2012 Mazda 3: An Additional Note About The Steering Type
May 10, 2012
I happened to be looking at one of our earlier posts (Steering Ahead of the Rest) and noticed a couple late comments. Specifically, they called out that the Mazda 3 has hydraulic steering but with an electrically driven pump, not pure electric power steering as originally described.
Well, they're right.
The 3 does indeed have a steering rack that is powered hydraulically with an electric pump. This is what is described as electro-hydraulic power assist (EHPAS). (A traditional steering setup would have an engine belt-driven pump.) Pop the hood and you can see that the 3 has a power steering fluid reservoir and lines that run from the pump to the steering rack.
According to our resident wonk, Dan Edmunds, there are two types of EHPAS. He wrote to me:
"There are two kinds of "electric over hydraulic." On type uses a constant-flow belt-driven pump. Full flow is used in parking situations, and at higher speeds a bypass valve siphons off a portion of the flow so less assist is generated (and more feel) at higher speeds. This would more accurately be described as electronically controlled power steering, or ECPS. Because it has a belt-driven pump, many dont consider it true electric. But Hyundai and Kia did promote it as such about 10 years ago.
"Another type -- and what's on the Mazda 3 -- uses a hydraulic pump driven by an electric motor, the output of which is managed by an ECU to create differing levels of assist.
"True EPS -- which the Mazda 3 is not -- has no pump or hoses. The motor can by located in more than one location, so EPS itself can be broken down to column-mount and rack-mount (sometimes called dual pinion) varieties.
But with any electric assist steering, the ECU and software are crucial to [steering feedback] success."
As such, I'd say the content of that original post -- that Mazda did a nice job tuning the 3's electric steering -- is still valid, even if the actual technical description isn't quite right.
Brent Romans, Senior Automotive Editor