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Carbon deposit removal
Well, I broke down and did the yearly MCCC treatment. My engine was knocking so bad I couldn't take it anymore. The amount of power loss from 3-4* timing retard was getting unacceptable. I was blaming the aftermarket cams for the heavy knock I was getting. I just couldn't figure it out, I've got big injectors, rewired denso fuel pump, big ass fmic, BPR7ES plugs, 20 psi pump gas. By all accounts, the car should not be knocking. Only thing I couldn't account for was carbon deposits in the combustion chamber.
First, I did the MCCC via the CBV intake manifold port. Got the smoke going and everything. This got rid of most of the lifter tick and the top end power went up fairly good. Must have cleared the carbon off the intake/exhaust valves or something like that. Figure I got the knock beat but then it gets warmer out and the car is knocking bigtime again.
So, I go to plan B, which is to soak each cylinder in MCCC overnight. Go back in and Mighty vac the MCCC out of each cylinder. This usually does the trick. Out of curiosity I look into the cylinder thru the spark plug hole and the piston tops are STILL covered in nasty looking carbon, even after all that. Since I don't have a flexable brush long enough to get into the cylinder head and wipe all the carbon off the piston tops, I just grabbed a long piece of silicon vacuum hose, feed it into the cylinder, and rotated it around. The silicon hose is fairly tacky and any carbon will stick to it pretty good. Did this about a 1000 times, pulling it out and wiped off the carbon each time. Finally, the piston tops looked moderately clean, best I could do with what I had at hand.
Now for the test. I get the car nice & warm and go out for an extended boot. I'm not too optimistic but I get on it in 1st gear thru 3rd gear. The result, 0 knock retard in every gear now, for the most part. Did this about 20-30 more times with the same result. Man, the difference in midrange torque and top end power with an extra 2-3* timing is noticeable. I just refuse to turn the boost down or back off the timing to avoid knock, a well setup and tuned car shouldn't have to.
From the look of my pistons, I'd have to say the MCCC treatment needs to be done in combination with a stiff brass brush and some agitation, and something to physically wipe up the carbon with. Soaking proved totally useless for me, as the carbon settles right back down to the bottom, which ends up being the piston tops. Cheers.
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