What Car? Q&A - Is 'chipping' a car a bad idea?

Q: I own a Seat Leon 2.0 TDI, which has 138bhp. I think it could do with a bit more performance, and I'm considering getting it chipped to increase the power by around 30bhp. Could this be a bad idea?
Alex Hewitt

A: 'Chipping' is a term for reprogramming the computer that controls a car's engine. Turbocharged cars in particular can benefit from big hikes in power for a relatively small outlay.

However, the extra power will place added strain on the car's engine. This could lead to serious problems and may invalidate the manufacturer's warranty.

Although some chipping companies offer an alternative warranty to compensate for this, you should scrutinise the cover and terms and conditions carefully before you sign anything.

Fuel economy may drop, too, and you will need to inform your insurance company about the modifications. Your insurer may than charge you a higher premium.

Also remember that car manufacturers design their engines to work on different fuel qualities to cope with markets where fuel may be poorer. Chipping often alters the engine management system so that it is optimised for the better quality fuel we use in the UK.

That's fine to a point - but if you encounter a batch of dodgy fuel or travel to a country where fuel quality can't be guaranteed, you could damage your engine, particularly your diesel's injectors. If that's the case, you could face an expensive repair bill.

Our advice is that unless you're offered a manufacturer upgrade, leave chipping alone - at least until the car is out of warranty.