Porpoise Hork
Well-Known Member
The carbon deposits the result of the PVC system. It's an inherent issue on all DI engines that lack any sort of pre-injector mounted on the intake plenum before the valves.And where would the carbon deposit come from?
Port injection engines spray fuel directly on the intake valves and the detergents in the fuel assist in keeping the valves relatively clean. On DI engines without a port or intake fuel injection system the intake valves never come into contact with the fuel. Over time the vaporized oil from daily operation gets drawn past the intake valves and over time slowly starts to build up as carbon deposits. This buildup can cause loss of performance, mpg, poor idle. and in some extreme cases minor damage to intake valve or seats. Over the lifetime of a DI engine the buildup can get to be this bad or worse if not addressed in some sort of maintenance.
Some manufactures have started adding a small pre-injector to regularly shoot small jets of fuel into the intake to help reduce this buildup, but most still have not as they see the added benefit does not override the increased expense. Add to that this issue does not typically present itself until well after the factory warranty has expired. Once it gets to this point cleaners like Seafoam and others like it are mostly useless. To clean this it would require pulling the intake and manually scraping the deposits off the valves, or using a walnut blaster and cleaning the ports and valves. Neither of these process is a quick and easy job.
By adding a oil catch can you are putting a device inline that can temporarily slow the vacuum coming from the PCV allowing the vaporized oil to collect in a small reservoir, thus reducing the carbon buildup significantly. Regular cleaning of the valves and intake with a catalytic safe solvent like Seafoam while possibly not as effective as a quality catch can can prevent the valves from looking like the previous picture and looking more like this after 100K + miles.
If you add a catch can and do regular intake valve cleaning on top of that, then the intake runners and vales will very likely stay nearly as clean as the port injected engines.
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