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After more than a year, I've finally gotten around to analyzing the dyno data I got from UL after he re-tuned my VAFC to match my I/H/E mods. There's not much new here, but perhaps this will encourage those considering spending thousands on forced induction that achieving good NA performance gains is not impossible.
The chart below shows the results of the two dyno sessions I had with UL. As you'll recall, his dyno is a Dynapack, which measures at the hubs and thus produces absolute numbers somewhat higher than Dynojets. Relative gains, however, should be comparable for any dyno.
The "Baseline" curves are for my stock '00 motor, with Spoon flywheel and iridium plugs. It's always been a bit on the strong side, producing 220hp in this configuration. The "VAFC" curves are the result of UL's careful tuning with this configuration. Finally, the "I/H/E-VAFC" curves are the result of his UL's re-tuning of the VAFC to suit my then-newly-installed AEM CAI and Mugen header and exhaust. In both tuning sessions, we found that my particular motor responded better than most to lowering the VTEC engagement point -- it's set at 5600.
Below are the air-fuel ratios from the tuning. Note that the AFR below VTEC was essentially unchanged after the first tuning session; however, this does NOT mean the VAFC settings were zeroed in this region! In fact, we got some nice gains in this region (see below). This is because the ECU is adaptive: its timing and fuel maps at one rpm range are not independent of those in other ranges. In this sense, tuning the VAFC is very much like shooting at a moving target, and anticipating this behavior is where UL really excels. As you can see, it was only with the I/H/E that the car "liked" to run leaner.
Finally, the net results: plotted below are the relative torque and hp gains. Note that there's no point where we lost power relative to stock -- another tribute to UL. Also note the sizable mid-range torque gains produced with the I/H/E. Despite the slight loss of top-end power, I've found this tradeoff invaluable at the track, where the car pulls strongly throughout each gear.
So that's it! I've been quite pleased with gains of up to 20 hp for "reasonable" expense ($1200 header + $200 CAI + $500 VAFC/tuning). Plus I get to keep that great normally-aspirated throttle response, and (yes I admit it) I feel like I'm staying true to Honda's philosophy of producing high output without going the "easy" route of forced induction.
Very nice gains. It's good to see when people do before & after analysis to show how their mods have impacted their power output.
Edit: Sorry... I just noticed that this thread is a month old. Oh, well... some times the "Search" feature turns up something interesting that I missed before!
Seems like the VAFC did great by itself. Adding the I/H/E increased low rpm range hp, and tq, but the upper rpm hp, and tq decreased. did you UL give any feed back regarding this? why the decrease?
Exhaust was $1300 but does nothing for power so I don't count it here -- it's purely a weight-savings/aesthetic mod.
Blitz, the Mugen header is known to sacrifice the extreme upper powerband in favor of mid-range gains. Right after I installed it, the Toda header hit the streets and was shown to provide good mid-range gains without sacrificing the high end. Oh well -- win some, lose some.
Looks good. As you said, the dyno numbers are good for comparing the effects of changes to your particular car, not in an absolute sense.
Looks like the VAFC/I/H/E is giving you the biggest gains at the same place where you are leaning out the most (no surprise). Any concern of 14.5 A/F in the 6000 range ... I realize that you're NA but what are people's thoughts on that?
Remember that the A/F measured at the exhaust is about half a point higher than what the engine really sees. I've had no problems with these settings in 1.5 years ~2K track miles, but I wouldn't advise going any leaner.
03-04-2004, 09:25 AM
As you can see, it was only with the I/H/E that the car "liked" to run leaner. 
