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Timmer

Fuel Injection Questions

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Timmer    0

Fuel injection, digital ignition, oxygen sensors, traction control, fly-by-wire, ABS.

 

Anybody have any questions about how this stuff works?

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Cobie Fair    13

Fuel injection, digital ignition, oxygen sensors, traction control, fly-by-wire, ABS.

 

Anybody have any questions about how this stuff works?

 

Good questions Timmer. Here's my thought: start a thread on each of these, and give us a brief description of how a system (or simply that part) works. Likely will bring to mind things we hadn't even thought to ask.

 

CF

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Timmer    0

Good idea Cobie.

 

Let's keep this post to strictly fuel injection stuff. Some of you guys may know some of this info already...but here is the quick history and how-it-works of fuel injection.

 

A little history...

Back in the old days of motorsports, fuel was delivered to the motor by way of a carburetor. A carburetor is strictly a mechanical device with moving parts and pieces. They work pretty good but they don't compensate for changes in air density very well and are not very precise by today's standards. This is why guys were constantly changing jet sizes(orifice that fuel flows through) from track to track.

 

Now that we are in the age of computers, electronic fuel injection has entered the scene. Pretty much all modern cars, motorcycles, ATVs, snowmobiles, etc. are now fuel injected. A fuel injector is like a squirt gun. It squirts fuel in the airstream going to the combustion chamber. The amount of fuel needed varies based on throttle position, RPM, air pressure, and air temperature.

 

Fuel Injector

A fuel injector is actually a pretty simple device. It has a metal plunger, a spring, and a coil of wire. It also has a pressurized fuel hose connected to it. When electrical current flows through the coil of wire it produces an electromagnet. This magnet pulls the plunger up and allows fuel to flow around it. After a specified amount of time the electromagnet is turned off, and the spring pushes the plunger back down. This on and off of the injector is done as quickly as 1 millisecond(1/1000th of a second)!

 

ECU(or ECM)

The ECU(Electronic Control Unit) is what turns the injectors on and off. It is also the brain of the bike. It takes in data from a bunch of sensors and decides when and for how long to fire the injectors. Since the ECU is constantly measuring things like throttle position, RPM, air pressure, and air temperature, it always knows how much fuel to deliver to the motor under any kind of riding/weather conditions!

 

Anyway...there's the quick and simple. Please fire away if anyone has questions. :)

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Cobie Fair    13

Thanks Timmer,

 

I didn't know exactly how the injectors worked, thanks for clearing that up.

 

I think I know, but just to be sure, what exactly is the mapping that is done, and how come some work better than others? If fuel injection is so cool, how come my car runs like and pings? Is it simply the map is unable to handle the exhaust system that was added?

 

CF

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Timmer    0

Good questions Cobie.

 

A map is similar to an Excel spreadsheet. It is a table or collection of tables inside the ECU that defines how to operate the fuel injectors(and other things) for different operating conditions of the motorcycle. A Power Commander or Bazzaz Z-Fi also have the same kinds of tables in them.

 

Attached below is a very simple map from a Power Commander. The ECU of the bike has tables inside it similar to this, only it has many more of them. It is basically a spreadsheet that defines how much fuel should be squirted for different operating conditions of the motorcycle(in this case throttle postion vs. RPM). The ECU also has other tables in it for other things such as ignition timing, fly-by-wire, traction control, etc....but for right now we'll just stick to the injector stuff.

post-711-0-70946900-1329782477_thumb.jpg

As you can see from the map I've attached, you can define how much fuel should be sprayed for almost any combination of throttle position and RPM. This is what makes fuel injection much more precise.

 

When a manufacturer "maps" a vehicle they are figuring out what values need to be put in these tables. They do not always get this right for EVERY operating condition of the vehicle. They also have to tune their vehicles to meet emissions standards, which is usually not the best performance.

 

Starting to make sense?

 

Pinging or knocking is most often caused by things surrounding ignition. Actually, there are a number of things that can cause pinging/knocking. Since this is more of an ignition thing, I'll start a separate post explaining this further.

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mugget    3

A great idea to have a tuning forum - I never knew exactly how fuel injection worked with the electromagnet, interesting stuff!

 

My question about fuel injection - everybody probably knows about the fuel additives that you can buy that will sort of 'clean out' injectors when they get gummed up or start to get clogged, although I've mostly seen this stuff for car (and older cars at that). Is this kind of thing ever likely to be a problem on a modern bike? Or is there some kind of cleaning/inspection that goes on during the routine servicing?

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Timmer    0

A great idea to have a tuning forum - I never knew exactly how fuel injection worked with the electromagnet, interesting stuff!

 

My question about fuel injection - everybody probably knows about the fuel additives that you can buy that will sort of 'clean out' injectors when they get gummed up or start to get clogged, although I've mostly seen this stuff for car (and older cars at that). Is this kind of thing ever likely to be a problem on a modern bike? Or is there some kind of cleaning/inspection that goes on during the routine servicing?

 

Another good question mugget.

 

Everyone that I have talked to seems to think that those fuel additives you can buy to clean your injectors are basically a load of BS. As long as the injector is regularly being used, it usually takes quite a long time before they will get gummed up. I think most of us don't own bikes old enough that would even start to have gummed up injectors...Haha.

 

You might want to get it checked after you have put some serious miles on the bike or if it has been sitting for more than a year, but for the most part I wouldn't worry about it.

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