Posted: Aug 30, 2009 9:10 AM
OP - As a fellow 520i owner, let me give you three suggestions.
First, go to the Wikipedia page on BMW M20 engines and learn about the different versions. M20 designates the basic design and components of this engine, but there were variations in the displacement size, head design, and fuel injection system. This research will help you figure out what's what.
Second, the easiest and most satisfying improvement you can make is to see that the engine you have now is running well. This means getting rid of any vacuum leaks, cleaning and adjusting the throttle body, making sure that your airflow meter, auxiliary air slide valve, and cold start injector are all working properly. Make sure that the timing is set correctly and the ignition system (spark plugs, ignition wires, distributor cap, rotor, and coil) is in good shape. With a little help from Google, you can find detailed instructions on all these matters online. Look for "vacuum leaks l-jetronic alfa" for a good write-up on the l-jetronic system, which many 80's Alfa Romeos also used. Chances are that your car needs some improvement in one or more of these areas, and you'll enjoy a nice improvement in drivability and perhaps performance as well. Plus, it's a great way to learn more about your engine.
Third, when I was in your shoes, after I had got my car running right but still wanted better performance, I found a good M20B25 engine with Motronic fuel injection and swapped it in (from an early e34 525i). It was an easy swap, as far as engine swaps go. The car runs great now and has much more power, though it's not fast by modern standards. Most important, a B25 can be modified in ways that a B20 can't: adding a chip, stroking for more displacement, replacing the AFM with a MAF.
Now, some people might chime in and say that M20s are inferior to M30s etc., and that may be true, but that doesn't mean they're not good engines.
good luck!
First, go to the Wikipedia page on BMW M20 engines and learn about the different versions. M20 designates the basic design and components of this engine, but there were variations in the displacement size, head design, and fuel injection system. This research will help you figure out what's what.
Second, the easiest and most satisfying improvement you can make is to see that the engine you have now is running well. This means getting rid of any vacuum leaks, cleaning and adjusting the throttle body, making sure that your airflow meter, auxiliary air slide valve, and cold start injector are all working properly. Make sure that the timing is set correctly and the ignition system (spark plugs, ignition wires, distributor cap, rotor, and coil) is in good shape. With a little help from Google, you can find detailed instructions on all these matters online. Look for "vacuum leaks l-jetronic alfa" for a good write-up on the l-jetronic system, which many 80's Alfa Romeos also used. Chances are that your car needs some improvement in one or more of these areas, and you'll enjoy a nice improvement in drivability and perhaps performance as well. Plus, it's a great way to learn more about your engine.
Third, when I was in your shoes, after I had got my car running right but still wanted better performance, I found a good M20B25 engine with Motronic fuel injection and swapped it in (from an early e34 525i). It was an easy swap, as far as engine swaps go. The car runs great now and has much more power, though it's not fast by modern standards. Most important, a B25 can be modified in ways that a B20 can't: adding a chip, stroking for more displacement, replacing the AFM with a MAF.
Now, some people might chime in and say that M20s are inferior to M30s etc., and that may be true, but that doesn't mean they're not good engines.
good luck!
