We thermal-wrapped the tops of the primaries as the stock cast manifold had already melted a distributor cap
HeaderHoping our good luck would hold, we installed the TRD four-into-one ceramic-coated tubular header to see if peak power would increase by magic. Conventional theory goes that a four-into-one header (where each primary merges into a single collector leading to the downpipe) will yield better high-end performance on account of the high-rev flow capabilities, while a four-into-two-into-one design (with two series of collectors) will yield more mid-range torque. We consulted with Jack Burns, guru of Burns Stainless, and a fabricator of Top Fuel dragster manifolds, to see how good the TRD header was out of the box. At an average length of 22 inches for each primary, this unit is a decent design for street use. According to Burns, an ideal primary length of 26 inches for this engine and cam combination would yield ultimate flow as well as a properly built collector.
If we were trying to make more power with the existing hardware, we'd probaly cut out the TRD collector for a race-quality unit from Burns Stainless, as well as increase the primary runner lengths and retun the EDC to work with a hot-wire MAF meter
We did see some signs of added flow, as our overall A/F dropped especially where the now-deleted EGR valve was supposed to open at around 3000rpm. The stock ECU is tuned to inject less fuel when the EGR is open, since there is less fresh combustible air in the cylinders. With the EGR deleted, the cylinder is now filled with fresh air, but still the same amount of fuel, causing the mixture to go lean. We think this is the reason for the huge dip at 3000rpm as well as the drop in power between 5000 and 7000rpm. Again with proper tuning and a higher rev limit, this set-up should be capable of more output. Regardless, we've seen an overall gain of roughly 10 percent, which isn't much on a 100hp car, but the same percentage gain on a S2000 would account for over 20 wheel-hp, something no S2000 bolt on-hardware could claim without a retune. n