Ecm question
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Stage I
Joined: Mar 2016
Posts: 1
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From: Great Falls
Ecm question
Ok I have tuned/programmed cars many times before. I have yet to come upon a car/truck that can't take a new exhaust or an air intake without having to re-tune the computer. Why is it I have to re-tune my Harley just for a new air cleaner?
Tourer
Joined: Mar 2015
Posts: 454
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From: Here
The lean AFR that engines run today cause the engine to run hotter. Free flowing intakes and exhausts cause the engine to run even hotter. Air cooled engines are not able to get rid of the heat as well as water cooled engines. So we tune them to run richer.
MODERATOR
Joined: Oct 2007
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From: New England
The answer is you might not have to re-tune at all...but it's nice to know that one can dial in a tune if needed.
People will tell you it's too lean, but they don't understand adaptive fuel. Now, in stock trim, the computer is set to run as lean as possible and with a tuner you can change that a few tenths of a point and still stay in closed loop.
If you want to really change it you will either go out of closed looop with the Harley ECM, or explore aftermarket tuners that will help build a new VE map. If that's the case I'd recommend exploring the PowerVision.
Road Master
Joined: Oct 2012
Posts: 777
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From: Beaumont, Ca
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It means that the exhaust has sensors called Oxygen Sensors that provide feedback to the ECM about the amount of oxygen left in the mixture after combustion.
The ECM then adjusts the next round of injector pulses to either add more or less fuel to achieve the desired air/fuel ratio.
The oxygen sensors close the information loop.
OPEN LOOP: ECM receives information from sensors - controls injectors and coil - doesn't know what came out the exhaust.
CLOSED LOOP: ECM receives information from sensors - controls injectors and coil - receives O2 sensor feedback - adjusts next injection event.
The ECM then adjusts the next round of injector pulses to either add more or less fuel to achieve the desired air/fuel ratio.
The oxygen sensors close the information loop.
OPEN LOOP: ECM receives information from sensors - controls injectors and coil - doesn't know what came out the exhaust.
CLOSED LOOP: ECM receives information from sensors - controls injectors and coil - receives O2 sensor feedback - adjusts next injection event.
Last edited by Ed Ramberger; Mar 20, 2016 at 02:30 PM.
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Road Warrior
Joined: Mar 2013
Posts: 1,923
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From: Alorton, Illinois
Another thing to consider is the exhaust system themselves. A car are truck usually has a system that is well over 7-8 feet long. With restrictive mufflers and cats.
Aftermarket Harley exhaust is much shorter and much more free flowing. This will all affect how O2's are sampled.
Aftermarket Harley exhaust is much shorter and much more free flowing. This will all affect how O2's are sampled.
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