The passenger seat experience nearly sold my housemate, a current BMW 318is owner. The occasion also happened to be my first A4 test drive, which sold me on the car from a driver's seat perspective... I hadn't even seen any A4 commercials, so their impact was zero.

The exact moment of falling in love happened while descending a fairly steep hill on a twisty country road with my roomie up front and the sales droid in the back (like R2D2). "There's a very tight curve at the bottom of this hill," said my R2 unit. "You'll want to slow down a lot." But I felt that the Force (the fours?) was with me in this quattro, so I barely slowed down and took the 10-mph posted curve at 35-ish, squeezing the gas on the way out... didn't even skim the centerline. My roomie told me later that he would've been really scared, if only he'd had the time to be.

For months afterward he kept saying "I want that car!" But then he decided that he doesn't want the payments yet, so...

G.

How is that possible that you extract 15 horsepower (7.5%) from the 1.8 liter engine while the 3"cat back for the S4 adds only 12(3.9%)? Are your figures accurate? The same goes for A4 & S4 chip upgrade. With the A4, the gain is (33%) over stock, with the S4, it is (22.8%). Could you please explain why? Thanks in advance

...due to the fact that in a stock S4, the K03 runs a higher boost than the K03 in a stock 1.8T. Therefore the jump to 1 bar in a 1.8T is bigger than in an S4....no comment on the exhaust figures though....unless the stock S4 exhaust manifold & system is a better flowing design than the stock 1.8T system...

-Ash 98.5 1.8TQMS APR/K&N

should be closer. Also, I would like to know how they did extract the extra 10-15 HP with the last revision of the chip without changing the boost level( I already know that you can gain a few by changing timing etc. but that is from stock). Seems like a huge difference and I would like to know how they accomplished it. Also, I can not imagine that the stock S4 exhaust is all that efficient to where you would gain more from a catback for the 1.8 cat-back system

Also, the figures for the exhaust gains are after the chip modification

The original post said 22.8% gain for the S4 and 33% gain for the A4.

22.8% of 260hp is a 60hp gain for the S4. 33% of 150hp is a 50hp gain for the A4. The S4 gains 10hp more than the A4 with the upgrade based on the information in the original post.

The exhaust on the A4 is a much more complete system due to a few factors. The A4 has only one cat that sits right behind the turbo. The S4 has 4 cats that are in 2 locations. The S4 exhaust starts in the middle of the car after the 4 cats. This alows for a change only in the second half of the system, which is where less of a gain can be gained. The A4 allows for a improved downpipe which is a very important element in a turbo exhaust system.
In regards to the chips. The A4 is more detuned then the S4 is from the factory. The chips are set at safe levels. Feel free to call with any questions.

Thanks

Stephen/APR
1-800-680-7921