There were a bunch of cases in the 1990s and early 2000s in which owners alleged that Ford’s cruise control was causing their cars to accelerate uncontrollably. Ford argued that its brakes could be used to overpower the engine such cases. Ford demonstrated this in a video that it used as evidence in many of those cases. I found this example of how Ford’s demonstration worked in an NBC news report about unintended acceleration.
Ford said it took 20 pounds of brake pedal pressure to stop the car. Note that the test begins with the car stopped and the car barely moving before the test driver applies the brakes. That is, the brakes don’t have to overcome any meaningful amount of inertia. I’m guessing that Ford used a car with brand new brakes and rotors. Thus, Ford is seems to be testing the brakes under the ideal circumstances to demonstrate whether the brakes will ever outpower the engine at wide open throttle. So yes, there are some circumstances when brakes on this particular car could outpower the engine.
But, consider if the car had been travelling at 50 mph and then opened to wide open throttle; the stopping distance would have been remarkably longer.
More importantly, video editing was Ford’s friend with this defense. Ford’s video did not include audio of the car’s test driver. After this test, the test driver reported the amount of force he applied against the brake pedal to stop the car (presumably based on a gauge measuring force at the pedal). At wide open throttle, the test driver reported pedal force at 175 pounds to stop the car.
Many drivers could not generate that amount of force. The amount of force required is probably increased in large measure because, at wide open throttle, engine vacuum is reduced and the power brake boosters are less effective. The mostly-elderly people who were major buyers of the Ford Crown Victorias and Mercury Grand Marquis that were having the problem would probably never be able to generate the kind of force necessary to stop the car under those conditions.
But, it gets worse in the real world. Stopping the car required the test driver to apply that amount of force almost instantly after moving off the line and when the car is barely moving (at maybe 5 mph?). Had the car already been at normal highway speeds, the test driver would have had to overcome all the cars inertia and the force of the engine simultaneously. This extended max-force brake application probably would have overheated the brakes, boiled the brake fluid, and caused complete brake failure while the car is still at wide open throttle. So, in the real world, brakes alone were not going to be enough to stop that car safely if, while moving at ordinary highway speeds, the car went to wide open throttle unexpectedly.
Brakes have gotten better over the years but cars have also gotten heavier and engines have gotten more powerful. I’m not sure how much better today’s cars would be at stopping under those same conditions.