I'm looking for some input on installing an external compressor bypass valve on my '91 745se. The integral unit on my td04-13c has sprung a leak and its a fortune to replace. I have a line on an external from a Porche 944. I'm unsure though about how to plumb it into the rest of the system. Thanks in advance.

Peter,

I too have a 91 745se and my cbv seems to have sprung a leak. I once found a site that had a "cap" so you could remove the cbv and use external unit. I will be looking for this site again. As far as putting one on, just get the fitting welded onto your intercooler piping. Vac/boost line hooks up to the external unit. You can vent to the atmosphere as when you let off throttle you will run rich not causing any internal problems, this extra fuel will quench the combustion chamber taking out some heat!
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91 745tiSE

To avoid running rich you could plumb it so it vents back into the system right after the air sensor (MAF or MAP not sure). I believe that will help eliminate some of the rich condition (at least it does when turbocharging nissans). That way all the air thats been metered is still in the system (albiet before the turbo).