DI
DI turns up in 2 fields: heat treating, automotive. Here is what it means to the people in each one.
DI in heat treating
Ideal critical diameter: the largest bar that would reach 50 percent martensite at its center in a perfect quench.
Ideal critical diameter, the size of round bar that would reach 50 percent martensite at its center if its surface cooled instantly (a quench severity H of infinity). It is calculated from chemistry and grain size using a multiplying factor for each alloying element, so metallurgists can compare steels and heat lots on one number. Real quenches are slower, so the actual critical diameter in oil or water is always smaller than the DI.
"This heat calcs out at a DI of 3.2, that's the low end for 4140, watch the cores on the big shafts."
DI in automotive
Direct injection is a system that delivers fuel directly into the engine's combustion chambers.
Direct Injection (DI) refers to high-pressure fuel systems that bypass the intake tract and spray fuel directly into the cylinder. Operating at pressures often exceeding 2,000 psi, DI systems atomize fuel perfectly for a cleaner, more efficient burn. While it maximizes power and efficiency, it often leads to carbon buildup on the intake valves since they are no longer washed by fuel.
"The high-pressure fuel pump on these DI engines tends to fail and dump gas straight into the crankcase."