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Electronic Trans Controllers - Part One

Aftermarket auto transmission controllers

By Michael Knowling

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At a glance...

  • First of two-part series
  • Basics of electronic-controlled transmission operation
  • The first in our selection of aftermarket transmission controllers
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Most car enthusiasts are pretty comfortable with the idea of rewriting management software or adding electronic modules to alter control of the engine. But electronic modification of auto transmissions? Uh-oh!

In this article we’ll introduce you to the world of aftermarket controllers that are designed for use with late-model electronic-controlled automatic transmissions.

But, first, let’s run through a quick run-down on how an auto transmission works.

Electronic-Controlled Transmissions – How they Work...

The operating principles of automatic transmissions have remained essentially unchanged for decades (with the exception of CVTs).

There are two main sections of an automatic transmission – the hydraulically-controlled planetary gear unit and torque converter.

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In older-style transmissions, the planetary gears are controlled by a valve body which relies on changing fluid pressure. Fluid pressure is controlled primarily on the basis of road speed and throttle position - this diagram shows how these two variables oppose each other from opposite sides of a spool valve. Movement of this spool valve directs fluid to a specific planetary gear control clutch and/or band, so controlling gear changes. A separate kickdown mechanism and P-R-N-D-L manual control valve are also necessary for complete transmission operation.

The automatic transmission is mated to the engine using a fluid coupling known as a torque converter. The engine drives an impeller to produce energy in the hydraulic fluid while a turbine (connected to the transmission) converts this hydraulic energy into mechanical force. When required, the torque converter also allows a considerable amount of slip between the engine and transmission. This allows the car to come to a stop without stalling and multiplies applied torque when accelerating (because the engine can turn faster than the transmission). The amount of torque converter slip varies at different rpm and, unless there’s a lock-up mechanism, there will always be some degree of slip.  

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As early-generation electronic transmissions were introduced, it became common to use electronic control for secondary functions - such as kickdown and torque converter lock-up. The torque converter lock-up mechanism (aka torque converter clutch) is used to improve engine efficiency and fuel consumption at cruise. In this situation, the impeller and turbine sides of the torque converter are locked together to eliminate slip.

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Today, automatic transmissions have evolved further to incorporate full electronic control. The vehicle’s transmission computer (which is now typically integrated into the main ECU) controls a set of solenoids to control fluid pressure and, as a result, gear change characteristics. Up to 14 inputs are used to determine shift properties and sometimes six solenoids are controlled by the transmission control unit. Note that hydraulics are still used to apply the clutches and bands that trigger a gear change – the electronic part of the system is used only for control.

Powertrain Control Solutions Universal Transmission Controller

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The Powertain Control Solutions (PCS) Universal Transmission Controller is a highly sophisticated stand-alone aftermarket transmission computer.

The US-built PCS Controller is programmed using a Windows interface with the availability of up to 16 digital inputs, six analogue inputs, two temperature inputs and four speed inputs. In most instances, the controller is programmed on the relationship between road speed, engine load, engine rpm and throttle position.

The PCS Transmission Controller offers programmable shift points, selectable shift modes (power, towing and economy), six pulse-width modulated outputs, six digital driver outputs (ideal for engaging a lock-up torque converter), four frequency outputs (including one for speedometer drive) and a data logging capability. It can also be configured to work with separately available paddle-style shifters.

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All electronic components in the PCS Controller are suitable for automotive application and a weather-sealed plastic connector is built into the case. The PCS Controller is claimed to control every type of electronic transmission from Ford, Nissan, GM, Toyota , Mazda, Chrysler and many other manufacturers. Note that the company is also interested in developing the Controller to suit currently unsupported transmissions.

Cost is around US$700 plus the necessary wiring harness (which typically cost US$150).

See http://www.powertraincontrolsolutions.com or www.transmissioncontroller.com for more.

Baumannator TCS

The Baumannator TCS electronic trans control is designed for use with the Ford AOD-E/4R70W and E4OD transmission (as used in post ’98 light trucks and Mustangs up to mid ‘90s). It is hoped that more transmissions will be supported in the future.

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Fitment of this stand-alone unit gives complete electronic transmission control and allows you to install either of these Ford transmissions into custom built vehicles. A throttle position sensor can be added when using the Baumannator TCS behind a carby engine.

The micro-processor based controller is tuned via Windows-based software to control shift pattern on the basis of road speed, throttle position and other inputs. The line pressure curve (versus load) can also be tuned to improve the torque capacity of the transmission and part-throttle shift firmness. Torque converter clutch operation is also adjustable on the basis of throttle angle and road speed.

Two different sets of calibration data can be stored into the Baumannator to give on-the-fly adjustment and there’s the option of sequential-style gear operation using OE cruise control switches.

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In addition to enabling fitment of the Ford AOD-E/4R70W and E4OD transmissions into custom-built vehicles, the Baumannator can also be integrated into the wiring loom of vehicles that are factory equipped with these trannies. The system has a reputation for being very easy to wire and tune.

The system retails for US$425 or US$550 including harness.

See http://www.becontrols.com/ for details.

Compushift

Compushift is another US-based product that’s designed to control popular Ford and GM transmissions. We believe that they support the GM 4L60/65 transmissions used in various Holden vehicles. The Compushift is supplied with a harness and throttle position sensor to enable transmission installation into any vehicle.

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Designed by HGM Automotive Electronics, the Compushift uses a digital processor that is delivered with predetermined programming. If required, simple changes to the program can be made with screwdriver adjustment. There is no PC or laptop interface.

The Compushift controls six shift solenoids and torque converter lock-up is user-adjustable based on road speed, rpm or gear. A backlit LCD display unit/programmer is also available as an option – this shows transmission temperature, hydraulic pressure, gear position, torque converter lock-up and throttle position. It also functions as tachometer, speedo, stopwatch and rolling dynamometer.

The components are contained in a powder-coated aluminium box with mounting flanges and features automatic protection against failed solenoids and over-temperature.

Cost is US$1185.

See http://www.compushift.com/compushift.htm

TCI Automotive TCU

Here’s another US-based stand-alone trans controller. At this stage, the TCU supports GM 4L60E and 4L80E transmissions with the Ford products yet to come.

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Using the TCU (Transmission Control Unit) and T-Com WP software, the user can program line pressures, shift timing and shift firmness. Tuning is quick and simple – initial calibration requires only basic information on tyre size, gear ratio and transmission type. After this information is entered you’re ready to program the shift data.

The TCU incorporates a waterproof case, complete wiring harness, T-Com WP software, instructions and a laptop connection cable. Adapters are available for fitment to carby engines.

Prices range up to around US$900 - visit http://www.tciauto.com/tci.htm for details.

Stick around for Part Two (the final) of this series – there are a bunch of other aftermarket controllers to check out!

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