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Citroën A-Type Tuning

DIY-EFI Megasquirt

© Copyright: J.Cats

Megasquirt practical application

Disclaimer: This page only provides information based on the personal opinion of the author. The author can't be held responsible for damage in any way that could result from modifications mentioned here.

From the Megasquirt site:
"The Most Efficient and Cost-Effective Electronic Fuel Injection Controller in the Universe - and YOU BUILD IT YOURSELF!"

Info: Parts:
  • MegaSquirt Kit
  • MegaSquirt Relay Board Kit
  • MegaSquirt Stimulator Kit
  • Temperature sensors: Opel Montery 3.5 petrol 1999 model water temp sensor and inlet air temp sensor.
    Pontiac Fiero wil also work (EFI model)
  • TPS: Opel Omega 3 liter 1990 onwards
  • Exhaust gas Oxygen Sensor (Lambda): any

Tuning engines has 1 big downside. There is only so much the carbutettor will take. Jetting is not very simple and takes a long time to get absolutely right. And every time you make a change you have to rejet. So let's look at EFI.
I got myself a Megasquirt DIY-EFI kit. I was planning on getting a professional MBE kit but since that costs over 10 times as much as the Megasquirt, thought the MS would do for now.

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The kit has arrived

I've collected all the relevant information for builting this thing and will put it here as I go along. Next step, call for help!

There was another bit in the packet. The stimulator, used for testing the megasquirt after assembly. I looked at the stimulator and it didn't look THAT difficult. Found the assembly guide at the megasquirt site. It lists what parts go in what hole and that's enough! So,without soldering I had this in 15 minutes (it took me 5 minutes to figure out the difference between a resistor and a capacitor, they just don't teach you the right things in school):

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I now have something with 6 knobs and 4 lights, this is great!

Next up: soldering
Started with the Stimulator first, this has all components nicely spaced. Could just as well have started with the relay board but that has some big components and I found it easier to solder small things. With the stimulator make sure you have the flats sides on the leds pointing the correct way (towards the turning knobs). Look closely, there realy is a flattened bit on the edge of each led. The rest is easy.

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The stim all finished!

I know nothing about soldering electronic components but this worked good for me: Put in a component, double check it's in the right place in the right direction. Turn the board upside down. Put the soldering iron on one of the metal pins sticking out. Heat it up for a few seconds then put some solder on the soldering iron tip / component's "leg". The solder just rolls down towards the board and forms a nice vulcano shaped connection. If it's not vulcano shaped, isn't right. Either not enough heat or the board / component wasn't grease-free. Cut off the legs so that they are not in the way when soldering the next bit. There is a much better guide to soldering on the megasquirt site.

The relay board was also easy but I couldn't get the relay sockets close enough to the board so after soldering I can't get the lid on the relay box. You have to make sure the relay holders sit tightly on the board, the round things on the bottom fall into holes on the board. Mine are now floating which isn't nice. You should fit the relays into the sockets when soldering the sockets to achieve a good fit (and you can get the relays in and out much easier that way!)

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The relay PCB front and back

I left the most difficult bit for a friend. He soldered the megasquirt together, thanks Aad!

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The megasquirt at the first test

All went pretty smooth and it's now all finished. Played with the stim until the battery was empty.

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Finish Megasquirt

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Ready to run and stim attached (hard to see the leds)

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Made the connector without burning my girlfriend's fingers!

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So the fuses used are not standard EU automotive then? Temporary install in the car.

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Screenshot! first cit 652 engine to do 22200rpm? tach pickup on coil - wire from the ignition black box, the blue shadow on the rpm bar is the rpm shooting up and down.

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Screenshot! tach pickup on one of the 2 sensor wires, connection 4 and 5 on cit 652 black box

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All you need for fully electronic engine management: Citroën Motorola 652 black box (VA4 here) doing the ignition, Megasquirt with relay board doing, well not much right now.

So I now have a very expensive fully electronic rpm counter. It works, so much for dry testing, I want to see fuel being squirted!

But first some brain breakers:

Fuel rail
The fuel rail will consist of 2 pieces, one on the left and one on the right cylinder bank. I've gotton some fuel rails with injectors of citroën 2 liter injection models (ZX, Xantia, XM). The yellow injectors are good for around 30bhp each at 3.0 bars fuel pressure, so 60bhp for a flat twin and 120bhp for a flat four. The fuel rails are fed from the fuel pump into the first rail. The second rail is fed with a hose from the first rail. From the second rail fule is being fed back to the fuel tank through the fuel pressure regulator. The injectors are fitted into steel tubes, 20mm OD, 13.5mm ID, which are welded into the intake manifold exactly above the intake ports with injectors pointing towards the intake valve. Another cool thing would be to fit the injectors underneath the intake tubes where they point towards the outside of the intake wall, this would hide the injectors from sight if this was needed.

Fuel pump and pressure system
There are 2 basic options here. First is a system where the high pressure pump is fed directly from the fuel tank. This works well as long as there is enough fuel in the tank and the pump can never pump air. It gets a bit problematic when the tank is far empty. The second system uses a low pressure fuel pump to feed a can in which the high presure fuel pump is located. The can is called a swirl pot or surge tank. There is an overflow line going back from the swirl pot to the fuel tank.

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