Hey, Sour Kraut can you sticky this when you get a chance?
I am trying to compose a frequently asked questions thread cause we are getting allot of the same questions recently. To regulars, please post anything I have missed, or you think this thread should contain.
So you're thinking of getting SCT and you have questions.
What is SCT?
SCT is an engine management system built on the factory hardware. Instead of employing a separate processor, and often sensors, as a piggyback or stand alone; SCT uses the stock PCM and sensors at its foundation.
How does it work?
SCT employs the use of a small handheld device called the Xcal II. The Xcal is plugged into the factory OBDII port located under the dashboard on the drivers side of the cabin. Via this port the Xcal can interface with the PCM and effectively erase and overwrite the factory computer program.
What can it change?
Well, in a word anything. Anything the factory computer does, you can change, that means calibrating different sensors, changing the fuel map, timing, almost any table that the factory PCM uses can be altered for good or bad. I mention that because just because you have the ability to change something does not mean it should be altered. In fact the majority of the PCM functions SHOULD NOT be altered. Only a select few tables are actually needed to actually tune the car. The Xcal can also read and clear OBDII codes. Because you have complete control over every aspect of the PCM you can turn OFF certain functions such as the rear O2 sensor to prevent a code. You also can control the engine environment like when the radiator fans turn on and off, or at what load the A/C compressor turns itself off.
What is the Xcal II?
The Xcal II is nothing more than a handheld "tune bank" it has three banks that can store three totally different tunes. For example you could have one bank with a tune for 93 octane fuel, and another with a tune for race gas.
Does the Xcal tune the car?
No, the Xcal is only a tool that is used to put information into the PCM, it cannot change any settings without the aid of the Advantage III software and a computer.
What is Advantage III?
Advantage III is the software portion of the tuning system. It is installed on a computer and is the user interface to make changes to the program/tune. You open the PCM code you are tuning with (or and MTF file which is a saved SCT tune) you then make the changes you want to make. Then you hook up the Xcal II to the computer via a USB cable and tell the Advantage III to move the program into one of three banks of the Xcal II. The Xcal is then unhooked from the computer and plugged into the OBDII port of the car and you go through a series of key on key off's to initiate the reprogramming of the cars PCM.
What does it look like?
You keep mentioning "tables" or "Maps" what are they?
A OBDII, or any other for that matter, automotive computer is nothing more than a collection of "Maps" that look like Excel spreadsheets with values entered into them. They have an X axis and a Y axis (the up, and across). These "Axis" values correspond to something, it could be alot of things depending on what table we are talking about. All the "values" in the table reflect something as well, often sensor feedback. When you tune with a reflash device you are physically altering what the computer is doing, or how it interprets various sensor input.
Can anyone use SCT?
Thats a tough question. Technically yes, anyone is capable of using SCT, however without some basic understanding about how modern automotive computers work it would be extremely difficult. The fundamental problem is that you have to know what the tables do in order to 1) select the correct table and 2) Alter it in a way that would have the desired effect.
How many different tables are there?
I don't even know, that's how many.
What about the "canned tunes" or "Pretunes"?
Yes, they are SCT tunes, however they are NOT the same as an SCT custom tune. They are mild base tunes that are similar to using a piggyback. Traditionally they are intended to be a safe alternative to getting a full dyno tune. The drawback is that in order to ensure safety they have to be tuned very rich and include very gentle timing curves. Every car is different and in order to be safe they must err on the side of caution, therefore they cannot provide the power that a custom tune wold offer.
Should i get SCT if I'm not going to a big turbo?
Yes, if you want to really tune the car.
Should I get SCT if I AM going to a big turbo?
Yes
Can I use SCT with my piggyback
I suppose you could but you would not want to.
Will my car make more power with SCT than a piggyback?
Yes
Will my car make more power with SCT than a stand alone?
Maybe, it will certainly run better.
Will my car run better with SCT?
Yes Yes Yes Yes, a resounding YES. Basically your car will be "as smart as stock" and therefore run as good as stock, provided your tuner knows HOW to make it run like stock.
The factory PCM has tables that reference barometric pressure (altitude) ambient temperature and others that modify the tune to account for these environmental changes. Your car will in essence BE stock but with performance parts.
How much more power will it make?
This is limited to the ability of your tuner.
I have a friend on the internet that said his car runs terribly with SCT
His car does not run terribly with SCT, it runs terribly on the tune that he put in. SCT is only as good as the person who is tuning with it is. Garbage in Garbage out, SCT is not anywhere near as forgiving as a piggyback in respect to tuning. You can make ONE change of ONE value on the wrong table and the car will not only run like shit, but could possibly destroy itself.
You are scaring me away from SCT it sounds too hard to use.
I am trying to get people to understand the power that SCT gives you. YOU are in control of EVERYTHING the PCM does. You are essentially Dodge motor company, whatever you tell it to do, it will attempt to execute. There is no reason to be afraid of SCT, it can be learned and if the proper amount of caution is used as safe as any PCM flash device can be. As long as you don't start altering tables that you don't at least have an idea of what they do, and ask questions you are completely capable of tuning your own car.
Who should I go to get help with SCT
That is up to you, I don't endorse any shop other than the one I am affiliated with, if your on the east coast feel free to contact me. You will find that there are not ANY shops that are willing to hold your hand through tuning your own car for free, or will give out secrets about what tables do, if you find one, let me know and I will certainly put their name here. This forum is likely the best place to get free help.
In conclusion, SCT is the best tuning platform available for the SRT-4 nothing else comes close. However, the tune is only as good as the tuner if you know that going in, and you're willing to learn, there are many people on this forum that are more than willing to help you learn your way around. It's an investment, not just financially, but mentally, but it more than pays for itself in the first few months when you get to drive a car that runs like stock, but accelerates like a big turbo SRT4.
I know I missed a million things, put your edits in the thread and I'll add them as we go.
