Believe it or not, the adjustable rising rate FPR (FMU) was originally specified for supercharged applications and not turbocharged. The adjustable rising rate FPR can be used for turbocharged applications, but one has to be careful because the turbocharger has different part throttle (vacuum) airflow characteristics depending on the gear chosen and the load. For example, at a few mm hg the volumetric efficiency differs greatly if the turbo is boosting or not. Since the FMU cannot read the throttle position (only the vacuum), it could easily underfuel the intake charge causing a lean condition, and in some cases detonation.

With a supercharger, the maximum VE of the engine is dictated solely by the engine rpm. Therefore, the VE of the engine can be predictably measured using the manifold air pressure.

With appropriate tuning, the Rising Rate FPR can be used for both turbo and supercharger applications. The tuning is the key.

Every once in a while an intelligent young fellow new to the tuning scene comes on and asks "ok, if all it takes is a wideband to tune an engine, why do people say it's so hard?" The truth is that technology has come so far in the past 10 years to the point where one can get on the internet and get the tools and information required to successfully tune on a small budget. The challenge nowadays is not in getting the tools to do the tuning, but in asking the right questions and getting the right answers. I'm still learning myself.