The Ecotek CB-26P is a car add-on with an interesting (if chequered) history.

The device connects to the engine inlet manifold where it allows extra air in under certain conditions. When it first appeared on the market in 1999, the makers claimed that the "swirl" and "turbulence" this produced would greatly improve the efficiency of the burn, giving around 15% fuel economy improvement on most cars (as well as improvements in performance and emissions). They seemed to have some pretty impressive test data (from the DTI's own Warren Spring laboratory) and magazine reviews to back this up.

Many car experts (such as myself) were sceptical right from the beginning. We said that the claims of swirl and turbulence didn't make sense, and that the only effect of the device was to weaken the air/fuel mixture (less fuel per amount of air). The sceptics admitted that this could perhaps help the economy of an old carburettor vehicle, but said it would do nothing on a car with lambda control (anything sold after 1992 in Europe).

The sceptics also pointed out that the Warren Spring tests were carried out on an extremely old car with a carburettor (as well as having other flaws), and that testimonials from magazines and satisfied customers counted for little since fuel economy is incredibly sensitive to driving style, traffic, type of journey, weather, etc - so any changes seen could be due to any of these other factors rather than the device itself.

The arguments rumbled on until 2004, when the Advertising Standards Authority ruled that Ecotek had failed to prove their product worked and so they could no longer advertise it as a fuel economy improving device. Stung by this criticism, Ecotek arranged a series of carefully controlled scientific tests using modern vehicles.

To the total lack of surprise of the sceptics, these tests definitively proved that the CB-26P does NOT significantly improve the economy of modern cars. The average benefit was around 1%, which would be totally unnoticeable in normal use and means the device would take typically 5+ years to pay for itself. Even Ecotek themselves stopped claiming large economy benefits when faced with these results.

So it's useless then? Well, not quite. By allowing extra air into the engine, it can alter the driving "feel" - the way the engine responds when the accelerator pedal is pressed or released. Some people prefer this altered "feel", even if the change to actual objective (measured) performance is very small. Having said that, many people find they can't tell any difference at all in "feel", or indeed actively dislike the change it makes.

Downsides? It can make a noise "like a duck farting", especially if used without the optional filter, and if not carefully "tuned" can cause engine running problems due to excess air entering the engine. Also, it is often fitted into the brake servo vacuum hose, so be VERY careful when fitting it if you want your brakes to keep working properly! Owners of newer vehicles should note that if your car is still under warranty and you have cut a hose to fit the device, you will probably need to buy a replacement hose from the dealer if you decide to remove it later.

So if you want to give it a go, by all means try it out - but be VERY careful when fitting and tuning it. If you like how your car drives with it on, then keep it, otherwise send it back under the 30-day guarantee.

Don't be fooled, though - any fuel economy change you might experience is almost certainly just coincidence rather than any effect of the device. If you read reviews and comments on the device written before 2005 - for example here on dooyoo - you will probably see comments about better fuel economy, but the scientific evidence against it is pretty conclusive.