Upper cylinder deposits: What should you know?

Upper engine deposit cleaning is probably a familiar term to you. Many consumers are even aware and recommended such cleaning done with regularly scheduled engine service.

Late-model vehicles with new engine technologies are prone to quick power loss. Primarily due to the rapid formation of restrictive intake valve deposits. These new deposits are different from those previously encountered. They are far more difficult to clean, appear with lower mileage and have a greater effect on engine performance.

BG Products Inc. Olympus H_7K, hd image borescope.

HOW ARE GDI ENGINES DIFFERENT?

The design of the petrol engine has changed a lot in the past ten years or so. The primary purpose has been to make the internal combustion engine more environmentally friendly. Manufacturers have put all of their effort to lower harmful emissions, fuel usage and greenhouse gases (CO2). This article focuses on intake deposit formation differences between Direct Injection (GDI) vs. Port Fuel Injection (PFI).

New engine technologies provide different operating conditions, and thus the deposit formation is quite different both in rate and consistency. From the mid-eighties, we have learned to understand that port fuel injection engines primarily create fuel-based deposits. This well-researched engine technology provided historical foundations to develop cleaning chemistry specific for fuel-based intake deposits.

GDI engines suffer from both oil and fuel-based deposits, a drastic difference.

The GDI engine is more demanding on the engine oil. The overall engine oil volume is often lower than its PFI counterpart, but the stress incurred is higher. Improved engine oil chemistry has been developed so that GDI engines can operate with lower viscosity and longer service intervals.

UPPER-CYLINDER DEPOSITS

When an engine cycles, positive crankcase ventilation (PCV) allows crankcase gases to go upward and dump into the intake, which is cooler than the crankcase. The cooler temperature causes these oil droplets to cool and stack on top of each other second-by-second as the engine runs. 

In gaseous form, these little droplets have a lot more surface area exposed than what they would have in liquid form. This means they have a lot of surfaces actively looking for a bonding opportunity. As they lay out on the metal surface (i.e. intake valve) one after another, the bonding action forms a matrix that can be very difficult to remove.

GDI Intake deposits

FUEL-BASED DEPOSITS

Fuel-based deposits generally accumulate quickly, but often in lightly formed varnish layers. With the correctly-tailored chemistry, they’re relatively “easy” to clean. Fuel-based deposits form when unburnt fuel hydrocarbons lay on a surface. When subjected to extreme temperatures, these hydrocarbons burn incompletely and slowly bake themselves into the residue. The substance slowly becoming a hard sticky substance (like spilled cola soft drink in the hot summer sun).  

Water on a rag makes spilled drinks easy to clean, but using a bit of traditional soap (traditional fuel cleaning chemistry) makes the job effortless. But what happens if both the “environment” and the “substance” change to a bit more extreme (like leaving bacon in the frying pan far too long)? A wet rag and hand soap won’t get you very far in that scenario. 

The GDI engine (environment) runs higher pressures, higher temperatures, and tighter tolerances than traditional PFI engines. Thus, the deposits (substance) that from in this environment are different in nature. 

Traditional fuel injector vs. modern gdi injector

OIL-BASED DEPOSITS

Oil-based deposits are more difficult to clean because the liquid is quite viscous (ie. super thick), and differs in consistency.

Let’s focus on oil-based deposits in the fuel/air induction system. These deposits are hard to remove because they form both in globules and in many layers. Their formation may start slowly, but ramps up exponentially as it binds to previously formed deposits. In this system, oil that lays out as a deposit begins usually in a gaseous (or almost gaseous) state, like in a fine mist or little droplet form. 

CLEANING MODERN ENGINES 

To point out the obvious, fuel-based deposits are commonly found in fuel systems, and oil-based deposits are found pretty much wherever the oil cycles. In an ideal world, the engine would have one section where oil stays and one where fuel stays and these two fluids wouldn’t cross paths. Unfortunately, in modern engines, it isn’t that simple. 

In the past, most vehicles had Port Fuel Injection (PFI) engines (and there are still many around today). PFI engines spray fuel into the intake port and onto the backs of intake valves. This means every time a PFI engine cycles, fuel spray gives these intake components a nice bath. 

However, a majority of modern vehicles have Petrol Direct Injection (GDI) engines. With GDI engines, the injectors spray the fuel directly into the combustion chamber rather than the intake port. This process is great for combustion efficiency and for helping to reduce emissions. Unfortunately, even engineers are held to the law of thermodynamics and these benefits have trade-offs. 

While fuel deposits are likely to build quicker in GDI engines, these systems are loaded with engine oil deposits. Due to the inherent design (which incorporates low tension piston rings), oil-based deposits in the intake and intake valves come from two different places—the top and the bottom. 

The top is from PCV, which is the largest contributor. The bottom is from poor piston ring function, allowing excess engine oil vapours into the combustion chamber. Some of this goes up into the intake due to valve overlap, which is when the intake valve and exhaust valve are open simultaneously (i.e. variable valve timing).

Then, to make matters worse, when these oil vapours make their way into the air intake and encounter hot valve surfaces or even hot exhaust gases. These vapours and droplets harden much like, (you guessed it) bacon too long in the frying pan.

One solution to the problem requires lots of elbow grease, the same way the neighbour cleans his barbecue with a pressure washer. Lots of disassemblies, manual cleaning, reassembly and a wasted afternoon. Surely there is a means to incorporate a fast and easy way of cleaning new oil-based deposits using old reliable PFI technology? BG Products Inc., set out to do so back in 2015. 

IS THERE A ONE-SIZE-FITS-FOR-ALL SOLUTION? 

Chemistry and common sense tell us that oil and water don’t mix. So why would traditional PFI fuel-based deposit cleaners be expected to clean GDI oil-based deposits? The importance of using the right tool for the job applies to chemicals and cleaning of deposits. “Like dissolves like”, a common phrase used in chemistry, means that a specific substance can only be dissolved by a similar “like” substance. Unfortunately, many traditional fuel system upper cylinder cleaners aren’t sufficient for the oil-based deposits found throughout modern GDI engines. 

The right tool for this job is the BG Platinum® Fuel System Service. It’s specifically designed to clean both fuel-based and oil-based deposits in the fuel and fuel and air systems. 

How about a tool that could prevent deposit buildup from happening in the first place? The BG Engine Performance Service offers a three-step premium engine oil and fuel system cleaning that reduces oil vapour production from the top (PCV), the bottom (piston ring function), and valve overlap (Variable Valve Timing). An even more simple and preventative approach to the source of the problem.

Do you offer your customers a solution to clean upper cylinder deposits, especially in GDI equipped vehicles? 

“With chemistry, there is always a solution...”

-Clinton J. Meyer ACS Certified Petroleum Chemist working for BG Australia.

BG Products Inc.

BG Products, Inc., the leading manufacturer and supplier of automotive fuel and oil conditioners, specialty chemicals, greases, tools and equipment, is ISO 9001, 14001, 17025 and 45001 certified.

As an ISO Certified company, BG Products, Inc. is obligated to provide transparent and factual information. All products are tested and proven to provide added benefits to equipment owners.

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