Helpful Information / Key Terms / Acronyms

• Megasquirt - (MS) A DIY project created by Bowling and Grippo that basically takes the job of a EFI car's job of controlling the fuel injectors. Note that the original project as created by B&G was to control fuel only. EFI cars require precise fuel, air, and spark timing by a computer (The air is timed mechanically by the cams 99% of the time, so a ECU has to control fuel and spark to be considered as a standalone ECU). Megasquirt consists of the PCB board, components (including a microprocessor), and the code running on the processor. MS may refer to either the code or the PCB board, or both, depending on context.
• DIY - Do it Yourself
• EFI - Electronic Fuel Injection, as opposed to that other form of "injection" that will not be mentioned in this site.
• ECU - Engine Control Unit (aka EMS, etc.)
• PCB - Printed Circuit Board (the (usually) green thing that electronic components are soldered onto).
• Megasquirt-n-Spark - (MSnS) This is a software upgrade to Megasquirt. That is, this is just a different software program that is uploaded into your MS hardware. It's just a different code that your MS hardware can run. It controls not just fuel, but spark as well. This is what you need to get MS to become a full standalone. There are many other code variants that do many different things, but I found this as the most applicable to the VG, and this is all I'm going to document in detail.
• Megasquirt II (MS-II) - A hardware and software upgrade to MS that controls fuel and spark. It allows more precision in your fuel and spark timing, but pales in other comparisons to MSnS. MS-II is hardware upgrade because it contains a daughtercard that plugs into a MS PCB board (like a PCI card that plugs into your computers main board).
• v2.2 PCB Board (v2.2)- A version of the PCB board that you can build your MS on.
• v3.0 - Another, more recent, version of the PCB board that you can build your MS on. It's way better than the v2.2 one.
• MegaTune - This is the tuning software that runs on your PC. It interacts with the MS computer in your car, allowing you to change stuff, like number of injectors, cylinders, VE tables, spark tables, etc. This is where you have fun with your car and start to blow things up.
• VE - Volumetric Efficiency, a percentage. Basically, when you specify a VE percentage for a specific RPM and load (kPa), you're telling MS how much fuel is needed to obtain a certain air to fuel ratio.
• kPa - Kilopascals. These are used constantly in MS. This is a measure of pressure, just like PSI. Although, with kPa it's a lot different. You don't normally use PSI to measure vacuum, you use inches of Mercury (like in Boost/Vacuum Gauges), or kPa. 101.35 kPa is atmospheric--it's what pushing down on you at sea level. Anything less than that is a vacuum, anything more than that is boost. 145 kPa is about 6.5 psi, stock boost for a z31 VG30ET. 101.35 kPa is also equal to 14.7 psi. That's right, there's 14.7 psi of atmospheric pressure naturally at sea level. You will have to keep in mind the atmospheric pressure when referring to kPa values in MS, otherwise you'll enter in load, boost, and other values wrong. In other words, keep in mind that boost is > ~100 kPa, vacuum is below ~100 kPa.
  
  Here's a nifty little conversion program: convert.exe (548 KB)
  
  It allows you to convert from PSI to kPa, and kPa to PSI, along with umpteen other units. Keep in mind that for boost, you have to enter in 14.7 + Boost. So, to find the kPa of 6 psi of boost, you enter in 20.7 psi, otherwise it will return about 50 kPa, which is vacuum! The correct return value would be 142 kPa. Also, nifty feature under the options menu in Convert is to Invert Selected Units.