I posted a response to a thread in the 144-250 "Small Block" Six Performance Section and thought I'd post it here for you all to mull on.
I've been following a thread on a BMW forum where the DME (Digital Motor Electronics) system found on the M50 24 valve engine has been installed onto the M20 12V engine with success. This has inspired me to research whether that Bosch EFI system found on the 2.5L M50 engine could be retrofitted onto our 200. This system is OBDI utilizing a MAF (mass air flow) sensor with COP (coil on plug) ignition.
The problems I've encountered with this system is the M50 is a 24V engine that utilizes an ignition map that is retarded for our 12V sixes so it would have to be reprogrammed with a more aggressive map, and the engine utilizes both a crank sensor and cam sensor that would have to be retrofitted. Also, the COP ignition units are normally installed on the top of the M50 head between the cams and away from the exhaust manifold heat, but would be adjacent to the exhaust on the M20 engine and our inlines. This may be a concern for longevity of the units so I am watching the vehicles on that forum who have the COPs on the sparkplugs instead of moved to the top of the valve cover as others have who are making room for a turbocharger. I'd prefer to install the COPs on the plugs with heatshields instead of remotely on the valve cover.
I've always thought that a MAF EFI is a very good system for our inlines, and if the above problems can be resolved, the Bosch system would be an economical alternative with the numerous 92 325s and 91-92 525s found in junkyards (sorry, auto recycling facilities). If you think the Bosch system is too small consider that the M50 engine, though only a 2.5L, is rated at 192 hp @ 6000 so it should be adequate. Plus, they are using the system with turbocharging which shows the flexibility of MAF, and some chip reflashing.
I've been following a thread on a BMW forum where the DME (Digital Motor Electronics) system found on the M50 24 valve engine has been installed onto the M20 12V engine with success. This has inspired me to research whether that Bosch EFI system found on the 2.5L M50 engine could be retrofitted onto our 200. This system is OBDI utilizing a MAF (mass air flow) sensor with COP (coil on plug) ignition.
The problems I've encountered with this system is the M50 is a 24V engine that utilizes an ignition map that is retarded for our 12V sixes so it would have to be reprogrammed with a more aggressive map, and the engine utilizes both a crank sensor and cam sensor that would have to be retrofitted. Also, the COP ignition units are normally installed on the top of the M50 head between the cams and away from the exhaust manifold heat, but would be adjacent to the exhaust on the M20 engine and our inlines. This may be a concern for longevity of the units so I am watching the vehicles on that forum who have the COPs on the sparkplugs instead of moved to the top of the valve cover as others have who are making room for a turbocharger. I'd prefer to install the COPs on the plugs with heatshields instead of remotely on the valve cover.
I've always thought that a MAF EFI is a very good system for our inlines, and if the above problems can be resolved, the Bosch system would be an economical alternative with the numerous 92 325s and 91-92 525s found in junkyards (sorry, auto recycling facilities). If you think the Bosch system is too small consider that the M50 engine, though only a 2.5L, is rated at 192 hp @ 6000 so it should be adequate. Plus, they are using the system with turbocharging which shows the flexibility of MAF, and some chip reflashing.