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Power Vision - Auto Tune FAQ

What is Auto tune, a product or a process?  At Fuel Moto we throw around the term Auto tune quite frequently, so let me do my best to explain what it is, and what it does.  This document is intended to cover the basics, and is by no means a comprehensive guide to EFI tuning, systems, or best practices.

A little EFI 101 may be beneficial to lay the ground work and better your understanding of all that’s going on in this sometimes confusing world of EFI tuning.

In the world off electronic engine management / EFI, most modern systems employ closed loop feedback for fuel control.  These systems are often based around narrow band o2 sensors that provide feedback to the ECM in regards to how rich or lean the vehicle is running.  The ECM uses it’s calibration (tune) to determine if it should maintain closed loop fuel control, and also references a target Air-to-Fuel Ratio (herein AFR) value during certain conditions (load vs. rpm).  If there’s error between what the ECM is asking for and what the OEM narrow band sensor measures, then a correction is made to adjust the lean or rich condition.  This sounds great, and it is, but here’s the kicker……..narrow band sensors are ONLY accurate at, or near, the stoichiometric value of the fuel being used, which is 14.7:1 for gasoline.  This value is where complete combustion would occur, if it could occur, and is where you would achieve the best fuel efficiency.  This value, however, is NOT ideal for all operating conditions of a Harley-Davidson motorcycle, or any engine for that matter.  Achieving a balance of fuel economy and best power / torque is the goal, and we’ve developed some handy tools to take the mystery out of tuning a fuel injected H-D motorcycle.

A typical Harley-Davidson ECM calibration has areas of closed loop and open loop.  In other words, there are areas where it can “see” the AFR and other areas where it can not.  When you’re in a range that requires precise measurement, but is outside the reliable window of a narrow band sensors operation (considered 14.3 -15.2 AFR), then a tuner / EFI specialist must rely on wide band O2 sensor data.  Since the ECM does not typically use or support wide band O2 sensors, a tuner must monitor / log the AFR values generated from a wide band O2 controller (like Dynojets’ Auto tune wide band O2 sensor control module).  The wide band O2 sensor values provide tuners or electronic tuning devices with data with which to make decisions on how they’ll address fueling in the open loop regions of the tune (those regions where the ECM has no idea what the AFR really is).  In either case, if the target AFR from the calibration is NOT achieved, the error must fixed by measurements acquired from the stock O2 sensors or aftermarket wide band sensors.  In the case of a Harley engine management system, we fix the error by adjusting the VE (volumetric efficiency tables).

Question: What does Dynojet offer to help me tune my bike? 

Answer: Auto tune.

As it pertains to the Power Vision, Auto tune is both a product and a process.  There are two different versions that you can use while tuning a bike:

  1. Auto tune Basic
    • Free and requires no additional parts for bikes that have OEM closed loop fuel control and O2 sensors
  2. Auto tune Pro
    • Not free and requires the use of our Auto tune wide band O2 control module that has dual wide band O2 sensors

The Power Vision can provide meaningful tuning feedback from EITHER the OEM narrow band O2 sensors AND / OR from the Auto tune module’s wide band O2 sensors……we call this Auto tune Basic or Pro respectively. 

So, with Auto tune Basic and without any additional modules (it’s simply a process) you could use the Power Vision to take advantage of what the ECM “sees” from its OEM narrow band O2 sensors and help it achieve the target AFR.  Not only can it fix the normal closed loop range, but the Auto tune Basic will actually temporarily extend the closed loop range to gain insight on the actual AFR in areas where it’s normally not allowed (high load / high rpm).   For the record >> At high load, high RPM ranges this “temporary situation” is not ideal, and this is where it’s advantageous to use Auto tune Pro.  We offer Auto tune Basic because essentially it’s free for the user, and it’s offered by the competition (V-Tune / Smart Tune ) as a band-aid approach to professional tuning.  This method works great in those areas where it makes sense to run in a lean state: idle, light load, and cruise conditions.  So, in any case, now the Power Vision can “see” what the ECM is commanding for AFR AND it can see what the actual AFR is in the exhaust.  Armed with this information and other data from the H-D OEM databus, the Power Vision can automatically fix the deviation between the target AFR and actual AFR by adjusting the VE tables.  The data is learned in real time, but processing the data and adjusting the tune is done in an “offline state” (key on / engine off).  In the end, the Power Vision can process the data, correct the tune, and then reflash the corrected tune into the ECM.

If you want to tune like a pro and get serious about developing a safe, efficient, and powerful tune, then you need Auto tune ProI’ll start by making this statement, “Any aftermarket EFI tuning system that does NOT use wide band O2 sensors inherently can NOT give you real time, valuable insight as to how rich or lean the bike is running in areas outside of the OEM closed loop range.”  Auto tune Pro is a process AND requires a product; that being the Auto tune wide band control module.  The Auto tune module uses wide band O2 sensors in order to measure the actual AFR in the exhaust, and these sensors can accurately sample AFR values from 10.0:1 to 18.0:1 (remember, narrow band O2 sensors are only accurate from 14.3 – 15.2 AFR).  When the Auto tune module wide band O2 sensors are installed in the exhaust and you’ve selected Auto tune Pro in the Power Vision, you’re on your way to a complete, refined, and powerful tune. The Power Vision, when running in Auto tune Pro mode, will actually temporarily set up your tune just like a professional tuner and datalog all required channels WITHOUT using a computer.  Just like Auto tune Basic, the entire process is attempting to correct the error from what’s commanded in the ECM defined as the target AFR, and the AFR that’s actually measured in the exhaust. Armed with this information and other data from the H-D OEM databus, the Power Vision can fix the deviation between the target AFR and actual AFR by adjusting the VE tables.  The data is learned in real time, but processing the data and adjusting the tune is done in an “offline state” (key on / engine off). 

Neither Auto tune Basic nor Auto tune Pro require that you interface with a computer when using this feature.  Power Vision sets up the tune, monitors and logs the data, and then corrects the tune to ensure what you ask for (in the AFR table) is what you get.  You essentially have a full time professional tuner inside your Power Vision with the Auto tune feature.

So, how do you know if your bike can be fitted with an Auto tune wide band O2 controller and the included 18mm wide band O2 sensors that are required for the Auto tune Pro feature?

  • On bikes that didn’t have factory closed loop fuel control / O2 sensors, you are left no choice but to weld 18mm O2 bungs into your exhaust OR buy an aftermarket exhaust system that had 18mm O2 bungs
  • On bikes that had factory closed loop fuel control / 18mm narrow band O2 sensors, you can simply remove them and install the 18mm wide band O2 sensors.  This requires that you temporarily (or permanently) disable closed loop……..or…..if you wanted to retain the OEM narrow band O2 sensors / closed loop fuel control AND install the wide band O2 sensors then they’d have to weld in bungs to their exhaust to accommodate the wide band O2 sensors.
  • If the bike has factory 12mm O2 sensors, and the guy wants to retain his stock exhaust, then there is no choice but to have 18mm O2 bungs welded into the exhaust.
  • On bikes with OEM 12mm narrow band O2 sensors, you could remove them and opt for an aftermarket exhaust that had 18mm O2 sensor bungs.  This will require that you disable closed loop.  If you wanted to retain the OEM narrow band 12mm O2 sensors / closed loop fuel control AND install the wide band 18mm O2 sensors, then you should look for aftermarket pipes that retain the factory 12mm O2 sensors AND had provisions for the wide band 18mm O2 sensors.

Note >> In 2010 Harley introduced the small 12mm O2 narrow band sensor on the Touring Models, and that has continued to be the case through the current model year for the Touring Model.  In 2012, Harley decided to use the small 12mm narrow band O2 sensors on Dyna, Softail, and V-rod as well.  Sportsters continue to use larger 18mm narrow band O2 sensors.

Note>> Not all aftermarket Exhaust systems have the needed 18mm bungs, it is best to check with the manufacture of the exhaust system.

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