If you recall from Part 1 of our “Keepin’ Up With The Joneses” series (Dec. ’12), our ’97 F-350 received a set of Unlimited Diesel Performance’s Stage 4 300/200 hybrid injectors and we made it a mission to make 550 rwhp on the 7.3L Power Stroke’s 185,000-mile, stock bottom end. After collecting an 8.26-second eighth-mile timeslip (high 12s in the quarter), we made it over to Randall’s Performance for some dyno time. Once the rollers stopped turning at 515 hp, it was clear we needed to find another 35 hp to reach our goal. What to do…
Since the S366 was living on the edge of its map—thanks to our 7.3L of displacement, considerably modified HEUI system, and aggressive tuning—we weren’t surprised to see horsepower flatlining on the dyno. Seeing the little S300 run out of gas meant it was time to upgrade turbos, but that wasn’t the only hurdle we faced. Getting the most out of the Stage 4 injectors would also call for a high-pressure oil pump upgrade, a tuning change, and more fuel supply. Tune in next time for the last piece of the 550hp puzzle: a competition-ready, DIY fuel system.
S366 & 300/200s on the Dyno
With the 300/200 hybrids installed and the S366 turbocharger still in the mix, you can see horsepower peaked at 2,800 rpm and held relatively steady until the dyno pull ended at 3,400 rpm. We believe this happened because the small charger was simply maxed out and couldn’t flow any more air at higher rpm.
| Dyno Chart
Boost: 38 psi (41 to 42 psi on the street)
ICP: 2,900 to 3,100 psi
Fuel Pressure (WOT): 45 to 50 psi
*SuperFlow dyno correction factor
*35 percent load applied
*Third gear (1:1), torque converter locked
*2.4-millisecond pulse width tune
Pushing the Limits
Prior to installing a bigger turbo, we realized the 300/200 injectors had caused two problems to surface: Injection control pressure (high-pressure oil, or ICP) and fuel supply pressure weren’t maintaining adequate levels at wide-open throttle (3,000 psi and 65 psi, respectively). On the dyno, we found that the settings on our six-position chip commanding the most pulse width were causing both parameters to drop, resulting in less horsepower. In fact, a tune calling for just 2.4 milliseconds of pulse width (injector on time) was as far as we could push the truck before power began to fall off, and it was the tune we used to achieve our 8.26-second eighth-mile pass. This was inconvenient because with a 2.7- and a 2.9-millisecond tune left in our arsenal, we were leaving potential horsepower on the table.
| Stealth Pumps Hpop
It was clear we had reached the limit of DieselSite’s Adrenaline high-pressure oil pump. To be fair, it’s not rated to support the 300/200 injectors we were trying to get it to work with, so that part is our fault. Although we’re getting away from the Adrenaline this month, we still have nothing but great things to say about it. The Adrenaline has been with us since our 7.3L Power Stroke’s horsepower journey began more than four years and 50,000 miles ago. It’s reliable, affordable, supported our 238/80 hybrids, and got us to the 500-rwhp mark without breaking a sweat.
We believe our fuel supply issue boiled down to the fact that we’d found the limit of the Walbro electric lift pump pulling fuel through the restrictive, stock selector valve (used on ’94½ to ’97 Fords with dual fuel tanks). We’ll tackle this problem next time, as the truck’s entire fuel system from tank(s) to engine will need to be reworked.
S468 & 300/200s on the Dyno
Before we got to work addressing our fuel pressure shortfall, we tried one last thing: more timing. After contacting Matt Robinson at Gearhead Automotive Performance, each “All Out” tune on our TS Performance six-position chip was treated to a 2-degree bump in timing at 3,200 rpm. The theory here was that the added timing might keep horsepower climbing at higher engine speed—and it worked! Even though fuel pressure was still only maintaining 45 psi, we squeaked an extra 22 hp out of the setup (peaking at 538 hp). Tune in to Part 3 in the months ahead, as we completely redesign our 7.3L’s electric fuel system, go after 550 hp, and return to the track.
| Dyno Chart
Boost: 41 psi (43 psi on the street)
ICP: 3,000 to 3,200 psi
Fuel Pressure (WOT): 45 to 50 psi
*SuperFlow dyno correction factor
*35 percent load applied
*Third gear (1:1), torque converter locked
*2.4-millisecond pulse width tune
Fast Specs
Engine Mods: Stock short-block 7.3L Power Stroke with ARP head studs, Comp Cams 910 valvesprings, and Hamilton Cams chromoly pushrods
Fuel: Unlimited Diesel Performance Stage 4 300/200 hybrid injectors, Stealth SRP1.1 high-pressure oil pump, DieselSite CPR electric fuel supply system with Walbro GSL392 lift pump
Air: Fleece Performance billet S468, Irate Diesel Performance T4 mount and stainless steel intercooler piping, Spearco intercooler
Tuning: TS Performance six-position chip programmed by Gearhead Automotive Performance
Transmission: John Wood Automotive Street Performance E4OD
Cost To Duplicate: $16,500 (labor not included)
