AZjeff
$50 Site Donor 2023
I'm not an engine builder so I just haven't seen inside many engines to know the answer. Was there a problem with other FI systems? If crankcase fumes weren't going into the intake would the valve deposit problems go away?
Is GDI the only cause of harmful intake valve deposits?
- Thread starter AZjeff
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For the most part but because you also have the oil seeped by the valve stem seals, which is not much, it does also contribute to the valve deposits, though over a very long period of time.
You could mitigate this by using oils with higher ester formulation
funny thing, on my car the intake runners closest to the pcv where the cleanest. all the valves looked the same. i think most intake valve deposits are egr soot, and the oil acts like a glue and lets the soot stick to the valves. no pcv=nothing to stick the soot to the valves, no egr=no soot to build up on the valves. engines with blown turbo seals are usually pretty clean in the intake.
Well, using crushed walnut shells to blast away intake deposits isn’t a new invention. It goes back some 50 years, so deposits have been a problem since at least then.
Some engines are known deposit monsters. The old Ford 2.3L from the mid-1980s was called the HSC, for High Swirl Combustion. Something about this design just invited deposits. So much so, that to this very day the EPA and most labs still use the 2.3L to test fuel detergent effectiveness.
Some engines are known deposit monsters. The old Ford 2.3L from the mid-1980s was called the HSC, for High Swirl Combustion. Something about this design just invited deposits. So much so, that to this very day the EPA and most labs still use the 2.3L to test fuel detergent effectiveness.
So having no EGR (my 05 Silverado 4.8 is a non EGR engine from the factory) would be a benefit for valve deposits? Unfortunately I was getting oil in the throttle body because of a sludged up PCV in the valve cover, causing occasional smoke on startup until I installed a catch can. This oil may have caused some deposits before that was taken care of too, I assume.
Generally speaking where was no problem. Due to the location of the injectors the fuel from PFI setups would travel over the backsides of the valve as it entered the combustion chamber. This presence of fuel would prevent build up on the valves. On some PFI setups the air/fuel mixture would be sitting there waiting for the valve to open.
If there were no PCV system then deposits would disappear but air quality would drop significantly.
There's no such thing as a free lunch unless you think living up wind is all that matters.
AZjeff
$50 Site Donor 2023
Not suggesting doing something illegal like valve cover vents or a draft tube dripping on the road. It's unfortunate when an environmentally friendlier improvement causes an eventual mechanical problem that will have to be addressed.
IMO the fear and impact of IV deposits is grossly overblown, but human nature operates on fear all the time. I mean I'm running LL04 for godsake. haha.
yes. I've taken apart some non-egr engines, and while there was a sticky oil layer everywhere there was no sooty buildup. i don't think oil alone can build up thick enough to cause problems, and I don't think egr soot is sticky enough on its own to cause problems. some diesels can completely plug off intake runners with egr soot, but diesels also have a pcv and make way more soot than your average gas engine. I don't think you need a catch can or anything like that if you have fuel injected before the valves.
I don't need the catch can anymore for sure, but I figure it can't hurt to leave it on there now. I installed it as a band aid/diag tool when it was smoking on cold start. The catch can fixed that as it kept the oil from getting sucked into the throttle body. But I was having to empty it daily until I installed a new valve cover/PCV.
Since that I can empty the catch can once a month to be safe, or an entire OCI in the summer. In winter it's mostly water in there and looks like milkshake, but it still takes quite a while to get full.
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