Carboned Intake Valves

[Rygrego]

You must be new to engine tech?
When DI came around valves started carboning up b/c the FUEL injector was no longer located behind the valve to keep it clean. Top Tier + has everything to do with helping with fuel & DI engine carbon issues (hence my suggestion you quoted to use TT+ in DI engines).
Please study up on the subject.

The carbon on the manifold side of the valves is caused by pcv mist not being washed due to the lack of fuel washing it off during intake.

You must be new to engine tech?
When DI came around valves started carboning up b/c the FUEL injector was no longer located behind the valve to keep it clean. Top Tier + has everything to do with helping with fuel & DI engine carbon issues (hence my suggestion you quoted to use TT+ in DI engines).
Please study up on the subject.

No it doesn’t. The fuel never touches the affected parts of the valves. The carbon buildup is caused by pcv vapors not being washed by a port injector. I believe it’s you that needs the schooling.

 

[97prizm]

Full time port fuel injection is the best way to keep the valves clean.

Don't buy a car with GDI, AFM, or VVT. Just say no to unnecessary complexity.

E D I T

I hope this thread gets moved to the Mechanical/Maintenance Forum.

I didn't know I was in the PCMO Forum.

I take pride for not posting there.

Variable valve timing is a good thing.

 

[fantastic]

The carbon on the manifold side of the valves is caused by pcv mist not being washed due to the lack of fuel washing it off during intake.

No it doesn’t. The fuel never touches the affected parts of the valves. The carbon buildup is caused by pcv vapors not being washed by a port injector. I believe it’s you that needs the schooling.

I think there's a misunderstanding...

1. You are talking about how carbon is created.
2. I'm talking about what OP can use to help or limit it from getting out of control by using Top Tier + fuel.

 

[fantastic]

Is this referring to the ASTM D6201 test? If so, that’s using a mid 90s MPI Ford Ranger and isn’t relevant for a GDI engine.
Or is there a newer IVD test on a 2.3 EB GDI engine?

The D6201 test is the basis for my point. The goal here is to show that Top Tier is not just a "marketing scheme," as some have implied. Regardless of its age, the test provides validated standards and real-world data confirming that even the original Top Tier requirements were effective at cleaning intake valves.

 

[jsean]

It is the D6201. The point being proof it's not a "Scheme", as was implied, & actually has testing standards old or not there are actual real life results that show proof of even the old Top Tier standard cleaned valves up.

Fair enough. But it’s for a spark injection / MPI engine. Different beast than a GDI engine. Top tier + gasoline will certainly help with cleaning the DI injectors. But I think folks have had good luck running Techron additive / Redline Si-1 and keeping their injectors clean. None of that is going to meaningfully impact or control IVDs.

 

[fantastic]

Fair enough. But it’s for a spark injection / MPI engine. Different beast than a GDI engine. Top tier + gasoline will certainly help with cleaning the DI injectors. But I think folks have had good luck running Techron additive / Redline Si-1 and keeping their injectors clean. None of that is going to meaningfully impact or control IVDs.

That is a fair point, but I would argue that cleaner combustion via well-maintained injectors leads to fewer overall engine emissions, which in turn reduces the severity of the soot and vapors passing through the PCV system.

It is also worth noting that the current Top Tier Plus (TT+) standards go well beyond the older D6201 testing. They now incorporate specific testing on GDI platforms, such as the GM 2.0L, to address modern carbon concerns. That is why I believe bringing TT+ into this discussion is relevant—it is actively being evaluated against the specific challenges presented by GDI technology.

 

[PandaBear]

Also I seriously doubt any OEM is going back to MPI.

Hybrid running Atkinson are likely still on port injection. Port injection has better part throttle response actually.

 

[SC Maintenance]

Regardless of its age, the test provides validated standards and real-world data confirming that even the original Top Tier requirements were effective at cleaning intake valves.

The original tests had fuel hitting the back of the valves. GDI does not. That is the entire point.

It is also worth noting that the current Top Tier Plus (TT+) standards go well beyond the older D6201 testing. They now incorporate specific testing on GDI platforms, such as the GM 2.0L, to address modern carbon concerns. That is why I believe bringing TT+ into this discussion is relevant—it is actively being evaluated against the specific challenges presented by GDI technology.

Maybe, but it cannot address the carbon on the back of an intake valve which it never gets to which is what the OP is asking. The carbon is not a function of the burn process, it’s from oil vapor outside the combustion chamber.

 

[Mainia]

So how does an additive that never touches the back of the valve clean it? Carbon deposits on the back of the valves also is not from the fuel so it’s not causing it. It’s a simple question?

PVC system fog and possibly valve overlap, Top Tier+ while running Valvoline restore and Protect, HPL oil, and other high based ester oils. I saw this in my intake ports before and after using some of the above oil. But it is so small, IE small rounder carbon donut under the valve guide turning into a flatter donut under the valve guide. I will take it, but it is not a very big win.

 

[demarpaint]

I would have thought this topic would have died off by now, it seems to still be a problem in a lot of applications.

 

[Al]

So how does an additive that never touches the back of the valve clean it? Carbon deposits on the back of the valves also is not from the fuel so it’s not causing it. It’s a simple question?

Here is what I believe. Gasoline matters little.

 

[Al]

Can we all though just agree that the problem is a function of DI?

 

[SC Maintenance]

Can we all though just agree that the problem is a function of DI?

I would say yes in cases where it happens. But not all GDI engines have this problem seemingly?

 

[PandaBear]

I would say yes in cases where it happens. But not all GDI engines have this problem seemingly?

Depends more on how hot the engine keep intake valve at. Supposedly if you keep it above 400C carbon gets burn off like self cleaning oven use heat to burn off the deposits.

 

[Al]

I still believe that redlining helps. Can't prove it.

 

[Patman]

I still believe that if you exclusively use fuel with a very high amount of detergents (like Costco or Shell V Power) that less IVDs will occur

 

[fantastic]

I still believe that if you exclusively use fuel with a very high amount of detergents (like Costco or Shell V Power) that less IVDs will occur

Agreed
These threads seem to show there are some here that believe it to be nothing but a marketing gimmick but I don't agree with that.

 

[crashz]

We have a 2013 VW Beetle with the 2.0 GDI turbo engine and I suspect the valves are carboned up. 141k miles, slightly rough cold idle. I tried a Gumout timer cleaning, but the bottle was old and I think something was wrong because it was half full at the end of the time.

I'm going to be driving it a little more and getting some highway runs in and will try the CRC cleaning and report back.

But - I feel like the cure to this is major work, and it will probably time itself nicely with a timing chain, guides, water pump and re-sealing the engine. I'm just kicking the can right now.

 

[jsean]

That is a fair point, but I would argue that cleaner combustion via well-maintained injectors leads to fewer overall engine emissions, which in turn reduces the severity of the soot and vapors passing through the PCV system.

It is also worth noting that the current Top Tier Plus (TT+) standards go well beyond the older D6201 testing. They now incorporate specific testing on GDI platforms, such as the GM 2.0L, to address modern carbon concerns. That is why I believe bringing TT+ into this discussion is relevant—it is actively being evaluated against the specific challenges presented by GDI technology.

Unless there’s a more updated TT+ spec than Jan. 2025 that I linked, this is not entirely true. All they’re testing is the injector spray pattern / cleanliness using the GM 2.0 LHU engine. There’s no mention of testing or setting an acceptable spec limit for IVDs.

1. Will TT/TT+ help with injector cleaning? Sure
2. Will TT/TT+ help with controlling IVDs compared to using non TT/TT+ gas? Sure
3. Will TT/TT+ clean up existing IVDs on a GDI engine (related to OP’s question)? Unlikely.
If there’s any testing spec or standard that attests to this, do share so that I can also learn.

 

[badtlc]

I disagree.

My testing with my cars showed it did.