Bizarre fuelling problem

[pyaap]

>At WOT it should be running closed loop @ 14.7 until about 4500 rpm and >then richen up progressively to the red line.

Hi Adam,

Thanks for this little nugget of info. I appreciate that Volvos do tend to run a little on the lean side for good power / torque and emissions reasons I guess but at WOT, don't they run open loop off the MAF (and / or MAP) and disregard the lambda sensor readings? I was under the impression that at WOT, the Catalyst serves no purpose other than that of a restriction in the exhaust and hence the lambda sensors are not really vital in fuelling. From VADIS, I have seen that at idle and part throttle, the ECU constantly switches between running closed and open loop but I assume again that is to keep an AFR as close to lambda 1 as possible. In addition, from most of T4 & T5 power runs I've seen, the majority produce peak torque at around 4000rpm and in that case, wouldn't peak boost and a stoich AFR be a recipe for disaster (assuming the engine runs stoich up to 4500rpm)? Thnx for your input.

On the ME7 cars like the T5 Alastair has, they run at lambda 1.0 even at WOT up to approx 4500 rpm. Only after 4500 rpm WOT do they richen up. I can show you loads of AFR dyno charts for standard cars which shows this.

Another example is BMW, whos later engines runs at lambda 1.0 everywhere, and are closed looped mapped everywhere. It's all down to newer engine design and emission regulations.

Adam.