It isn’t widely known that you can improve your feel for what you car is doing on the race track by tuning your power steering pump, but it is something that’s possible and many of the more savvy racers do it regularly.
Optimizing feel to the racer’s steering is a bewildering task for most of us. But KRC Power Steering has made it easy by introducing a range of replaceable flow control valves for their hydraulic steering pumps.
The flow control valves work similarly to jets in a carburetor. There are nine of them in varying sizes, and they can vary power steering fluid flow from four to 12 liters per minute, which is approximately one to three gallons. The largest orifice provides maximum steering assistance while the smallest provides maximum steering feel.
Though the standard KRC pump flows 8 liters per minute, by using flow control valves with larger orifices, those marked B, C, D, or E, the flow rate can be increased to 12 liters per minute (3.17gals) in one-liter increments. The higher letter indicates greater hydraulic assistance, but you get less feel through the steering wheel. In contrast, flow valves marked with numbers 4, 5, 6, and 7 provide less assistance; the lower the number, the greater the feel but the less assistance.
Momentary loss of power or “pump catch”
“From an engineering perspective it was such a tricky thing to get right,” says Roper. “The critical orifice is created in the -6 flow control valves and each valve is drilled undersize and then brought to the exact size by reaming. The difference in diameter between each orifice is a mere two-tenths of one millimeter (0.007 in), and each orifice is held to a tolerance of 0.0002 inch.” Such precision is necessary because while the steps between each flow control valve are just two-tenths of one millimeter (0.007 in), each one increases the flow rate by one liter of fluid per minute. Without maintaining these strict tolerances the technology won’t work. In fact, it was when KRC first experimented with tighter tolerances throughout the pump’s design that they discovered its fuller potential.
To the best of Roper’s knowledge the KRC pump is the only one that can be tuned this way for steering feel. “For years, most of our competitors have just modified OEM production power steering pumps,” he explains. But OEM pumps, by necessity, have relaxed tolerances to accommodate mass production and cost requirements. In contrast, KRC’s Flow Control Technology uses exacting tolerances that are impractical in the OEM environment. “Although several of our competitors have tried over the past 16 years to duplicate this process,” adds Roper, “it cannot be duplicated in mass-produced OEM pumps—that’s the difference between a $200 production pump and a $600 proper racing unit. Wide tolerances cause excessive internal leakage that makes it impossible to regulate the output flow of the OEM-style pump.”Source KRC Power Steering