbingly loud exhaust systems. Each product was chosen for its ability to work within our stated goals.

APR Chip Upgrade

For many first time S4 owners the car -- in stock form -- will have more power and acceleration capability than any other vehicle that they have owned in the past. This doesn't stop the typical owner from considering a performance chip, and we were no exception. With the opportunity to boost already very capable output numbers to the gawdy 300+ hp range it is hard to resist the temptation.

You may be wondering what place a chip upgrade has in a vehicle intended to retain an "everyday driver" feel. That is one of the exact reasons we chose this as an early modification. Nearly all of the performance chips on the market will feel fairly benign if the vehicle is driven moderately. In the absence of a heavy foot, the driver might not even know one was there. In our case we wanted to take this idea step further with the ability to actually shut off the chip if so desired. This was why we choose APR's chip with EMCS (Enhanced Modular Chipping System).

What should be clear is that since this is not a particularly performance-oriented project car series, there was little or no analysis of the performance characteristics of the APR chip versus other brands on the market. We did not examine boost levels, actual dyno'd output versus manfacturer claims or acceleration gains. In other words, this is not a chip shootout article. On the other hand there were some definite peripheral reasons for going with APR, such as the aforementioned EMCS.

We started by purchasing a brand new ECU to be upgraded. The reasoning was simple: we wanted to be able to store the stock ECU in the trunk of the car as a backup. That way if anything were to ever happen to the modified ECU we could (hopefully) flip in the stock ECU and be on our way. Similarly, we would always have the ability to remove the chipped ECU from the car altogether if necessary.

APR's website has detailed information on removing and replacing the ECU. Using an 8mm socket and flathead screwdriver it's as simple as opening the box to expose the ECU itself, disconnecting and removing the ECU, replacing it with the new one and putting everything back together.

The idea behind the EMCS system is to give the chip varying functionality, as well as providing a way of adding additional functionality in the future. In our case we opted for a fully loaded chip. The FlipSwitch gives us a way of switching between different chip programs using the cruise control stalk. For example, while we normally keep the chip in standard performance mode, we recently put it back to stock mode when we loaned the car to a friend who was just recently licensed. Other FlipSwitch modes include valet and race-gas. There are also specialty modes available for certain applications (not applicable to our S4).

Another chip feature bundle we bought was Fault Code Erase/Throttle Body Adjustment (FCE/TBA). FCE is a tidy way of clearing potential engine trouble codes without using a VAG tool; this is a handy method of clearing potential engine codes before a visit to the dealer. We have not used the TBA feature, so can't report on it.

Lastly we opted for the Security Lockout chip feature in order to protect our chip preferences and prevent any tampering. When we choose to turn the chip "off" it doesn't matter who knows we have a chip in the car because they can't change any preferences without the security code.

We have put over 10,000 trouble free miles on the car since installing the APR chip and have not experienced any problems whatsoever. As previously stated, the chip in this car can be likened to a power reserve. Although we are not taking this car to the track and are usually driving fairly moderately around town, we know that firm pressure on the gas pedal will result in a surge of acceleration. The effects of the chip are most often felt while merging or passing traffic on the highway. Third and fourth gears pull with a feeling of sheer abandon, and the driver can easily accelerate at highway speeds while in fifth or sixth.

Milltek Cat-back Exhaust

The next performance mod for Project Audi S4 was replacement of the stock exhaust system from the catalytic converters all the way back. It was not a forgone conclusion that a modified exhaust system would be installed on this vehicle. After all, we were not out to wring every last bit of performance from the vehicle and we were obviously not willing to make the car sound heavily modified.

However, after driving S4's with nearly all of the different aftermarket exhaust offerings we knew we had found the perfect system for our car in the Milltek exhaust from Stratmosphere. There are two things that in our opinion set this exhaust apart from the rest. The first is the overall sound/tone of the system. The second is the cosmetic look. We'll acknowledge upfront that both of these criteria are highly subjective to different individuals. Objectively speaking we believe we can say that the Milltek exhaust is quieter than a lot of the competition, which is exactly what we desired.

The Milltek exhaust offers a deeper idle tone than stock and while enthusiasts would definitely notice it, it is not harsh or annoying. If you get on the gas then you will hear an increased hum that sounds aggressive but not overly loud. At highway cruising speeds the exhaust noise will typically fade away among the other road noise. All-in-all it can be described as a multifaceted exhaust; for the enthusiast there's enough tonal feedback to please the performance appetite, while for the oblivious non-enthusiast passenger there might not even be recognition that something is different.

Cosmetically the system is spot-on. The exhaust fits tight underneath the car just like the stock system, not looking droopy from behind. The dual tips are totally classy in chrome with "Forge" etched on top. They protrude from the rear perhaps just slightly more than the stock tips which we were happy about. From the rear they appear more aggressive than stock, but do not exude visions of the homemade "coffee can" exhaust.

Another plus of this system is that the installers had no problems bolting it onto the car. The stock exhaust pipe unbolts, so no cutting is required. The entire Milltek kit fit properly, making for a quick and painless installation.

The exhaust is a good performance complement to the chip upgrade. Again, since we are not focussing on performance in this series we never performed before-and-after horsepower tests. We'll take Stratmosphere on their word that the exhaust can yield 7-8% in horsepower gains and 7% additional torque. AudiWorld Technical Editor Don Pavlik had put an identical Milltek exhaust on his own S4 and reported a gain of 21 hp versus a chipped car with stock exhaust.

Clearly there is performance potential from replacing the stock exhaust. We are happy to report that we were pleased with the asthetic gains, both in terms of sound and "look".

Up Next . . .

Project Audi S4 will continue its quest to become a fully-modified "everyday driver". With Spring and Summer nearly upon us the updates will come more often -- we promise!

Parts Installed:
Prices reflect retail pricing at time of publication and are subject to change.

Qty. 1 Spare S4 ECU (from APR)


Qty. 1 APR S4 2.7T 1.0 Bar Chip, including FlipSwitch Technology, FCE/TBA and Security Lockout (from APR)


Qty. 1 Milltek Stainless Steel Cat-back Exhaust (from Stratmosphere)




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