Need help on Turbocharging a 318

I have been running the drain lines in to the front cover for decades, on lots of systems. Never had an issue. There is plenty of room to drain back to the pan,and the chain does not mind a little extra lube.

We ran TO4's decades ago. The T70 works, and spins lower speeds to do the job. The T72 is loafing on a stock 318, unless you run 12 psi or more.

That series of islands on the compressor map represents the efficiency of the compressor. the island in the center is the highest efficiency, and should be your target when choosing a unit for any application. The "sweet spot" covers a range of conditions that generally track for an engine if you choose the right unit. Like I said with that T72 map, you will stay in the high efficiency area from 6psi to 24psi.

The more efficient the compressor is the less it heats the air. Running to the right side of the islands (the choke area) makes for very hot discharge air. It also bogs the shaft speed down, which slows the exhaust flow down.

The surge line is just what it indicates. Working past the surge line will cause the turbine to surge, and can cause mechanical damage as well as make it run like crap.

Operating anywhere within the islands is ok, but the best plan is to pick a compressor that most closely matches the engine needs.

Hybrid assemblies are not new. We were using them in 1975 on aircooled VW engines. They are simply the result of choosing the compressor that has the best match to the engine, then sizing the hot side to provide the performance in the proper range. A bigger compressor (T4) on a smaller hot side (T3) gives more airflow at lower engine speed & displacement. It can however restrict exhaust flow at higher RPM, and you wind up relying on your wastegate for a significant amount of exhaust flow.

You can't select a turbocharger based on pictures, case polish, or the "horsepower claims" from an E-bay auction. Sure you can put something together, it may even seem to work well. You will never know how much performance you left on the table.

B.