Quote:
Originally Posted by SS_Firehawk
Hard to compare yours to mine with my O2 sensors flip flopped and miswired. The second was PPEs, y pipe & hfc, and CBE. The last run was with pulleys and CAI I felt power should have been higher and tq was a bit soft. But from one run to the next, it is at least indicitive of the gains possible for your car. CAI was ARMs, which seem to get a bit of a poor rep because of filter and MAF placement, but they pick up power all over the place. Those numbers are in DIN as well. It was closer to 310 SAE. Car only made like 265 stock at best.
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I know you had some major sensor issues and also a few different mods (as well as a different trans!), but the shape of the torque and power curves, including the narrow area where it dips is very, very similar. That said, the O2's job is to create fuel trims to get sensor readings close to the target map. Primary fueling is all handled by the MAF and MAP to assess air and pressure respectively and then command injector duty cycles based on calculated load and RPM. It probably didn't start really wreaking havoc with your trims, giving unstable AFR's and other weird driveability quirks until after driving around for a bit. Anyway, if your fueling was that far off, it would have never made anywhere near those power levels on the dyno.
Also note: Blue, flatter, and even slight bump in the 4 - 4.5 range; red, slight drop to match or just barely dip below the blue line in that area; green, much flatter across the board, but still slight drop off in that RPM band.
That makes me think the low end dip is just characteristic of the header design -- it seems to be primarily a mid to high end power maker at the cost of some minimal low end grunt.
Basically, vs. a stock set up, cat delete, or probably shorty headers, it just doesn't pick up as much down low, and virtually nothing (or very minimal loss) in that narrow range, but offers massive gains everywhere else.
I suspect your inclusion of the cat actually helped you down low -- the slight restriction may change the speed of the exhaust pulses at lower RPM's to better match the OEM valve timing.
I think with some VVEL tweaking, that dip would flatten right out. That dip is also reminiscent of the drop in torque we see in the FR-S motor before cam switch and also the dip characteristic of the 2ZZ (Celica GT-S and Lotus Elise motor) before cam profile change.
I know Sh0velman had virtually the same set up I have -- I think he mentioned a similar torque curve in another thread too, but I couldn't find a dyno graph for him.