Author Topic: is there any truth to the whole "let the ecu relearn" new exhaust thing?  (Read 1579 times)

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iblastoff

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i've seen people mention it in plenty of videos. i've also seen people say its a lie. others have said they replace an exhaust and let the engine run for 10 minutes and have noticed zero difference (in terms of popping, etc).

does anyone have any insight if this is a real thing?

planning on replacing the stock pipes real soon! (scorpions from a fellow forum poster here)
« Last Edit: October 21, 2021, 04:01:52 pm by iblastoff »


Blazes Boylan

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I don't doubt you could glean some benefit from using a Power Commander on even a stock bike, properly mapped.  If I installed a high performance cam or high compression pistons I'd definitely modify the ECU.  As of right now I'm running the standard ECU with a TEC 2-into-1 exhaust (no catalytic converters) and I'm very happy with the performance.  I get a little popping on decel but it's barely noticeable.


viczena

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A learning ECu needs a lambda sensor. And these ECUs dont use the lower and the upper 20% of the map with the lambda sensor. So the ECU does not adapt near idle and near high load.

Therefore its a good idea to use a PC or something similar. A popping exhaust is botch by a lazy mechanic.
« Last Edit: October 21, 2021, 04:44:36 pm by viczena »
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ideola

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I don't know specific details about the RE ECU, so take my comments with a grain of salt.

It depends upon what you mean by "learning". In my view, it is something of a misnomer. OBD2 compliant ECUs are required to be "adaptive", wherein they have a fixed set of maps in the ECU, and the ECU's sensors have the ability to detect environmental changes such that it can "adapt" from the preloaded map and adjust the values on the fly to deliver optimal functioning; in the case of OEM ECUs, "optimal functioning" is tends to be biased first toward meeting emission requirements, secondly for reliability (keep stupid people from blowing things up), thirdly for efficiency, and last performance).

There are some stand-alone ECUs that have the ability to dynamically update the fuel and ignition maps based on changing conditions. I would be mildly surprised if the RE ECU has this capability. I don't know the extent to which true "learning" ECUs are in use in other OEM vehicles.

All of this to say, adding aftermarket
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iblastoff

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I don't know specific details about the RE ECU, so take my comments with a grain of salt.

It depends upon what you mean by "learning". In my view, it is something of a misnomer. OBD2 compliant ECUs are required to be "adaptive", wherein they have a fixed set of maps in the ECU, and the ECU's sensors have the ability to detect environmental changes such that it can "adapt" from the preloaded map and adjust the values on the fly to deliver optimal functioning; in the case of OEM ECUs, "optimal functioning" is tends to be biased first toward meeting emission requirements, secondly for reliability (keep stupid people from blowing things up), thirdly for efficiency, and last performance).

There are some stand-alone ECUs that have the ability to dynamically update the fuel and ignition maps based on changing conditions. I would be mildly surprised if the RE ECU has this capability. I don't know the extent to which true "learning" ECUs are in use in other OEM vehicles.

All of this to say, adding aftermarket

yah i feel it has to be 'adaptive' in some limited sense but i have no idea. i just dont get the whole "10-15 minute" wait part and why that has become sort of an accepted truth for these bikes. i mean its not like it'll hurt the bike if i do that but im wondering if its just turning into some weird myth.


ideola

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yah i feel it has to be 'adaptive' in some limited sense but i have no idea. i just dont get the whole "10-15 minute" wait part and why that has become sort of an accepted truth for these bikes. i mean its not like it'll hurt the bike if i do that but im wondering if its just turning into some weird myth.
I agree, I think it's a myth. In order to comply with Euro4/5 OBD2 requirements, it has to adapt period. All the time. So I definitely don't buy the 10-15 minute wait thing, unless and until someone can demonstrate empirically why it would be necessary.
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NVDucati

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yah i feel it has to be 'adaptive' in some limited sense but i have no idea. i just dont get the whole "10-15 minute" wait part and why that has become sort of an accepted truth for these bikes. i mean its not like it'll hurt the bike if i do that but im wondering if its just turning into some weird myth.
Under the premise that two things can both be true, at the same time ...
There is adaptive learning. It is limited to idle and "steady throttle" operations. The learning is dynamic and temporary. So yeah, it will adapt during the 10 minute idle thing. It will adapt in the same way while idling at a stop light or at steady throttle riding and as the ambient temperature changes and your elevation above sea level changes. In my personal opinion while not untrue, the idle thing is unnecessary.
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AzCal Retred

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https://en.wikipedia.org/wiki/Oxygen_sensor

Function of a lambda probe
Lambda probes provide feedback to an ECU. Where applicable, gasoline, propane and natural gas engines are fitted with three-way catalysts to comply with on road vehicle emissions legislation. Using the lambda sensor signal, the ECU can operate the engine slightly rich of lambda = 1, this is the ideal operating mixture for a three way catalyst to be effective.[2] Robert Bosch GmbH introduced the first automotive lambda probe in 1976,[3] and it was first used by Volvo and Saab in that year. The sensors were introduced in the US from about 1979 and were required on all models of cars in many countries in Europe in 1993.

By measuring the proportion of oxygen in the remaining exhaust gas, and by knowing the volume and temperature of the air entering the cylinders amongst other things, an ECU can use look-up tables to determine the amount of fuel required to burn at the stoichiometric ratio (14.7:1 air:fuel by mass for gasoline) to ensure complete combustion.


The sensor does not actually measure oxygen concentration, but rather the difference between the amount of oxygen in the exhaust gas and the amount of oxygen in air. Rich mixture causes an oxygen demand. This demand causes a voltage to build up, due to transportation of oxygen ions through the sensor layer. Lean mixture causes low voltage, since there is an oxygen excess.

Modern spark-ignited combustion engines use oxygen sensors and catalytic converters in order to reduce exhaust emissions. Information on oxygen concentration is sent to the engine management computer or engine control unit (ECU), which adjusts the amount of fuel injected into the engine to compensate for excess air or excess fuel. The ECU attempts to maintain, on average, a certain air-fuel ratio by interpreting the information gained from the oxygen sensor. The primary goal is a compromise between power, fuel economy, and emissions, and in most cases is achieved by an air–fuel ratio close to stoichiometric. For spark-ignition engines (such as those that burn gasoline or LPG, as opposed to diesel), the three types of emissions modern systems are concerned with are: hydrocarbons (which are released when the fuel is not burnt completely, such as when misfiring or running rich), carbon monoxide (which is the result of running slightly rich) and NOx (which dominate when the mixture is lean). Failure of these sensors, either through normal aging, the use of leaded fuels, or fuel contaminated with silicones or silicates, for example, can lead to damage of an automobile's catalytic converter and expensive repairs.
 When the engine is under low-load conditions (such as when accelerating very gently or maintaining a constant speed), it is operating in "closed-loop mode". This refers to a feedback loop between the ECU and the oxygen sensor(s) in which the ECU adjusts the quantity of fuel and expects to see a resulting change in the response of the oxygen sensor. This loop forces the engine to operate both slightly lean and slightly rich on successive loops, as it attempts to maintain a mostly stoichiometric ratio on average. If modifications cause the engine to run moderately lean, there will be a slight increase in fuel efficiency, sometimes at the expense of increased NOx emissions, much higher exhaust gas temperatures, and sometimes a slight increase in power.
When an internal combustion engine is under high load (e.g. wide open throttle), the output of the oxygen sensor is ignored, and the ECU automatically enriches the mixture to protect the engine, as misfires under load are much more likely to cause damage. This is referred to as an engine running in "open-loop mode". Any changes in the sensor output will be ignored in this state. In many cars (with the exception of some turbocharged models), inputs from the air flow meter are also ignored, as they might otherwise lower engine performance due to the mixture being too rich or too lean, and increase the risk of engine damage due to detonation if the mixture is too lean.

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lucky phil

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People are confusing a few things here. Some ecu's have a "self learning" function. So the ecu monitors the engine parameters including the Lambda and can detect for instance a partially blocked fuel filter. The ecu will compensate for this partially blocked fuel filter by increasing the fuel injector pulse width to inject more fuel and keep the lambda reading within the required range for stio correct ( a blocked fuel filter means lower fuel pressure so a greater injector pulse width is needed to compensate). It retains this " learned" information until the condition is corrected (fuel filter replaced in this case) or battery is disconnected or the ecu fuse is pulled for example. When the engine is shut down normally the ecu "remembers the learned" condition and is ready to apply the new parameters on the next start. This system also compensates for normal engine ageing and wear or a blocked air filter or a under performing worn fuel pump, dirty injectors etc. There are other strategies involved such as short term and long term fuel trim and the ecu monitors changes and initially and applies first short term trim and then if the condition remains moves to long term trim. This is independent from normal closed loop fuel trim and all the other engine temp, baro aitr temp, MAP, etc trims.
The separate issue is idle speed control which is done by the idle control stepper motor. The engine "knows" or has "learned" if you like the required idle stepper motor position for correct idle speed for each particular engine. If the battery is disconnected depowering the ecu or the plug falls off the idle stepper motor while the engine is running the ecu loses this information with regards to the idle stepper motor position and needs to re establish the correct position. It will do this by cycling the stepper motor to fully close the air bleed and establish a "null" position and then adjust the idle speed to what it's target range is. It now knows again(or has "relearned" if you like) it's established idle position for this engine and "remembers for the next start cycle. When I fitted my aftermarket exhaust there was no difference to the engine idle and I didn't expect there to be because the exhaust has no real bearing on the idle speed in any meaningful way. I did however experience the ecu re learning the idle speed after I had disconnected the battery when I fitted a battery charger extension lead.
I have had the exact same experience with several of the injection systems on my cars after battery replacement. On initial start the idle isn't perfect however the ecu will re establish the correct parameters and "relearn" quite quickly. Does the RE system have these strategies? Idle it does for sure but I doubt it has the short term and long term trim learning/compensation functions because motorcycles haven't in the past needed to meet the same emission and running obligations of automotive world and have used less sophisticated systems.   
Ciao
« Last Edit: October 21, 2021, 11:09:25 pm by lucky phil »
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Blazes Boylan

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This is a very informative thread, thank you.  For what it’s worth, my Interceptor idles at around 1800 rpm at startup and drops to about 1100-1200 after it warms up.  Is this standard?


whippers

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My understanding is that while not strictly necessary (the adaptions will come with time anyway) letting it Idle from cold with no throttle input lets the ecu understand the changes with just engine temperature changing rather than load and throttle position etc..
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lucky phil

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This is a very informative thread, thank you.  For what it’s worth, my Interceptor idles at around 1800 rpm at startup and drops to about 1100-1200 after it warms up.  Is this standard?

Yes.

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lucky phil

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My understanding is that while not strictly necessary (the adaptions will come with time anyway) letting it Idle from cold with no throttle input lets the ecu understand the changes with just engine temperature changing rather than load and throttle position etc..

I don't believe the RE needs to "learn idle after a muffler replacement". The mufflers have no real influence on how an engine idles, there's just not enough exhaust flow at idle to cause a restriction on a std muffler. The ecu has a cold cranking map and and an engine temp trim map among others. So it is base fuel map+engine temp trim+cranking enrichment+ambient temp trim+barometric pressure trim. Add them all together and you get the total fuel fuel injector duration. In extreme conditions like below zero for a short period at start up the fuel enrichment can be almost 250%. This is why fuel range suffers so badly with a lot of cold starts in a tankful of fuel. Cold cranking enrichment usually lasts for a defined number of engine revolutions. So it adds a lot of fuel at the first push of the button and then tapers it off over say 4000 revolutions, not rpm but counted revolutions. Then it's off and the rest of the trims are still there. So the next trim that will reduce is engine temp until you get to full engine operating temp. It can also add fuel again at temps above operating temp if it's so programmed. Some do this.
The same applies to the ignition mapping. The base map and all the trims also modify the base ignition map as well. So you can see at cold start the system has a bit going on and running parallel to this is the idle speed control via the ecu and idle stepper motor. Older systems don't use an idle stepper motor and the elevated idle speed is controlled from a "high idle" lever on the l/h bar. All this is is a mechanical throttle stop adjuster exactly the same as cracking the throttle.
So sometimes after a cold start when the engine arrives at normal operating temp you will be on the base map+air, and baro trims because thats what the ambient conditions dictate. baro trim is usually not a massive trim and if you ride around at sea level up to 2000 feet you won't need or feel any difference in engine operation even with it not working. This has happened to me and I rode the bike for years with a failed baro sensor because I ride at seal level and when the sensor failed the ecu just reverts to a "default" setting. On top of this you also have the Lambda trim in "closed loop" operation which is used at "steady state" throttle only. This is the "basics" there a lot going on in the background as well such as fuel density correction which is a calculation between engine and air temp and calculating fuel density to correct injector duration based on calculated fuel density changes.

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« Last Edit: October 22, 2021, 01:57:11 am by lucky phil »
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GSS

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Precisely as a majority have stated, this permanent learning myth over a 15 minute idle has been around since the advent of the Classic 500s.

While the ECU adapts within preset parameters while running, there appears to be no permanent remap that it is capable of saving. Thanks.
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Blazes Boylan

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So, if I’m following this thread correctly, the gist of it is, every time I start my bike the ECU is in exactly the same state it was when it came from the factory, no matter how many modifications I’ve made to the bike.  (Unless of course I’ve actually gone in and remapped the ECU.)