Project Megasquirt finally comes to a successful close. Last time, I got the computer installed, and interfaced it with a Ford Electronic Distributorless Ignintion Sytem. The final step in doing a complete programmable electronic engine management retrofit to my 1973 BMW 2002 was to install the fuel injection system.
I used the intake manifold from a 1984 E30 318i, which ran a late derivative of the same M10 motor that is found in my ’73. I chucked the puny throttle body from the 1.8 litre engine, and bolted up a 58mm TB from a 325is using an adapter plate jointly developed by myself and Tom rafalski at 02 Again.
I bent up a couple of throttle cable brackets from some 1/8th ” steel and bolted those to the bottom of the manifold, and hooked the cable to the throttle body. The throttle body also recieved a throttle position sensor, Intake Air Temp sensor, and an air intake boot from a 325is.
For idle control, I plumbed in a VDO Idle control valve. Megasquirt sends a Pulse Width Modulated variable current to the valve to open and close it as needed during engine warmup (based on coolant temperature).
Update: The E30 type VDO idle valve does not really work very well with the PWM circuit modification as outlined in the MSIII manual. The circuit was designed to drive a Bosch or Ford type idle valve. I will be switching to a Bosch valve soon.
In its carburetted state, the 2002 uses a plastic (low pressure rated) fuel feed line. The fuel return line runs beneath the car, and for durability, is made of steel, so I did what others before me have done, and reversed the feed and supply lines using the steel as a high pressure feed, and the plastic line as a return to the tank. All flexible lines were replaced with proper high-pressure rated fuel injection hose.
I removed the cylender head mounted mechanical fuel pump and blocked it off with another nice Tom Rafalski piece.
A Bosch high pressure elctric pump was mounted to the subframe near the tank, using some split rubber hose, conduit clamps, and a couple of 1 penny washers.
I went with Bosch #24/hr high impedence injectors, which are driven straight from the Megasquirt relay board without the use of resistors.
When you are at the yard getting your intake manifold, also grab the water distribution neck, fuel rail, pressure regulator, and the coolant bypass pipe.
Romove the old
Your stock intake manifold is water cooled (or is it water warmed, I’m not sure) so when you yank the carb and intake, you will need to route the coolant straight back to the heater. The 318i water pipe works great for this, so grab it. I had previously installed the smaller M3 starter motor, but if you have a stock starter, you will have to trim down the bracket to make room for the new intake manifold. You might as well take the opportunity to upgrade to the more powerful and smaller M3 starter now.
To transfer the up-and-down motion of my old throttle linkage rod, to the pull-a-cable action of my new setup, I made a simple bellcrank linkage out of aluminum ( inspired by the engineering work fellow bmw experimenter Mike Koch). The bellcrank mounts to the brake booster bracket. I cut about 3 inches as required off the end of the linkage rod and threaded it to accept a rod-end bearing, which bolts to one end of the bellcrank. The throttle cable hooks to the other end.
So, there it is, done. Of course, it is never really done, as there is an endless amount of tweaking to do. There are Volumetric Efficiency tables to tweak, Air fuel ratio maps to optimize, and accelleration enrichment settings to fine-tune. You never feel that it is quite perfect. But one thing’s for sure, it’s a huge improvement in performance and tuneability over the old weber downdraft.
Finally, my once high-tech sports sedan can keep up with today’s econo-box hybrids.