Overview

Most modern cars have some sort of traction control - even the Jetta Sportwagen with a diesel engine has it!  That's because it has proven to be an inexpensive boon to safety.  In motorsports applications, it is also well-known to improve performance. 

Traction control is part of every modern sports car as well, for both safety and liability reasons, but also because it makes fast cars easier, and hence safer, to drive- even for professionals.  It's so helpful, that it was thought to be making Formula 1 cars too easy to drive, and subsequently banned in competition.  It's also banned in many forms of motorsports (and often snuck in for the performance benefits it provides).

The factory race SL-C that won a National Championship did so while racing in the rain- with a Racelogic Traction control system that helped put down power in damp conditions.Not an SL-C, but don't be this guy

If even the best pro drivers want traction control on their race cars, it's clear that it makes sense for SL-Cs, even those driven on the street.  It only takes one lurid slide on a damp corner (or a dry one, with leaves on it) to wipe out a corner of the car, or worse.  So traction control for the SL-C is generally a Very Good Idea.  Your right foot is never as fast as the engine controller! 

Wheel Speed Sensors

Whichever TC system you select, the SL-C will need wheel sensors.  At a minimum, any serious TC system will require that you fit four wheel speed sensors which typically involves fabricating brackets and adjusting the sensor gap to the rotating object from which wheel speed will be captured. 

The traction control system will have a minimum and maximum number of pulses per wheel revolution with the higher number always being more granular, and preferred. For example, the Racelogic unit supports 4 to 80 pulses per wheel revolution. The method used to locate and trigger the wheel speed sensors is absolutely critical. You can have a different number of pulses per revolution between the front and rear wheels in some cases like Racelogic, but in most cases, both front wheels must have the same number of pulses and both rear wheels must have the same number of pulses.

The typical approach for the SL-C is to install the dedicated Hall Effect sensors from Racelogic (part# TCWSSSET) to read the back of the wheel studs on the fronts,  and get a custom "cog" from The Driveshaft Shop to press fit over the half shafts on the rears for the rear sensors.  Those cars that fit two-piece rotors can also count the back of the rotor fixing bolts for more resolution than is available just counting the back of the wheel studs.

Programming and Advanced Features

Most systems, like the racelogic system, offer some advanced features including adjustable slip (i.e., degree of oversteer), launch control and full throttle shift. These can be very useful, and are typically configured through external software on a laptop or dedicated tuner  connected to the ECU via a USB or serial port.

Be sure to validate that the system you choose has the exact features you need, and don't rely on sales staff alone to make the decision about which system to select.  This is a difficult thing to undo once selected, so be sure that you are satisfied with every feature, and how it is implemented.

Sources

The following sources provide traction control systems that can be integrated with the SL-C (see below for more detail):

  • Racelogic (most popular for SL-Cs)
  • Holley
  • Motec 
  • Megasquirt 

Racelogic

The most popular standalone traction control system for the SL-C is the system from Racelogic.  If you are using the GMPP controller setup, this is the easiest way to go.  It has several options, including the default button-based control for managing the degree of tire slip and launch control, as well as a digital adjuster that permits fine-grained adjustment and a small display of certain parameters.  It's suited for race or street applications, and is reliable and proven to work well with the GM controllers that most SL-Cs use.

Here is a quote from their web site:

Once you have driven a powerful car with RACELOGIC Traction Control, you will never want to be without it.
  • In a rear wheel drive car you can use full throttle around a corner with greater confidence that the rear end isn't going to suddenly break away.
  • In a front wheel drive vehicle push-on understeer is cured, with the system setting the correct level of power to finely balance the vehicle.
  • In wet and slippery conditions the car accelerates as fast as grip allows without skidding all over the road.
 It does not only positively enhance the performance of the vehicle, RACELOGIC Traction Control also dramatically reduces the chances of an accident. This is why companies like Gumpert and Koenigsegg choose to fit our system into their cars.

This system controls slip by the safe method of completely cutting out fuel injector pulses in a random order when slip is detected.  This is much safer than retarding timing, or varying the duty cycle of injectors, which could cause a lean condition and engine damage.

The Racelogic system can use either existing ABS tone rings or dedicated sensors to detect wheel movement. The corresponding Racelogic ECU  must be specified in advance based on the sensor type you elect to use, as the two ECUs are not the same and cannot be upgraded or traded to get the other version.  In most all cases, the SL-C will use the separate sensor approach, as there are no ABS tone rings for the rear, and the front ones are very hard to access.

In late 2015, Racelogic discontinued sales of their traction control product.  Support is still available, but there are apparently no more new units available.  The discussion below is left for historical purposes.

Racelogic Installation

Installation requires mounting the dedicated ECU, providing switched power to it, and modifying the GM engine harness to wire the system into the injectors.  You also need to fabricate brackets for the wheel sensors, and mount them.

This is conceptually simple, but requires some skills, and should be left to someone who is competent on automotive electrical systems.

Basic setup can be done with the digital adjuster alone, but more advanced setup can be done with a connected PC.  The RL system comes with software to download to easily setup and monitor the system.

The installation manual can be downloaded from the RL site here.

One builder (Ken) installed the RL TC system on his SL-C and fabricated brackets from aluminum angle to hold the wheel speed sensors from RL.  Here are a couple of pics that show the details of his very sanitary install.

This picture shows the bracket and sensor for the front wheel.

This pic shows the raw brackets for the front wheels:

Here's another picture of the front suspension and sensor:

The rear sensors aren't actually mounted on the wheels at all, but on tone rings from The Driveshaft Shop that fit over the CVs.  A simple, elegant solution.  Note the simple but elegant bracket this builder crafted.  These tone rings don't have a part number, but cost about $50 each from The Driveshaft Shop- call them and let them know the application is for the 930 CVs on axles they provide for the Superlite SL-C.

Be sure that when you run your lines to not have them parallel to high frequency or high power lines.  Always cross those lines at right angles if they must be crossed at all.  If you are having erratic readings on the wheel speed sensors (something you can detect on the digital adjuster or oi the software, it's probably because the sensor distance from the bolt or stud varies, or there is interference from other power lines.  

The digital adapter on the left can be in silver (as shown) or black.  It can be mounted anywhere in reach and in view.  The ECU is pictured on the right.

The standard "button" control looks like this:

Racelogic: Ordering the Correct RL system

There are many variations for the RL TC system, and it's easy to be confused.  Essentially, you need to order the following part numbers for V8-powered SL-Cs:

Description  Part Number  Notes 
Adjustable Traction Control (8 Cyl) + Launch Control + Data Logging + Digital Adjuster (TCWSSSET required)  RLTC8DIAW  Use this number if you want an included digital adjuster. Specify color, silver or black. 
Adjustable Traction Control (8 Cyl) + Launch Control + Data Logging + (TCWSSSET required)  RLTC8ALWD  Use this WITHOUT the digital adjuster, but with the standard button control. 
Black Digital Adjuster  TCDIABLK  Included with RLTC8DIAW, but available if you decide to upgrade to a digital adjuster later. This one in black , though silver is also available with part number TCDIA.
Set of 4 Wheel Speed Sensors   TCWSSSET  Needed for the SL-C in almost all cases, and compatible with RLTC8DIAW. 
Full Throttle Shift Upgrade for all systems  TCCLUSHIFT  Optional system allows full-throttle upshifts. Requires a clutch switch (so plan ahead when you are in the pedal area) 

 This chart assumes you want the digital adjuster- most everyone does.  If you don't, you can select part number RLTC8ALWD and you will get the button-style adjuster.  You still need the wheel sensors, of course.

There are a few distributors of RL products in the USA. RL keeps a current distributor list here

Holley

Holley offers a complete engine control system that includes a traction control capability.  Using technology from Davis Technologies, a well-known provider of concealed traction control for race applications, the system gently ramps down power when slip is detected, and allows power to build back up when traction is resumed.  

The advantage of this approach is that the integration is tighter, and so can theoretically be managed more tightly through a common interface.  Holley also notes that the total expense of their integrated system is likely to be lower than purchasing standalone engine control and traction control products.

This TC system is designed to be run with the Holley Dominator or Holley HP systems only.

Motec

This is the high-priced spread, as most everyone knows.  Motec offers race-quality products that are used everywhere in top-level motorsports for engine control, power distribution and dash displays.  The advantages to this line include an extremely wide product range, a well-proven support infrastructure, extreme standards for reliability, and deep integration with every part of the car, including telemetry.

The single disadvantage is that the products are priced for the professional race teams, and by "normal" standards, are eye-wateringly expensive to buy, install and configure.  You'll nearly always need a pro to select, install and configure these systems.

Traction control is offered as a module in the engine control line.  Here's a fragment of the discussion on their web site about implementing TC:

"There are several ways to utilize Traction Control. Ultimately we need at least 2 inputs for wheel speed connected to the ECU. We can either run these 2 inputs directly to the 2 digital inputs the ECU has or we can use a Traction Control Multiplexer (M TCMUX). The TC MUX allows up to 4 wheel speed channels to be sent to the ECU using only 1 ECU input channel. This allows better sensing signals and allows the additional switched input to the ECU to be used for a separate function as desired.

The TC MUX requires 8 V and 0 V supply from the ECU and its output is connected to the ECU's Digital Input 1 or 2. Then the Hall Effect Sensors can be connected to the TC MUX directly and they can measure wheel speed or shaft speed. The Sensors do not require a magnet to trigger so they can be easily adapted to read the bolts holding a sprocket or a brake rotor. For the best results especially at low speeds, a minimum of 12 teeth per revolution is desired."

It should be obvious that this is not for the casual user.  It's the way forward if you are running a 911 GT3 Cup car or the SL-C in a pro race  series, though.  

Megasquirt

Megasquirt is an extremely popular engine control system that is open source, and supported and used by a wide range of people around the world.  It has deep home-brew roots, and was formerly sold only as a kit- you had to actually solder in the components on a circuit board.  Those days are long past, with the availability of pre-built and tested boards, and even harnesses for popular engines.

Users have reported that they have successfully implemented traction control using the latest versions of Megasquirt, though checking for your engine combo is always a good idea before committing to the MS approach.

This is your solution if you want to do everything on your own, aren't afraid of wiring and electronics, want to tune your engine by yourself, and want to spend the absolute least amount in hardware.  You'll have a lot of company, and base maps are available for many popular engines to get your engine tuning started.

Others

There are many other solutions for traction control that are either integrated with the proffered engine control systems, or as standalone units.   If you select one of these or other vendors for your engine management needs, check into the options for traction control as well.

Pricing and Availability

Eric T has made up a document with sources and prices for some of the popular engine management and traction control options.  You can download it by clicking here.