Fire gear on…
I’ve known about the switch in a 153 and the reported ability to soft switch a 173 (or later) for a long time. But I have studiously avoided mentioning it (or playing with it) because I think that would not be in line with the spirit of the class. And there are other ways to cheat that won’t be caught unless the inspector knows exactly where to look. And if done correctly won’t be caught by a dyno session.
In one sense this is a case where a MegaSquirt with a “standard tune” and data logs could potentially level the playing field with respect to the engine management system. All it takes is a laptop to download the tune and run an md5sum to tell if the tune is “standard”. A peek at the data logs will tell if sensor inputs have been fiddled with.
But really, if the engine is actually legal a proper tune has an upper limit that anyone can reach. And pretty economically. We are racers and want to get the most out of what we are allowed to run. And for the most part we are talking about 20’sh year old sensors and electronics. Fiddling with the parts used can have a noticeable affect on performance. It makes more sense to me (and is probably cheaper) to allow folks to tweak the tune.
Now back to our regularly scheduled programming…