No, no, no, no, no
Not acceptable on an £80k+ car.
DTUK type boxes work by manipulation of the boost sensors, example below...
Standard ECU boost pressure = 1.2bar
Manipulated DTUK boost pressure = 0.9bar
Corrected manipulated ECU boost pressure = 1.2bar
Real boost pressure = 1.5bar
Your ECU will be reading 1.2bar in the tables but the turbo will be pushing 1.5 bar in reality. Now this is all very well and good in extracting more horsepower but unless you understand what's happening in the background then I would strongly advise against going down this path. The engineers at Audi have fine tuned the engine and written boost fuel and ignition tables for 1.2 bar of boost pressure. If you up the boost pressure, you need to make finely tuned adjustments to the other fuelling and timing tables too. Why? Well, cast your minds back to your physics lessons, an increase in pressure = an increase in temperature. In this case, the most important aspect of safe and reliable horsepower is controlling your EGT's. Run them too hot and you will begin to melt things.
The piggyback DTUK type boxes rely on the inbuilt ECU safety features to protect the engine hardware. They do this by recognising an over temp and going into a limp home protection mode. Essentially this means that boost and ignition is pulled back and the fuel mixture is richened until a point where EGT's are back within normal range.
For example, 1.2 bar standard map may see a peak of 950c EGT, this is finely controlled so that the inbuilt protection measures do not ever go into a protection mode. If you now ask 1.5 bar from the turbo (but still have 1.2 bar written fuel and ignition tables) things are going to get hot, very hot. You may run the turbo up to 1050c before the inbuilt protection measures kick in and then start to go into protection mode. When the ECU goes into protection mode, it richens the fuel mixture substantially in order to cool everything back down. (You would likely get a rev limitation and the car would run poorly during this time)
In summary, DTUK type boxes run lean due to the fact they run off of standard fuel and ignition maps (but manipulated boost) Lean means hot.
Now for the odd blast here and there, they are fine. You generally only drive hard for a few seconds on the road before coming off throttle and slowing down (giving the turbo time to cool). However, if you were to run a tuning box at a track or on a vmax type run then you would likely run into protection issues at some point. 9 times out of 10, the standard protection measures will catch it all in time but you're always running that risk, you'll always be over temping and you'll always be reliant on the inbuilt EGT protection trigger protection.
Now compare that to a properly tuned car with properly written fuel and ignition tables. The horsepower is more reliable and repeatable with the protection measures never breached. A piggyback 'tuned' car may produce a good run on a dyno of say 675hp (ONCE) run it a 2nd time and that will drop to 650, run it a 3rd time and that will drop to 625 and so on and on, eventually it will hit protection and not even pull standard horsepower. Now run the properly tuned car back to back in the same manner and you would likely consistently pull 700hp run after run after run.
That's the difference between a DTUK type car and say an MRC or APR type car. in addition to that, a properly tuned car will remove the 155/174/189 speed restrictions. A piggyback car will not.
I run a DTUK box on a £30k Audi S3 a couple of years ago and had no issues at all, the only reason I run the box was because at that point in time there were no other options. The ECU hadn't been cracked by any of the mainstream tuners. I have good experience with
Vagcom logging so I'm familiar with how it all works in the background. I always had sustainability in the back of my mind, if I was on the throttle 15-20secs accelerating, I would back off and allow for cooling down time before going at it again. I was able to see how hot and how lean I was running things from the tables I was recording. I only ever hit limp mode twice during my time with a tuning box and that was after back to back dragstrip runs. I was mindful though and always knew when to back off.
There are some advances in piggyback boxes for sure where they start manipulating fuelling and timing sensors too but these will never be as good or as safe as a properly tuned car.
The whole TD1 thing is a huge scaremongering tactic used by these companies to sell their products. They preach on the warranty safe aspect but in reality, tuning boxes can be traced back too. Once removed from my S3, I had a few sensor out of limit messages on the boost sensors, going deeper I'm sure the Audi boffins would be able to determine max stored values too.
MRC for example can reset the flash counters and remove all traces of TD1. I just last week had my ECU restored back to factory and all traces removed. I live the opposite end of the country too and the turnaround time was a couple of days in the post, saved me the long drive back down to them. ECU can be removed from the car within 30secs, it's just held in by two snap back plugs in the scuttle panel, you don't even need tools to remove.
On an £80k+ car, my advice would be to do things proper, not half hearted.
Just my tuppence worth anyway.
