Valve gunk is nasty stuff that comes from the toxic vapor of steam, oil, gasoline and hydrocarbons circulating around the inside of your engine. A normal process of combustion in any gas powerplant, this vapor is a result of heat and pressure – and it’s vented back into your vehicle’s intake system where it’s sucked into the cylinders and burned up cleanly.
En route to the cylinders, that nasty vapor or ‘blow-by’ passes the intake valves, where it can leave deposits behind in the form of valve gunk. Over time, this buildup can cause issues.
Lately, more and more reports of these issues are surfacing on owner forums, often posted by folks who own machines powered by direct-injected engines. Apparently, the effects can be even worse on turbocharged DI engines, which operate with even more of the heat and pressure that cause blow-by.
What’s the supposed issue with direct-injected engines? In an older engine with conventional port injection, fuel injectors sit above the intake valves. When these injectors squirt their fuel into the cylinder, that fuel can ‘wash’ the tops of the intake valves clean.
The new breed of direct-injected engines have fuel injectors directly inside the cylinders – not outside and above the intake valves. Only air and blow-by goes past the intake valves in a direct-injected engine. There’s no repetitive pressurized squirting of gasoline over the DI engine’s intake valves to help keep them clean.
Translation?
Same oily blow-by, same potential for deposits, but no cleaning system.
Yours truly spoke with GM’s Glenn Bryksaw, a Vehicle Environmental Specialist, about valve gunk, blow-by, and direct-injection engines. GM is cranking out naturally-aspirated and turbocharged DI engines like they’re going out of style – and more are on the way.
En route to the cylinders, that nasty vapor or ‘blow-by’ passes the intake valves, where it can leave deposits behind in the form of valve gunk. Over time, this buildup can cause issues.
Lately, more and more reports of these issues are surfacing on owner forums, often posted by folks who own machines powered by direct-injected engines. Apparently, the effects can be even worse on turbocharged DI engines, which operate with even more of the heat and pressure that cause blow-by.
What’s the supposed issue with direct-injected engines? In an older engine with conventional port injection, fuel injectors sit above the intake valves. When these injectors squirt their fuel into the cylinder, that fuel can ‘wash’ the tops of the intake valves clean.
The new breed of direct-injected engines have fuel injectors directly inside the cylinders – not outside and above the intake valves. Only air and blow-by goes past the intake valves in a direct-injected engine. There’s no repetitive pressurized squirting of gasoline over the DI engine’s intake valves to help keep them clean.
Translation?
Same oily blow-by, same potential for deposits, but no cleaning system.
Yours truly spoke with GM’s Glenn Bryksaw, a Vehicle Environmental Specialist, about valve gunk, blow-by, and direct-injection engines. GM is cranking out naturally-aspirated and turbocharged DI engines like they’re going out of style – and more are on the way.
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| Photo: General Motors |