I am considering designing a crankcase vacuum system for a 1988 240dl. I think I can do better than the flametrap setup.

What I have in mind is something we did in drag racing. You cut a hole in the exhaust pipe just before the catalytic convertor and weld a threaded fitting at a 15 degree to 30 degree angle to the flow of the exhaust gas. The idea is to use the flow of the exhaust gas to create a suction thru the fitting. To the fitting attach a one way valve designed to use with the old air injection systems from the 80s. This would insure that at times of low exhaust flow, that exhaust gases would not flow upstream.

Run a hose from the valve to the valvecover. Here I would have to make a new filler cap/oil separator to attach the hose. I would them plug the smaller line from the flame trap to the intake manifold. I would leave the other larger hose in place to proved a source of filtered air to the crankcase.

The only difference from a racing engine is that it does have a source of air so there is no actual vacuum in the crankcase. I feel this is good because it wont pull anymore blowby past the rings. The seals will be fine since again I am not worried about creating a vacuum, just good scavaging.

This would end the problem of the hoses clogging and oil sludge accumulating on valves and the throttle body. The only thing I can think might be a problem is the oil vapors not being burned before they get to the catalytic convertor. Not sure about that, it might not even be a concern.

I am wondering if anyone has done this before, and also will the computer and idle control system be able to compensate for removing the small line to the flametrap? From reading the BB on the flametrap, it seems the small tube plugs frequently and doesnt affect idle.