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Originally Posted by mbtoloczko
Chike,
I have that same fuel consumption vs cylinder pressure plot in my locker. :-) As far as I know, the 2.5 RS fpr is working fine. I haven't looked at the vacuum line though. I haven't touched the fuel pump in any way. I suppose its possible that the ram air is having some effect, but keep in mind that the ecu does not just blindly add fuel. It meters fuel based on the MAF sensor reading (among other readings), so if the ram air is somehow messing up airflow at high rpm, the MAF would see this, and the ecu would add less fuel accordingly.
I'm fairly convinced that the afr reading is representative of what the SVX ecu is programmed to do. The other EG33 afr readouts from dyno runs that I've seen (SVXRide, LAN) show the afr progressively richening as the rpms increase. And if I look at the afr readings from your dyno runs, I see the same basic trend too. The afr on your car does richen as the rpms increase, and at peak rpm, there is a slight lean out. My afr runs show the same thing, and so do LANs.
As deruvian said, a little more power may be possible with the 2.5RS fpr by leaning out the mixture a bit at higher rpm using an SAFC-II (or something like it).
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Mychailo,
While the SVX ECU richens the afr to a degree in the upper rpms, the increase you got above 5000 rpms was much larger than I expected. I guess I'll have to see your runs with the SVX fpr before any definite conclusions can be drawn...
I must say, I've always been wary of non-factory ram-air systems - and I still wonder if your system might not have supplied enough air to the engine above 5,000rpms (which in turn would have richened the afr). As you did your runs in 3rd gear in a 5spd car, you must have been going 90+mph as you approached redline. At these speeds, the air flow over your car would have caused more 'pronounced' regions of low and high pressure to form - and if your ram-air was placed in a non-ideal location (e.g. hole at bottom of the inner fender per Terry's SVX FAQ), air would be sucked out and not in at those speeds...
If possible, while you still have the Impreza fpr installed, repeat your wideband afr test - this time in 2nd gear and on a level road. I'd be interested in seeing whether your results will be the same.
-Chike