FAQ ECU Learning

I heard my vehicle’s ECU learns out performance modifications. Will my OEM computer learn out the changes being made by the Unichip?

Short answer – No.

Long answer – The technical term for learning is “adaptation.”  All OBD2 compliant ECU’s adapt, they all adapt roughly the same way, they all adapt roughly the same amount, and they all adapt in roughly the same time frame.  Adaptation is a critical part of OBD2 compliance, drivability, reliability, and maintenance.  The OEM wants the ECU to adapt, Unichip wants the ECU to adapt, and you want the ECU to adapt… assuming you have an aftermarket computer to handle it for you.

No OBD2 compliant ECU will learn out a correctly programmed Unichip and in fact vehicles modified with bolt-on intakes and exhausts will always be “less” adapted with the Unichip than without it.

Technical answer – Vehicle manufactures want to cost effectively mass produce vehicles and must comply with strict emission requirements. Faced with manufacturing stacking tolerances, variable ambient conditions, changing driving styles, and parts that begin wearing out the moment the vehicle leaves the factory, they nonetheless must produce vehicles that consistently and precisely comply with governmental regulations and deliver good performance.  To do so, they use a “learning” computer to control the engine’s operation.  “Learning” computers, called adaptive computers, benefit the OEM in two ways…

o   First, if the computers didn’t adapt, the parts would have to which means every individual vehicle would have to be tuned because of stacking tolerances.  That would make everything cost significantly more and might make production prohibitively expensive.

o    Second, using the adaptive computer to enable each vehicle to age gracefully and not have to come in for service every six months.  Without these computers, even after being individually tuned after production, each vehicle would need to be tuned frequently as its components wear out.  With these computers, wear and tear is automatically compensated for and when you finally do have to get a tune up at 100,000 miles or so, you’re really replacing worn out parts not tuning.

Stacking Tolerances

The first challenge the OEM faces is known as stacking tolerance which means that every single vehicle is a unique “stack” of thousands of parts, each of which has individual manufacturing “tolerance.”  If you’ve ever made anything, you know from experience creating two identical widgets is very difficult, which means time consuming, which – for manufacturing companies – means expensive.

Creating “close” widgets is much easier, quicker, and less expensive than producing identical widgets.   If you can somehow adjust differences between your close widgets, they effectively become identical which means you can reduce widget cost while getting the same performance out of them.  The engineering term for that adjustment “normalization.”  All OBDII and later ECU’s normalize so that every vehicle performs correctly despite each one’s different widgets.

Emissions requirements

All around the world, pollution and emissions are a priority and many governments mandate specific emissions compliance for vehicles.  Regardless of the circumstances, the vehicle’s exhaust gasses must either be within a narrow chemical range or the vehicle must indicate that it is not compliant.

Last month in the How much will my gas mileage improve with the Unichip blog I went into some depth about OBD2 compliant ECU’s normalization for emissions and rather than rehashing all that here, take a look at that blog entry.  In this entry, suffice it to say here that without ECU adaptation your vehicle wouldn’t be legal and that it’s engine is operating in places where the OEM ECU monitors and corrects performance (Closed Loop) and areas where it doesn’t (Open Loop).

ECU learning

So, the OEM computer learns to eliminate variances caused by parts so those parts all work as required.  The OEM computer corrects variances arising from stacking tolerances and wear and tear but there’s yet another variance… aftermarket performance components.  Even though these aren’t planned for by the OEM, to the OEM computer a variance is a variance and regardless of what causes it and the computer uses exactly the same adaptation schemes to correct it.

Modified engine operation without the Unichip

Assuming a vehicle is a nominal production article with fairly light miles on it, the stacking tolerances and wear and tear typically yield LTFT’s (read adaptation) of + 2 or less.  In the case of a +2 value, that means the engine is operating slightly lean and the OEM computer is compensating (adapting/learning) by increasing fueling 2%.  As the operator, you would never know anything is happening because the vehicle operates exactly as it is and no lights come on… exactly as designed.  The OEM computer will continue quietly adapting until it reaches (depending upon programming and varying by manufacturer) between + 20-25% at which point it will pop a Check Engine Light (CEL) to tell you something is wrong.

Take that same vehicle and install a typical aftermarket Cold Air Intake (CAI) and exhaust and the LTFT’s will quickly jump significantly… generally somewhere around +15.  That’s because the CAI is designed to trick the OEM computer into believing the engine is processing less air than it really is… because there’s less perceived air, the OEM computer injects less fuel.  Because the actual airflow is unchanged, the reduced fueling makes the engine a little leaner which makes a bit more power.  The problem is that with “fixed” mechanical parts, the CAI engineer’s Open Loop changes made for power (where the OEM computer isn’t watching) also cause changes in Closed Loop (where it is).  To the OEM computer, those “power” changes are variances and it’s going to adapt to correct them.  Sometimes that adaptation is complete and sometimes it’s partial but in any case there are impacts when you put on those bolt-on parts.

o   On vehicles with very low LTFT’s, the vehicle is immediately much closer to the CEL trigger point as soon as the CAI goes on and it will probably get a CEL much quicker as wear and tear sets in.  If your vehicle has a few more miles, or if it’s not a nominal production article from a stacking tolerance perspective, you might get a CEL as soon as the intake is installed.

o   On any vehicle, because the fueling changes required at high engine airflow (called load) and at low engine airflow aren’t the same, and are generally very different, bolt-on parts that create fixed changes will always be seem as a problem by the OEM computer and create LTFT’s.  Depending upon the vehicle and the bolt-ons, you may lose all of the performance benefit from the bolt-ons as the OEM computer adapts.


Modified engine operation with the Unichip

Because each Unichip calibration is built for specific kinds of parts, each is designed to eliminate the problems those parts create as the OEM computer tries to adapt to them.  The OEM computer doesn’t see anything to adapt to because we literally build the adaptation normally associated with those parts into the Unichip maps which does two things.

o   First, if a set of parts creates a +15 LTFT without the Unichip, the adaptation values in the Unichip map mean the OEM computer’s LTFT’s will settle out back down at the same + 2 that it had (in our example) because of stacking tolerances and wear and tear.  That means your vehicle with the Unichip will enjoy years of OEM designed adaptation – none of which will reduce power – to correct for wear and tear before triggering a CEL.

o   Second, each Unichip calibration optimizes the bolt on parts by optimizing values at over 90,000 points not relying on a single mechanical change.  Not only does the Unichip clear up the adaptation, it optimizes values so that the bolt-ons make more power even where their making the desired correction.

Bottom line

All OBD2 compliant ECU’s adapt.  Unichip maps are designed to work with that adaptation so that your vehicle makes optimum power the day you install our kit and continues to make optimum power for years.  Whether stock or with bolt-on parts, the only adaptation the OEM computer performs is because of wear and tear just like the OEM intended, and just like you want.  It will never “learn out” a properly programmed Unichip regardless of what kind of vehicle it is.

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