Sunday, March 21, 2010

Audi RS6 - Lightweight Battery Install

The Audi RS6 is a high-performance luxury vehicle and along with that status comes a lot of weight! Even though 500hp+ sounds good, the weight of the car is over 4,000lbs. The car is still quick, but handling, performance, and fuel economy could be improved through weight reduction. The general rule of thumb is that every 10lbs lost, is equivalent to gaining one horse power from the engine. Not only do you get increased performance, but you also get increased fuel economy.

My previous Audi was a S4 and at one point I had an Odyssey PC680 battery installed. The PC680 weighs less than 15lbs., and with mounting brackets, it weights 17lbs. The custom aluminum PC680 bracket for Audi's can be purchase from a person known as Jet Jocket in Canada. When I sold the S4, I kept the lightweight battery so that I could install it in the RS6. The only negative side to a battery this size, is that you could accidentally drain the battery very quickly. You do not want to sit in the car with the radio playing or lights on, for more than a few minutes. It drains as quick as it charges! Don't dispose of your stock battery, as you will probably want to put it back in during the winter.

You will first need to remove the battery cover in the truck by removing the two 1/4 turn fasteners.

Next, with a 13mm wrench, remove the two black brackets on the front and side of the battery.

You will also need to remove the negative battery terminal, as you will have to later relocate it. The negative terminal needs to be relocated, because the PC680 is much shorter and the cable won't reach in the stock location.

Disconnect the terminals from the battery, and you should now be able to remove the battery.

How much does the stock battery weigh compared to the PC680 (with brackets)?

That is almost a 40lbs weight savings!

Next, slide the PC680 battery into the battery tray with the positive terminal closest to the back seat. Slide it all the way up and toward the outside of the car. The custom aluminum bracket I am using is the same width as the stock battery, so it should fit snug.

Take the black side bracket, remove the rubber washer on the bottom, and loop the negative terminal through the bolt. Screw the bolt, negative terminal, and bracket into the threaded hole near the corner of the battery's aluminum platform.

You will want to angle the bracket as seen above and then tighten down. After this bracket is installed, the battery should not be able to move in any direction.

Reconnect the battery terminals, charge the battery, and enjoy a nearly 40lbs weight savings!

Audi RS6 - Replacing Vacuum Lines

Turbocharged cars like the Audi RS6 require many attributes of the engine to be performing perfectly to maintain optimum performance. One of the cheapest fixes and hardest to diagnose, is vacuum and boost leaks. Many of the emissions and accessories on cars are controlled from vacuum generated in the intake system of the engine. Components related to performance and accessories, are all tied together into the same system. One leak in any rubber hose can lead to degraded performance from a turbocharged engine.

I was inspecting the condition of my stock rubber vacuum lines in the RS6, and a few of them fell apart in my hands. I decided that instead of replacing one, I would replace them all with quality silicon hoses. I ordered 15' feet of blue silicon hose from ECS tuning, which is my usual preferred vendor for Audi/VW performance parts. In this blog post, I am only replacing the small braided rubber vacuum hosts on top of the engine.

To replace the hoses, you first must remove the carbon fiber air intake system on top of the engine. This requires removing the silver air intake tubes, two nuts on the bottom of each black air intake tube, and a large center bolt.

After you have the air intake system off, you should located all of the vacuum hoses. I previously replaced the vacuum line to the bypass valves, but I am still going to replace them again with the quality hosts from ECS Tuning.

Before going any further, you should stuff rags down inside the turbo inlet ports on the back of the engine. If anything falls into them, you are going to have serious problems.

The most difficult task of replacing the vacuum lines, is removing the stock metal clamps on the ends. I don't have a special tool for this and if you can find one, I would recommend it! This could have been a thirty minute job, but removing all of those clamps turned into two hours.

While I was installing the vacuum hosts, I also relocated the pickup line for my boost gauge to the fuel pressure regulator. The distance between the fuel pressure regulator and the intake port, was not a far enough distance to connect a boost guage T-fitting. I had to loop the silicon hose around the regulator and back to the intake port to allow for enough distance to install the T-fitting. If you do not have a boost gauge, then you will not have to worry about this problem.

I used small zip ties to tighten the ends of the silicon lines. Pull the zip ties snug and then cut them off with a side cutter. Once you are complete with changing all of the lines, reinspect all of the ends to make sure you didn't miss installing a zip tie.

When complete, you should have something that looks like the following.

Before putting the intake back on, make sure that you remove the rags from the turbo inlet ports. You should also unplug the batter for ten minutes, and reset the ECU codes, to ensure the engine takes advantage of any leaks fixed.

I hope this has been helpful and let me know if you have any question.

Sunday, March 7, 2010

Audi RS6 - Transmission logging

I'm still trying to figure out why I am unable to hold more than 10psi of boost in the RS6. It may be a boost leak, but I'm also trying to rule out anything else that could be wrong. Today I logged the transmission values and which include engine RPM, input shaft RPM and output shaft RPM. The reason for this test is to see if the three RPM values move linearly to each other. If they were not linear it would mean the transmission is slipping, which can cause the transmission control unit (TCU) to send a signal to the engine control unit (ECU) to turn down boost.

The logging seems to confirm that there is no transmission slip as seen from the data below. The torque converter locked up around 5100-5400 rpms and from there on the graphs are linear.

I guess I can rule out transmission slip as a cause of my problem! On to the next diagnosis.....

Launch to 3rd gear pull:

3rd gear pull with TC closed: