Background:
While working on a recent turbocharger swap, I examined my collection of diverter valve (DV) parts and noticed some unusual wear on the stock DV piston.
Compared to the new OEM DV that I have, this used one looks rough.
I do subject the part to higher temperatures than the stock setup generates.
As shown in the chart below from dyno testing, the stock setup’s peak air temperature leaving the turbocharger ranges from 250 to 275 degrees F. With the custom-tuned IS38, the peak air temperature is just short of 400 degrees.
Typically, I use a GFB DV+ T9381, which has a brass piston and a silicone seal.
I have used this primarily due to its low profile and performance, which has been indistinguishable from that of the stock DV.
Of course, now that we can see the wear the stock DV piston is presenting, the robustness of the T9381 is a compelling reason to continue using it.