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Tacho out


Fredrik Pettersson
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SO im wiring up my BMW M54 harness right now and i can't wrap my head around how i should wire the tacho. Stock it works like this: Hall effect sensor for crank sends signal to ECU which then sends RPM signal over the CAN-bus to the gauge cluster. Im thinking either : 1. Hall to link, then from link use AUX to stock ECU (how should i do this , stock ecu has GND and sensor(is it safe to wire them together?) 2. Does the LINK supportoutputting the RPM through CAN ? I've got a question about VVT asweel : What is the difference between LH and /LH ? Thanks // Fredrik

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If you wish to retain the stock ecu to keep control of the dash or any other accessories then the way will be to share the crank / cam signals. To do this you will need to tee off the signal wiring. If it is a hall or optical  sensor then the link ecu will need to have the pull ups on the trigger inputs turned off through PC link.

We will not be able to drive the display through can.

The /LH comes into play on V or boxer engines where you will have two inlet or exhaust cams one being inlet /LH and one inlet RH

So for an inline engine with both exhaust and inlet variable you would use Inlet /LH and Exhaust /LH

 

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Thanks for the help So my though of doing it like this works : Stock ecu sensor GND to Link sensor GND CPS sensor out to Link Trigger 1, then configure AUX 7 as Tacho out and run it to the stock ecu sensor in. I'm doing it this way to have the tacho sweep function(as i'm wiring in the link to the speedo aswell for LC) Also i have a AEM UEGO wideband AFR gauge with digital ouput for datalogging , can i wire this output to a Voltage In and use it to lay down a base quicktune ?(is there any config files avaliable for this or will i have to enter it manually?) Thanks for a great EMS and great customer service ! :)

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Im picking using a aux out wont drive the tacho if the dash was driven via can.

However if the tacho did have its own control then no problem.

You can feed the AEM uego controller into the ECU you just need to know the voltage output and corresponding AFR figure.

 

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Thats why i was thinking of using the stock ECU to process the AUX to CAN so the Cluster can use it, in my mind this should work but better ask then be sorry , right ? :) I was hoping i wasn't the first to use an AEM gauge(ie a calibration avaliable online) , guess i'll share the table once i have it calibrated. Thanks // Fredrik

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