Project Street-Max: 2006 GMC Duramax

Project Street-Max is taking a turn toward serious for the final installment. This month, we’re upgrading our ’06 LBZ’s injector nozzles and CP3 at Knoles Performance Solutions and also having the truck dyno-tuned by Fleece Performance. First, the factory injectors were sent to Fleece, where they were fitted with 60 percent larger nozzles. To keep up with the larger nozzles and maintain rail pressure, we shipped the factory CP3 to Motorsport Diesel (formerly Wicked Diesels), where it was transformed into one of the company’s infamous stroker pumps.

With the engine buttoned back up, Fleece tied the combination together using EFILive software while on a dyno, effectively optimizing the truck’s power, driveability, and fuel economy. The final step was heading back to Randall’s Performance for one last dyno appointment.

In order to be fitted with 60 percent larger nozzles, we sent our stock injectors to Fleece Performance as complete units. This way, they could all be batch-tested and balanced to flow accurately once the nozzles were installed.

In order to be fitted with 60 percent larger nozzles, we sent our stock injectors to Fleec

Between the fully built Sun Coast transmission, necessary fuel modifications, and the 68mm Cheetah turbocharger, we think we’ve built a max-effort, street-driven, late-model Duramax. And by limiting the truck’s power level to less than 650 hp, the LBZ engine under the hood is still well within the safe zone. We’ve also included a recap of what it took, parts-wise and dollar-wise, to get our Sierra to the 600-rwhp mark. If you’re looking for the ultimate, daily-driven Duramax yet aren’t quite ready for a built engine, this is the setup for you.

Stroker CP3 Injection Pump
Many areas of the LBZ CP3 are addressed when Motorsport Diesel converts one to a stroker pump. A 2mm increase in stroke equates to a 25 percent increase in displacement, which is pretty substantial. Other modifications include enlarging the ports on the gear-supply pump (which is responsible for providing fuel to the plungers at high pressure) to match the passage size of the pump body, adding 50 percent more to the lift of the delivery valves, and several other things that are kept proprietary. Like the 60 percent nozzles we went with, its stroker pump can also support trucks making in excess of 800 hp.

*Motorsport Diesel does not utilize used cores to build its stroker pumps, although some exceptions can be made for fresh, wear-free pumps. The fact that our pump had just 50,000 miles on it made it an exception to the rule (although it was thoroughly inspected and any questionable components were replaced).

Dyno-Tuned
The farther you move away from the stock hardware, the more important it is to make sure your modifications work in conjunction with each other. This is where custom-tailored, EFILive tuning comes in—you meet with your tuner in person to get the most out of your given combination of parts. What’s even better is conducting your tuning on a chassis dyno, where you can track your progress, tweak and monitor key parameters (timing, pulse width, rail pressure), and make sure you obtain the horsepower number you’re after.

We met up with Brayden Fleece of Fleece Performance at DC Chassis Dyno in Brownsburg, Indiana, to not only make sure we cracked 600 rwhp, but to make sure we did it as safely as possible. Thanks to the larger nozzles, less timing and duration (pulse width) can be commanded in the tuning, all while making more horsepower. The combination of running a maximum of 30 degrees of timing and 2,650 microseconds of pulse width led to an impressive 642 hp and 1,180 lb-ft on DC Chassis Dyno’s DynoJet 224xLC dynamometer. With the stock nozzles, our maximum horsepower tune was commanding 32 degrees of timing and 3,200 microseconds of pulse width (an earlier start of injection, with a longer injector on time).

Street-Max Recap
(Part 1, Sept. ’11)
Air intake: K&N with Amsoil dry filter
Exhaust: 4-inch MagnaFlow single exit (stock downpipe)
Fuel System: AirDog 100-gph lift pump
Transmission: Sun Coast GMax 6-pac, 1058 converter
Horsepower: 254 hp at 3,000 rpm
Total Spent: $3,319

(Part 2, Oct. ’11)
Fuel pressure relief valve: Shim kit
EGR: Blocker plate
PCV: Reroute kit
Tuning: EFILive via Fleece Performance ECM and DSP5 switch
Horsepower: 475 hp at 3,000 rpm
Total Spent: $1,319.99

(Part 3, Nov. ’11)
Turbo: Fleece 68mm Cheetah turbocharger
Exhaust: HX40 downpipe
Emissions System: Full EGR delete
Engine Modifications: Head studs
Horsepower: 525 hp at 3,200 rpm
Total Spent: $3,741

Back on Randall's Performance's SuperFlow dyno, we saw 588 hp and 1,000 lb-ft in our all-out performance setting-with the Chettah turbo never exceeding 38 pounds of boost. While we know the 588 hp we made at Randall's rather stingy dyno is lower than the 642hp number we earned on the Dynojet, it proves no dyno is the same, and the truest number may lie between the two. The only way to know for sure is if we hit the local dragstrip, which we plan to do once the weather warms up. Either way, we've added at least 335 hp and 535 lb-ft to the truck since our first installment.