Here’s a little riff on the last entry. (See, instead of fixing the car I can play with the data logger?)
You won’t be able to see this unless you click on the graph. Of course, when you do that you won’t be able to read my matchless prose but I’m sure you’ll work out how to resolve that.
The two plots here are for the fastest lap I did in testing at Snetterton on the Friday afternoon before the race meeting and the fastest lap I did in qualifying on the Saturday morning. The interesting thing is the air/fuel ratio plot. If you look at the upper one then it’s sitting pretty close to the line I’ve drawn on which is at 13.8 which is a sort “goodish” number. During the periods of WOT down the Revett straight it’s actually pretty much at 13.8 all the time.
However, for comparison, look at the lower one. Here the line is almost always some distance below 13.8. (That is, a lower air/fuel ratio meaning a richer mixture.) In fact, at the same WOT segment it’s sitting around 10.1. Curiously, and I’ve no explanation for this, it’s dropped markedly when I’ve changed into 5th gear. I’m assuming this is a coincidence for the moment as the ECU doesn’t know what gear I’m in.
I’ve been discussing this whole sorry situation with all the petrolheads I can think of. The only causes that we’ve thought of are:
- The engine management is somehow or other broken or
- The cat has collapsed inside the exhaust meaning that that’s blocked and combustion is happening properly as a consequence.
I have to admit that I’d have even less idea how to fix the second one than the first…