CRC Intake Valve cleaner...worth it as early prevention of carbon build up?

[JTK]

Not that I would ever recommend doing so, but how could bypassing the PCV system NOT prevent intake valve carbon build up on a DI engine? With no PCV vapors, all you'd have is filtered air rushing across the intake valves on a DI engine (with no port injectors of course).

The only thing I could think of is combustion gasses getting upstream of the intake valves if/when there's any valve overlap called for.

My fear with these spray cleaners is, when done often, they may take a bit of life off the catalytic converters with each use.

 

[doublebase]

This is what I’d say...if it makes you feel good do it.

I‘m a tech, I’ve seen how virtually impossible it is to spray away carbon. Not going to happen. And as far as prevention or slowing things down? Unfortunately the only thing I think can think of is a steady and constant stream of cleaner (which prior to direct injection we had with port fuel injectors constantly spraying the backside of valves). So I do not think a treatment every 3,000-5,000 miles is going to do much of anything but waste your money. And people are now starting to actually take pictures and document this stuff, it’s mixed results to say the least.

But I swear to god, if it makes you feel good do it. Just do it. Honestly. Because feeling good about maintenance will only help your car in some way shape or form in the long run.

 

[oggb]

Most modern engines with variable valve timing don't have a separate EGR system.
And this study found that bypassing PCV did not reduce intake valve deposits:

Considerations on Carbon Deposit Formation in Gasoline Direct Injection Engine - PDF Free Download

Considerations on Carbon Deposit Formation in Gasoline Direct Injection Engine Gyu-Sob Cha GS Caltex Corporation Contents Introduction : Motivation & Objective of Research Preliminary Test

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His engine has EGR. The direct injected engine in that study does not.

To the question of "are intake valve deposits even a problem?"

I dunno. It was for Ford, and they've begun adding port injection in addition to direct injection on some (maybe all? I don't remember) of its engines. Toyota has been using an identical system for some time now. Hyundai has started using it. That says something.

Direct injection is young. We (well, some of us...) are just paid beta testers while the manufacturers figure it out.

 

[circuitsmith]

how could bypassing the PCV system NOT prevent intake valve carbon build up on a DI engine? [snip]
The only thing I could think of is combustion gasses getting upstream of the intake valves if/when there's any valve overlap called for.

Overlap is not necessary.
All that's needed is more pressure in the combustion chamber than the intake manifold at the beginning of the intake stroke.

CRC GDI Valve Cleaner Trial - Before and After (Never Again)

CRC GDI Valve Cleaner Trial - Before and After (Never Again)

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