Semi-active suspension, finally a soft riding good handling solution

[wibby]

All,

This spring I completed the installation of a custom built Tractive Suspension semi-active shock package on my MKIII. The ride quality improvement on my car with a 3-link rear and front and rear sway bars is significant and the system maintains good handling. The system offers 4 parameters that are adjusted with a touch screen or they can be adjusted with a remote knob (although that's a little tricky without the screen in view) which includes front stiffness, rear stiffness, pitch, and roll. I have the knob located on a pigtail wire that I can hide under the seat or rest and use near the shifter. The system also offers 5 user programmable memory presets. I mounted the touch screen in the trunk and the controller with the built in accelerometer behind the driver's seat (the wires exit the rear of the cockpit just above the rear left lower control arm). The system cost including 4 shocks, springs, controller, wiring harness, touch display, and shipping (excluding the 3% U.S. customs duty) was 5415 Euros (keep and eye on the exchange rate for USD). If you are interested in having a greater control of the shocks, DSC Sport offers a controller that will integrate to Tractive's shocks (no need for Tractive's controller or screen) and you can program a G table to fine tune the shocks which would probably be better for track use than Tractive's controller as DSC's solution allows the user to tune each shock individually for breaking while turning in or accelerating while turning out as well as accelerating, turning, and braking only. Tractive will sell the shocks separate. My goal was just to improve the ride quality on the street and the Tractive controller is a little less expensive than the DSC Sport controller. Attached are a few pictures. If you would like more information about the system feel free to reach out to Julian Van Dijken at Tractive Suspension (Please note that I am in no way affiliated with Tractive Suspension or Julian Van Dijken). One really nice thing about the shocks designed for my application is that they are all small body shocks and will fit on my car with 94 donor rear disk brakes without having to relocate the calipers to the front side of the rotor. They are all also the correct length and stroke, and properly limit the travel at full droop and compression.

The shocks have an internal servo controlled valve that actively controls the compression and rebound. The valve can react within 6ms.

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Wibby

[CraigS]

Very interesting. Can you show a pic of the shock unit pls?

[JohnK]

That's pretty cool. One thing I really like about my daily driver (MBZ) is the ability to switch to different driving modes (comfort, sport, sport+) simply by turning a small dial on the console. If you mounted the rotary dial on the dash, would this give you the ability to cycle through the memory presets you mentioned without having the touch screen in sight, or does this system not work that way?

[wibby]

It does work that way with one minor caveat, the rotary switch is also a push button, so I push the button to turn on the highlight, rotate that button to the thing that I want to change, or to a memory preset and then push the button to make the change or to use that memory preset. The caveat is that upon the initial key on and rotary button push, the highlighted item is the "pitch", I can then rotate the knob 2 clicks (the knob does click) and then push the knob again to engage memory preset #1. However, if I push the knob again (to turn the highlight back on), the "front" stiffness is highlighted, not the "pitch", so to go to preset #1 takes 4 clockwise rotary clicks instead of the previous 2. Hopefully they remedy this in later versions because it would be nice if the highlight always started at the front stiffness so the number of knob clicks to get to a predetermined preset is the same. Any subsequent knob activation will highlight "front" stiffness, so I have to ask myself, "is this the first time that I have activated the knob since I started the car?" If yes, then its 2 clicks to memory 1, if no, then its 4 clicks to memory 1. You can also use the knob to change the individual parameters, but without the screen it is extremely difficult to do. Honestly, I would rather the knob only work the presets and then use the screen to program the 5 presets. I will make this suggestion back to Tractive Suspension. The knob is wired to the screen, so the current version requires the screen to utilize the knob.

Wibby

[wibby]

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The shocks are controlled by a current loop. The wires come out at the bottom of the shock. I added loom and non-adhesive vinyl tape to the wires. Other than that, the shocks just look like normal small body shocks.

[wibby]

Here are the shock dyno graphs. These graphs are not necessarily what my shocks do with the current controller parameter ranges, but rather show the shock performance at minimum current to the servo (full hard, in orange or red), maximum current (full soft in blue), and mid-current graphs in green. The shocks can operate anywhere between the red (or orange) and blue lines. The first graph is the front shocks and the second is the rear shocks. You can see that the base valving is slightly different. The front is more digressive than the rear and the rear is more progressive than the front. Tractive can set the base valving how you want for your application. 127931127932

[wibby]

Julian from Tractive Suspension informed me that they offer a button that replaces the screen and know and allows for uses to navigate the memory presets only. The user would first program the shock parameters and presets with the screen and then unplug the screen and plug in the button. I'm considering putting Tractive shocks on my 33 and this could be a nice option.

Wibby