We've long heard it argued that while the oe 240SX fuel pump will flow an SR at stock boost levels, it has a hard time keeping up with increased fuel demands when boost is turned up. Until now, Carter's SR drew 91-octane California pump gas through the car's stock fuel pump with no apparent cause for alarm, but its ignition timing had been retarded to 10 degrees of advance as a buffer (and since the SR's oe tune requires higher octane fuel). Before we moved any farther in our testing, we wanted to see for sure whether or not there was any danger in running the SR at its suggested ignition time in this condition. G-dimension's Stephen Rhim advanced the SR's ignition to the factory 15- degree setting, replaced the cat with a test pipe and monitored a digital readout of its resultant air/fuel ratio as I floored through a fourth gear pull. A new high power mark was reached, of 201.7 whp and 186.6 lb-ft of torque; a gain of nearly 40 whp top-end and over 30 lb-ft of torque-our biggest jump in power yet recorded! The SR's A/f ratio fell proportionately as engine speed increased, to a steady hold at just over 12.0:1, while fuel pressure readings remained within a safe range; seemingly 'busting' our worries that the SR might lean out under usdm circumstances.
Another point that we've often heard argued in SR circles, is whether or not a front mount intercooler could offer added power over the stock side-mount unit at the low 7psi boost level. Fmics are usually regarded as a prerequisite for increasing boost, not added to produce power themselves; but with the car strapped to the dyno and a greddy front-mount kit going on anyway, we thought we should see if any additional power could be found just by bolting it on. The greddy unit's cooling area is roughly four-times that of the sidemount unit's and its plumbing much larger and smoother than the oe. The Phase 2 hot pipe we used followed suit; if the combination didn't bring power gains, we'd be shocked. After three pulls, the truth was graphed-an additional 19 whp and 20 lb-ft of torque were found at certain parts of the SR's powerband, bringing our peak numbers up to 214.7 whp and 199.1lb-ft of torque.
Now it was time to get to brass tacks. After replacing the 240's oe fuel pump with a Walbro 255lph unit from Alamo Motorsports and the SR's fpr with an adjustable (though locked in at the factory setting) Nismo unit provided by Performance Nissan, Stephen installed a blitz sbc i-Color Spec-C boost controller and prepared to see just how much power the stock S13 SR could produce. As its MSRP might suggest, the blitz unit is absolutely the finest boost controller on the market. After a quick 20-minute installation, the sbc can graph boost, horsepower, torque, or A/f over engine speed; display water temperature and oil pressure; and can even calculate fuel consumption in real time-all in full color. Engine displacement, vehicle weight and desired power levels can all be in put in the unit's "self-learning" full auto mode, but we were more impressed with the manual controls. Peak boost levels can be set, as well as variable wastegate actuation-a feature that offers a distinct advantage. Cheap-o, mechanical boost controllers only allow for peak boost adjustment; once the set boost level is reached, the wastegate opens and excess airflow bleeds off. With smaller turbos, like our stock S13 unit, this can cause peak power to be made early in the powerband-with a subsequent large fall-off at top-end from a lack of airflow to keep the turbo spooled. Using the blitz sbc, we were able to keep the wastegate closed longer and open slower to build more boost top-end, meaning longer sustained power and higher gains across the board.