High Pressure Cross Over Hose (HPX)
In a Power Stroke, the injectors are activated using high pressure oil delivered to them in two high pressure oil rails. During the firing order, there are times when each bank will fire two injectors in sequence, one after the other. On the driver side it is the two rear cylinders, #6 and #8, and the passenger side will see the same problem between #7 and #3. The first injector in sequence will fire with full oil pressure, but the second injector fires with a slightly lower oil pressure since the high pressure oil rail is in a low state when it starts injecting and has the lowest pressure dip as it uses up the available pressure remaining. At this time, the opposite side will experience a high-pressure spike because it is not firing at all. The High Pressure Crossover (HPX) hose will transfer fluid between the high-pressure oil rails.
As the HPX allows excess oil pressure to travel from one oil rail to the opposite oil rail supplying better pressure for the injector firing second in sequence, a beneficial side affect is that it equalizes the pressure between the rails. Since the ICP (Injection Control Pressure sensor) is located in the driver side rail when the two rails equalize in pressure it will have a more consistent reading to give the PCM (Powertrain Control Module).
In theory, it would be beneficial to have the driver side pressure delivered directly to the #8 injector and the passenger side to #3, but in practice it is not easily done. The port over the #8 injector is positioned under the turbo and there is not enough room to properly install a 90° fitting without removing the turbo. Plus, adding a 90° fitting increases resistance in the line, which lessens flow and builds heat. You would also increase the hose length that would also build resistance and heat, which would affect flow rate. It works out better to deliver more flow with a shorter, straighter routing than less flow to the perfect location.
Almost universally, everyone notices quieter injector operation at freeway speeds. You will not notice more horsepower from the driver seat, but some have also reported a smoother idle. What you experience individually will be highly dependent on the matching of your injectors and the condition of your high-pressure oil system. Some guys see a marked improvement, some a mild improvement. But, so far, everyone has liked it.
The main issue with the HX modification is the hose. Some kits are using hoses under rated in temperature, pressure, or undersized for the flow needed. A proper hose will have a pressure rating over 3500 psi operating since your oil rail pressures are normally 2800 psi +/- 500 psi with rare spikes up to 4000 psi, a temperature over 330° since the oil is not flowing through the hose and “pulses” back and forth between the heads, and be at least –06 in size to effectively flow the volume needed. The hose supplied with this kit is rated 4000 psi operating pressure, 400° temperature, and is –06 in size and couplers.
The Tymar HPX Kit comes with everything you need. (2) #5 boss 0-ring to #6 JIC oil rail fittings
(3 fittings for the 94-97 crowd), (2) 45° JIC fittings, and the properly rated high pressure hose.