Combustion chamber porn: N/A PFI vs. Turbo DI

Discussion in 'General' started by brick, Sep 9, 2016.

  1. brick

    brick Answers to "that guy."

    I thought you guys might find these two videos interesting. I've had intermittent ping/knock in the S60 under load. A bunch of us with the new 4-cylinder engines have experienced it and Volvo has yet to provide any help beyond telling us to use higher-octane fuel. (I already feed it 93, which helps compared to the ethanol-free 91 octane I was using but hasn't entirely resolved it.) I think it's a spark and boost mapping problem but I figured it can't hurt to pull the plugs and borescope the cylinders. The plugs looked fine (other owners have seen damage up to and including ejection from the engine) but I thought I'd show you the video. For comparison I have a video from my V70 that I shot a couple of years ago just because I had a borescope and it needed new plugs anyway.

    First the V70's 3.2L naturally aspirated and port fuel injected inline-6 and roughly 90,000mi on it (with a completely wrong date stamp):

    Next the S60's 2.0L turbocharged and direct injected inline-4 with 12,500mi on it (and another completely wrong datestamp):

    Unfortunately you can only see the piston crowns because I haven't figured a way to get the right-angle mirror into the cylinder and back out again. Still, the differences are interesting. You can see a little buildup on the old 3.2L engine but you can see a fair amount of bare metal. With the newfangled turbo-4, not so much. It appears to be completely covered in carbon of varying thickness. There are a few shiny spots where the carbon failed to adhere or, I think more likely, was blasted off by detonation. You can also see the spray pattern from the fuel injector. Interesting, no?

    This level of carbon buildup on the pistons seems pretty common for DI engines. It can't be great, though. This plus all of the carbon that collects on my exhaust tips also illustrates why we're going to start seeing particulate filters on DI engines in the very near future. Nobody wants to breathe what's coming out of these things.

    I might try again with the 45 degree mirror if I can find a way to make it fit though the tight spark plug holes. Carbon on the pistons is probably less important than carbon bulding up on the valves.
    BillLin and xcel like this.
  2. seftonm

    seftonm Veteran Staff Member

    Interesting! I wonder if a fuel like Shell V Power would be able to help clean that up.
    xcel likes this.
  3. brick

    brick Answers to "that guy."

    That's a good question. I've done most of my miles using ethanol-free 91 octane from a local vendor so I don't have any idea what kind of additive pack was blended into that fuel. Concern over the knock issue pushed me to 93 from Exxon/Mobil, which is the only "top-tier" vendor that serves my market. Unfortunately Shell doesn't exist here otherwise I'd give it a shot. PEA fuel additives are supposed to address combustion chamber carbon so I suppose that's on the table.
  4. ALS

    ALS Super Moderator Staff Member

    I mentioned before on the Shell V-Power thread that I filled the old 97 Volvo 960 (2.9L straight six, 24V, FI) up with a tank of Shell V-Power and tossed in a bottle of Techron for an extra kick. I like you fed her what ever was cheapest in high test for many years. I took her out for an Sunday afternoon highway drive and after about 200 miles things got interesting. She always ran OK but never like this. The old girl with 117K miles runs like a brand new car. The engine is so smooth you almost can't believe that an engine with this many miles on it, could purr like a kitten. I was sold I will never run another car on anything but top tier gas. Both the Volvo and the Prius are being fed Shell gasoline exclusively.
  5. Jay

    Jay Well-Known Member

    I'm unable to view the first video. YouTube says it's a private video.
  6. brick

    brick Answers to "that guy."

    It should be fixed now. Apparently I forgot to hit "publish."
    BillLin likes this.
  7. brick

    brick Answers to "that guy."

    After a little research I threw a bottle of Gumout All-In-One fuel system cleaner into the tank when I filled today. It appears to be the heaviest-dosage PEA additive out there and claims to work all kinds of magic on DI fuel injectors, combustion chamber carbon, name it. I'll run the tank and scope it again just to see. I don't honestly expect much but I'm down for an experiment that costs $7 and a half hour of my time.
    BillLin likes this.
  8. brick

    brick Answers to "that guy."

    After an unusually heavy driving week (lots of time on the highway) I have results. Just to consolidate everything into one post, here's the before:

    And here's the after which I just shot:

    I'm not typically a believer in these things, but there's a definite difference following treatment for one tank and a little under 500mi with All-In-One. There are fairly large swaths of what appears to be clean-ish metal, especially in cylinders 1 and 4. The visible surfaces of all four pistons have taken on a shiny, almost "wet" appearance. Maybe that's just what you get when polyetheramine attacks carbon?

    I haven't heard any pinging during this tank, and the idle has noticeably smoothed-out. (When I first got the car I had to look at the tach to know if the engine was running but it got worse over time. Now it's back to barely noticeable.)

    I'm not exactly doing hard science here but I'm impressed to see any tangible difference at all.
    BillLin likes this.

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