Those that aren't into cars can safely skip this post.
So I like to drive fast cars through twisty mountain roads. I'm probably the guy ruining a peaceful scenic drive you are having on the weekend. (Although the same could be said for you).
So I've been working on my car the last few months. It has a much bigger turbo now (a garrett gt2871r to be exact). Which should have me right about 425 bhp for now. Once I've sorted out fueling issues and replace pistons, valves, valve springs, and rods I should be right about 600 bhp. I'll have to move to a larger turbo again in the process, and boost to around 30 PSI. I'm currently about 25 PSI on wide-open-throttle. I think that is a good place to be. It is about the right amount of power for this car.
I had to go to a larger injector to get more fuel into the cylindar. I like direct injected vehicles due to reduced issues with detonation, but getting injectors that can withstand the amount of PSI required to inject into a compressed cylindar is difficult. I opted for the S3 injectors that are modified to flow more. It maintains a similar spray pattern as the stock 2.0T engine.
In addition to adding more power, I upgraded the suspention to an adjustable coilover setup (along with larger sway bars to combat roll). I still need to have some of the camber removed since I have reduced the amount of body roll. My next alignment will sort that out.
For braking, I went to a 345mm two-piece slotted rotor. The aluminum hat on the rotor saves about 10 lbs of unsprung weight on each corner. Lovely. The A4 and S4 use the same caliper with different rotors, so I'm keeping the caliper for now. After another 100 hp added, I'll probably switch to the Brembo kit from the F40. Oh, I moved to stainless braided lines as well, which makes the pedal feel a bit more direct and much better when the lines would normally start boiling.
An upgraded clutch and aluminum flywheel is in progress and should be done this week. The flywheel is rotational mass and the lighter it goes the faster your RPMs can raise and drop. Definitely helpful for heal-tow breaking through the corners. These cars tend to understeer, so I'm switching from a 2:1 center-diff to a 4:1 center-diff at the same time. This means that 80% of the power will be sent to the rear wheels when hard accelerating out of a corner post-apex.
The new front-mount intercooler is gigantic. San Francisco has an amazing amount of fog which is perfect for these things. The intake temperature drops significantly. Remember that since cold air is more dense, you can fit more of it into the engine, and make more power. This had a pretty dramatic change from the stock dual side-mount intercoolers.
Anyway, below are a few pictures from the process.
-- Christian Hergert 2012-08-06