On the Road Again

I'm finally done with the latest phase of repairs and upgrades to the S4. It's been two solid weeks of greasy fingers and though it was fun and satisfying, there were enough frustrating moments to quell any urges to become a professional mechanic.

Over the winter I took advantage of some year-end sales and amassed a pile of aftermarket upgrades in my attic. The stack included new high-efficiency, all-metal intercoolers, a stainless bipipe, new diverter valves, and a cat-back exhaust. I also had an accessory belt tensioner left over from when I was going to replace the belt but ended up having the dealer do it during a warranteed timing belt replacement.

I learned a lesson a couple weeks ago about not trying to charge a dying battery with the alternator. After the battery was replaced, the volt meter (thank goodness the car has one rather than just an idiot light) was registering just over the minimum 12 volts, about 2 volts shy of where it should be. I picked up a remanufactured Bosch alternator at the local parts store.

Supposedly, all of the upgrades and the alternator replacement I had planned can be done without taking the front of the car off. However, since I've done it before and it's really not that big of a deal, I did it this time to give myself more room and make things much easier. It took me about fifteen hours the first time I did it, but this time, with checklist in hand, it took about three. In the process though, I dropped the front bumper assembly and snapped the air temp sensor bracket into pieces and broke a headlight washer hose connector. A trip to the dealer for a $5 bracket and generous amounts of superglue fixed those two problems respectively.

On paper, replacing the alternator is very simple. Just unclip the charge wire, unscrew the grounding cable, unscrew the three mounting bolts, pull it out, and reverse the procedure with the new one. In reality, it's a tight area in there and unscrewing the grounding wire is all blind work with your hand and a wrench jammed up in behind the thing. The tolerances on the mounts are super-tight, so I literally had to shave off some of the aluminum on the new alternator mount to create just enough of a beveled edge to get it started enough so I could pound it the rest of the way in with some high-tech tools (a piece of wood and big hammer). I wanted to take the least amount of metal off as possible of course, so it was a trial-and-error process of shaving off a tenth of a millimeter and trying to put it in. Each try took about ten minutes of squeezing, turning, wrenching and pounding then reversing to get it back out when it didn't work. About eight hours from when I popped the hood, the new alternator was in place.

While the alternator was out, I took the time to clean up the area that had been sprayed over time by the cam seal oil leak I had fixed under warranty. A clean bike is a fast bike, so I figure a clean engine is a fast engine, right? Plus, it just looks nicer having things shiny instead of covered with black sludge.

I popped in the new belt tensioner. That took about four minutes and required nothing more than a hex wrench. After the toil over the alternator, it was nice to do something very simple.

With the required repair done, it was time for the fun part: upgrades. The upgrades are basically all preventive measures to beef up the after-turbo part of the air intake system. Especially if I decide to put in a chip and ask more out of the turbos, I want to know I've done what I can to make it as easy as possible on them. The bipipe and diverters help prevent leaks which would cause the turbos to work too hard, and the high efficiency intercoolers that cool the pressurized air more also help decrease the load on the turbos.

I pulled off the old intercoolers and had a bit of a surprise. About a tablespoon of oil spilled out of the left intercooler and surrounding hoses. The photo shows the new intercooler in place with the old, oily one behind on the floor. Some research helped alleviate my panic about a turbo seal about to blow. "Blow-by" gasses that blow by the piston seals are re-circulated into the air intake via the PCV valve to help cut emissions of nasty gases into the atmosphere. The gases pick up little bits of oil as they pass through the crankcase and that oily air empties into the Y-pipe intake. The oil dribbles down the left side, through the left turbo, and ends up collecting in the left intercooler. Some S4 owners, especially those who track their cars and demand a lot from their engines, install a catch can between the crankcase and the PCV valve to collect that oil. I put that project as a possibility on my "to do" list for the future.

The stock rubber boot over the throttle body is notorious for tears at higher pressures, so I replaced it with a stainless metal bipipe from APR. The installation was pretty easy, though I did have to shave some off the diverter valve hoses to get the pipe to fit without hitting a wiring harness and to get the diverters to sit low enough to clear the engine cover. Still, the boost sensor sits high enough to interfere with the cover, so I'm leaving it off for now.

When you're heavy on the boost, and then let off the gas to shift or slow down, there's suddenly a build-up of pressure between the turbos and the closed butterfly valve in the throttle body. The diverter valves are then triggered by the vacuum system to divert that extra boost back into the pre-turbo air intake. I replaced the stock diverters (model 710A) with new, more robust diverters from the Audi TT (model 710N). As a point of interest, the short little fabric-covered vacuum hose on the driver's side diverter in the photo costs $41 to get a replacement from the dealer. I'm glad I didn't need a replacement. That seems like too much for a little rubber hose. Must be that German engineering, eh?

With bits around the throttle body assembled, I worked back down and started putting in the new intercoolers. The larger intercoolers required some cutting of sheet metal and plastic bits. Pulling out the Dremel, I took a deep breath, and started cutting.

When you start cutting pieces of your car off, it's a scary moment, let me tell you. Forget about "measure twice, cut once." Try "measure five times, check for other items in the way that you don't want to cut about three times, phone your mom and donate some money to charity to build up some good karma, then cut once." The intercoolers were a tight install, and I had to drill a couple new holes in the right fiberglass intake shroud and cut a bit of the left horn mount before everything was back together.

Last but not least. I pressed on the new snub engine mount. Again, easier said than done. I applied quite a bit of silicone lube and it took lots of pressing and wiggling to get that sucker on. Good thing I've been lifting a little recently. The mount is larger and tougher than the stock version, and is supposed to decrease and improve the play in the engine/transmission linkage.

I reassembled the front of the car. Reconnected the headlights, turn signals, horns, fog lights, headlight washers, air temp sensor, electric fan drive, air conditioner condenser, radiator, coolant temp sensor, condenser wire, and hood release cable. It took a couple hours to get all that stuff back together.

I replaced the coolant with G12+, refilled the windshield washer reservoir, and decided to change the oil while I was at it. I emptied the oil pan and then broke my rubber strap tool trying to get the filter off. Sigh. One last insult. The next day, I went to Sears and picked up the best damn filter wrench in the universe. That sucker made short work of the filter and it was off in no time.

I came close to putting the cat-back exhaust on, but after looking under the car, decided that I was too close to wrenching burnout. I put that project off for later, and might consider having a pro with a lift do it. My jack stands are fine, but it's still gonna be a bee-atch laying under there wrenching rusty bolts under close tolerances. It's an easy and not to costly job for a pro, and it's not a complicated job I'm worried about someone screwing up.

I started up the car, turned the heat on full, and warmed her up to coolant operating temperature to circulate it well and get all the air out. Then I tightened the snub mount bracket and took off for a test drive.

Sweet. None of these upgrades was supposed to make any big differences, but my seat-of-the-pants performance meter told me something was different. The shifting definitely seems tighter with less "thunking" from the transmission between lower gears. I swear the boost gauge is showing an extra psi or two of boost - up to about eight to nine from seven to eight - but it seems like it shouldn't be because the computer is still only asking for the stock amount.

In any case, everything seems very quick and solid, just a hint moreso than before and there are no obviously hissing leaks, no dentist drill turbo noises, no dripping oil, etc. She's good to go and back on the road.