More Sound, More Power, Less Money.
Part II

By: Biker Chad

As we learned in part one of this article you can add a slip on muffler to get better sound without adding fuel.  As long as you stay with a 2” or 1.75” baffle, and keep the stock air filter assembly, you will not need to modify the fuel settings on your bike.  If all you want is better sound, a slip on muffler is all you need. To those of you who have added a muffler or some other exhaust along with a high flow air filter, and not added an E.F.I. (electronic fuel injection) modification you are running too lean and asking for trouble!

So how can you tell if you are running too lean?  Does your bike pop and backfire (commonly called a lean misfire) when you let off the throttle?  Are your mufflers turning blue or yellow?  Are your spark plug electrodes white in color when you change them?  Does your bike run way too hot?  Do you feel a lack of acceleration and power when you try to pass at highway speeds?  If you answered yes to one or more of these questions, you need to add some fuel to the mix!  To correct this lean condition, or to complete part two of a stage one set up, I will share what I know in this article.

Some dealers will have you believe that EFI boxes are bad, and the only way to correct your AFR (air to fuel ratio) if you have caused a lean condition by adding mufflers and a high flow air filter is to get a dealer download.  Lets examine that, your bike came from the factory set too lean to be happy in the first place, with an AFR set at around 14.7 to 1 (this means for every 14.7 parts of air you have 1 part of fuel).  Any download you get from a dealer will be costly.  One download may not be enough to correct your AFR, requiring another download or costly and punishing dyno time.  After all that your AFR will be only be set to the required lean setting of 14.7-1 that Harley recommends. A dealer download may help, but in my opinion it is not the best use of my hard earned money.  Don’t be mad at your dealer, it is not their fault, as they have rules to follow.  The main reasons that Harley sets their bikes at a lean 14.7-1 AFR is to meet EPA pollution requirements, as well as to try to get the best mix of power and fuel economy.  So as you can see even a bone stock bike will benefit from adding a good EFI box.  So what do I recommend the AFR be set to?  I run my bike at about 13.0 – 1 across the board, I get 39-42 mpg average at this setting.  My bike is more powerful, runs smoother, has quicker throttle response, and runs cooler.

Question, what is one to do if a dealer download is not what you want?  Answer, get an EFI box and install it yourself!  It is not that hard to do.

There are a lot of EFI boxes out there, what is the one you should you buy?  Well opinions are a dime a dozen.  I will share what I know and leave it up to you to do your own research.

A lot of the myths and rumors about these boxes that you may have heard come from the bad ones on the market.  If a box has generation II technology it is the kind that tricks your bike into thinking it is in a constant state of  “warm up” mode, this is how it adds fuel.  These boxes will usually be the cheapest, and have a simple 3-mode design.  Problems reported with these boxes are things like a check engine codes, and poor performance.  Gen II boxes will not always add fuel across the entire rpm range, leaving lean or “flat” spots.  Gen II boxes usually bypass the O2 sensors on the bike by way of a resistor cap.  Remember, bypassing your bikes O2 sensors is illegal.  I do not recommend these boxes.

The next level of EFI boxes employ generation III technology.  These boxes are a little more than their gen. II cousins (around $300.00), but they are way worth it.  The typical gen. III box has a 6-mode design.  Gen III boxes are much smarter, faster, and better in many ways.  They will work with your engines O2 sensors (not bypassing them), allowing your bikes diagnostic system to do what it was designed to do.  Gen. III boxes will add fuel across the entire rpm range.  Your bikes computer will not know the gen. III box is there, as it is installed in-line with the fuel injectors (between the computer and injectors) in a piggyback set up.  Installing a gen. III box will correct the AFR, help your engine last longer, run cooler, run better, increase power, allow you the freedom to change the settings as you please.

The next level to correct your AFR is a fully auto-tuning system.  Although these are some of the best options to correct you AFR, I will not discuss them in this article as they cost around $1,000.  The installation of an auto-tune system is usually beyond the realm of most at home mechanics.