Direct Injection carbon & other 2.0T issues

[jellis4148]

Direct injection engines get carbon buildup on the non-combustion chamber side of intake valves due to unburned fuel. The detergents in the fuel help keep that from happening and clean them. Audi, BMW, Ford, GM, Honda, Mercedes, Stellantis, and a few more are sponsors and recommend that. We fill up all new vehicles that are purchased. GM and Stellantis won't let us use a fuel station that isn't top tier.

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[AnnDee4444]

You're right. it doesn't. Nice job. You're smart.

I assume you're replying to me.

I guess you're suggesting they use bad gas?

Nope.

I'm not getting into tit for tat.

Calm down.

To reduce sludge and engine wear EVERYWHERE in the engine and fuel system DO 5500 mile OIL CHANGES (MOBILE 1 OR IF REALLY CRAZY AMSOIL) AND USE GOOD GAS.

And most importantly use API SN+ grade.

 

[AnnDee4444]

Direct injection engines get carbon buildup on the non-combustion chamber side of intake valves due to unburned fuel.

What is fuel doing on that side of the valve?

 

[jellis4148]

An engine with only direct injection has a “dry” intake system; no fuel is introduced in it. The emissions controls of the engine will cause crankcase vapors containing oil and fuel vapor to be introduced to the intake system to be combusted in the cylinder. With prolonged exposure to heat, those oil-bearing crankcase vapors will build up a thick layer of hard carbon (called coke) on the intake.

Engine with regular port or throttle body fuel injection don’t have this issue because 1) the fuel being sprayed into the intake has a significant cooling effect due to phase change from liquid to vapor (latent heat of vaporization) and 2) the fuel is an excellent solvent that tends to dissolve the intake deposits.

 

[jellis4148]

I've seen sooo many DI engines come in with hard to start or CEL complaints and they have to do a top engine clean. When they ask the customer what fuel they use it's usually the Murphy's, or Casey's gas that is the cheap shit around here. Even though the Top tier is the exact same price. T

 

[speedymart]

I've seen sooo many DI engines come in with hard to start or CEL complaints and they have to do a top engine clean. When they ask the customer what fuel they use it's usually the Murphy's, or Casey's gas that is the cheap shit around here. Even though the Top tier is the exact same price. T

The gas has 0 effect on carbon build up issues in the 2.0L. At no point is gas introduced to the top side of the valve during intake stroke. This is true for ALL DI engines. Some manufacturers are going to dual injection to help alleviate this issue. For example the 2020+ Alfa Romeo Stelvio/Giulia 2.9Ls now use dual injector due to carbon build up causing all kinds of issues on low mileage quadrifolgios.

The carbon buildup causes ineffecients in air inlet flow pass the valve during opening. Eventually this will cause the engine to start running rough, usually around idle. Sometimes driving the piss out of it will cause the carbon to heat up and break down naturally, but it's nothing compared to port injection's cleaning effect.

 

[AnnDee4444]

I've seen sooo many DI engines come in with hard to start or CEL complaints and they have to do a top engine clean. When they ask the customer what fuel they use it's usually the Murphy's, or Casey's gas that is the cheap shit around here. Even though the Top tier is the exact same price. T

Correlation ≠ causation.

An engine with only direct injection has a “dry” intake system; no fuel is introduced in it. The emissions controls of the engine will cause crankcase vapors containing oil and fuel vapor to be introduced to the intake system to be combusted in the cylinder. With prolonged exposure to heat, those oil-bearing crankcase vapors will build up a thick layer of hard carbon (called coke) on the intake.

Engine with regular port or throttle body fuel injection don’t have this issue because 1) the fuel being sprayed into the intake has a significant cooling effect due to phase change from liquid to vapor (latent heat of vaporization) and 2) the fuel is an excellent solvent that tends to dissolve the intake deposits.

Re-read your own post. The guy you copied it from got it correct.

 

[jellis4148]

Why do I need to read it again? I copied it to answer the question that keeps getting asked over and over, because he explains it very well and is 100% correct.

 

[AnnDee4444]

Why do I need to read it again? I copied it to answer the question that keeps getting asked over and over, because he explains it very well and is 100% correct.

Your posts imply that you don't comprehend it.

 

[jellis4148]

I comprehend 100%. I keep saying you need to use top tier fuel. I know using top tier fuel will stop carbon buildup on the valves and help keep the engine running better. I see it quite often in the service department, and even the techs will say the same thing.

 

[JT1]

I comprehend 100%. I keep saying you need to use top tier fuel. I know using top tier fuel will stop carbon buildup on the valves and help keep the engine running better. I see it quite often in the service department, and even the techs will say the same thing.

Oil vapors reintroduced to the intake path via the PCV are where the coking comes from. Not some odd additive pack in the fuel.

A port injector spraying fuel or a methanol injector in the intake will alleviate the issue.

 

[AnnDee4444]

I comprehend 100%.

I know using top tier fuel will stop carbon buildup on the valves

These statements contradict each other.

An engine with only direct injection has a “dry” intake system; no fuel is introduced in it.

Direct injection engines get carbon buildup on the non-combustion chamber side of intake valves due to unburned fuel.

These statements contradict each other.

 

[jellis4148]

OMG, no they don't. DI engines get the carbon build up on the intake valves for the reason stated in the article I copied. Top tier fuel helps keep that from happening because of the additives they put in the fuel. Those are my statements. Customers come in with engine problems because they don't use the top tier fuel ever causing the carbon build up. Had they used top tier fuel for the life of the engine they more than likely wouldn't be having that problem. I'm not contradicting myself at all. I've never said DI engines have fuel that wash over the valve. The top tier fuel helps keep the unburned fuel and oil vapor going through the emissions controls and back through the intake over the intake valve causing carbon build up. Now, the exact science as to how that happens, and what additives do what I have no clue. I'm no chemist.

 

[AnnDee4444]

The top tier fuel helps keep the unburned fuel and oil vapor going through the emissions controls and back through the intake over the intake valve causing carbon build up.

Ahh, I see. The 2.0 appears to have a pretty good air-oil separator, to the point that catch cans don't catch much. Not much coming back around should result in cleaner intake valves regardless of fuel.

I could see this being a problem on other engines though.

 

[jellis4148]

Ahh, I see. The 2.0 appears to have a pretty good air-oil separator, to the point that catch cans don't catch much. Not much coming back around should result in cleaner intake valves regardless of fuel.

I could see this being a problem on other engines though.

I actually haven't seen any of the 2.0's having the problem. It's mainly the GM engines with it. The 3.6 in the GM vehicles is pretty prone to it. I run it in my Jeep with the 3.6. It doesn't cost anymore, and surely has to help a little.

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