Dirty Intake Valves with DI

[Boomer]

So after posting a message about my VW Golf AllTrack and getting responses about having to clean the intake valves after a while, I got to wondering. Why do diesel engines not seem to suffer from dirty intake valves like DI gas engines seem to do? I know that if you run the intake valve at a high enough temperature, the debris will not collect. Is that what they do in diesel engines? Are there other tricks up the diesel builder's sleeve to prevent intake valve deposits? After all, these guys have been running DI for decades. What gives?

 

[Skippy722]

Diesels definitely can get deposits on intake valves, I found this thread that has some pictures

Intake valves deposits, Gas vs Diesel

I have a hard time understanding why carbon build ups are a problem on modern direct injection gasoline engines but not in diesels. I understand that there's no fuel constantly washing the valves but diesels are the same and this problem doesn't seem to appear or only marginally. I never heard...

bobistheoilguy.com

 

[Surestick]

So after posting a message about my VW Golf AllTrack and getting responses about having to clean the intake valves after a while, I got to wondering. Why do diesel engines not seem to suffer from dirty intake valves like DI gas engines seem to do? I know that if you run the intake valve at a high enough temperature, the debris will not collect. Is that what they do in diesel engines? Are there other tricks up the diesel builder's sleeve to prevent intake valve deposits? After all, these guys have been running DI for decades. What gives?

Errrrr, some diesels are notorious for forming deposits in the intake.
Oil vapour from crankcase ventilation plus soot from EGR can seriously clog up the intake manifold and cake onto valves.

 

[UG_Passat]

So after posting a message about my VW Golf AllTrack and getting responses about having to clean the intake valves after a while, I got to wondering. Why do diesel engines not seem to suffer from dirty intake valves like DI gas engines seem to do? I know that if you run the intake valve at a high enough temperature, the debris will not collect. Is that what they do in diesel engines? Are there other tricks up the diesel builder's sleeve to prevent intake valve deposits? After all, these guys have been running DI for decades. What gives?

You never had an old TDI with the VE injection pump. While the intake valves didn't get the buildup, the EGR valve got it buildup first.

Then came ULSD regulation which helped tremendously with the soot, but before that, we did the "EGR mod" using VAGCOM, where one would dial back on the EGR PWM to just before a CEL would be triggered, so less EGR, less buildup, but more NOx output. Or people would get the EGR delete and delete the EGR altogether, at the risk of not being able to turn off the engine.

 

[dfarr67]

I don't think Honda's have a reputation for buildup- but installed a air/oil separator and dump it biannually of black sludge,