ECU MOD £5

That was damm quick, I thought as much as the site is full of the cheap sort of stuff you find at car boot sales.

no yes

or you can spend £20 on eBay for it :)

PhilÅ ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

The theory is that the resistor persuades the ECU that the inlet air is colder - and therefore denser - than it really is, so more fuel can be injected, giving more power.

The drawback with that theory is that the lambda will see that it's too rich and adjust the mixture leaner again.

No it's not a 10p resistor. It's a 1p one.

It's more subtle than that. It _also_ persuades the ECU that, due to the extremely cold intake air, the mixture is very unlikely to knock, and hence ignition timing can be significantly advanced.

On most cars, this will indeed produce more torque and power - right up until the point where the engine explodes...

(I see the same people also sell a magnetic fuel saver, which ought to start the snake-oil alarms ringing straight away.)

Tony

Most modern engines have knock sensors fitted, so the ECU will just readjust the ignition timing to prevent knocking, just in the same way the ECU uses the lambda sensor to adjust fuel mixture.

Fair point, but there are a few engines around (eg the 4-cylinder Rover K-series) without knock sensors. And even when you have them, there is a limit to how much retard they are allowed to apply - screw the air intake temp up enough and you might just run out of adjustment.