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Walnut Blasting Intake Valves - 2016+ SKYACTIV-G ND MX-5 Miata

We have a fair bit of experience with the carbon buildup problems of Direct Injection systems in other platforms, we had always been curious if Mazda had come up with any interesting solutions to combat the carbon buildup that happens on the intake valves and intake tract. Excessive carbon buildup can cause poor sealing, hesitation, poor idle, etc. 

When we cracked everything open for the Edelbrock E-Force Supercharger Install, we were eager to see what we would find. The answer to our question was...nope. Our shop ND only has 19,000 miles on the clock and we were a bit surprised at what we found.

Initial Inspection

There were various levels of carbon buildup but cylinder 1 was the worst. The buildup accumulates along the intake tract and on the valves themselves. 

Since everything was already out we decided it was a good time to walnut blast the intake tract and valves.

Walnut Blasting

The walnut blasting procedure involves using a media blaster to break down and remove the carbon from the walls of the intake tract and the valves. Crushed walnut shells hit the carbon buildup at high speeds, breaking it down and removing it from the affected areas. It's tough enough to eat through the buildup, but at the same time, it is soft enough to not damage any of the metal. This makes it the ideal material for this job.


This is one of the valves in cylinder 1 again after cleaning. Valves and tract are now free of buildup.

Cleaning success! Definitely worth doing while everything is already out for the Edelbrock E-force. At 19k miles, our car was a bit gunked up but probably not enough to make problems quite yet, so we would probably recommend doing this service around the 30k mark. 


Keywords: carbon buildup, miata, nd, skyactiv-g, 2016, walnut blasting, intake valve cleaning, maintenance, mx-5, edelbrock supercharger, turbo

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1 comment

  • Ray

    Very informative. Mazda has always said they’ve solved the carbon build up issue by reducing bypass and controlling valve temperature by re-routing coolant away from the valves so that the valve can get up to 400 degrees (preventing build-up). The fact of the matter is that gasoline never get sprayed on the back of the valves. There’s just no way getting around that.

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