Crank Signal Question FIC or Stand Alone ECU | AEM
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bsparkman
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Joined: 03/11/2019 - 11:31
Crank Signal Question FIC or Stand Alone ECU

Hello- thanks for reading this post.

I'm in the process of installing an FI/C-6 30-1910 on my normally aspirated 1997 Jaguar XJ6 in preparation for turbo charging it. Before installing the turbo I wanted to data log and base line the car's sensor readings before introducing the turbo. I've built a custom harness extension and have interfaced the FI/C's harness to the custom harness extension. The car runs perfect with just the harness extension, FIC bypass jumper or just tapping the VR signal; all is fine except when I try and "intercept" the VR crank signal and use the MAGO+ output to feed the ECU. The car will  just not rev higher than 2500 rpm. I've tried every value of resistor (i bought a large kit) accross MAGI+ and MAGI- inputs, in addition I've tried a couple different low pass filter designs without effect. I should not say without effect because some combinations of resistors and RC filter circuits have made the issue occur at lower RPM's (i think I might be lowering the amplitude of the MAGO+ output signal) but none have helped above 2500 RPM. When I view the issue on a data log after intercepting the crank signal it appears the ECU cutting off the injectors; the injector signals indicating 99% on graph when the engine cuts out at 2500 RPM. When I look at the VR signal input and the MAGO+ on my dual trace scope both appear to be very clean and in sync at the zero-crossing point. The VR signal varies in frequency and amplitude and the MAGO+ signal, a 9V square wave just varies in frequency. Is it possible the Jag ECU just wants to see a VR signal at a sufficient frequency and amplitude and the square wave from the MAGO+ not sufficient to drive it above 2500 RPM? Because I want the ability to pull timing out of the car under boost could a stand alone ECU be programmed to output a "shifted" VR signal to the factory ECU to modify timing? I guess at that point I should just let the stand alone ECU control the coil firing and fueling as well... Is there a device that would allow me to amplify the MAGO+ output near the VR amplitude levels to test if the ECU is wanting a higher square wave signal above 2500 RPM?

Thanks,

Bob