A practical guide on how to understand and tune your engine/car with Electronic Fuel Injection and Ignition with an aftermarket Standalone Engine Management System 

Updated September 2022 by Jerry Hoffmann

Our EFI Tuners Guide is aimed first and foremost to the DIY EFI installer, configurer, and tuner, this guide will help you understand WHY you want to consider Electronic Fuel Injection, how these systems work, and how you can get the most out of them! We’ll start with the basics, understanding how an Electronic Fuel Injection System ECU like the MegaSquirt line of Engine Management Systems work, how that compares to using a carburetor and/or distributor, and what makes it better! Then we’ll help you understand the sensors and switches (inputs to the ECU) as well as the injectors, relays, solenoids, and other ECU outputs. And we’ll tie it all together with information with a guide on how install, configure, and tune these systems, helping you understand how to give your engine EXACTLY what it needs for maximum automotive performance. 

The term ‘DIY EFI’ in this regard does not require that you’ve built your EFI System from a box of parts, like we offer with our MegaSquirt Hardcore DIY EFI Kits.  This series/guide will apply equally well and in some cases even better to the MS3Pro line of ECUs, the MSPNP and MSPNP Pro lines of Plug-N-Play ECUs, the MicroSquirt ECU, and heck… really anything else you may be working with even if it’s not ours.  We’re talking concepts, principles and best practices here.  And we’ll get into the nitty gritty of how you can successfully tune your engine for maximum automotive performance!


What’s your motorsport? We’ve got you covered! 

At DIYAutoTune we have customers all over the map, both worldwide, and in regard to racing/motorsports styles.  We’ll do our best to cater this Tuners Guide to ALL of you!  Drag racers, land speed racers, solo/autocross, road racing, drifting, rally, burnout competitions, you name it!  Even streetcars from the pre-emissions era like some of my favorites I have sitting next to me in my shop and home I my garage as I write this.  A 67’ Camaro, tube chassis fiberglass body drag car that if I keep (and I’m likely to), I’ll be converting to Pro-Street duty.  It’s currently running an MS3Pro controlling the 6.0 LS engine and our MicroSquirt Transmission Controller on the 4L80E Transmission.  And chances are… it’ll end up turbocharged.  A ‘65 Mustang that is currently still carb’d as I bought it, with a 289 and auto trans.  I’d love to convert that to EFI, turbocharge it, and convert it to a 4speed manual transmission to make it a fun street toy.  And lastly—my favorite.  A 1964 Lincoln Continental with 430 MEL Engine.  All original.  I didn’t buy that car to keep it original though, I bought it specifically looking to find the perfect car to wrap around a 460-based 572 BBF I have sitting here as well.  With that 572 and a blower sticking out the hood, that car rocking it’s suicide doors and miles of perfectly straight sheet metal will be a dream to drive.  And as I get to each of these, and other projects – I’ll add another chapter here.  A case study if you will—to help others like yourself to do your own Carb-To-EFI conversion and/or simply to tune a RestoModded classic with a modern engine already fitted with EFI.  To help you get the most out of your project.  I may even bust out an old project I did an article and video series on years ago, and planned to continue with a twin turbo conversion—a 1977 Chevy Nova with a small block 350.  I’ve got the parts-  the MegaSquirt-II EFI system could be run as is, or updated – I have the twin turbos and turbo manifolds, I even started welding up the downpipes!  I just never finished it.  And I’ve got plenty of turbo on that thing to scatter that little 2-bolt main block to pieces.  It could be fun.   


So what is our goal of this DIY EFI Tuners Guide? 

The goal of this guide to installing, configuring, and tuning EFI is to help you to understand automotive tuning thoroughly, to provide and equip you with the car tuning how to knowledge you need to provide you with confidence that you can do this.  Confidence built not on fluff, but on helping you build the knowledge you need to be successful at every stage of the process.  From installation and wiring, to configuration of base parameters and sensor calibration along with first start and base idle tuning, to full tuning of the fuel and ignition tables, idle, closed loop EGO corrections using a wideband o2 sensor, and ultimately having a well tuned, easy cranking, fuel efficient tune that unleashes all of the beast within when you drop the hammer on that switch being controlled by your right foot.   Then furthermore perhaps we’ll delve into configuring and tuning some more advanced features.  Boost Control, different launch control/2-step/3-step/flatshift schemes and strategies, use of EGT sensors, use of multiple wideband o2 sensors even up to using a wideband PER CYLINDER allowing you to tune each cylinder to perfection as if they were each they’re own individual little one cylinder engine—and synchronizing them all with each other so that you can KNOW that your fueling is spot on in every hole.  And maybe we even take that a step further—using those individual wideband o2 sensors per cylinder to allow Closed Loop EGO/O2 Correction enabling real-time fueling corrections to keep that AFR exactly where you want it at all times.  It’s really sexy stuff.  MS3Pro does it all.  And a whole lot more.   >>> Go Straight to Chapter 1: Why should you convert to Electronic Fuel Injection? >>>


EFI Tuners Guide – Table of Contents  

  1. Why should you convert to Electronic Fuel Injection? 
  2. Why should you convert to Electronic Ignition Control? 
  3. Garbage In, Garbage Out:  A properly installed, configured, and tuned Engine Management System makes all the difference!  (The Three Stages of Success)  
  4. Electronic Fuel Injection Options – Throttle Body Injection (TBI), MultiPort Fuel Injection (MPFI), Sequential Point Fuel Injection (SPFI), and Direct Injection (DI) 
    • Batch and Bank Injection versus Sequential Fuel Injection
  5. Understanding the EFI Fuel System
    • 5A – The EFI Fuel System: Overview
    • 5B – The EFI Fuel System: EFI Fuel Tanks and Fuel Pumps (Coming Soon – 10/27/22)
    • 5C – The EFI Fuel System: Fuel Filters, Lines, and Pressure Regulators
    • 5D – The EFI Fuel System: Fuel Rails and Injectors
  6. Ignition System Options – Single Coil Distributor, Wasted Spark, and Coil On Plug / Coil Per Plug Ignition Systems 
  7. Sensors, Switches, and Inputs:  Crankshaft and Camshaft Position Sensors
  8. Sensors, Switches, and Inputs:  Everything else – How the ECU knows what’s going on with your engine
    • Control Algorithms – Speed Density, Mass Air Flow, Alpha-N, and various blended modes
    • Inputs required for Electronic Fuel Injection control
    • Inputs required for Electronic Ignition Control
  9. Fuel Injectors, Ignition Coils, Relays, Solenoids and Outputs:  How the ECU controls your engine 
  10. Three Stages of Success: Stage 1 – Engine Management System Installation 
  11. Three Stages of Success: Stage 2 – Engine Management System Configuration 
  12. Three Stages of Success: Stage 3 – Engine Management System Tuning 
    • Manual Engine Tuning versus AutoTune
    • Naturally Aspirated Fuel Tuning and AFR Targets
    • Forced Induction (Turbocharged/Supercharged) Fuel Tuning and AFR Targets
    • Nitrous Fuel Tuning and AFR Targets (wizardry!)
  13. Engine Safeties  
  14. Datalogging and Analysis 
  15. The Next Step – Configuring and Tuning Advanced Features 
    • Open Loop Boost Control
    • Closed Loop Boost Control
    • Closed Loop EGO Correction (Single Wideband o2 Sensor)
    • Closed Loop EGO Correction (Per Cylinder Wideband o2 Sensors)
    • Launch Control/2-Step/3-Step/Flatshift
    • Traction Control/Power Management
      • Wheelie Control
    • Flex Fuel / E85
    • Individual Cylinder Tuning
      • Manual Tuning
      • Auto Tuning
    • Tuning for different fuels at the flip of switch – found a tank of race gas?
  16. Automotive Math – Broad array of ‘calculators’ that help people to make educated decisions when sizing various components in the design of their fuel injection system.   
    • Fuel Injector Size
    • Fuel Pressure required
    • Fuel Rail Size (Fuel Rail Plenum Volume)
    • Intake Manifold Plenum Volume
    • InHG to kPA to BAR pressures
    • And more!
  17. Glossary of Terms – Quick Reference to every TLA and more (that would be Three-Letter-Acronym) 
  18. Further Reading and Education  (books, mine and others, online training courses, In person live classes, etc)

    >>> Read Chapter 1: Why should you convert to Electronic Fuel Injection? >>>

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