Volume 2 Issue 2 - Diesel Articles

EFILive Diesel Tuning for a Common Rail Diesel Engine

efi-live-flashscan-v2-tnWe buy diesel pickups because we appreciate the simple pleasure of push-you-back-in-your-seat torque. As long as it smokes, whistles and stinks, we assume it is running like it should. The details of engine operation are somebody else’s job. Why worry about how long our fancy electronic injectors pulse open or how our variable geometry turbos go about tightening their exhaust housings to supply our engine with just the right amount of boost? The answer is because now you can control it! Lean in a little closer… Enthusiasts no longer have a screwdriver-carburetor relationship with the power parts on their diesel trucks. Long gone are the days of throttle cables, wastegates and mechanical injectors. Computers are officially running the show.

Hold on, before you go out and buy a fifth of Southern Comfort, consider this: where there is a computer, there is software, and where there is software there is hope. We have software. It is called EFILive. What’s more, the Duramax is the only new diesel with software available to you, the user. I will wait while you laugh at the Dodge and Ford guys in the room. Some of the skeptics out there are probably saying “Yeah, we know its computer-controlled, that is why we have programmers and modules to tune it. What is so great about this software?”

The greatness lies in the wide range of parameters that users now have control over and the fine tuning tools the software offers users.

While typical module and program type boxes allow the user to select something like:

Stage 5/150 HP

Once you have selected this setting, the module makes all the decisions for you.

EFILive’s custom diesel tuning software, on the other hand, allows the user to do something like:

  • Ramp in 70% more fuel
  • Eight pounds of boost
  • 12 degrees of timing in range from 2,800 to 3,500 RPM.

Then the software records all of the truck’s parameters, allowing you to verify your changes on a test drive or pass down the drag strip. The above example is not a stretch of EFILive’s capabilities: you are now the master of your Diesel Domain.

By now, most guys are either really scared of potential mistakes one might make with such a powerful tool or really excited about the possibilities. My advice? Relax and take your time. It is important that users know their limits and respect their new found power or they risk breaking expensive parts. Nobody wants to wait for a tax return check to get back on the road. The following is a short guide to help new users learn what is involved with proper use of EFILive.

EFILive Diesel Tuning Basics

The costly part of this package is the hardware ($799.00). There is a black box and two cables that connect your laptop computer to the truck. The Flashscan V2 is the fancy name for the black box. It stores all licensing information and has some stand-alone features such as code reading and black box logging. It is your link to your truck’s brain. This cable allows you access to the engine control module (ECM) using EFILive’s software, which is available as a free download from www.EFILive.com. The software remains in demo mode until you enter the license information. After downloading and licensing the software you should get connected to your truck using your laptop and Flashscan. The first step is to read GM’s factory program on your truck. This will allow you to display the tune file you have been working with before any changes are made. The file (also called the tune or calibration) contains all of the maps used by the truck’s computer to determine its behavior under any given situation.

These maps, or tables as they are also called, contain the information that we will tweak in order to change the way the engine and transmission behave. After making adjustments, we will save the file before flashing it to the truck. The read-adjust-save-flash cycle will become very familiar to you as you spend time with the edit software. Subsequent cycles will not require the read step since the existing tune can simply be flashed (copied over) with the new file.

Flashing an LB7 Duramax with EFILive Diesel Tune

Building a Diesel Tuning Fuel Curve

The diesel engine is throttled by fuel; no throttle blades here. When fuel is commanded into the engine and burned adequately, it produces torque. The amount of torque produced by the engine at any given RPM constitutes its horsepower output. Our job in diesel tuning the engine is to command a smooth fuel curve so that as the throttle input and RPM come up, the driver is able to predictably control power output. Aggressive fueling at low throttle input makes for a touchy throttle pedal; however, if you under-fuel you get low throttle sensitivity and the truck feels lazy. Ideally, we would like to see power output consistent with throttle position. Tuners should work to build a smooth fueling curve which tapers down with RPM. This is true because as RPM rises it takes less torque – and consequently less fuel – per stroke to maintain horsepower output. Consistent horsepower output relative to throttle position is the ideal for drivability.



(Click on either image for more information or to enlarge.)

Actual fuel quantity injected can be visualized as a cube, with one side representing the injector nozzle size, one side representing fuel pressure and one side representing the pulse-width or the length of time the injector is open. Modifying any of these sides will change the volume of the cube, that is, the volume of fuel injected and, likely, the engine torque.

The algorithm for commanding a fuel quantity is roughly as follows:

In this article...

  • Limiting Torque
  • Boost Command: Fuel + Air = Fun
  • Diesel Tuning 101

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Comments (1)add comment

bgordon61 said:


Excellent article!

Under Diesel Timing 101 (Fourth), you stated "The truck should not rattle under heavy acceleration".

My 2004.5 stock LLY has always rattled, "very loud", under heavy acceleration.

1) What causes this?
2) does it cause engine damage?
3) How can it be cured?


December 23, 2010
Votes: +0

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