The Fuel Injection computer I have assembled can be found here:

May 11th 2002:

02assembly1.jpgI have started to build the Megasquirt FI computer. I have all the parts necessary to assemble Megasquirt hopefully it will come together without any problems. See the book to the left? Can you guess what kind of car Megasquirt will go into? 1979 Fiat Spider 2000! Here are some pictures of the Megasquirt assembly.

May 12th 2002:

02finished.jpg 02abouttotest.jpgIts fully assembled now. I have also ordered a USB to Serial adapter ( so I can hook the unit up to my Apple iBook. Hopefully it gets here soon. Next step is to test this thing out. Behold Megasquirt!

I have taken time to get my windows machine running again, (Its hard without a floppy drive or bootable CD!). This way I can test the unit. I am using an extra computer power supply to provide the necessary 12 volts to power Megasquirt. If anyone was wondering, to turn on an ATX power supply without motherboard you must jumper pins 6 and 7. It should be a green wire and a black one. Megasquirt is pretty low power so I really doubt there will be any current supply issues. To test it fully I am going to need a number of potentiometers and something to simulate a coil signal. See the picture!

May 17th 2002:

02donations.jpg 02testingsetup2.jpgI have been working on the car that this unit will be going into. I recently rebuilt the engine and I am now fitting it back into the car. You can read about that on the cars section of this site, if I get around to it :-) To test Megasquirt I took some parts from an old DJ mixer

Using these parts and a little clock circuit I was able to simulate all the necessary sensors. Everything works! As can be seen in the photos I tried a car battery charger as a power supply just to see if it would make any difference. The voltage from the charger is not stable, DUH, probably to help condition the battery. The next step is to get it into the car. Here are some pictures from the testing.

June 20th 2002:

02airtempsensor.jpg.jpg 02tempsensor.jpg.jpgThe car that this unit will be put into is now running using a carburetor. I will break the motor using this then switch to the F. I. The break-in period is very important so it could be detrimental to run the wrong fuel mixture. I have pictures but they were taken with a conventional camera and will have to be scanned.

July 10 2002:

02extraground.jpg.jpgI have bought the air and water temperature sensors. I decided to use the GM sensors to avoid having to upload new temperature lookup tables into Megasquirt. However the GM sensors are a different thread point than the Fiat sensor bungs. A machine shop solved this for 10 bucks. If you have your own tap set it would be even easier! You can see the Water temperature sensor mounted (left). I will put the air temperature sensor into the air filter, whenever I get it.

July 22 2002:

02fuelpumpg4.jpg.jpg Today was spent finalizing the install of Megasquirt. I decided to run a power line directly from the battery to a solenoid triggered by the ignition switch to power Megasquirt. With the battery being in the trunk this gave me a chance to run a second battery cable that I took out of a fuel injected version of the car. This way I can use the original battery cable as an engine ground line which should help remedy some ground problems. The new FI battery cable has an extra brown lead I can use to power Megasquirt. This brown wire was originally power for the Bosch FI system.

Mounting the fuel pump was an exercise, I am not sure of the stock Fiat install location. I tried to place it in a good location. From what I know its best to have the pump level with or below or the base of the fuel tank. This way siphon action will pull fuel from the tank to the pump, thereby taking strain off the pump. A second mounting consideration was to place it somewhere safe, if I do something stupid like run over a bush it will not rip the pump out from under the car and shoot gasoline everywhere. I still have not mounted the fuel filter. I do not want it under the car. At this point I will mount it inside the engine compartment, there could be a reason not to... besides the fact that the Fiat FI filter is huge

On to the fuel lines. There are two fuel lines in my Fiat, one big one small. The larger one is to supply fuel from the tank to the carburetor, the smaller one is to run excess fuel from the carburetor back to the tank. Since fuel injection systems move allot more fuel around the lines to and from the engine have to be larger. To solve this I kept the larger stock carbureted Fiat fuel line as the return and I installed a used a fuel line from a ~1990 Del Sol for fuel delivery. This line had a nice rust proof coating and was more than long enough to reach from the pump to the engine. This gave me the chance to design out a number of factory breaks in the fuel line. I prefer one long metal line so there is less flexible hose to worry about degrading. The last segment of the fuel line is from the fuel tank to the pump. This line must be quite large, I could not find a big enough diameter metal line so I used flexible tubing. Its all proper fuel line so it will hold up for a number of years. I also installed new bits of fuel line at the injectors as the original tubing from 1982 was not in good shape. The original line used clips to hold it in place, also used metric fuel line. I did not save the clips as 5/16th line could not be used with them. Instead I just used hose clamps. Here is a close up of one mounted injector.

02injector.jpg.jpgI am using the original Fiat FI fuel rail but I am not going to hook up the vacuum lead to the rising rate fuel pressure regulator. This way I will have a higher pressure at all times. Due to the small size of the injectors I will not have a rich at idle problem. I am still trying to figure out how I am going to mount an air filter. I think A conical K-N performance filter will look cool but there may be hood clearance issues. I will try to figure this out once I get the car started. The TPS is a problem. The Bosch/Fiat throttle body uses a D-Shaft throttle position switch, I need a position sensor. I spent time at the local parts store going through the TPS sensors they had in stock. Looks like everything with a D-Shaft is a switch. The best thing I could find was a Ford sensor, it does not have a D-Shaft but I believe I will be able to use it with some glue or something.

July 24 2002:

I tried using JB weld to fill up the gaps. This worked but I think there is too much play. When I pulled it apart the JB weld had not stuck to the plastic either. I think I will try epoxy, if I use a syringe it will make the task of gluing it together much easier.

July 28 2002:

I tried to start the car yesterday but it did not work. I believe this car is cursed. The fuel pump I had so carefully installed was bad, luckily I have another one, this is from a Volvo wagon. After finding the pumps performance specs I think it should be OK. I\u2019m going to purchase a pressure gauge to make sure the fuel system is on the up and up. The TPS is still hacked on there, I tried super glue gel but that was no better than the JB weld and created more of a mess. So what happened when I turned over the engine? It back fired but would not catch I do not have my laptop so I can not see what is going on within Megasquirt. I will check through the wiring again.

July 29 2002:

I reviewed the wiring harness and went through testing all the leads. The Megasquirt hardware only provides two injector banks but there are four leads for injectors. I forgot to install jumpers between the 1-2 and 3-4 injector leads. Somehow this was causing two injectors to stick open. The lead for the MAT sensor has also come undone. I have re-soldered these leads. This should make a difference, we will find out tonight.. or maybe tomorrow.

July 30 2002:

The TPS has been destroyed by my attempts to make it work. Time to find another one. The local junk yard has decided that letting people in the yard is unsafe. GRRR. Time to find another one of those too. According to the tracking number my laptop should be back by tomorrow. (it was gone, broken screen) The second fuel pump I installed does not provide sufficient pressure. AUUGHH. It was old and my guess is its on its way out. Thankfully it was free so only a little time wasted.

July 31 2002:

02tpsinstall.jpg.jpgI bought another fuel pump and TPS. The pump is off a 98 Volvo with only 35K :-) That should be good! I used little shims to make the TPS work. There is some play but it is functional. I have read on the internet that Volvo did used a D-Shaft TPS SENSOR on a number of their cars. I have the part number and need to see if it exists in the United States.

It also turns out one of the injectors was bad. I used a spare piece of wiring harness and a tin can to test all 9 Fiat injectors I have. One would not open, one would not close, and one had a cracked cap. The rest functioned properly and I chose the 4 with the most uniform spray pattern. After all this I turned the car over, it started! It is running too lean to keep going though. I need to raise up the after-start enrichment and probably the base pulse width to get more fuel into the engine. On a side note I am surprised by the injectors Fiat used in the car. According to the spec sheets they only run around 14 lbs/hr which is not much. I think once everything has settled down I will try to find higher flow rate injectors. I think ~24 lbs/hr would be better suited to this engine, or maybe just how I drive ;-)

August 7 2002:

02extraignmodule.jpg.jpg 02running.jpg.jpgThe car now runs! I can feel a huge difference! Great throttle response! It feels like this system provides much more low end torque, and a much smoother power. Of course I am comparing it to a POS 20 year old carburetor. Another issue preventing the car from running on the 31st was the lack of tach signal. To fix this I used a second ignition module, per suggestion, Megasquirt group ( I had to splice into the lead coming from the hall sensor inside the distributor and split it to reach both modules. The new module only triggers Megasquirt and runs a small resistor for load. The second module is out of sight under the coil on the left. (See left picture) On the right is a picture of the running motor. I need to go out and get some tuning done now! Notice the motion blur on the cam wheels.

August 9 2002:

02megaincarwiring.jpg.jpgOK, it stopped running. :-( While performing WOT tuning runs the engine started back firing and bucking. Shortly thereafter capacitor C-30 exploded. My passenger swore we were being shot at :-) Thankfully the car still sort of ran and was driven home. The unit was not mounted very well, aka exposed wires, so something may have touched, see pic. New mantra, take your time, do it right.

August 14 2002:

02flybackpt1.jpg.jpgAfter asking on the Megasquirt group ( and looking over the new version 2.0 schematics posted on the Megasquirt site ( I have made some modifications to my Megasquirt board. C-30 is an electrolytic capacitor which means it can explode if polarity is reversed. I placed a diode before C-30 to prevent any reverse current flow. I have also preformed the voltage flyback mod ( With such small injectors I was not having a problem with injector closing time but I have the unit out and it could help in the future. I need to get a less powerful soldering iron, I managed to burn out one of the contacts on the PC board so I had to run a jumper wire, see the pic.

I will re-install the unit in a much more orderly fashion to prevent problems.

August 20 2002:

Much nicer install this time. I tried to put it near where the FI Fiats had the computer. Thankfully the car also runs, although with the flyback mod the duty cycle has to be at 80%. I have a wedding to attend so tuning will have to wait till next month.

September 2 2002:

Still trying to nail down the tuning of the system, It remains elusive. I am running into a problem with Megasquirt using the O2 sensor at idle. This is causing a lean/rich condition, and a rough idle. I rather have it run rich at idle to ensure it is smooth.

September 7 2002:

I have managed to break off the fuel pump relay line from the wiring harness. I have to bring the whole thing inside and re solder, I think I will just put a new 32 pin connector on there. The current one has allot of sloppy soldering!

September 9 2002:

02flybackmod2nd.jpg.jpgAfter removing the unit and wiring harness I noticed the resistor used in the flyback mod was burnt. It still functions as a resistor but I am not sure how much longer it will last. Also the nail polish I used to lock the flyback transistor hold down nut has gone from red to black, must be getting hot! I have two carbon 1 watt resistors that I will use, if it burns these out then I have more serious issues. Here\u2019s a pic with the new mods in place. Notice the diode hacked in by the large blue capacitor to keep it from blowing up.

September 12 2002:

I have upgraded the software in Megasquirt to the newer revision code. This allows me to adjust the RPM at which the O2 sensor is used as well as a number of other options. The car runs and idles much smoother! I will now start logging to determine crossover points.

September 20 2002:

All is well! I drive the car almost every day and it performs nicely. There is a flat spot here an there but with logging I am sure those will be tuned out.

Additional Note: A number of people have asked me about performing the conversion. Here is a list of parts I used. Some of them are not absolutely necessary but can make the job easier.

Fuel Pump, from Volvo Fuel Pump/Filter Mounting Bracket, from 82 Spider Fuel Line (lots of different kinds) Fuel Filter, Fiat type from auto parts store Fiat FI Fuel Tank, from 82 Spider Fiat Spider FI Intake Manifold, 82 Spider Fiat Spider Exhaust Manifold with O2 bung, 82 Spider Fiat Spider Exhaust Down Pipe (FI has 6 bolts), 82 Spider Fuel Injectors, Lots of FI spiders TPS sensor (almost any will do), Ford not sure of model Water Temp Sensor, GM ~88 Chevy Caprice Air Temp Sensor, GM ~90 Chevy Caprice O2 sensor, Fiat FI Type Fiat Spider FI Wiring Harness, 82 Spider 3\u201d Exhaust pipe, Monroe Muffler Air Cleaner, Pep Boys Extra Ignition Module, GM type Lots of spare wire Vacuum Hose Water neck with sensor bung, Not sure, I just had it. 2 X 12V Relays (pump & unit) Mechanical pump block off plate