The files nobody admits to buying in

How it works

A tuner reads your file, uploads it to a supplier, and a file comes back. Turnaround is minutes. The person who wrote it has never seen your car.

For a common engine in standard condition, that file is often perfectly good. The supplier has data from thousands of examples and the calibration is sound.

Where it stops working

The moment your car is not standard, or not healthy. A generic file assumes a healthy engine with the factory hardware, because that is the only assumption it can make.

On a car with a tired turbo, a partly blocked filter or aftermarket parts, it is a guess wearing a confident number.

The file is not the problem. Selling a generic file as a bespoke one is.

How to tell

Ask three questions. Do you write files in house? Do you measure the car before and after? Can I see the graph before I pay?

Nobody reselling generic software can answer all three comfortably. The measurement question is the one that does it, because a dyno makes the difference visible.

When it is genuinely fine

A standard car, a common engine, a reputable supplier, and a tuner who tells you that is what is happening. That is an honest transaction at a fair price.

What is not fine is charging bespoke prices for it, or claiming a car was measured when it was not.

Why the cheap quote is cheap

A generic file costs the tuner a small fee and about ten minutes. A file developed against a dyno costs a morning of somebody's time and the running of the equipment.

When one quote is a third of another for nominally the same job, that gap is usually the explanation. It is not always the wrong choice — for a standard car it may be perfectly adequate — but you should know which one you are buying.

What is genuinely objectionable is the middle option: generic-file turnaround charged at bespoke prices, with the customer told the car was measured when it never left the car park.

Three questions that settle it

Do you write files in house? A straight answer either way is fine; hesitation is the signal.

Do you measure the car before and after, on your own equipment? This is the one that cannot be talked around, because either there is a dyno on the premises or there is not.

Can I see the graph and have it explained before I pay? Anybody confident in the work says yes without thinking about it.

You are not being difficult by asking. You are asking what you are buying.

What we do, so you can judge it

Files are written here against our own dyno data. That is slower and it is why we cost more than the cheapest quote you will get.

For a standard Golf the difference in the finished file might be small. For anything unusual, unhealthy or modified, it is the entire job.

We will also tell you when a generic file would genuinely have done, because pretending otherwise would make everything else on this page worth less.