I know I already have a few threads going at once and I wanted to do a more instructive post to my thread along with a proper start to the thread but it looks like I’ll be hopping around a bit.
With the ownership of these cars comes a little mystery as they were very expensive cars when new. Due to the price, a different kind of enthusiast owned the cars. A good portion of those owners did not perform the inspections or work themselves. Many of them were drive only owners. There’s nothing wrong with that, but it can lead to the next owner needing to do some much-needed maintenance. One maintenance biggie is carbon and cleaning it. Carbon is nasty if left on checked on FSI motors. On SI motors, you’re showering the valves with fuel everytime the car was running.
On FSI (Fuel Stratified Injection) cars, the fuel injector is after the valve. So you don’t get any valve cleaning from the fuel. If left unchecked your valves can look like this, or worse.
https://audirevolution.net/addons/albums/images/341858523.jpg
Here is another picture. This is a mild case of carbon.
This is what the same valves are supposed to look like.
Now that we have a quick introduction to carbon, what can carbon effect? Carbon buildup can affect your injectors, your intake manifold, the motor and even the cats. Carbon can do everything from damage our cars mechanical parts to your cars performance.
Audi has answered the carbon issue in the past by, changing the calibration to the cars ECU. Using a different strategy as it related to the intake of air at low speeds to see if that would help. Audi also started doing a BG fuel system cleaner.
The BG fuel system cleaner is a great idea and I actually suggest everyone use some sort of fuel system injector cleaner regularly to help keep the injection system happy. However, the BG fuel system treatment won’t fix the actual carbon problem.
When the carbon gets really bad, the FSI cars will start to misfire. This is, in part, due to the injectors having partial carbon blockage, build up or damage. The BG fuel system treatment would help clear the injectors but it wouldn’t do anything to actually remove the carbon or repair the damaged injector.
So, how do you actually remove the carbon you ask? There are a few ways. Here are the two I tried and tested on my S8 to see what gave me the best result.
There are two standard ways. The first way, is with media blasting. Where you load up walnut shells and use a high-pressure blasting set up like this.
The second way is with brushes and chemicals to soak then brush off the carbon.
Now that we have that part up. What way is the better way?
That seems to be different depending on who you ask.
I wasn’t a big fan of the blasting for several reasons, but I can’t exactly make a thread about carbon cleaning and ways to do it if I never tried blasting.
For blasting. I just sourced the BMW tool in plastic form as it was cheaper and I wanted to try it before I made an ever bigger investment. The blasting method isn’t cheap depending on how you do it. I had to buy the blasting unit, a hose walnut shells the BMW carbon tool and then build the attachment to introduce the walnut shells into the cylinder.
For blasting, you need this.
This is the media blasting unit where you fill the walnut shells and pressurize the tank
You will have to pressurize the tank and run a line to a wand that can direct the walnut shells into the cylinders. The top black tool fits into the cylinders and has a hole that you feed the wand through while running a vacuum cleaner attachment to the side shown with the tape. The walnut shells come in via the wand and get pulled out via the vacuum cleaner all in one working movement. The high pressure of the walnut shells getting blasted onto the valves makes an impact but it can be very very messy
If you choose the blasting technique you would be smart to cover everything as the walnut shell bits get almost everywhere. So you need to tape off all the fuel lines each cylinder and I went the extra step to put moving blankets over the rest of the motor and car for coverage. Here you can see one little area that isn’t covered that’s the one port I worked on at the time for the blasting.
Here you can see the vacuum hose attached to the tool and you can also see the high-pressure line attached to the wand. This gives you an idea on what it looks like.
As for the blasting technique, I found it super messy, expensive and I didn’t have the accuracy that I wanted to have when delivering the blasting material. I wasn’t able to really see what I was doing due to the fact that the tool was in the cylinder and the wand and the hose were always blocking any view. I did make a plexiglass panel to replace the BMW tool and to give me the ability to see in the cylinder while I was delivering the blasting compound but, as expected, it didn’t take long before the blasting compound started to scratch up the plexiglass and my visibility was reduced again.
Overall the blasting did work. I did one side of the motor with the blasting and one side of the motor with the chemical and brush. The blasting probably took about just as long to do as the chemical method due to the setup time tear down time and cleaning of all the walnut shells.
Now let’s look at the chemical and brush. Way.
For the chemical and brush, you’re going to need what you see here as well as a vacuum and maybe a hand drill.
The delivery system for the chemical and brush is still messy and you really should tape off any and all fuel lines including the HPFP connections.
There are a few good chemicals you can use. I started suggesting guys used oven cleaner as it’s meant to clean off carbon and really harsh backed on grease. The difference with the chemical Vs the blasting is the chemical needs to sit and work where the blasting technique you can fire up the wand and start whenever you’re ready.
I found with the chemical method the longer you let the chemical sit the less work you’ll have with the brushes. Don’t wait too long if you use the oven cleaner as it is harsh and with any of the chemicals if you wait too long you’ll just have a gummy mess to clean up.
I started out spraying the cleaner into one cylinder at a time
By the time, I set up my brushes, drill, hose for sucking out the chemical and I sprayed all the cylinders that were still closed on the one bank (I did one bank chemical and one bank blasting) I was ready to start with the brush.
After you get each cylinder with the brush really good you go back with your vacuum and the hose you taped to the end of the vacuum attachment to suck the nasty goo and sludge that you pulled off with the chemical and the brush.
It takes a while and you’re going to have to do each cylinder a few times. Starting with the soaking of the valves in oven cleaner and moving to other cleaning products that you might choose from like brake cleaner to denatured alcohol. The longer you let the oven cleaner sit the less follow-up work you’ll have to do.
As for the chemical technique. I found it less messy than the blasting. The accuracy is much better when you get down to it. Keep in mind you’re using a brush on a shaft so, not super easy to get the brush where you want it but I found I was able to see what I was cleaning and where the brush was the entire time. I was able to get the brush on the back side of the valves much easier than I was with the blasting.
Overall. The chemical system takes longer requires a little more work, but I found it costs way less and I felt less frustrated than I did with the blasting. With blasting, I would have to get to certain spots that I found difficult to reach and difficult to see if I was getting to. With blasting as long as you have a good seal on the cylinder and your blasting tank never clogged (good luck they clog and it sucks) It’s not bad. You just stick the wand in and run it around for about 5 to 8 min while running the vacuum. You will have to go back for those stubborn areas but with enough pressure you generally don’t have to do too much follow up work.
If you put it in cost for cost perspective. Chemical is cheaper. If you use an impact driver and need to go buy one just for this job it would change the price difference but you would still be cheaper.
If you care what my thoughts are and what I would use. I would use the chemical system each time. I didn’t like the potential mess of the walnut shells as they got everywhere. I hated when the delivery system clogged and overall the chemical was just cheaper and more in my line of how I like to do things. I felt I could concentrate more effectively in the areas that needed help with the chemical approach.
Now you can always bring a combination of both into the mix but what I figured out was if you really try to do this. You’re actually going to favor one way over the other anyways. So, you might as well just go with that method.
For the final thought, what is the difference in the end product. Can you tell the difference between chemical and blasting? You tell me.
slim chance that exists though