Common AFM Problem
The OEM E30 AFM contains a copper arm, which rides along a carbon track intended to provide an electrical interface critical to the operation of the sensor. This interface wears over time, resulting in abnormal output from the sensor to the ECU. Typically this manifests itself as a lean condition somewhere along the power band. SE30 cars tend to wear the track towards the end, which corresponds with high air flow events. This behavior can be difficult to predict and results in the owner spending significant money and time trying to finding “good” AFMs. The intent of this change is to provide a non-contact digitized replacement that offers more consistent performance.
Digitized AFM Overview
A contact free sensor utilizes the sensors ability to track the angular displacement of a magnet which rotates with the flap and converts this to a voltage that is then sent to the ECU.
The magnet assembly replaces the OEM copper arm assembly.
The custom circuit card houses a magnetic sensor and other components that takes in and outputs the same signals as OEM design.
Magnetic sensing architecture are used in automotive sensors i.e. as electronic power steering and transmissions.
Significant time and effort have been put into designing a robust digitized AFM product.
104 units have been built to date, with different levels of run time on each assembly. Digital AFMs have had 2 complete NASA SE30 seasons over 8+ different cars, in which 2 were installed onto “daily” driver E30s that have had 750+ issue free miles. Also, installed in Champcar VIR 8+7 hour Enduro on 12/2021 (Champcar VIR 12 hour Enduro (Car spun rod bearing 8 hours in) 3/2022). NASA SoCal 3 hour Enduro 3/2022 (3 AFMs across 3 different cars) . 50+ dyno runs were conducted to verify consistency and to compare against stock units. 2 units were also built for a Porsche 944 and 911 testing. Only ever had a single issue with a unit that was traced back to damage that occurred during shipping due to the black lid not being bonded on.
Dyno Testing
A copy of Dyno testing performed on 3/14/2020 with Tom Panzarella’s BMW Spec E30 car (#88), shows the runs that were made with a stock AFM and a modified AFM. The results show a near identical peak HP trace (>5kRPM). Where as, a modified AFM shows a slight advantage in 4.4-4.5kRPM against this particular stock AFM

