Boost Controller-BMW E36 wiring

[S.Violette]

I need to add a boost controller for my turbo charged E36.   Which wiring signal should I use for the boost controller?   I have deleted the A/C.   Should I use the compressor signal wiring?

 

G4X- plug in ECU

[Vaughan]

Any of Aux 1-10 or a spare injector output. I can't look at a pinojt right now to confirm which pin the ac clutch is bit you would have to use the wire going into the relay not the output of the relay.

[koracing]

The AC compressor control output pin is IGN7 - that should work for boost control as well with one pin on the solenoid going to +12V switched source and the other pin to the ECU compressor output pin.

[S.Violette]

I am showing Pin 48 on ECU = IGN 7 Air Conditioning Compressor (Aux) in Link manual.   Assume that wire goes from ECU to fuse box/relay in a loom.   The wire going to the actual compressor is after the relay which Vaughan is NOT recommending.   So, the difficult part is finding a way to “scab” into this routing and redirect to the Mac Valve.   I figured that all the people drifting the E36 would have an easy solution and I would not have to trial/error a solution.    Like to know what everyone is doing and they know works well. 

Not really sure what Vaughan is recommending in using “any Aux 1-10” as they are all assigned (eg Idle Speed Control). 

Help me understand why I would not use the power after the relay.   burn out the relay?   The connector for the compressor is sitting right next to the location for the Mac valve and it appears that it has 12V power and a ground which I could control by “reassigning Pin 48/Ign 7” to the boost controller function in software. 

[koracing]

The boost solenoid will be operting via a PWM funciton - pulse width modulation.  That means it will be adjusting how long it is off/on at a given frequency - usually 20-32 Hz 0r 20-30 times a second.  Most relays won't be able to repeatably and precisely control that level of precise movement as they are mechanical devices.  I wouldn't try to switch a relay faster than about 1-4 times per second and even then the mechanical armature will likely fail in short order.  A solid state relay without mechanical moving parts and with sufficient output response time could be used for this.  Alternatively, just remove the AC relay and use the pins 85 and 86 to run to your boost solenoid.  That would provide your switched 12v power via pin 86 via the 5A F16 fuse, and then the pin 85 would go to ecu pin 48 (IGN7 output).  

Also - Merry Christmas!

[S.Violette]

Thank you.  Merry Xmas.   Makes sense regarding PWM and mechanical relay.     Is there a ‘professional” way to use pins 85 and 86 of the AC relay without 2 wires sticking out of top of relay box?

[koracing]

Not really a slick professional way to tap those pins that I can think of short of rewiring on the back side of the fuse box to an external 2 wire connector maybe.  The solid state relay option - if you can find one that drops into the AC relay location - would be a cleaner install.