A modern combustion chamber really shouldn't have any buildup on the pistons/head. All the honda and mitsu heads i have pulled were clean here. They would get this super hard coating on the exhaust valves that was only removed by replacing the valves or chucking them up in a drill and sandpapering off the deposits.
However the EGR valve does a number on the intake runners and back of the intake valve. I think this is where most of the gains are coming from with these cleaners. I had good results years ago cleaning my 4g63 with the mopar stuff. So it helps, but the reasons why I think are different on each engine design.
Another thing, many NAPA locations are now doing fuel injector cleaning service. People don't realise how much dirt is in the fuel they buy. Evo's either clog or for some reason damage the stock injectors easily. Many of my friends evo's throw a cyl misfire after about 50K miles and then they have to clean or replace the stock injectors to get rid of the cyl misfire code.
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“ the only people that care about this aren't car people anyway. we don't consider EVs for anything other than point to point transportation like a bus or a plane. do you care how fast your plane can taxi down the runway?
the dodge is a drag strip monster, and a hell of a good one at that.”
-Rex B16, June 11 2024
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I'd imagine you could eat off the pistons.
just wanted to hear anecdotes.
