The best way to lock out tuners would be for the stock ECU to provide as much power as possible.
Although with turbocharged engines, you can turn the power up to the point where longevity goes way down. Still, you could give people a power limit knob they could turn at their own risk to have access to the whole Pareto frontier of performance and longevity. That'd leave no room for tuners.
Giving users a knob that essentially amounts to "reduce the life of your engine" is a terrible idea. Most people are SUPER ignorant about their vehicles and would be pissed when their turbo died early because they assumed a higher number on that scale was better without trying to figure out what it is.
There are at least two problems with this. First, the history of tuning suggests there is no level of stock performance that enthusiasts will be happy with. They will always want more than the OEM provides.
Secondly, there’s a reason you see this with EVs (Tesla’s “ludicrous speed” mode) but not ICE cars apart from “sport modes” and the like: the ICE cars can’t be offered with the knob you suggest, because the car has to meet emissions requirements at any tuning level, and any level of tuning is going to have a performance/emissions trade-off.
Emissions are tested on a standardized driving cycle that doesn't include full-throttle acceleration, so emissions at full throttle aren't counted. Which is reasonable: high-performance cars spend only a tiny fraction of their time at full throttle so it doesn't contribute much to overall emissions.
> Emissions are tested on a standardized driving cycle that doesn't include full-throttle acceleration
Depends on the car. See Supplemental Federal Test Procedure US06[0], required by the EPA for light-duty vehicle certification since 2007.
It is also largely irrelevant in the real world: nobody is going to tune a car to have mediocre part-throttle performance but then go all-out on full-throttle.
It has a 10 second 0-50 mph section, which for the kinds of cars we're talking about (those that people might buy aftermarket performance ECUs for) isn't close to full throttle.
Although with turbocharged engines, you can turn the power up to the point where longevity goes way down. Still, you could give people a power limit knob they could turn at their own risk to have access to the whole Pareto frontier of performance and longevity. That'd leave no room for tuners.