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Although the breakthrough seems like a dream come true an unwanted side effect has been emerging. Letter writers have complained to Consumer Reports and the National Highway Traffic Safety Administration (NHTSA) that over time DI can lead to clogged fuel systems and engine carbon buildup. The result can be engine hesitation and a loss of power — and the need for expensive repairs.

Some carmakers, including BMW and Kia, have issued technical service bulletins (TSBs) to their dealers recommending drivers use only name-brand detergent gasoline — without ethanol additives — and periodically add a fuel-system cleaner when they refuel (a TSB is an alert that the automaker sends to dealers to warn about ongoing problems with individual models and how to fix them. It may allow dealers to make repairs at little or no cost to the customer as a goodwill gesture).

This is the big problem with most current GDI engines. Due to modern unburned hydrocarbon (UHC) regulations, vapors from the crankcase are usually vented into the intake stream in order to prevent oil droplets from escaping through the exhaust. In a port injection engine, these droplets are washed off the neck of the intake valve by a relatively constant stream of gasoline droplets. In a GDI engine, the gasoline doesn’t touch intake side of the valve. As a result, the droplets have a tendency to bake onto the valve and significantly reduce performance. To add to this effect, many advanced GDI engines also include exhaust gas recirculation in order to lean out the combustion mixture and reduce in-cylinder temperatures for certain combustion modes (reducing NOx emissions). Since GDI combustion has the ability to produce far more soot than premixed combustion (port injection), the problem is magnified.

Even more alarming is these deposits can dislodge and damage other downstream components (turbochargers, catalytic converters, etc.). Manufacturers have added systems to capture these oil droplets and particulates but no system is 100 percent effective. As a result, there are many disappointed early adopters with large repair bills. Even diesel engines haven’t been immune to these issues.

A U.S. patent application filed in 2002 by Volkswagen AG explained the DI-engine carbon-deposit dilemma this way: Gasoline engines with direct injection of the fuel into the combustion chamber, suffer especially from the problem of the formation of carbon deposits, especially in the neck region of the intake valves.

The document described these deposits as a sticky coating of oil and fuel constituents that, once formed, serves as a base for further deposits, creating a circular process, by which the coating thickness of the carbon deposits continuously increases. Excessive carbon deposits have extremely negative effects, the patent application concluded, citing significant performance losses, sporadic ignition failures and potentially, holes burned in the structure of the catalytic converter (should bits of carbon break from the valves and pass though the combustion chamber).

Last month I started the discussion on carbon and GDI fuel systems. This month I plan on sharing some of your options to help your customers prevent and cure these issues before they destroy the customers’ wallets.

This technology is the future, even with these known issues. The OEs are trying to meet more onerous CAFÉ requirements mandated by the federal government. You should now be starting to see these systems in your shop. Estimates now put the number at 20-30 percent of your cars that have them. This will continue to grow.

Experts agree prevention is the best option for consumers. Regular addition of a quality fuel system cleaner can help. Based on what we know about the cause, speed of deposit formation and the expensive alternatives when they’ve gone undiagnosed, once an oil change is stretching it, but is the minimum preventative level.

Unfortunately, as always, choosing the right formula is tough for you and almost impossible for them. I have four different formulas myself that all make similar label claims, but are vastly different in strength. They are also specifically designed for the type of system to target the location of deposits effectively. Most of my competitors have the same variety of choices.

Ask your vendors for the safety data sheets (SDS) to see what’s inside. How do different products vary? Beware of re-labels of old formulas with a new GDI claim on the package. In this issue there are countless options to get you started. The upcoming shows provide another great opportunity to analyze.

The important thing is to get what your customers need. If they get too far down the road they are going to need more help.

Preventative maintenance are the watchwords, GDI is your new opportunity to serve and yes, making a buck means providing needed goods and services. God bless America, land of opportunity. 

DAVID PRANGE is currently assistant to the chairman at Next Generation Mfg. He can be reached at 630.699.6813 or: daveprange@aol.com

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