Many lament the phasing out of the simple Bowden cable-operated throttle. There is, after all, often an immense amount of gratification to be derived from what could feel like a direct, responsive link between driver and engine.
There are drawbacks to cable-operated throttles, though, many of which could ultimately annoy those not otherwise fussed by the perceived immediacy or purity of an engine's response to their inputs.
Firstly, there are problems with wear and improper adjustment, resulting in binding or partial throttle openings. There's also only so much you can do with a cable-actuated throttle. If you wanted to enable a traction or cruise control system, you'd have to add a motor- or vacuum-actuated module that would interact with the throttle body - increasing cost and complexity.
Then you have the issue of a physical connection between engine and pedal, along with a cable that runs through the bulkhead. This could, if you were focusing on refinement, induce NVH-related complications. Routing a cable and hooking it up adds several assembly steps on the production line, too, which could be a concern for those seeking the most streamlined production process possible.
The amount of throttle commanded by the driver might also not be ideal for the engine at that given moment. Allowing the engine to automatically modulate its throttle could help cut emissions in certain conditions, for example. This capability could further be used to help stabilise the engine's idle when it was undergoing heavy ancillary loads, or warming up, or serve as a form of speed regulation - instead of a spark- or fuel-cut limiter.
The way to overcome these problems is fairly obvious: ditch the physical connection between pedal and throttle. This move might have initially sounded questionable to some but the aerospace industry had comprehensively proven the potential of 'fly-by-wire' systems. Besides making the aircraft easier to pilot, the increased degree of control afforded by these electronic systems made them more flexible and capable - accomplishments that could be replicated in the automotive industry.
The concept of electronically actuating a throttle was itself not a particularly new one. Production cruise control systemsintroduced the late 1950s had utilised electric motors to adjust the throttle position in order to achieve and maintain the desired target speed, yet these setups still otherwise involved a physical connection between the pedal and throttle.
As demand for improved functionality and safety increased, additional systems were added - such as Bosch's 'Automatic Skid Regulation' traction control, which would override the driver's input and adjust the throttle position to reduce wheel spin. These, however, were again still cable-based setups.
It was Bosch that seemingly got ahead of the curve with the development of a production throttle control system that did away with cables; reputedly, it began trialling such a set-up in motorsports applications in the 1980s. Using an electronic system could potentially grant improved performance, or address design issues ranging from packaging problems to enabling functions such as traction control without bulky add-on units.
Bosch had long been supplying BMW with engine management systems, among other things, by this point. Then, in 1986, BMW unveiled its second-generation 7 Series - the E32. It was a remarkably advanced car, featuring a CAN bus, traction control, electronic damper control and common creature comforts such as cruise control.
The quest to build the ultimate luxury saloon didn't stop there, though, with BMW announcing a V12-engined flagship version that would be unveiled in March 1987. It would utilise the new 'M70' 5.0-litre V12, which was designed to be as smooth and as quiet as possible.
Achieving this would require precise control systems and, of course, it would be preferential to not clutter the top of the powerplant with servomotors and numerous awkwardly routed cables. To facilitate this, along with all the required driver aids, BMW equipped its advanced V12 with twin Bosch Motronic engine control systems - and a pair of Bosch-produced electronically controlled throttle bodies.
Each Motronic ECU controlled one bank of the V12, while throttle control and synchronisation was carried out by BMW's 'Electronic Power Regulation' system - or 'Elektronische Motorleistungsregelung', dubbed with the acronym EML. It would monitor the accelerator pedal position, process information from the Motronic units and safety systems, then deliver a signal to the throttle bodies that would move the throttle blades to the optimum position.
This meant that the EML could accurately control the engine speed based on a host of inputs, including temperature, air-con load and transmission modes. It could alter the idle speed by cracking the throttles open, work with the traction control system to cut wheel spin, comply with cruise control requests and limit maximum engine speed.
It also, for the first time in BMW's history, would automatically close down the throttles to limit the top-spec V12 7 Series to 155mph. Both banks could function independently, too, allowing the owner to continue driving if one bank suffered a fuel or ignition-related failure.
The M70 engine, which produced a silky 300hp and 332lb ft, went into the 750i and 750iL initially. It was then used in the 850i and 850Ci, and later revisions included Siemens throttle bodies with a dual-motor drive for redundancy. The expense and complication of 'throttle-by-wire' systems meant that they didn't suddenly dominate the market overnight, but BMW and Bosch's innovation drew much attention from rivals - including GM.
GM was so curious about this new technology that, in 1988, it bought a new 750iL and pulled the electronically throttled heart out of the $69,325 luxury saloon. It didn't just test it in the BMW and on the bench, though; the V12 ended up in a Chevrolet Caprice, which GM used to further evaluate this new 'drive-by-wire' technology.
It took until 1997, and the public release of the new Corvette C5, for GM to emulate BMW's configuration in production form. The new Corvette's LS1 V8 was equipped with 'Electronic Throttle Control', which enabled the integration of traction control, cruise control and more into a compact, lightweight assembly. It was also cited to improve the engine's response and performance, further bolstering the system's credentials.
As the cost of the required components fell, and the need for more comfort and safety functions rose, the use of throttle-by-wire systems began to increase exponentially. Careful pedal calibration could also deliver the ideal amount of resistance and predictable throttle behaviour; this, in conjunction with advances such as different accelerator pedal maps depending on drive mode or gear, could grant an engine response that would sate even the most enthusiastic driver.
You don't, for example, hear many complaining about the responsiveness of the Ferrari 458 Speciale's electronically throttled 4.5-litre V8. That said, some manufacturers sometimes entirely misjudge their pedal calibration - resulting in myriad mildly annoyed motorists.
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