Custom ECU functions

We carry out all of these functions both for private customers and for track cars, Pop&Bang, FLAP OFF and VMAX OFF included. What changes is how you use them: for each one we tell you what the rules say if the car is driven on public roads.

Pop&Bang

What it is. The crackling you hear from the exhaust when you lift off the throttle, typical of competition cars.

How it works. On the overrun, the stock ECU cuts injection. With Pop&Bang a small amount of fuel is still injected and the ignition is retarded, so part of the mixture burns in the manifold and the exhaust rather than in the cylinder. It's a petrol engine function; on diesels, what gets programmed under a similar name is something else (see Hardcut).

What it wears. That combustion outside the cylinder raises exhaust temperature considerably. It punishes the catalytic converter, the turbo and, over time, gaskets and silencers. A damaged catalytic converter ends up turning on the engine warning light and failing the ITV.

Legality. This is where the main problem lies: noise. The Reglamento General de Circulación (Spain's General Traffic Regulations, art. 7) prohibits driving while exceeding the established noise limits.

Hardcut Limiter

What it is. A sharp cut when the engine reaches maximum rpm, instead of the stock soft cut. On diesels it's often called "popcorn", after the stuttering sound it makes.

How it works. As standard, as the engine approaches the rev limit, the ECU gradually trims torque. With Hardcut the engine revs freely up to the limit and then cuts injection abruptly, again and again for as long as you hold the pedal down.

What it wears. Repeated shocks through the transmission and engine mounts if it's overused. On diesels, each cut produces a spike in temperature and smoke.

Legality. It doesn't change the power stated in the documentation, but it does change the vehicle's noise at the limiter. Reasonable use, and the track if you want to push it.

Launch Control

What it is. An aid for pulling away from a standstill with maximum traction: the engine is held at a fixed rpm while you wait and, when you let go, the launch is repeatable.

How it works. On manual cars, the ECU detects the clutch pedal pressed and the car stationary, and limits revs to a chosen value; when you release the clutch it lifts the limit. Many sporty automatics already have it from the factory, and it's adjusted in their transmission control unit.

What it wears. It's the function that's hardest on the drivetrain: clutch, dual-mass flywheel, driveshafts and differential. Every launch is a load a stock car isn't expecting to take often.

Where it makes sense. Track starts, drag racing or hill climbs. On the road, launching like that serves no purpose.

Torque delivery

What it is. Changing how torque arrives in each gear, not how much total torque the engine has.

What it's for.

• Softening first and second on cars that spin their wheels when pulling away or on wet roads.
• Protecting the transmission by limiting torque in the lower gears, where loads are highest.
• Making the curve more linear if the car delivers everything at once and is hard to modulate.

It's one of the most useful and least known functions. It's often ordered together with a Stage 1 so that the extra torque doesn't just turn into wheelspin.

Throttle pedal

What it is. The accelerator on a modern car doesn't pull any cable: it's a sensor that tells the ECU what percentage of pedal you're pressing, and the ECU decides how much torque to request for that percentage.

What gets adjusted. That relationship between pedal and torque. It can be made more direct (more response in the first part of the travel) or more progressive (easier to modulate). It doesn't add power: the engine delivers the same at full throttle, only how you get there changes. For economical driving, the approach is the one in Eco remapping.

FLAP OFF (exhaust valve)

What it is. Many sports cars have a valve in the exhaust that the ECU opens or closes depending on rpm, load or driving mode. With it closed the car is quieter; open, louder.

What gets adjusted. Having the valve always open, always closed or opening under different conditions. It's also used to clear the fault warning when the valve has failed and been removed.

Legality. The vehicle was type-approved with a specific way of managing that valve. Leaving it open all the time increases noise and, as with Pop&Bang, the limit is in art. 7 of the General Traffic Regulations. If what you have is a faulty valve, the sensible thing is to repair it after diagnostics.

VMAX OFF (speed limiter)

What it is. Many cars have a top speed limited electronically by the manufacturer, for commercial reasons or because of the tyres fitted as standard. VMAX OFF removes or raises that limit.

Which functions can be combined

If a function changes data shown on the ITV card or what was type-approved, it may be a modification: it's explained on legality, ITV and insurance. On motorbikes, similar functions are requested with their own particularities: see motorbikes. And if you're a garage, you can order any of them through our file service.

Price

Each function is price on request, because it depends on the ECU and on whether it's programmed on its own or alongside a remap. Ordered with a Stage remap, it's quoted as part of the same job; our remaps start from from €200 + VAT (€242 including VAT).

Reviewed on 15 October 2026.