When direct injection came onto the scene 10 to 15 years ago, it seemed to cure many of the world’s problems, offering more power and improved fuel economy. Where traditional injection setups squirt the fuel into the intake port, direct injection delivers a very precise amount of fuel right into the combustion chamber.
But a problem tended to crop up: carbon buildup in the intake manifold and on the backs of the valves, especially the intake valves. Too much buildup, as you can imagine, isn’t good for engine health or efficiency. Regular maintenance for many owners of direct-injected engines included walnut shell blasting, including the laborious disassembly of the top end of the engine.
Two factors, notes Zachary J. Santner, senior specialist of quality at Sunoco, contribute to that buildup: oil that has seeped past the valve seals and the oily crankcase blowby vapors that are rerouted back into the combustion chamber. When those hydrocarbons are super-heated yet not burned, they form solids via the coking process.
In a traditional, port-injected engine, Santner continues, the incoming fuel cleans away those oil deposits. A direct-injected engine, of course, lacks that feature.
So, what to do? Use of a Top Tier fuel, like all the pump products from Sunoco, he continues, will still help clean several major parts of the engine–specifically the injectors, combustion chamber and piston tops.
In addition to walnut shell blasting of the intake and valves, Santner notes some other measures that can help. While he has no direct experience, he does note that motor oils specifically designed for direct-injected engines are coming onto the market. These products claim to be more resistant to the coking process.
Solvent cleaners also exist, and Santner notes that the safety data sheet for the GDI IVD Intake Valve & Turbo Cleaner from CRC Industries lists a rather large dose of detergent. The product also contains a carrier suitable for delivering that solvent to the right places, the intake manifold and backs of the valves.
Comments
So, those with GDI engines, what are you finding? All going well? Using some kind of intake cleaner? Is walnut shell blasting part of your maintenance schedule?
In reply to David S. Wallens :
Not every DI engine suffer from intake system deposits the same. Some are really bad some barely have any.
Trent
PowerDork
3/29/23 10:08 a.m.
With R56 MINI's the answer is a catch can system.
I hate to say it but "Staff Writer" really phoned that article in. I clicked the link genuinely interested in a solution and was instead told to buy gasoline that won't have any effect and then a "perhaps these chemicals we have no experience with might help"
Cool, another Sunoco advertisement. 
Trent said:
With R56 MINI's the answer is a catch can system.
I hate to say it but "Staff Writer" really phoned that article in. I clicked the link genuinely interested in a solution and was instead told to buy gasoline that won't have any effect and then a "perhaps these chemicals we have no experience with might help"
Agreed.
People: What's the solution to DI engine sludge build up?
"Staff Writer:" lol ¯\_(ツ)_/¯
Berck
Reader
3/29/23 2:28 p.m.
About as good advice as: Buy a new car that has both direct and port injection so you get the best of both worlds:)
In the Korean world catch cans are a lifesaver. Seafoam through the pcv hose helps. On some honda vehicles a friend that runs an independent shop does he walnut shell treatment but pulling the intakes.
Monitor oil consumption. Use a catch can if you can and keep a fresh PCV valve on. If it's been ignored too long original seafoam or GM Top engine cleaner works decently but makes a helluva smoke show. Finally you can have a shop (or if you're adventurous) use walnut shells to blast the valves/ports.
EDIT: maybe I need to start writing for y'all
I've run a couple of cans of this stuff through the Expedition:
It's honestly hard to know how much of a difference it's made without getting a borescope and peeking down into the heads. At 85k miles, the truck still runs great, makes (seemingly) full power and gets the same crappy fuel economy it always has. The one symptom of buildup that it does have is that it idles rough when it's cold. I've looked into walnut blasting. Interestingly, it was easier for me to find places that do do that for VW and BMW engines around here than my Ecoboost 3.5, which is in approximately a zillion vehicles in the Detroit area.
With the EGR valve failure last year, (due to carbon buildup) I suspect at some point we'll do the walnut shell treatments. But till then, we've been running a 70/30 mix of fuel. 70% reg & 30% eFuels. I can go slightly higher on the eFuels. But last time we got a lean code.
My Buick with the LCV Ecotech 2.5 just turned 100k miles, DI no issues yet.
Boroscope is on my Xmas list for investigating. This is a non EGR engine, interwebs tell me that there is a tube that can get plugged, still waiting for a CEL.
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