Getting your car tuned

[ford12]

When getting your car tuned by whom ever.
Do they have full access to everything that ford would have access too.
The reason why I'm asking is, all the people who tune your car say that it can be returned at anytime to your factory tune.
My understanding is, and I could be wrong is that no one has full access to the factory tune. If this is the case can the full factory tune be returned to your car.

[JasonACT]

I'm pretty sure that whatever a programming device (I've got a SCT X4) can alter, it can also read & save first. Maybe there are things Ford know that no-one else knows, but for the things being changed by a tuner, they would be able to save a copy of the original parameters first. Only the things changed need to be put back to original for it to be "factory".

[ratter]

Dealers have very little access, they can change a couple of things like tyre size etcor just flash an updated version of software

[simon varley]

some tuners will have full access, especially where there is a partnership with Ford (Herrod, Premcar) but most wont. It also really depends on what you mean by a 'tune'

however, as above, most any tool can download and save the factory settings

[cs123]

Originally Posted by ford12

When getting your car tuned by whom ever.
Do they have full access to everything that ford would have access too.
The reason why I'm asking is, all the people who tune your car say that it can be returned at anytime to your factory tune.
My understanding is, and I could be wrong is that no one has full access to the factory tune. If this is the case can the full factory tune be returned to your car.

The program or code executing in your car's ECU has access to memory which contains calibration information or maps.

Say for example your ECU needs to work out how much fuel is needed under open loop operations for X engine load and Y RPM. The guy who originally wrote the code at Ford will have a development tool where he says lookup variable Blah using X and Y. When that code is compiled it is loaded into the ECU as instructions the CPU understands (machine code). These are low level instructions to the CPU which to you and me are unreadable. They are often referred to as binary code. And a single statement made by a programmer in a language like C will be compiled into many, many low level CPU instructions.

Someone with some inside knowledge or someone who is very determined with the correct sort of emulator and debugger can reverse engineer this to the point where they may know specific memory locations in the ECU data segment. The two very basic ones are fuel maps and ignition timing maps.

If you know these memory locations and how the code access them then if you alter the values of these memory locations then you alter the "tune" of the engine. So for example if your factory tune has 25 degrees of timing at 3000RPM and your tuner knows that it will go better with 27 degrees, then he can alter that memory location.

The term flashing refers to the process of electronically erasing these memory locations that are stored on non-volatile RAM and overwriting with new values. The tuner box, will first copy the contents of the RAM and then upload new values. If you want to go back to "stock" you select your factory tune and that set of data is uploaded into RAM.

So in summary, tuning software is interested in altering the engine run characteristics, like boost, ignition, fuel and transmission.

There are a lot more calibrations available in the ECU and some are not really of interest to a tuner, but they may be of interest to a dealership. During the life of a vehicle there will be issues found, some of these may be due to calibration of the ECU. When that occurs the developers will provide a new calibration or make recommendations on settings in the ECU which are put into a Technical Service Bulletin and if the mechanic is investigating a complaint they will look for a match in the symptoms. If you complain about your fuel range being inaccurate, the mechanic will refer to any relevant TSB and if there is a known fix he will apply that fix.

Some dealer fixes may clash with your tune, most probably won't.

Typically a dealer wont investigate a defect or proactively apply a fix unless you complain or a TSB says to do it proactively.

So in a round about way I'm saying
- Tuner software copies the original memory locations relevant to what it's going to change. It applies new values and allows you to go back to factory tune
- Dealerships have a much more comprehensive set of tools, but they are not tuning tools. They apply fixes for known issues described in a TSB
- Dealerships rarely do proactive changes and it will be under instruction from the manufacturer .
- There is a small chance that the fix a dealer puts into your ECU could clash with a config change a tuner has made if he is trying to fix a problem related to the same configurations
- If you are going to a dealer and having changes made to the ECU, then there is a good chance your car is under warranty. You shouldn't alter the tune of a car under warranty
- If your car is out of warranty and you have it tuned ask the dealer to check first about any fixes he may want to apply.

Sorry, a bit of a rambling post. I hope it answered your question