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Fuel Injection, Beginners primer.

7K views 25 replies 10 participants last post by  Road dawg 
#1 · (Edited)
There was a recent thread where fuel injection and specifically the function of O2 sensors was discussed. Rather than continue a useless argument in that thread, I decided to provide a little tutorial. A little tutorial from the MoCo.

In a nutshell, there are two types of fuel injection used on Harley's. Way back when, it was a Magneti-Marelli Alph-N system. And they had a lot of issues. Poor parts quality, limited processing power and most of all, poor tech training. This system was used to try to satisfy the EPA's demands for cleaner running motorcycles. And it did, within its abilities, and when it was in proper working order and properly adjusted.

A while later the EPA demanded that the scooters run even cleaner, so much cleaner as to include catalytic converters. The MoCo knew that the MM system was not up to that task, so they adopted a Delphi built Speed Density system.

Here is a power point presentation on the Harley fuel injection system and the tuners that were used to tune it. It predates the epa clampdown, so it includes a little info on the ways to tamper with the oem system

Electronic Fuel Injection for Harley

OK so here are some points from the presentation.

But first, I've added a couple of fuel table representations. Take note of the number in the individual cells. That's what is important.

The system uses pre installed fuel maps to determine how much fuel to provide under any given condition. Many of us have seen visualizations of these. There are many ways of presenting them to the human eye. What's important is the numbers in the cells. 14.6 is the target for closed loop fuel trim. 14.6 is the ratio of air to fuel. 14.6 grams of air per gram of fuel. A lower number calls for a richer mix (more fuel), and a higher number is a leaner mix (less fuel)

Notice how the table avoids 14.6, more on that later.





The MoCo has no choice but to attempt to target the fuel mix at 14.7 to 1. Its the law.



To do this, harley build the fuel tables and then uses a narrow band O2 sensor (Oxygen Sensor) to maintain the fuel trim. This is called closed loop operation. This is only available during idle and light load cruise conditions. The rest of the time the ecm just uses the apropreate setting from the fuel tables. This is called Open Loop. In open loop the O2 sensor has no function. And this is because of the limitations of narrow band sensors. They can only function at fuel settings of 14.3:1 to 15:1 to one or there abouts.



So how does that work?

In closed loop the ecm trims the fuel based on O2 input. In open loop the ecm uses the stored fuel tables (maps).



OK so how does the ecm know when its in closed loop or open loop? If 14.6 is the entry in the look up table for the applicable cell, it tries to operate in closed loop. This is call the Air Fuel Ratio Switch. And its the reason why trying to trick the ecm with resistors in the O2 sensor circuit don't always work well.



OK enough of that.

Some of us don't like the way these scooters run as delivered from the factory, so we make changes. And most of that involves replacing the oem fuel map with one written to make better power.

So Harley says that the fuel targets should look more like this. 12.8:1 to 13.6:1



But wait, remember that narrow band O2 sensor, it can only function at 14.3:1 and leaner. How does this work. The way it works is that the ecm is reprogrammed to ignore the O2 sensor, and no longer trims fuel based on it. No cells in the fuel map will have 14.6 entered. So there is no closed loop operation.

Or, a devise is added to the system that allows for the use of Wide Band O2 sensors.

So what is a Wide Band 02 sensor.



Wow, it works sooty rich, 10:1 all the way to piston burning lean 18:1. So why the hell doesn't Harley uses these? Its simple, they cost more, and are not needed to keep the fuel at 14.7 to one. The $9.95 narrow band sensor can do this. But Harley will sell you what you need to install these sensors. Fact is, these very sensors can be used during the dyno tuning process.

So how does this tuning thing work? And why do I need it. You don't need it. Your scooter will run well enough as delivered. But if you want it to run better or change parts, you might need to have it tuned. There are three main ways it works. You can load an new map into the ecm, or flash it. This is what Harley does when you do a stage one. You can add a device to the system, or you can replace the system (ecm) Add on devices run the range of allowing you to load new maps (flash), build new maps on a dyno, or build new maps on the fly.

And there are two types of tuning. Using legal EPA approved maps that are within the 14.7 limits and still use closed loop function, or Race only maps that are not approved for street use by the EPA. Harley dealers are only allowed to install EPA approved maps. And that's all I'll say on that.

So now you have the basics.
 
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#2 · (Edited)
So now that you are versed in Harley fuel injection, you might be wondering about this Alpha-N and Speed density stuff.

Basically there are three types of electronic fuel injection used in the automotive industry. Alpha-N, Speed Density, and Mass Air Flow. Harley uses Speed Density (Delphi), and in the past has used Alpha-N (MM).

So what's the difference?



In a nut shell, Alpha-N is not emissions or EPA friendly. But it is race friendly. Many race tunes and devises actually use Apha-N emulation in the Delphi ecm. This is because the MAP sensor output is adversely affected by high performance cams.
 
#4 ·
Unless somethings changed in the last 2 or 3 years, no manufacturer has adapted a mass airflow injection system to a bike. Very difficult to do for a multitude of reasons, not the least of which is packaging.

That tutorial has been floating around for a few years. IIRC it was something that a tech put together for a tuning class, not an "official" Harley document. Regardless of the source, it's a good primer for people who are just getting into tuning.
 
#9 ·
Yes, the space it would take. The sensor itself wouldn't be the issue, Delphi already makes some small form factor sensors

Mazda mass airflow sensor.

410187


The issue would be air flow and the ducting needed to clean it up. A section of straight ducting at the sensor and some distance from the air filter to calm the airflow.

Then you would need to add the NoX cat to the exhaust package. And control the engine temps.

We already know they MoCo is working with water cooling. if they get forced down this path by NoX, the additional converter will be a real issue. NoX cats run hotter than HC cats. And people are already complaining about the HC cats. Its doable, but will probably be real ugly by the time the cats and the needed heat protection all get packed into a down pipe.
 
#15 ·
If warranty retention is your goal, stick with whatever Harley offers. Anything else will void the warranty, as the dealer is required to flag your VIN if/when they see any unapproved parts. Flagging is not discretionary, as they're audited.

The factory tune isn't horrible. It's designed for maximum longevity, emissions compliance, and efficiency. There are literally millions of stock bikes out there and they're all running just fine.

If you want "more", and you're willing to forego your warranty, you can do very well with both of the flash tuners out there. Both TTS and Dynojet (via FuelMoto) offer good starting base maps. But it's then on you to street tune them. That can be problematic if you live somewhere without hills. Depending on where you are in Ohio, you may be good, or you may be in that area southeast of Toledo that's like riding on graph paper.

Tuner's $400. Figure another $400 for mufflers, $150 for your air cleaner backing plate & filter, and another $600 for your head pipe. You can do all this cheaper if you buy stuff used, but this puts you in the ballpark. A professional tune is going to be another $400, and you'd need to find someone who knows what they're doing.

So the question you have to ask yourself is whether or not the couple of HP your tuner will find and the additional smoothness that someone who knows what they're doing is worth $400, or are you interested in learning way more about fuel injection than you ever wanted to know, doing it yourself, and recognizing that you're leaving a little bit on the table.

My answer was simple. My Stage 1 RGU was tuned by me, and I couldn't care any less that there may be a slightly smoother curve that's $400 away. My beast of a Night Train with its $9,000 motor was dyno tuned by one of the best in the country.
 
#20 ·
If warranty retention is your goal, stick with whatever Harley offers. Anything else will void the warranty, as the dealer is required to flag your VIN if/when they see any unapproved parts. Flagging is not discretionary, as they're audited.

The factory tune isn't horrible. It's designed for maximum longevity, emissions compliance, and efficiency. There are literally millions of stock bikes out there and they're all running just fine.

If you want "more", and you're willing to forego your warranty, you can do very well with both of the flash tuners out there. Both TTS and Dynojet (via FuelMoto) offer good starting base maps. But it's then on you to street tune them. That can be problematic if you live somewhere without hills. Depending on where you are in Ohio, you may be good, or you may be in that area southeast of Toledo that's like riding on graph paper.

Tuner's $400. Figure another $400 for mufflers, $150 for your air cleaner backing plate & filter, and another $600 for your head pipe. You can do all this cheaper if you buy stuff used, but this puts you in the ballpark. A professional tune is going to be another $400, and you'd need to find someone who knows what they're doing.

So the question you have to ask yourself is whether or not the couple of HP your tuner will find and the additional smoothness that someone who knows what they're doing is worth $400, or are you interested in learning way more about fuel injection than you ever wanted to know, doing it yourself, and recognizing that you're leaving a little bit on the table.

My answer was simple. My Stage 1 RGU was tuned by me, and I couldn't care any less that there may be a slightly smoother curve that's $400 away. My beast of a Night Train with its $9,000 motor was dyno tuned by one of the best in the country.
All great info, I wasn’t thinking of the head pipe was just going to do air cleaner and already bought used mufflers. I know that stock is fine and the M8 really shines above the twin cam, as you know I also have a Night Train with a $9,000 motor as were most of my previous bikes. I’m just finally realizing cost doesn’t justify the means the small differences between our dyno sheets on the street wouldn’t matter, it would come down to the better rider more than the horses. I just want a good clean running bike, the best part of my SG with a 107 wasn’t the speed, I would still be at a 1/4 tank while all my stock buddies were empty. I’m also a little on the anal side like I said in previous post “ know enough to be dangerous “ if I know it can be better I want it to be just not to the extreme and would like to hang on to this one for a while.
I do live in the flat lands but when I do get out to ride it’s in the hills of PA or my favorite spot is down in the NC hills you can be in 4 different states within an hour and too many awesome roads to mention, the only downfall being you have to ride an hour for beer as well being it’s the last dry county in the state. Who knows which way I will go but as always great info not just from you but everyone here and I wish you were not so far away so we could see how the 2 trains run!! Thanks
 
#25 ·
"The engine ECM has been changed from a mapped (command) system to torque-based (rider throttle position is interpreted as a call for a specific torque level, not a specific throttle angle)."
—Kevin Cameron

i remember delving into race math on my evo. learned a lot about how these big v-twins work.
the more sophisticated the engine management software becomes, the more efficiently they run.

the new 131 underscores the old adage "there's no replacement for displacement."
i know it's a bandaid solution to a political proclamation (EPA), but it's a beautiful thing, listening to these engines, no matter what the size.

thanks for the post, @Thermodyne
it's always great to learn!
 
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