^^does the Cat comunicate to the ecu to tell it what air fuel Ratio to give depending on atmospheric temp? (lamda sensor?)
Im a tad confused because cooler intake temps will alter ratio.
My 3 GTi's have all been run slightly worse for economy on colder days.
The cat itself doesn't communicate with the ECU, but the pre and post catalyst lamba sensors do communicate with the ECU. And, with the exception of the cat warm up phase (where the engine runs at WOT, and includes a fuel injection pulse on the exhaust stroke, which then gets burn in the actual cat), the engine ECU will aim to run at a lambda value of 1.0 all the time - hot day or cold.
The actual mixture will always be closest to 'stoichometric' - ie, 14.7 parts air to one part fuel (by weight) - when the engine is at normal operating temperature. All cooler air intake temperature will do is alter the density, or 'weight per volume' of air. But an identical number of V Power molecules will still burn with an identical number of oxygen molecules. <where is the 'nerd' icon?>
The only reason cars use more fuel in the winter is down to two simple issues
- the engine will take longer to heat up, and will over fuel the catalyst for slightly longer
- you will be using more 'electricals' such as headlamps, heated rear windows and heated mirrors, seat heaters, fan blowers, wipers etc - which all need 'fuel'
Does this make it clearer
