As many of you know I'm now the proud owner of a 2015 GMC Sierra with the Direct Injection LT based 5.3L "Ecotec" V8.
I've been doing some rummaging around the Interwebs about Direct Injection engines and carbon build up in the intake track and valves.
Basically my readings only confirmed what I assumed, and what I have heard before in the form of stories at the coffee shop on warm summer nights.
Direct Injection engines have an inherent issue in that they lack any sort of natural way to clean off the top surfaces of the intake valves. This is because the fuel injectors now deliver fuel directly into the combustion chamber of the engine, where fuel is almost immediately atomized and burned. Good for efficiency, but it creates work for mechanics in the long run. In the case of the older style fuel injection, or "port fuel injection", fuel is delivered to the intake port where it is atomized, passes over the valves (where the detergents in today's fuels would clean the valves), and then burned in the combustion chamber.
"But I have an air filter, my intake track shouldn't be getting dirty."
Wrong. This is where an old emissions control technology becomes the thorn in your side. The EGR and PCV systems which are recycling junk through your engine to complete the "burn" and to keep engines running cleaner create carbon and gunk buildup. EGR (Exhaust Gas Recirculation) sends unburned fuel, oil, etc. back through the intake and out the engine again, reducing emissions. PCV (Positive Crankcase Ventilation) is a crankcase vent that's used to keep a constant pressure in the engine's crankcase. That being said, it recycles oil fumes through the intake. Again, THOSE are the sources of carbon and gunk buildup on the valves. So you have an old problem that old technology used to manage quite fine, but now it's coupled with new technology that no longer takes care of it. I urge you to watch that YouTube video as they have a really good example of what Direct Injection engines look like after 33k miles and 75k miles.
"What's the best way to combat carbon and gunk build up in the intake and on the intake valves of my Direct Injection engine?"
Beyond deleting EGR systems, run a catch can. Catch cans are run inline with these emissions systems. There are 2 types. You can get those that are vented to atmosphere, or those that vent to the PCV return on the intake. Both filter out the air that the engine is sending back through your engine for re-circulation and burning, but only the PCV return style will send air to your intake. Note that cans that are vented to atmosphere could lead to an oil smell coming from your engine. The PCV return style will greatly reduce the threat of carbon buildup, but it will still build up. Those vented to atmosphere should theoretically eliminate the problem altogether.
Why worry about carbon build up in the intake?
If you don't already know, you can find anything and everything you need to know about carbon build up and engines here: Let me google that for you
The Dangers of Direct Injection | CorkSport Mazda Performance - Blog
I've been doing some rummaging around the Interwebs about Direct Injection engines and carbon build up in the intake track and valves.
Basically my readings only confirmed what I assumed, and what I have heard before in the form of stories at the coffee shop on warm summer nights.
Direct Injection engines have an inherent issue in that they lack any sort of natural way to clean off the top surfaces of the intake valves. This is because the fuel injectors now deliver fuel directly into the combustion chamber of the engine, where fuel is almost immediately atomized and burned. Good for efficiency, but it creates work for mechanics in the long run. In the case of the older style fuel injection, or "port fuel injection", fuel is delivered to the intake port where it is atomized, passes over the valves (where the detergents in today's fuels would clean the valves), and then burned in the combustion chamber.
"But I have an air filter, my intake track shouldn't be getting dirty."
Wrong. This is where an old emissions control technology becomes the thorn in your side. The EGR and PCV systems which are recycling junk through your engine to complete the "burn" and to keep engines running cleaner create carbon and gunk buildup. EGR (Exhaust Gas Recirculation) sends unburned fuel, oil, etc. back through the intake and out the engine again, reducing emissions. PCV (Positive Crankcase Ventilation) is a crankcase vent that's used to keep a constant pressure in the engine's crankcase. That being said, it recycles oil fumes through the intake. Again, THOSE are the sources of carbon and gunk buildup on the valves. So you have an old problem that old technology used to manage quite fine, but now it's coupled with new technology that no longer takes care of it. I urge you to watch that YouTube video as they have a really good example of what Direct Injection engines look like after 33k miles and 75k miles.
"What's the best way to combat carbon and gunk build up in the intake and on the intake valves of my Direct Injection engine?"
Beyond deleting EGR systems, run a catch can. Catch cans are run inline with these emissions systems. There are 2 types. You can get those that are vented to atmosphere, or those that vent to the PCV return on the intake. Both filter out the air that the engine is sending back through your engine for re-circulation and burning, but only the PCV return style will send air to your intake. Note that cans that are vented to atmosphere could lead to an oil smell coming from your engine. The PCV return style will greatly reduce the threat of carbon buildup, but it will still build up. Those vented to atmosphere should theoretically eliminate the problem altogether.
Why worry about carbon build up in the intake?
If you don't already know, you can find anything and everything you need to know about carbon build up and engines here: Let me google that for you
The Dangers of Direct Injection | CorkSport Mazda Performance - Blog
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