I was contacted by another member from the site ( My S5(afe) hyden ) about help on a carbon clean. He like many people is concerned about carbon and how to remove it. That started this post.
There are new challenges that face ALL FSI motors. One of them is carbon. Let’s be honest and open, carbon, if left unchecked can be a serious issue, both in power and potential damage to your motor.
There is no debate on this. Carbon is an issue and it needs to be dealt with. Carbon buildup isn’t new, its been around for years. Fuel manufactures started to put chemicals in there fuel to help keep carbon at bay.
Carbon isn’t an issue for the Pre FSI cars due to the fact that your fuel injectors were constantly spraying fuel (A cleaner by nature) on to the face of the valves. FSI sprays fuel past the valves directly into the cylinder See picture below.
http://audirevolution.net/addons/albums/images/565142169.png
As you can see the Green represents fuel and air, Notice how they both come into contact with the face of the valves. That makes for a clean valve surface. So the face of your valves looks like this (thanks to countvohn and his carbon thread)
http://audirevolution.net/addons/albums/images/267880414.jpg
VS. this of a FSI motor, where the fuel is sprayed past the valves into the cylinder
http://audirevolution.net/addons/albums/images/197276516.jpg
carbon can do more then just disturb flow. It can damage one of the most important parts of your motor for making power.
Your spark plug. look past how bad the carbon is on the actual valve and look at the plug.
http://audirevolution.net/addons/albums/images/341858523.jpg
This is an example of just the plug alone. (I found this picture on a non Audi site)
http://audirevolution.net/addons/albums/images/114917765.png
If your asking me. A carboned plug is worse then a carboned valve, here is why.
Carbon by itself is going to hold in heat, for any motor this is a bad thing. We want to expel as much heat from each power to exhaust stroke as possible. Having carbon on your plugs can and will, if left unchecked lead to pre ignition or better known as detonation or pinging. This isn’t something that you want to have happen.
I just did my carbon service, I felt I could wait longer but I started to hear slight pinging when accelerating. I changed my gas and it didn’t fix the ping. After time it started to get worse. Being a Audi tech I knew it was time to look into doing the carbon clean service in hopes of fixing the issue.
Below are some shots of my clean.
It took some time but I stripped it down to the open heads
http://audirevolution.net/addons/albums/images/415818930.jpg
From there I took the first looks into the runners to see if there was any serious carbon.
http://audirevolution.net/addons/albums/images/514138110.jpg
Turns out that there was some carbon really starting to build up. Still I expected to see worse then this given the fact that I was having detonation or pinging issue.
Still this amount of carbon build up is going to rob power so I started the clean. I got out my tools.
http://audirevolution.net/addons/albums/images/58823780.jpg
I have to say that these cleaners really do help. I can bend them around the back of the valves and get to some serious spots.
My technique might differ from others so take that for what its worth. I start by making sure the valves are closed. THIS IS VERY IMPORTANT. Below shows valves that are not sealed shut and there on the intake stroke.
http://audirevolution.net/addons/albums/images/566171623.jpg
Its very important that you make sure the valves are shut all the way. You don’t want debris getting into the cylinders. This is a picture of the valves closed and seated
http://audirevolution.net/addons/albums/images/489642675.jpg
The next part differs from person to person. What I do is spray each closed runner completely to the top with carb cleaner
http://audirevolution.net/addons/albums/images/480885962.jpg
The end result looks like this
http://audirevolution.net/addons/albums/images/30484924.jpg
I let the chemical sit and the carbon to soak for a few hours. The longer you let it sit the easier the end cleaning will be. This picture is after 5 hours of sitting. You can already see parts of carbon have broken off and are floating to the top
http://audirevolution.net/addons/albums/images/276920322.jpg
From there you get your tools and go to work. Scrubbing and cleaning around the valves and the runners.
After the clean I decided to do a oil change and air filter. The results were as expected. The car felt and ran much better. There was more power but STILL there was a pinging that was present.
After all this what was the culprit. It turned out to be my spark plugs. I changed out the plugs and there was a small amount of carbon on them. I’m sorry I didn’t take any pictures of the plugs, I have to admit I wasn’t sure it was even going to be the issue. Turns out it was.
The new plugs made about the same difference in power and acceleration as doing the carbon clean. Or so I felt anyway. You really feel the difference with good plugs Vs. bad plugs.
So as a side note It might not be a bad Idea to add the spark plugs in every few carbon cleans. It might just be needed. No telling how much power your loosing there.
This thread wasn’t intended to be a deep technical thread more so then my experience and findings