Decarbonizing GDI Engines....

[5030]

Yeah, that was my point too. I wouldn't try to clean anything when 1) it isn't needed, and 2) you could cause damage.

But... I have a borescope too and you are looking in the WRONG place. The carbon won't be in the combustion chamber (other than maybe a tiny bit on the piston crowns)...

The carbon will be on the intake side of the intake valves, IOW, where you cannot see it without pulling the intake manifold. You ain't gonna see it with a borescope unless you drill a hole in an intake runner to see the intake port. of course then you'll have to replace the manifold because you trashed it.

 

[5030]

It's been a while since I posted in this thread, but I would not worry about deposits in the 3.5 ecoboost. Just for fun I ran a bore scope into the cylinder of my truck with 16,000 miles on it when doing spark plugs and did not see any carbon or sludge. I'm not worried about it.

You can't see whats not there. It's on the other side of the intake valves, not the combustion chamber side, the OTHER side....

 

[5030]

Lets put it this way to make it all in perspective.... The blowby vapor from the crankcase (water vapor from condensation, microscopic oil droplets that get past the oil seperator on the engine, the hot blowby gases, all pass through the PCV valve and appropriate piping and are introduced into the intake where they mix with ambient temperature air on the way to the combustion chamber, the last part of the journey for this contaminated vapor and air mix is the intake cavity where the intake valves reside. It's HOT there...HOT. The cooler mix of crankcase vapors hits the HOT cavity... What happens? A small amount of that vapor attaches itself to those cavity walls and forms CARBON. All engines do it.

However, in a GDI engine, the mix of air and crankcase vapor is devoid of any gasoline (with it's added cleaners ((it's in all pump gas BTW)) so, the gas is injected directly into the combustion chamber, bypassing the intakes entirely. In a wet intake engine, the valves are cleaned by the additives in the gas. Not so with a GDI engine.

It's very elementary, no wet intake, no valve cleaning. GDI ENGINES ARE DRY INTAKE NOT WET.

I don't get what is so hard to comprehend about that. But then, it's your engine. I'll deal with my GDI engines by eliminating the blowby vapor either with a catch can or by filtering.

Your engine... It's your wallet
Good luck

If you don't understand that, well, you must be a Democrat....:laughing:

 

[3930dave]

I want to thank all the mechanics on this long but interesting thread....I now understand much better why when I borrow my wife's 2012 Elantra and step on it on highway merge, I have at times got huge black smoke result.......scares the crapp out of me and the drivers beside me. She drives much more sedately however we are fortunate that our drive into work each day is a 25 minute drive at highway speeds. But with 80,000 miles (130,000 kms ) on it I was getting worried about that four cylinder and that random black smoke. We use good oil (synthetic in winter) and have lately learned you must use Hyundai's oil filters as per a TSB they issued about valve train noise. Too late that engine already doing the tell tale clackity clack!.........Also have a 5.3 litre 2014 GMC truck so read with interest the modifications some made.............thanks

I like to understand the pros and any cons of most technologies. Once I understood the basics of GDI, I wanted to ping the braintrust here to see what real-world experiences people are having. Thanks to everyone who has taken the time to drop by and describe what they've seen.

I haven't had a good look at a typical GDI intake yet..... on my old MPFI, it is relatively easy to remove the throttle body - if that is still doable, I'd pull it on a GDI I suspected of heavy buildup and thread the borescope into the intake manifold from the fresh-air side. GDIs are a bit different, but are still only really air pumps....

Rgds, D.

 

[Snobdds]

You can't see whats not there. It's on the other side of the intake valves, not the combustion chamber side, the OTHER side....

Actually, I don't really care what the intake tract looks like. I'm only concerned with the valve stem carbon buildup, period. Which my scope shows me clearly, ironically. I've never really seen a clean intake tract on a port injected motor either, this whole clean thing is misleading.

 

[5030]

Actually, I don't really care what the intake tract looks like. I'm only concerned with the valve stem carbon buildup, period. Which my scope shows me clearly, ironically. I've never really seen a clean intake tract on a port injected motor either, this whole clean thing is misleading.

I want to see that picture. How do you look at the stem area from inside the combustion chamber with a borescope? Inquiring minds want to know.... I own both a Gradient Lens and a video scope so my curiosity is aroused.... in as much as entrance through the spark plug hole brings you basically vertical to the top of the piston with the valves above the entrance...................

X ray vision maybe?

 

[5030]

You should care what it looks like anyway. If the intake tract is all funky, chances are your IAC is gummed up and your throttle body looks like it was living on unfiltered Camels....:thumbdown:

 

[Snobdds]

I want to see that picture. How do you look at the stem area from inside the combustion chamber with a borescope? Inquiring minds want to know.... I own both a Gradient Lens and a video scope so my curiosity is aroused.... in as much as entrance through the spark plug hole brings you basically vertical to the top of the piston with the valves above the entrance...................

X ray vision maybe?

You're bound and determined to be right. After looking at the combustion chamber on a 3.5 ecoboost, how can you keep beating your drum? I can clearly see the valve stems through the spark plug hole, which is really the only place one needs to be concerned with...

 

[tcartwri]

That's an interesting chamber. Very diesel like...

 

[Snobdds]

That's what I thought also. The motor is also built a lot like a diesel engine. It's the only gas motor I know that has a bed plate or girdle supporting the crankshaft, with 6 bolt mains. It's has an incredibly strong bottom end.