[ErvGotti]

Originally Posted by cleex024

i dont get it...why would there be carbon build up in the intake portion if the combustion takes place else where? the combustion is not in the intake valves...

im pretty sure the reason why there is carbon build up is because the oil from the turbos get all the way into the intake valves and the heat from the engine sort of hardens/burns the oil onto the vales.

i bet that if there was no oil going into the intake valves there would be no carbon build up.

The PCV valve on all modern cars routes that excess pressure to the intake side so that the engine can burn it off. They do this for emission reasons. That pressure is full of oil vapors. With port injection the fuel helps clean the valves, with direct injection no fuel ever sees the intake valves. So with direct injection even though the intake valves are closed during the combustion process they are still extremely hot, and when the oil vapors from the PCV valve hits them they start to build carbon around them and the ports.

[MDORPHN]

Originally Posted by ErvGotti

The PCV valve on all modern cars routes that excess pressure to the intake side so that the engine can burn it off. They do this for emission reasons. That pressure is full of oil vapors. With port injection the fuel helps clean the valves, with direct injection no fuel ever sees the intake valves. So with direct injection even though the intake valves are closed during the combustion process they are still extremely hot, and when the oil vapors from the PCV valve hits them they start to build carbon around them and the ports.

This together with blow-by.

Neil

[SkySoldier]

Waste of money. The carbon buildup is really caked on my valves, even a walnut blaster only got them about 80% clean, had to scrape the rest off and use carb cleaner.

[Sniz]

Originally Posted by ErvGotti

The PCV valve on all modern cars routes that excess pressure to the intake side so that the engine can burn it off. They do this for emission reasons. That pressure is full of oil vapors. With port injection the fuel helps clean the valves, with direct injection no fuel ever sees the intake valves. So with direct injection even though the intake valves are closed during the combustion process they are still extremely hot, and when the oil vapors from the PCV valve hits them they start to build carbon around them and the ports.

which is why i route my CCV to the exhaust

[cleex024]

Originally Posted by Sniz

which is why i route my CCV to the exhaust

how do you do that?

[eric@helix]

Originally Posted by SkySoldier

Waste of money. The carbon buildup is really caked on my valves, even a walnut blaster only got them about 80% clean, had to scrape the rest off and use carb cleaner.

Then the walnut blasting operator did it wrong. If done correctly, your valve stems and caps should be shiny metal, no matter how built-up they are before hand.

[Sniz]

Originally Posted by cleex024

how do you do that?

the parts are sold by Vibrant.

[SkySoldier]

Originally Posted by eric@helix

Then the walnut blasting operator did it wrong. If done correctly, your valve stems and caps should be shiny metal, no matter how built-up they are before hand.

Take a look at page 20 of the bmw carbon blaster manual, even it shows some carbon deposits left as being "clean".

[VSmotorsports]

Originally Posted by SkySoldier

Waste of money. The carbon buildup is really caked on my valves, even a walnut blaster only got them about 80% clean, had to scrape the rest off and use carb cleaner.

thats odd, we have done over 20+ cars and they have come out shiny clean, must of been the person doing it

Before

After


You can check our walnut blast thread and you can see that all the cars that come in leave like new

[DanielGonz]

Originally Posted by Jeff@topgearsolutions

I think there is a misconception what is actually going on here in terms of why there is carbon build up on the intake valves.

There is simply carbon build up because it's a by product of direct injection motors.

In your typical port injection motor, fuel is run over the valves and therefore is in theory always cleaning them. Since a direct injection car has the fuel injectors in the combustion chamber, there is no fuel hitting the intake valves, therefore no cleaning.

A by product of combustion is carbon build up and by no accident, if there is nothing cleaning the valves like fuel, the result after usage is build up.

The purpose of an oil catch can is to limit the amount of oil in your intercooler, charge pipe, and entering back into the valves. The oil that a catch can would normally capture is only a small portion of the build up on valves. They will inevitably build up with carbon no matter what anyone does.

Methanol could subtract a tiny amount of build up but it is not a cure either.

Fuel injector cleaner won't do anything because the fuel injectors are in the combustion chamber, so no fuel will see the top of the intake valves.

I hope that clears up everything.

[boostaholic786]

I have a buddy that has a shop and also owns a FBO 335i. He has done over 25 different cars and walnut shell blasting by its self, works very very well. I dont know why you would have to scrub with a wire brush and carb cleaner...Thats why everybody uses "walnut shells" because they are abrasive enough to take off the carbon build up without damaging the intake valves.

[zltm089]

Originally Posted by VSmotorsports

thats odd, we have done over 20+ cars and they have come out shiny clean, must of been the person doing it

Before

After


You can check our walnut blast thread and you can see that all the cars that come in leave like new

link to your thread please?

[VSmotorsports]

Originally Posted by zltm089

link to your thread please?

here you go
http://www.e90post.com/forums/showthread.php?t=717785

[zltm089]

Cheers mate.

[VSmotorsports]

Originally Posted by zltm089

Cheers mate.

no problem, and if you had it done and it was not pretty clean then I would talk to the dealership and have them do it again