Originally Posted By: Mykl
badtlc, where did you get the pictures and info on that method?
In the past I've been skeptical of that because I wasn't convinced that running at high RPMs at cruising throttle would get enough heat into the valves. I'd like to read more about that particular experiment if there's more to read.
Start here:
http://www.google.com/patents/US6866031
The last 1/3rd is the most interesting.
here is the critical part:
"An additional approach for reducing the formation of carbon deposits on the intake valves 20 is to increase the intake valve temperature, at least temporarily, since, surprisingly, it was found that any carbon deposits possibly present are removed at temperatures above 380° C. To this end, the intake valve unit, which comprises, among other components, the intake valves 20 and the valve stem guide 28, is designed with means that hinder heat dissipation in such a way that increased surface temperatures of more than 380° C. develop at least in the area of the neck 68 of the intake valves 20 in at least one predetermined region of the load characteristic diagram 74 of the internal combustion engine. This is illustrated in FIG. 4. The intake valve temperature is above 380° C. in the shaded region 112 b of the characteristic diagram. At these temperatures, carbon deposits on the intake valves 20 are removed. This region 112 b of the characteristic diagram occurs, for example, at speeds over 3,000 rpm, and in that speed range. extends essentially to full load. Even if the internal combustion engine is not operated most of the time in the region 112 b during normal driving operation of a motor vehicle, nevertheless, carbon deposits that could adversely affect the operation of the internal combustion engine cannot build up, since their removal in the shaded region 112 b of the characteristic diagram occurs very quickly. For example, operation of the internal combustion engine in this region 112 b of the characteristic diagram for a period of, for example, 20 min., is sufficient to remove even a thick layer of carbon deposits. In other words, a routine expressway trip cleans the intake valves 20 sufficiently. In addition, this region of the characteristic diagram can be entered in the course of maintenance or repair work on the internal combustion engine in an automotive workshop."