Question: How do you get consistency in an ET bracket drag racer with fuel injection?
Answer: A consistent racecar setup is probably as difficult to do as other performance goals such as all out performance in open ended racing classses. In our ET bracket case, we worked towards a LINEAR setup. That result is one in which the shift point determined the ET. A higher shift point results in a faster ET, and a lower shift point results in a slower ET, and in a relatively proportional manner. With this setup, our life became simple. That is not always the case in many combinations. Many are not linear. I often see race vehicles where the shift point is not known or it is changed with unpredictable ET results. In our case, our fuel injection high speed bypass opening was conflicting with our shift point. Changing only the main bypass jet caused a whole lot of changes to the setup: different air to fuel ratio, different system pressure, different high speed opening point, different ET, etc. Fuel Injection Racing Secrets describes a lot of what we did to sort out those variables. And that is where tuning fuel injection got to be a lot of fun. With that knowledge, it becomes interesting and customized to the individual tuner and race vehicle as well.
FOOTNOTE: A linear setup involves building and engine that does not push the design limit of its components. Fore example, the intake and exhaust flow are not pushed to the limit. When either one is at the limit, pushing the engine power further up with engine speed often becomes non-linear. That is it noses over at higher speeds. Modulating the ET with engine speed becomes difficult.