Is it necessary? Some engines do just fine with them never being touched.
Carboned Intake Valves
- Thread starter Al
- Start date
CRC doesn't do much, you need mechanical scrubbing. If you can't walnut blast, I heard scrubbing by hand with some nylon tool (i.e. zip tie on a stick) might redneck enough carbon out.
The only ones that seems to do ok without dual injection are the ones keeping the intake values at 400C to burn those carbon off (i.e. Skyactiv G). Think of it as self cleaning oven temperature.
Dry ice is not needed if you are not worried about a bit of walnut residue like engine. Usually after walnut blasting they spray compress air and vacuum out the remaining media anyways. It is not sand and any tiny amount remaining would just burn up. I have seen people dry ice blast industrial equipment that can't tolerate any residue, but not engine.
The only ones that seems to do ok without dual injection are the ones keeping the intake values at 400C to burn those carbon off (i.e. Skyactiv G). Think of it as self cleaning oven temperature.
Dry ice is not needed if you are not worried about a bit of walnut residue like engine. Usually after walnut blasting they spray compress air and vacuum out the remaining media anyways. It is not sand and any tiny amount remaining would just burn up. I have seen people dry ice blast industrial equipment that can't tolerate any residue, but not engine.
There is no effective solution for DI only other than mechanical removal (walnut/safe media blasting). I had two DI only cars back in 06’, a FSI VW and a N54 BMW. You would think 20 years later we wouldn’t still be having the need for this discussion. There isn’t any easier or cheaper solution that works. Chemical solutions that actually touch the back of the valves (running anything thru the fuel system does nothing for obvious reasons) don’t remove ALL, if any, of the carbon. When you don’t remove all the carbon you merely leave a surface for more carbon to build up and carbon is going to build up and need servicing much earlier than had you done it the right way and walnut blasted the surfaces COMPLETELY clean. If you buy a DI vehicle without port injection BUDGET WALNUT BLASTING at least every 40-50k miles. For most people that’s about every 3 years of a few times over the time you keep a vehicle. If you could “occasionally” spray some potent chemical behind the valves or thru the fuel system do you think the manufacturers would have started adding cost reintroducing port injection to DI engines instead of just adding a factory maintenance service they could charge you for?
Does anyone have a dyno test before and after a walnut blasting session? If carbon was disruptive enough to require walnut blasting, the difference should show up. 
Heavily carboned valves should show up in the misfire counters even if you don’t have a misfire code. Would be interesting and very inexpensive to do a before and after on those.Does anyone have a dyno test before and after a walnut blasting session? If carbon was disruptive enough to require walnut blasting, the difference should show up.
Also I seriously doubt any OEM is going back to MPI.
No way of knowing. Every reason to believe it is occuring.
No clue what the SkyActiv-G runs the valves at, but I've seen plenty of evidence that at least the USDM ones (which runs a lower temp thermostat than the rest of the world) that carbon build up does happen with them anyway
Fuel has nothing to do with intake valves developing carbon on a GDI engine.
fuel detergents probably not but fuel octane can.
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