Originally Posted By: wallyuwl
.........What do you guys think is more important in a direct injection engine (I have a 2.4L DI 4 cyl in 2010 Equinox), low Noack or a good cleaning oil in terms of dealing with intake deposits since the fuel doesn't pass by them with DI? ........
Apparently, low soot production is important.
"Ameer Haider, GM’s assistant chief engineer for V6 engines, certainly knows the problem, telling AutoObserver, “DI engines are prone to forming oily deposits on the intake valves, unlike in port fuel-injected engines, where a constant spray of fuel into the port allows any deposits to wash away. With DI engines, the fuel gets injected directly into the combustion chamber, so there isn't a chance for the deposits to wash away. Typically, deposits form when soot – which is an end-product of combustion – adheres to the valve stem.”
"Haider, GM’s V6 assistant chief engineer, explained how GM has designed its DI engines to combat carbon buildup: “We maintain great engine function and performance in our all our DI engines through an optimization strategy with our valve events,” he said. “Our intake-cam timing, injector targeting and timing of the injection events are optimized to avoid direct fuel contact on the intake valves. This strategy keeps smoke and soot formation to an absolute minimum, which in turn prevents excessive deposit formation.”
"Stephen Russ, technical leader for combustion for Ford’s 2-liter Duratec DI engine, said that similar to GM, engineers have determined the proper injection-timing calibration to help eliminate the carbon deposits. But Russ also said the technology of injection components – particularly the high-pressure solenoid injectors – has quickly matured, meaning excess valve deposits in most DI engines should become a thing of the past as these improved components are incorporated into production."
http://www.autoobserver.com/2011/06/direct-injection-fouls-some-early-adopters.html
