In the past 10 years or so, electric power assisted steering (EPAS) has gone from a newfangled thing to commonplace on new cars. More and more cars have begun adopting it thanks in large part to the Energy Independence and Security Act of 2007, which bumped Corporate Average Fuel Economy (CAFE) requirements (the average fuel economy of an automaker’s passenger cars) up to 35 mpg by 2020. Among other things, this mandate made engineers take a hard look at what could be done to increase efficiency and reduce unnecessary parasitic drag on drivetrains. One of the most obvious sources was the ever present and ever-turning power steering pump.
So, as hot rodders and racers, do we care about innovations spurred by CAFE regulations? When it comes to EPAS, the impetus might have been increasing MPG, but as we’ve learned through this series, removing parasitic drag also has the potential to increase usable horsepower, performance, and reliability. Let’s dig a little into why this is a win-win scenario for efficiency, driver experience, and power.
To begin, most factory hydraulic power steering pumps are not designed for high-performance use. They’re intended to reduce effort in standard street driving scenarios, so they must provide adequate pressure and flow not only when driving at highway speed, but also when the engine is idling and maneuvering at parking lot speeds or stopped.
The vast majority of hydraulic power steering pumps operate in a linear fashion, which means they move more fluid the faster they turn. When the engine is operating at higher rpm, such as on a race track, that usually means they’re pushing more fluid than is required. The GM Type II power steering pump on LS engines, for example, has a roughly 15 percent overdrive pulley, which means the power steering pump is turning 15 percent higher rpm than the crank speed to ensure there is sufficient pressure and volume at idle. Of course, this also means the pump is spinning 15 percent faster at all engine speeds, so at 6,500 rpm, the pump is turning just under 7,500 rpm. Not a big deal for street cars that spend most of their life below 4,000 rpm, but the picture is different at higher rpm.
So, what does this look like in terms of parasitic loss? Well, a nice race modified Type II pump might only require 3 to 5 hp at 6,500 rpm, but a factory pump at the same speed can require 7 to 10+ hp. If you’re a vintage muscle car lover running an old Saginaw pump, the numbers could be roughly double that. We’re not picking on the GM Type II here, this is a common scenario for most street cars with hydraulic power steering, even performance-based ones.
The excess fluid volume produced is internally bypassed inside the power steering pump, which translates into not only wasted power from the engine, but also increased heat absorbed by the fluid. While stock power steering systems operate around 200 to 225 degrees F, in autocross and track day situations, fluid temps can easily exceed 300 degrees F. That can result in increased wear and pump failures if you’re seeing those temps regularly or for extended periods. We’ve seen a lot of power steering fluid puddles under cars on warm track days.
Some of these deficiencies can be addressed by using an undersized pulley (1:1 ratio or lower) that slows the pump down so that it’s flowing less at high rpm. While that may work well for a pure track car, heat will likely still be an issue requiring external coolers to compensate. And any low-speed driving will be substantially more laborious. This is where EPAS shines. If you do it right, you get the right amount of boost regardless of engine speed, zero parasitic drag, no heat issues, and increased tire feedback.
Good thing for us, S197 Mustangs made the switch more than a decade ago.
For older many cars, an EPAS swap means installing an aftermarket kit or finding something from a different make and model that you can adapt. Fortunately for us, when the S197 Mustang got a major facelift and the new Coyote 5.0 engine in 2011, it also received EPAS, which makes this swap a whole lot easier. Now for most street cars, the stock Mustang GT rack from 2011-14 will work fine, so we’ll preface this tech article by saying that if you’re looking for a budget EPAS swap on your 3V Mustang, and you don’t track your car on sticky tires, and your front suspension is stock or only mildly modified, you can opt to use one of these. The downside is that you will lose the ability to select from the factory calibration modes and it’s unclear what the default setting will be (comfort, sport, or something else). Our intent for our project is much more track focused, and we want a calibration that is designed to handle any level of suspension or tire upgrades, so we’ll be using Ford Racing’s Boss 302R rack.
The main reason to opt for the Boss 302R rack is that it will not fall prey to the steering shutter and Electronic Stability Control (ESC) intervention that occurs when street calibration racks are paired with aftermarket control arms, stiffer control arm bushings, and/or wide sticky front tires. The results can be pretty scary and fairly random, so certainly not something you want to experience while on track. Though these issues can happen to any factory S197 GT, they are most reported with 2011 and 2012 model year cars. Model year 2013-14 cars seem to be less susceptible, and there is a rumor that street version of Boss 302 doesn’t fall prey to these issues because it runs a calibration that is more track focused.
In any case, for those who love road racing, the Boss 302R rack is the go-to upgrade. Thanks to specific calibration intended for racing, there is better feedback that allows you feel exactly how the front tires are reacting. If you have a 2011-14 car, this is an easy plug and play swap with no issue. Swapping the 302R EPAS into a 4.6 3V powered car requires a little more work since they used traditional hydraulic assist pumps and do not have a CAN Bus interface to power up the rack, but there is a way around that! Let’s dig into how to make it happen.
Christopher Campbell has been heavily involved in the automotive world since he began building his first car, a 1967 Ford Ranchero, with his dad at the age of 14. That started a lifelong passion with custom hot rods and muscle cars. After graduating from Cal State Long Beach, he went to work for HOT ROD magazine as Associate Editor. From there he became Technical Editor at Popular Hot Rodding magazine. Currently he creates freelance content for OnAllCylinders as well as many diverse enthusiast magazine titles such as HOT ROD, Muscle Mustangs and Fast Fords, Mopar Muscle, Super Chevy, Mustang Monthly, and 8-Lug.