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Discussion Starter · #1 ·
So I have read many threads about pulling #2 fuse and how it wakes the car up again. Well I pulled said fuse guess what ran the same as it always has awesome. So I guess its the same as when guys add C.A.I and exhaust system's its 100 hp more power.
 

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So I have read many threads about pulling #2 fuse and how it wakes the car up again. Well I pulled said fuse guess what ran the same as it always has awesome. So I guess its the same as when guys add C.A.I and exhaust system's its 100 hp more power.
It is supposed to reset the adaptive learning from the cars computer. Did you pull it and wait a few minutes?
 

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Yes while I serviced my catch can
Well I'm not sure how Dodge set up internal programming for drive adaptive "learning" but I would assume you would get the biggest change , if you drove it grandma-style for a few months and then pulled the fuse. If you already drive it kinda hard, I can't see how it would do much.
Just guessing here
 

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The effects of pulling fuse #2 is completely dependent upon how you drive the car normally every day.

If you drive around like a granny, rare WOTs, and just generally follow the law - you will see a difference because the long term fuel adaptive and knock sensor will be reset. It will give you a little more timing for a few runs.

When does this help? Let's say you are traveling out of state and you can't find as good of fuel octane/brand as you normally get at home. Your car will adapt to that less quality fuel you are running. Now when you get home you put in your BP 93 or whatever it is you run, that is when you will want to pull the fuse.

If you drive around pretty aggressively day to day, you do WOT runs, 0-60 runs for fun, etc etc, you aren't going to see much if any change by pulling the fuse.
 

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So I have read many threads about pulling #2 fuse and how it wakes the car up again. Well I pulled said fuse guess what ran the same as it always has awesome. So I guess its the same as when guys add C.A.I and exhaust system's its 100 hp more power.
you must already be beating on the car enough that it knows how to act, you have probably tapped it's full potential. The #2 fuse is for guys that baby their car and wonder why all of a sudden when they want to show off it won't spin the tires, its because the car isn't use to a sudden WOT. I guess it's time for some engine work if you're hoping for the #2 fuse to get you any quicker.
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I pulled the number 2 fuse at the track and the car went slower guess my car is just weird lol
 

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I drive a lot of highway miles....pulling the fuse works!!
 

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Top Challenger Tips and Tricks

From the Top Challenger Tips website link above: (There's plenty more on this informative site!)

Here's what it does exactly!


Pulling Fuse F2 resets;

- All PCM DTCs erased.
- All OBD2 monitor results erased.
- All "long term fuel trim adaptive" values reset to Zero.

Long term Fuel Adaptive trim will now start over the next 100 engine start cycles.
Cycle the headlights as described above will create a Short Term Fuel Adaptive trim table over the next 50 start cycles.

Driver Adaptives?

Driver Adaptive's and related fuel table trim is probably the least understood algorithm contained within the NGC - Next Generation Controller (also called PCM)

There are long term fuel adaptive trim (100 start cycles) and short term fuel adaptive trim (50 start cycles). The NGC looks at what the fuel requirements to operate are during "closed loop" operations. The fuel trim algorithm is slowly and gradually attempting to bring the fuel consumption to best suit driving conditions and optimize the MPG by feedback from O2 and other sensors.

Short term and long term fuel trim are also used in analyzing KR (Knock Retard) and attempting to have the NGC (PCM) calibrate the engine timing based on quality of fuel. With different quality fuels and octane's, the NGC tries to always adjust for the best engine timing (advance/retard) to protect the engine from knock or prevent detonation. The knock sensors on the HEMI engine are quite sensitive and can be considered to be "engine microphones".

What is Knock Retard?

Knock Retard (hereafter referred to as KR) is the response from the PCM to cylinder detonation. KR is the measure of the number of degrees of overall ignition timing advance that must be removed from the engine to prevent detonation from continuing, thus protecting the engine from damage.

What is REAL KR and what is FALSE KR?

Real KR is KR that grows with engine RPM and engine load. It depends entirely on detonation, which is dependent upon throttle position, IAT or MAF, MAP, engine load, engine temperature, and RPM. As RPM and engine load increase, the chance for KR (or higher KR) increases. As the vehicle shifts to the next gear, KR will usually make a small jump up as well due to the higher engine load.

False knock is characterized by a sharp spike to an immediately high value of KR followed instantly by the KR Recovery Rate. It doesn't grow with engine RPM or load, it jumps to a high value on throttle input and then recovers to a low value, or zero perhaps, as engine RPM continues to increase. Note that this is exactly opposite to the characterization of REAL KR. Remember, knock is simply specific noise detected by engine microphones. Because it happens to fall within the frequency of real KR does not necessarily mean that it IS real KR.

To learn more about "What is Knock" read this excellent and detailed write up below;

http://www.stlclubgp.com/tech/kr/

The PCM has the ability to do some rudimentary fuel tuning (all modern vehicles now do this) via "closed loop mode". It has two main modes of operation, closed loop and open loop. When the engine is started and heated up past 160 deg. F, the NGC (PCM) now goes into "closed loop" control whereby it takes feedback from sensors (ie. IAT, MAP, O2, Knock, etc.) and looks at the fuel efficiency and attempts to tweak out the current fuel tables to get the best MPG and engine efficiency.

Tromping the accelerator to the floor puts the PCM into OPEN loop where it now goes to fixed tables to do fuel mixture and o2 sensors are now bypassed.

So where does this wind up over time. Well, there is a number of "learn cycles" that The PCM goes into for fuel Adaptives, normal 100 start cycles, or a "quick learn" of 50 start cycles (using the headlight ON/OFF trick). During these times (cycles) fuel trim adaptive algorithms work on trying to get the best MPG. After the 100 cycles, the MPG magic is pretty much done until something is done to initial another "learn cycle" like clear memory.

These start cycles are a fixed "time-cycle" effort to build a fuel trim table and the algorithm will stop fuel trim after these 50 or 100 start cycles.

So if you have been driving around for a number of weeks, months in a laid back fashion, the PCM has learned this and attempted to get the best MPG for you and tuned down (slowly) performance. So, one day you tromp the gas hard or do some spirited driving and you notice the car "sluggish", or not quite as peppy as before. This could be the reason. Clearing out long term fuel table adaptive memory can sometimes help.

The PCM has a number of classes and types of internal memory. The fuel table Adaptive's are stored in volatile memory and when the fuse (F2) is pulled for at least 20-30 seconds, this memory is cleared and you can start over building a new set of Fuel Table Adaptive's for closed loop control (next 100 start cycles).

If you granny drive around town your car adapts to that type of driving. Then when you want to do a lot of quick aggressive driving the vehicle may seem sluggish and not "as responsive" as you remember. You may need to do something to the PCM called clearing driving fuel Adaptive's.
 

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Discussion Starter · #12 ·
Well I guess she likes the way I drive her. All I am saying is this trick, tip did nothing to my car.
 

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I live 3miles from work 30mph stop and go.
Did the fuse pull,and the key on,light off and on,turn key off per tips and tricks instructions.
Can feel the difference .It will now burn the tires more on a roll.And is more responsive .
 

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From what I have found, if you drive it hard (like everyone should) the matured fuel trim is the best.

I went on vacation and forgot to unplug my trinity, battery was completely drained by the time I got back (2 weeks). I have a custom tune and it took a couple weeks till the adaptives relearned and it was back to normal.

So if you drive it hard regularly then resetting adaptives may hamper performance.
 

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I’m a believer that the cars that feel the most change after resetting the driver and fuel adaptives are the cars whose fuel trims are off the farthest. If your car’s fuel trims are off by more than a few percent, resetting them back to the factory defaults has a big difference. There are 26 fuel tables that the ECU will trim to based on input from the narrow band sensors (front 02s). If your ECU has to trim seven or ten percent to obtain the target A/F ratio, you will feel a big difference until all the fuel trims have matured and adjusted themselves back to the target A/Fs. My stock ECU has a huge difference when I reset the ECU. My custom tune doesn’t as the fuel trims have been tweaked to be as close to target as possible. A couple of gradual 0 to 75 MPH logs will enable your tuner to see all the fuel tables and they can make adjustments to each table to get them to where they don’t have to deviate so much to obtain the proper A/Fs. Most custom tunes and tuners won’t mess with getting all the trims dead nuts on as it really doesn’t make that much of a performance improvement. In fact most tuners will just keep the factory trim defaults.
Resetting the driver adaptives will also change the shift pattern and firmness in the autos if you have been driving like a granny.
I may be all wet but this is how it was explained to me and it does tend to make some sense as to why some cars see more of a difference than others.
All things considered, I think that the removal of tq mgmnt in the autos has the largest performance gains, more so than the measly 5 or 10 HP a custom tune can give you.
 

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Soooo, what I'm gathering is, I should just keep driving her the same every day. Along with taking her through the brushless auto wash and then, ahem, "blow drying" her weekly?

Works for me! :D
 
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