Before I get into the tune itself lets first go over a little bit of a history lesson.
A tuneup when it comes to carburetors was necessary and common. This was before fuel injection was around. If the weather changed drastically or you went to an area with different elevation or humidity you would need a tuneup for your car to run smoothly. You also needed to get one over time as you engine rattled itself to death it needed to be tweaked back. This was done by adjusting the air/fuel ratio on the carburetor. This was also where they did performance tuning by playing with this adjustment. This is where the term tuning came from.
The term ‘chipping’ came from when you had to actually solder off an on chips with different Roms(software) consisting of settings on them. At this point in time “flashing” was not a thing yet so unless you replaced the whole ECU unit with a standalone engine management system this is what you did. The term chipping is still used but today typically refers to flashing and not soldering on a chip like we used to do. My early 1999 A4 was one of these were we had to solder chips.
Flashing is what we typically use today which requires hooking up a device to the ODBII port and pushing software to the ECU. If you have ever updated a BIOS on a computer its kind of like that.
Now lets take step back and talk about the stock software on cars. There are many reasons why we can squeeze out so much performance over the stock software today.
The stock software is designed for a whole region. When you are talking about the US that’s elevations from below sea level to 10k feet, a temperature ranges from negatives to over 120 degrees Fahrenheit. The software is designed to work with a wide variety of environments and be smooth running. Because of this, things are not necessarily tuned optimally for your area. For example APR’s software for the MK7 R doesn’t work so great in the higher regions of Colorado.
These cars are mass-produced. They are not hand crafted and tuned each one individually. That being said the ECU does adapt and change to fit the needs. What I am getting at here is even though the engine is the same, it’s not exactly the same and does run slightly different, This is why if you take two identical cars, same model year, options, weight they will perform slightly differently. They need to account for this in their software settings.
There are lots of regulations for each state/country/area that they must adhere to and most of the time they play it safe with these. It could be safety or emissions related. Vendors will typically take the most harsh of these regulations of these and use settings that work with those even it areas with more lax regulations.
Lastly and surely not least is that the vendor is using values that are very safe/tame to give the car the best reliability they can. They also are trying protect their higher performance priced cars market share. This is especially true for the GTI when all you have to do is put a STG 1 tune on your car and you just went from 220hp to over 300hp. Thats Golf R territory with just software and no hardware changes!
What is a tune?
Like I mentioned before it used to be in the days of soldering a tuner just tweaked values in the stock Rom and solder a new chip on. The software wasn’t encrypted and anyone could just read it if you had the right tools.
Today it’s very different. ECU’s are encrypted and need to be cracked/unencrypted before tuners can access certain areas. This is why it takes time for software to come out for a new model year even though it’s the same platform. These tuners typically have their own software now that they replace the stock software with. It still may be based on what the stock was but is highly modified compared what used to be done. This allows them much better control over what they want to tweak and better access too. This is part of the reason we can have things like multiple profiles we can switch between, flat floor shifting and launch control.
The general high level overview is they are changing air/fuel ratios and timing. There is so much more to this but that’s the short of it. I highly suggest you read over this page here. It’s from a standalone engine management suite where you completely tune a car from scratch. Reading this will give you a great idea of what tuners are tweaking and the mentality/restrictions they have. This is the bread and butter of tuning.
Typically the engines are 4 stroke, these are the 4 stages that an engine is in at any point of time. Intake, Compression, power, exhaust.
- Intake: Fuel and air are added to the combustion chamber
- Compression: Piston compresses air
- Power: Spark plugs do their thing and a controlled explosions(combustion) happens in the piston chamber.
- Exhaust: The aftermath of the explosion is evacuated from the chamber and we go back to the beginning.
The obvious things they are changing the fuel/air mixture and timing to change the combustion so it produces more power but not too much they it grenades the engine. You also need to make sure multiple or unexpected explosions don’t happen. This is referred to a knock or pinging. When a knock or ping happens the ECU will retard the timing in which it fires the spark plug later in the piston travel to control the explosions better. Advance Timing does the opposite where it fires the spark plug earlier in the piston travel. Timing is very important, at each stage in the process you can modify the timing to be most efficient as possible. When someone says they are getting timing pull, the ECU decided it need to reduce the value to stop the engine from doing a bad thing. It’s ok to pull timing occasionally but you don’t want to be doing this a lot.
This is what you are doing if it’s a naturally aspirated car, now lets add forced induction to the mix by either a supercharge or turbo system to the mix with boost pressure and their own RPM’s.
So now its all a balancing act between how fast you can push each area of the engine without something going awry. There are loads of sensors in the car tuners are watching to see if everything is going right. Again im explaining this in a simple high level overview, its much more complex than this. Tuners have the ability to change values based on boost, rpm, gear and not just what the engine is doing at that point of time. If you get anything out of this it’s that you need to make sure the person tuning your car is a professional and not some hack with tools. Its much more complex than in the days of carburetors.