The Hemi was dialed in using the XFI/XIM engine management from FAST. It can control both
Finishing off the stroker Hemi was a Milodon oil pan, pick up and windage tray combined with a new (factory) oil pump. Prior to the installation of the pump, we installed a double roller timing chain from Comp Cams that included the necessary spacers for oil pump clearance. On the induction side, we installed an aluminum SRT8 intake manifold and stock throttle body. The drive-by-wire throttle body was converted to manual (dyno) use by welding a shaft and rotator in place. It was also necessary to mill the front cover (it was from a truck application) to provide adequate clearance for the front-mounted throttle body (better to get a core or front cover from a car application). In anticipation of the expected power levels, we replaced the factory injectors with a set of 75-pounders. Tuning was provided by the Fast XFI/XIM management system and factory coil packs. Unfortunately we had no Hemi headers available for testing, so we were forced to run our normally aspirated test with a set of factory SRT8 exhaust manifolds feeding 2.5-inch collector extensions. Dedicated long-tube headers would likely increase the power output by 15-17 hp over the stock manifolds. The final step was to fill the crankcase with break-in oil from Lucas, and we were ready to roll.
After a computer-controlled break-in procedure, the normally aspirated Hemi was run in anger. Tuned by Westech's Ernie Mena, the stroker Hemi responded with peak numbers of 523 hp at 6,700 rpm and 456 lb-ft at 5,500 rpm. Torque production from the 370-inch Hemi exceeded 425 lb-ft from 4,300 rpm to 6,300 rpm. Now we were ready for some boost. On went the turbo kit from HP Performance, bolting directly to the factory SRT8 exhaust. The kit included an air-to-water intercooler, a turbo capable of supporting over 700 hp and the necessary plumbing to direct all that wonderful boost into our awaiting Hemi. After hooking up the plumbing, we were rewarded with 765 hp and 764 lb-ft at 8.8 psi of boost. Torque production exceeded 700 lb-ft even down at 3,500 rpm (the starting rpm for our dyno pulls) and carried this value all the way out to 5,600 rpm. Those were some impressive numbers considering the modest boost level and the fact that the small turbo from CX Racing was nearly out of steam.
Prior to the installation of the turbo kit from HP Performance, the 5.7L stroker was treat
Since the idea was to put the turbo kit from HP Performance to the ultimate test, we decided to step up in turbo size. The 76mm unit from Precision Turbo represented a huge jump in both power and price compared to the smaller unit from CX Racing. Sized to feed four-digit power levels, the Precision turbo would surely demonstrate whether the rest of the kit from HP Performance was up to snuff. Running dyno water through the massive air-to-air intercooler core (ice water would add even more power), the Precision turbo cranked out a peak boost pressure of 16.5 psi and easily topped the 1,000hp mark. The best numbers of the day were 1,051 hp and 915 lb-ft of torque. The stroker not only survived the abuse, but thrived and was ready for even more. Having successfully reached our goal of 1,000 hp and demonstrated the merits of the Hemi Helper turbo kit from HP Performance (to say nothing of the power potential of a turbo Hemi), we packed it in and called it a day.
* Provided with kit
** Base kits
+ Price from www.summitracing.com
The kit from HP Performance was supplied with a single 38mm waste gate. The loads imposed
The turbo kit from HP Performance featured a dedicated air-to-water core but we stepped up
Installation of the turbo kit from HP Performance did not require removal of the SRT8 exha
The smallest and most affordable turbo in the test was this 76mm from CX Racing. It has a
Turbine sizing is evident in this comparison between the .96 A/R CX Racing (far right), an
The final test was with a Precision 76mm turbo. It featured a 4.0-inch inlet, a 3.0-inch d
Scat 5.7L Hemi Stroker-NA vs. CX Racing Turbo-8.8 PSI The power curves illustrate two very important points, the first of which is the fact that our 5.7L Hemi stroker was no slouch in normally aspirated trim. Offering 523 hp and 456 lb-ft of torque, the 370-inch (6.1L) Hemi was plenty potent. Adding 8.8 psi of boost from the CX Racing turbo and HP Performance turbo kit improved things substantially. The Hemi Helper pushed the power numbers to 765 hp and 764 lb-ft of torque.
SCAT 5.7L Hemi Stroker-NA vs. Precision Turbo-16.3 PSI Sized for street boost levels on a stock motor, we knew we had to step up from the turbo from CX Racing to an even larger unit. Precision Turbo came through with our four-digit turbo by providing a 76mm unit of their own with a larger turbine and AR ratio. Running 16.4 psi, the turbo Hemi pumped out 1051 hp and 915 lb-ft of torque. If there is one thing better than a Hemi-it's a turbo Hemi!
At just over 16 psi, the Precision Turbo produced 1,051 hp, with at a little more power left in reserve. Since we officially exceeded our goal of 1,000 hp with two of the turbos, we saw no reason to get greedy and crank up the boost beyond that point.
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