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what are the advantages of fuel injection on a bike?

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It puts fuel in the cylinder from a little injector, instead of the carb.....that's about as simple as it gets.

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No jetting. Thats the only advantage because to be able to tune it for performance upgrades you either have to pay someone or by a tuner which gets costly. But its really nice to jump on and have a bike with awesome throttle response every time.

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EFI can be more accurate across all thottle positions and running situations. A carb only has a few little brass jets to adjust fuel flow along with a single tapered needle valve, FI can read all the running parameters and provide the exact correct amount of fuel. However.... most small bikes do not have the capability to self adjust and the setting up must be done by a pro with proper tools. If the bike changes or the riding air density changes it needs to be reprogrammed. So in this respect, it is still just like a carb. The differnece being you do not get gas on your fingers., A good tuner can make a carb work just about as well as FI. In the long run, FI is a much less expensive system.

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Complications on dirtbikes though. Buddy has an injected Husky and it was giving him fits most of the last trail ride ( 50+ miles). he thinks it was a sensor that had the thing cutting out in the upper rpm range.

Joe

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However.... most small bikes do not have the capability to self adjust and the setting up must be done by a pro with proper tools. If the bike changes or the riding air density changes it needs to be reprogrammed.

Yes and no to the above. If you make changes to the bike such as an exhaust, high comp piston, cams, etc... you do need to reprogram, but the systems do adjust for air density (changes in temp, humidity and elevation). Using my '13 KTM 450XCW as an example, it does have a Manifold Air Pressure sensor to go along with the Throttle Position Sensor and engine temp sensor, the MAP is what senses the air density and allows the computer to make adjustments for changes in air density. What dirtbikes don't have that cars and streetbikes do have is the O2 sensor in the exhaust and the ability to go closed loop. If they had that, then modest mechanical changes would be compensated for as well.

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Yes and no to the above. If you make changes to the bike such as an exhaust, high comp piston, cams, etc... you do need to reprogram, but the systems do adjust for air density (changes in temp, humidity and elevation). Using my '13 KTM 450XCW as an example, it does have a Manifold Air Pressure sensor to go along with the Throttle Position Sensor and engine temp sensor, the MAP is what senses the air density and allows the computer to make adjustments for changes in air density. What dirtbikes don't have that cars and streetbikes do have is the O2 sensor in the exhaust and the ability to go closed loop. If they had that, then modest mechanical changes would be compensated for as well.

None have a humidity sensor. Humidity is one of the three components of air density. A MAP sensor is only able to determine what the relative air pressure is. Few bikes track out side air temp and only track engine temp. The system on your KTM is pretty much the same as on all MX bike FI. Engine/coolant temp, MAP, RPM, throttle position. It uses what data it gets to make small changes to the predesigned fuel map. Some carb'd bikes have had these 'self adjustable' maps for years (AKA 3D map) though it only varied ignition timing. It is not a big leap to ad a fuel mix.

To fully learn and self adjust you need:

Air Temp (ambient)

Humidity

Inlet (ambient) air temp

MAP

Coolant temp

Oil temp

Crank position

Wide band O2

RPM

Throttle Position

Gear selected

You are not going to see these on a race MX bike because of the weight, electrical power needs and expense. Just like a carb'd bike, a mechanic will set the bike up for the race. All the FI does on an MX bike is meter the fuel for that race. I dobut you will ever see a full self adjusting FI settup on any bike other than massive adventure tourers.

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The idea that a carb is superior is what someone that has never owned a fi bike would think. I upgraded and would never go back.

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Sleds have been FI'd for years now. They've got it pretty well figured out - there's rarely any problems with them and the power a modern stock sled puts the old carb'd stuff to shame. Then when you roll it down a hill, you pull it over rubber-side down at the bottom of the hill, snap the windshield back on, and one or two pulls to fire it up again.

To be able to go from 6k ft to 12k ft without having to change anything is real nice.

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Using my '13 KTM 450XCW as an example, it does have a Manifold Air Pressure sensor to go along with the Throttle Position Sensor and engine temp sensor, the MAP is what senses the air density and allows the computer to make adjustments for changes in air density.

The MAP (Manifold Absolute Pressure) sensor measures intake manifold vacuum.

A MAF (Mass Air Flow) sensor measures air density.

Dirt bikes have a Speed Density type fuel injection system.

Fuel "mixture" is based off a matrix with inputs provided by the MAP, coolant temp , and throttle position sensors.

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i wasn't very keen on FI at first but never had a hiccup on the last three bikes so getting used to the idea. and out of countless rides with multiple riders over the past three years no one has had a FI problem so my experience is they are quite reliable systems on most bikes.

definitely not fix-it-on-the-trail friendly like a carb but i'm using a fuel filter sock to minimize the chances of fine particles creating blockages.

only thing i'd add to the benefits mentioned is usually the fuel economy is significantly better, handy when you have a small tank.

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just a fuel pump to go bad, fuel injectors to go bad. computers to go bad. a carb is proven. ill stick to carbs

I guess that's why cars are still using carbs :goofy:

Carbs are simple but require constant attention. FI is more of a set and forget it type system.

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