Fuel Injection & Ignition

For a BCC engine conversion, there are currently two choices for fuel control and ignition.

The engines we are using should already come from the factory with sensors, injectors, coil packs and wiring.  They would have been controlled from the same ECU that controls most everything in the donor car, from ignition timing to vehicle security, to courtesy lighting. What is required is some way to control just the engine and not bother with the rest of the system.

The first option is to use a modified GM ECU with a matching harness.  These ECUs have been set up to only control the engine independently of anything else it might have controlled originally.  These ECUs have programmable chips that can be swapped out to further tune engines for specific installations. The harness comes pre-terminated to hook up to the engine and to the vehicle's wiring. Approx. $900

The second option is to use one of the new generation of aftermarket ECUs.  There are many out there, but I feel the one with the most potential is the open-source MegaSquirt project. An ECU, relays and wiring harness kit can be had for about $500.  Bear in mind that this is a universal ECU and will require set-up for each engine. Harnesses are in kit form, and will need to be routed and terminated.

For someone looking for a plug-and-play ECU, the Wade ECU from BCC would be the better choice.  For someone who likes to tinker a bit, the MegaSquirt offers on-the-fly tuning via a laptop PC and the ability to route the wiring and locate components as desired.

Either way, the engine will need a full complement of sensors, most of which should be on the engine when purchased.  You will have a throttle position sensor (TPS), coolant temperature sensor (CLT), inlet air temperature (IAT), and a manifold air pressure sensor (MAP).  The MegaSquirt has an onboard MAP sensor.  Either ECU will need a tach signal and a crank position sensor for injection and ignition timing.  Generally the one built into the engine will work, but later GM engines use an oddball signal, so an external trigger wheel and sensor will be utilized.

The ECU will output signals to control the injectors and to trigger the ignition. Generally, the ignition will be the GM direct ignition system (DIS) which uses three coils on a control module, each coil firing two cylinders, also known as wasted spark ignition. There may also be outputs for an idle air control valve (IAC), to control throttle bypass for smooth idle under various loads and for additional air during warmup.

For fuel supply, we will need at the minimum a high-pressure supply pump and a return line.  The earlier engines will have a regulator on the injector fuel rail, later engines will need a separate regulator, since the factory system is in-tank, and not easily adapted.  I like to use a low-pressure supply pump to feed a swirl pot, which will overflow back into the main tank.  The high-pressure pump will take its supply from the swirl pot, feed the engine, and return to the swirl pot.  That way, the high pressure pump will never starve for fuel, even going over bumps or cornering.   The low pressure supply pump may momentarily starve, but that will not affect fuel supply to the engine, since the swirl pot acts as a reservoir.

Recently, a fellow has started selling high volume MGB fuel tanks, with a high-pressure pump built in, along with a sending unit and return fitting.  Though not cheap, it can save in the long run, since all the engineering is done for you.

Bradley Restoration

Andrew Bradley, Proprietor

14093 Riverbend Rd.

Mount Vernon, WA 98273

(360) 848-6279