Intake valves deposits, Gas vs Diesel

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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 of it and i live in a place where most cars are diesels since at least 25 years and oil used to be pretty crappy. Is there a correlation between the volume of air entering the engine (presence/lack of throttle body) and the oil deposits building up on valves ? Enlighten me.
 
Diesel engines do not have PCV systems. So, there are no oil-laden crankcase vapors being drawn into the intake side of the engine.
 
But they still have a breather that send blow by and vapors back in the intake, at least all the diesels i had or worked on.
 
I'm guessing it's the efficiency. Because it combusts with more compression and more of the fuel is burnt, it doesn't get stuck on the valves etc. But this is a total guess...
 
Diesel engines do not have PCV systems. So, there are no oil-laden crankcase vapors being drawn into the intake side of the engine.
In this study eliminating the PCV system did not reduce intake valve deposits:
I think the main reason why diesels don't have the IVD issue is the intake manifold is never under substantial vacuum, so exhaust gases never get drawn back past the intake valves at the beginning of the intake stroke.
 
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 of it and i live in a place where most cars are diesels since at least 25 years and oil used to be pretty crappy. Is there a correlation between the volume of air entering the engine (presence/lack of throttle body) and the oil deposits building up on valves ? Enlighten me.

Deposits can a big problem for diesels. A quick Google shows many articles. IMO the lower deposits in Europe probably has something to do with the fuels found in Europe being cleaner.



 
Is it possible that diesel engine oils have also something to do with it?

Just asking please don't get excited. lol
 
Sorry, no pictures of intake valves, but these are intake manifolds and ports. First are from a Mazda Bounty with a WL engine, 2nd a Mitsubishi Triton, 4M41.

2016-03-24 13.14.19.jpg
2016-03-24 13.14.19.jpg
2016-04-18 15.40.19.jpg
2017-08-18 09.50.45.jpg
 
I stand corrected. I thought I knew what I was talking about and apparently did not.
 
I've read arguments that higher Noack oils help reduce IVD in gas DI engines ... Not sure if I believe that since I still chase lower Noack oils. lol

just curious what is the typical Noack range for diesel engine oils? Same as petrol or similar specs?
 
Some very interesting reading for me tonight, thanks guys. Just started reading the first link from circuitsmith and i remember that my intake valves looked pretty carboned up, i couldn't see the metal at all on the valves and intake ports looking through the injectors hole with a flashlight. What could explain that ? The lack on detergent in E85 fuel ?
 
VW TDI owners (especially old ALH 1.9L TDI) would dispute that they don't have buildup issue problems - here is one of many images on Google search of a ALH TDI intake manifold cleaning - with a slight amount of buildup. :ROFLMAO: The runners immediately below on this example are probably just as clogged as the throat.

g2gJvsK.jpg
 
I owned a 2014 Chevy Cruze 2 litre Diesel.I got rid of it at 70000km due to it being coked up so bad the head had to be pulled and redone,fortunately under warranty.I did not do a lot of highway,mostly city,many short trips.This spelled disaster for it.I used Mobil 1 esp,one of the lowest noack oils out there.This car had egr as well as pvc with a type of catch can system.Others driving a LOT of highway didn't have this issue.So,city slow speed driving,crummy Canadian diesel fuel plus probably poor engine design/emmissions regulations did this engine in.BTW,it was only produced for 2 years.The dealers warranty cost was close to 3k,they said if out of pocket my cost would have been over 4k.
 
The cruze had a lot of different diesel engines 3x 2 liter engines. They started with a VM design, then used a daewoo/gm design, and the latest once have been derivatives of a fiat design.

I'm not 100% on the timeline, but if you say it was only used for 2 years I think this was the daewoo/gm engine. Soewhere in 2014 they switched to the fiat engine it seems, so both are possible
 
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