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How do flash tunes actually work?

nonbiodegradable weasel

Ready to race!
Location
US
What gets changed in the ECU when a car is flashed?
Is the ECU completely overwritten, or just specific data structures within the ECU modified? What structures?

To what extent can flash tunes insert their own programmatic logic into the ECU?
Do companies like APR, Unitronic, etc. reverse engineer the ECU to develop their tunes, or is this stuff documented somewhere?

I don't have any practical reason for asking this. I'm just curious.

Has anyone eavesdropped on what a flash-at-home tune actually sends to the car?


Edit: I know that tunes change boost, timing, fueling parameters, etc. I'm more interested in the "how"
 
Last edited:

wordsthatiwrote

Ready to race!
Location
Ohio
What gets changed in the ECU when a car is flashed?
Is the ECU completely overwritten, or just specific data structures within the ECU modified? What structures?

To what extent can flash tunes insert their own programmatic logic into the ECU?
Do companies like APR, Unitronic, etc. reverse engineer the ECU to develop their tunes, or is this stuff documented somewhere?

I don't have any practical reason for asking this. I'm just curious.

Has anyone eavesdropped on what a flash-at-home tune actually sends to the car?


Edit: I know that tunes change boost, timing, fueling parameters, etc. I'm more interested in the "how"



I'm guessing they take some 0's and turn them in to 1's and take some 1's and turn them in to 0's

watch this: https://www.youtube.com/watch?v=6bkDKqoGSdU
 

ExcelerateRep1

Go Kart Champion
Location
Branford, CT
What gets changed in the ECU when a car is flashed?

On these car? A LOT! I'll use APR for example, they employ factory level engineers to extract the factory VW software and completely de-code the code structure to individual maps. There are hundreds (maybe thousands) of maps in this ECU.

Is the ECU completely overwritten, or just specific data structures within the ECU modified? What structures?

The entire ECU is overwritten. The APR software is built using all factory maps, controls, sensors etc. Just to their standards with their proprietary changes.

To what extent can flash tunes insert their own programmatic logic into the ECU?

Size is really the hold up here. The factory storage space in the ECU is very small. When changes are made, the file sizes only get larger. This is a draw back. This has been part of why program (map) switching hasn't been introduced yet.

Do companies like APR, Unitronic, etc. reverse engineer the ECU to develop their tunes, or is this stuff documented somewhere?

See above, APR does, not sure about a lot of the other tuning companies. Highly doubt there is much (if any) documentation on it. But APR basically takes the OE software makes the changes they need to and reflash the ECU. Some maps may not be touched, but I have no idea.

I don't have any practical reason for asking this. I'm just curious.

We all are!

Has anyone eavesdropped on what a flash-at-home tune actually sends to the car?

It is a pretty similar process to those who use a dealer network to flash, except you are at the mercy of making sure your battery is constantly charging properly when flashing, flashing the right file, and making sure you can get out of a jam if you end up in one.

I am sure some tuning companies are different in what changes are made, and that is the beauty of having options.

Edit: I know that tunes change boost, timing, fueling parameters, etc. I'm more interested in the "how"

Like the gentleman above mentioned sure its about changing 0's and 1's but that happens before the calibrators get it. The code structure if built/transformed into their own ECU composer, basically their own calibration editing software, so the calibrator can visually see the changes in the MDF. There are many steps in this process and there is a lot more involved in making software great and not just good.

In these ECU's there are hundreds more parameters changed other than boost, timing and fueling. Such as IAT, Baro, turbine speed, throttle position, rpm, torque... there are hundreds more. :eek:

Hope this helps.
 

Bdurrell

Ready to race!
Location
Florida
Car(s)
2019 Z06
......APR is a professional tuner. $800 for the Stage 2 tune is an understatement for how good it actually is that how much time they put into it to deliver the amount of horsepower and torque that you get for your money.

They do things right they do things professionally and as far as I'm concerned the only tuners that know what they're doing.
 

geebob

Ready to race!
Breaking the encryption is a bigger job than reverse engineering the code.

On my Mazda, the boss of bosses at Cobb said once (they used to have their own forum) that changes are made in a sidebar (my word, not his.) So, if you want to change a value of 12.5 to 11.8, you're separately adding a negative .7 to it. So you're overwriting the whole thing, but you're not changing one value to another, you're adding a correction value to the original. That was a 1st gen ms3, no idea on others.
 

drrck

Go Kart Champion
Location
Zeeland, MI, USA
......APR is a professional tuner. $800 for the Stage 2 tune is an understatement for how good it actually is that how much time they put into it to deliver the amount of horsepower and torque that you get for your money.

They do things right they do things professionally and as far as I'm concerned the only tuners that know what they're doing.

If profitability is your metric for knowing what you're doing then I would agree 100% (the APR of old is not the current APR). UM, Unitronic, Eurodyne and GIAC all seem to make tunes that people love. You can't please everyone and everyone has different goals. JB4 is no slouch either on MK7.
 
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