Assessing Steering Feel And Flow Rate Adjustability With Turn One

Unquestionably, steering is one of the most important aspects of any motorsport, especially with road racing, and one of the key components in obtaining a tight steering feel with hydraulic steering is the power steering pump.

There are two main functions of the power steering pump: to provide a constant flow rate to the power steering rack, and provide enough pressure to assist the driver in overcoming steering loads. When input is applied through the steering wheel, the flow rate determines the sensitivity of the control valve in the steering rack. This means that a given flow rate will result in a given steering feel and performance. Adjusting the flow rate will alter the amount of input needed when turning the wheel.

Power steering pumps with different flow rates can be purchased or built. Turn One High Performance Steering Systems builds application-specific, and also offers a vari-flow valve that installs in place of the pump’s factory flow restrictor, which allows the flow rate to be adjusted via the turn of a knob. We reached out to Turn One for one of its power steering pumps with the vari-flow valve to install on a vehicle and test it out. We also talked with Junior Roethlisberger of Turn One about power steering pumps and vari-flow valves.

The Hardware

Turn One’s power steering pumps are not an updated design over the factory power steering pumps; they are cast aluminum factory units, with internals that are fully customized based on the customer’s application. This means that you can call Turn One, give them specifications, and they will build a pump specifically for your vehicle.

Thanks to Cunningham Motorsports in Murrieta, California, our install candidate is a Pro-Touring 1968 Pontiac Firebird with a LS3 engine and trans combo swapped in place of the factory unit. Turn One sent us its C5/C6 Corvette power steering pump with the adjustable vari-flow valve to install on the Firebird, which is great, because the accessory drive remained the same upon dropping the engine in.

“We use specially-designed internal components to achieve the reduced horsepower consumption and reduced fluid temperatures,” Roethlisberger explained. “Our pumps will save three horsepower on average. Coupled with the internal components, we set our pumps to 1,500 psi to handle the high wheel loads that auto-crossing and track use produce.”

Although Turn One builds GM Type II-style pumps for the LS engine line, they also build pumps for swapped vehicles (like our 1968 Firebird), and offer universal-mount pumps. If you choose to not buy a new power steering pump, you can send your factory power steering pump to Turn One and they will modify it for you. In addition to rebuilding power steering pumps, they can rebuild and upgrade most factory pumps for C4, C5, and C6 Corvettes.

“The unique part about our pumps is that we build them for high-performance use and base them off of our NASCAR pumps,” Roethlisberger added. “They will handle virtually anything you put them through.”

The vari-flow valve is a really neat component that can be installed to virtually any GM Type II power steering pump. Replacing the factory flow restrictor, the vari-flow valve allows the user to adjust steering feel at the wheel, without having to remove the pump or lines from the car, making it a breeze to calibrate the car’s steering for track days, as well as normal street driving.

The vari-flow valve allows for flow rate adjustments to be made in .5 gallon per minute increments in a range of .5 to 3 gpm,”  Roethlisberger explained. “The lower the flow rate, the stiffer the steering effort; the higher the flow rate, the lighter the steering effort.”

For easy adjustment, a knurled aluminum knob sits atop the valve, and has a positive detent feature to lock at any chosen flow rate setting. The vari-flow valve installs into the power steering pump with an AN-6 banjo fitting, meaning that it is 360 degree-clockable. Anyone who employs an LS engine with a Corvette accessory drive for duty can benefit from Turn One’s custom pumps, as well as the adjustability of the vari-flow valve.

Installation

As we aren’t installing the pump in a Corvette, but rather in an older LS-swapped 1968 Firebird, our installation procedure will be a little bit different. But since it does has a Corvette accessory drive, the pump will bolt up the same way as it would on a modern ‘Vette.

It should be noted that you don’t need to jack the car up, or get it on a lift, to perform the installation. To kick the install off with a bang, we removed the intake tube from the throttle body to free up space. Next, we loosened the tensioner pulley to create some slack in the belt so we could pop it off of the power steering pump pulley. Once the belt was out of the way, we unlatched the power steering fluid reservoir and backed the three bolts out of the power steering pump to free it. Another thing to note is that the car was already outfitted with an AN-6 line from the power steering pump to the steering rack.

With the pump and reservoir freed up, we proceeded with removing it from the car by disconnecting the AN-6 line that runs to the steering rack. After the pump was removed from the car, we removed the fluid reservoir from the pump by moving the spring clamp up the hose, and pulling the hose off of the outlet.

We sat the factory pump next to the upgraded Turn One pump after we got it out of the car to compare the two, and there’s really not much of an aesthetic difference. They are both GM Type II pumps, except the Turn One pump has a billet aluminum, black anodized pulley and vari-flow valve in place of the factory flow restrictor. The real difference is in the internal components.

From left to right: The AN-6 fitting attached, and the test-fitting of the pump with the vari-flow valve. No rubbing whatsoever!

When it came time to install the Turn One pump, we simply reversed the steps we used to remove the factory pump. First, we connected the AN-6 line to the vari-flow valve. Once the line was secured, we loosely fitted the pump back in its spot to see if the feed line would rub on the idler pulley directly next to it. It may look like it rubs in photos, but there is about 2 mm of clearance between the fitting and the pulley.

From left to right: Tightening the three bolts that hold the power steering pump in place, the fluid reservoir installed on the Turn One pump, and the belt re-installed.

With the fitting clearing the pulley, we tightened the three bolts that secure the pump to the accessory drive and torqued them to factory spec, which is 18 ft-lb After the bolts were tight, the power steering fluid reservoir was re-installed by attaching the hose to the outlet on the new pump, and sliding the reservoir into its mount. Next, we put the belt back on and tightened the tensioner pulley to secure it in place.

From left to right: Installing the intake tube, filling the fluid reservoir with fresh fluid, and the install was complete. Since you can't really see the upgraded pump and vari-flow valve with the hood popped, it's hard to tell anything has been swapped out in the first place.

After the belt was back in place, we installed the intake tube to the throttle body and secured the clamps. When all of the components we removed were back in their respective places, we added power steering fluid to the reservoir and proceeded to bleed the system. For those that haven’t bled a power steering system before, all there is to do is get the front wheels off of the ground, and cycle the steering wheel from lock to lock until there are no bubbles emerging in the reservoir.

“You can definitely feel the difference in the steering wheel with every move of the adjustment knob,” explained Mike Franz of Cunningham Motorsports. “The install went really smooth, and it’s nice to know that we can change the steering feel with the vari-flow valve for the different tracks that we attend.”

This photo was taken from under the car, and you can see that it’s not hard at all to reach the knob to adjust the flow rate.

From our point of view, the higher, softer settings would be great for a tight, technical autocross track so you won’t have to fight the wheel at every fast-approaching turn. In addition, the higher settings would inspire confidence on the longer sweeping tracks, like Buttonwillow. Ultimately, the driver’s preference will determine how they want steering to feel in certain environments.

Overall, the install of the pump went very smooth, and we’re pleased with how well it works with the vari-flow valve. It’s great to have adjustability of the steering system for any given racetrack or road condition. Don’t overlook Turn One when you’re looking to reinvigorate the steering on your vehicle!

Article Sources

About the author

Josh Kirsh

Born in Van Nuys, Raised in Murrieta, Joshua Kirsh is a SoCal Native. With a love for anything on wheels since the ripe young age of two, Joshua Managed to turn his love for automobiles into a career. As Power Automedia's newest writer, he plans to bring you some of the industry's hottest news topics while he's not out in the shop wrenching on some of our badass in-house project builds.
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