Magnum Lives!After a long and painful journey through uncharted territory, most of it in schematic wiring land, Magnum TPI is almost ready to rumble. In review, our 1988 Firebird Formula has a 396 cubic-inch stroker engine built by Strope Speed Shop which sports a ported ACCEL SuperRam intake, CNC-ported AFR 190 cylinder heads, Comp Cams valvetrain, an Evans cooling system, a Cola forged crank, 11:1 Lunati pistons and Pro-Mod forged rods. Fuel system upgrades include 26 lb./hr. ACCEL squirters and a high-output in-tank pump from Cotton's Performance.
After Strope installed our ACCEL Gen 7 DFI system with a jumper wiring harness from Fast Track Performance, we moved the car to Second Street Speed in Perkasie, Penna. to troubleshoot some minor electrical gremlins and to tune on its Dynojet chassis dyno.
A complete story will run in the January issue of GMHTP, but we've gotten so many inquiring letters from our readers that we wanted to update you as soon as possible on these new developments. With ACCEL's Windows-based DFI and wide-band tuning option, the Second Street crew got up to speed quickly and produced 323.9 rearwheel horsepower through the restrictive stock mass airflow sensor, skinny ductwork and our old, small K&N filter. Not exactly what we expected, but the lack-o-power was very predictable. The restriction of the MAF and skinny inlet tract was so great, it caused a loud sucking noise over the roar of the engine!
With no real reason to keep the non-functioning MAF sensor (the DFI is a speed/density system), the meter was ditched and an open throttle body was used for the next series of tuning pulls. Power swelled to 354 hp (up a whopping 30.1 hp!) at 5800 rpm and torque peaked at 486 lb.-ft. at a stump-pulling 3700 rpm. After backing out driveline loss, that's about 450 smog-legal flywheel horsepower. Providing we can fabricate a free-flowing inlet, we think that's enough power to get us into the 11s with pump gas. If that's the case, we will have reached our stated goal of running 11s with a full complement of emissions equipment-including dual cats-and doing it on ordinary pump gas.
Of note is the fact that our fuel system was found to be well within the capabilities of this power-a major consideration considering the difficulty of installing an in-tank pump in an F-body. (Thanks, Jack!)
Also, you may recall from our November 2001 issue that our Desktop Dyno simulation for this engine called for slightly more flywheel horsepower (470 hp). However, we actually got far more torque-approximately 600 lb.-ft. at the flywheel-compared to the Desktop Dyno simulation which predicted only 480 lb.-ft.
If we can get the intake air properly ducted with the hood closed, we may even include a dragstrip test with our results next issue. Stay tuned!