Volvo Amazon MegaSquirt Conversion

Eric Reuter - Portsmouth, NH

The Car

The car is a 1966 Volvo 122 Coupe. It has been heavily modified - mostly by the previous owner. Most noteworthy is the engine swap.

The engine is a Volvo B20F from a 1973 140. This is a 2.0L 4-cylinder fuel-injected engine that has the same form factor as the original 1.8L B-18.

Swaps from B18 to B20 are fairly common for Amazons. However, the carbureted versions are typically used.

The B20F (and B20E) variants use the Bosch D-Jet EFI system. This system, although revolutionary in the early 70's, is a relic today. It is nearly impossible to do any tuning, and the open-loop operation means that it doesn't adapt itself to worn parts.

The photo to the right shows the engine bay before the MegaSquirt conversion. Click for a larger version. Interesting bits are labeled.

Photo by Greg Wong

The Conversion

Click on the photo to the right for a high resolution photo of the post-installation engine bay.

I haven't gone into detail about the theory of operation of the MegaSquirt itself. All the technical information you could ever want is available on the MegaSquirt web site and in the MS FAQ and MegaManual.

A parts list can be found at the bottom of the page.


I am using the original fuel injectors from the D-Jet system These are Bosch 0 280 150 036. I sent the injectors to Rich Jensen at Cruzin Performance for cleaning and flow testing. The injectors turned out to be a very good match, so I didn't need to replace any.

These are low impedance (2.5 Ohm) injectors, so they require some current limiting. I've chosen to use resistors in series with the injectors instead of using the MS peak-hold driver. This is the way D-jet did it, and it works fine.

The resistors I'm using are 25W, 6 Ohm power resistors (value based on Bosch recommendation for these injectors - thanks Ola). I've mounted them in the MS power/relay enclosure under the PCB. I had to mount the PCB in the top slot and grind down the pins on the relay sockets a bit. The photo below shows this installation.

The two common wires shown will connect to the fused +12V terminals on the power board.

Fuel Pressure Regulator

MegaSquirt bases fuel calculations on the assumption that the fuel pressure is held constant across the injectors. This can only be achieved by using a fuel pressure regulator that monitors the manifold pressure and adjusts fuel pressure accordingly. The original FPR used in the D-jet system did not have this functionality. It held a constant pressure behind the injector, and not across it.

I have chosen to replace the FPR with one from a 1980 Datsun 280ZX. (See photo of engine bay above) I chose this one because it was the only one I could find with a barb fitting on the inlet. Most regulators are attached directly to the fuel rail with some sort of o-ring seal. D-jet (and the Datsun system) used a piece of hose to attach the rail to the FPR. I don't know the part number, but it can be found used at

Fuel Pump

I'm using the stock D-Jet fuel pump. Works fine.

Temperature Sensors

MegaSquirt is designed for use with GM temperature sensor P/N 12146312 for both manifold air temp and coolant temp. Other sensors can be used by measuring a few resistance/temperature pairs and using EasyTherm to create new .inc files for MegaSquirt.

I chose to use the existing Bosch coolant temperature sensor. As it is threaded into the head, it would be difficult to replace.

I'm going to use the GM sensor for MAT. It is mounted in the duct between my K&N filter and the throttle body, as shown in the photo below.

Throttle Position Sensor

My new TPS is the one used on the Volvo 850 and other late model European cars. Bosch 0 280 122 001. I cut up an old D-jet throttle switch and used the back plate as an adapter, as shown in the photos below. The D shaped shaft fit right in, but I had to cut about 1/2" off of it to get the plate snug with the throttle body.

Tach Source

I am using the negative terminal on the coil for my tach signal. D-jet has contact switches in the base of the distributor that could probably be used, but they are a known weakness in that system - one that I don't want to inherit.

Parts Summary

ItemPart NumberSource
Fuel InjectorsBosch 0 280 150 036Original Equipment
Fuel PumpBosch 0 580 464 007Original Equipment
Fuel Pressure Regulator?Datsun 280ZX
Throttle Position SensorBosch 0 280 122 001Volvo 850, 960, others
Coolant Temperature SensorBosch 0 280 130 014Original Equipment
Manifold Air Temperature SensorGM 12146312Most GM Products in the 80's
Wideband Oxygen Sensor
(With DIY-WB Kit)
NTK L1H1Honda Civic VX
Connectors D-jet Injectors
and Sensors
Part Number
NAPA or other B-A Dealer
2-pin Shell158-0002Box of 5
3-pin Shell158-0003Box of 5
4-pin Shell158-0004Box of 5
Pins158-0005Box of 25