Turbo Small-Block Chevy Build - Plan Of Attack

How Do You Build A 1,000hp Small-Block? Two Turbos, New Computer Software, And A Lot Of Forethought

Barry Kluczyk Jan 1, 2001 0 Comment(s)
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You can throw a camshaft, a carburetor, and plenty of other catalog parts at your small-block, but without some forethought-without a plan-your new motor is likely to be nothing more than a 120hp anchor that doesn't idle and spits raw gas out the headers.

Joe Alameddine is a man with a plan. He's an engineer with Dana Engine Controls and works in the company's research and development center, so developing and implementing plans is what fills his day-planner. Like many Detroit-area engineers, Joe is a dedicated car nut whose off-hours interests are hard to distinguish from his 9 to 5 routine. He's owned plenty of fast street cars over the years, and when he decided to boost the performance of his '96 Impala SS, he started with a plan.

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Beneath all that plumbing lurks 935 horsepower and the twisting strength of 880 ft-lbs of torque. Although the engine is intended for a late-model Impala SS, it's not based whatsoever on the car's original LT1.

So, with a stated project goal of, in his words, "1,000 horsepower on pump gas with a fuel efficiency of 20 mpg," it quickly became apparent that boosting his SS's horsepower was going to require some serious boost. Like, 23 pounds worth.

"A power adder was definitely going to be required," Alameddine says. "Turbocharging was selected because of the exemplary mass air quantity it produces, without sacrificing efficiency."

Of course, building a 1,000-horse small-block isn't as simple as plumbing a couple of hairdryers into the stock LT1's intake and exhaust systems. And with all that extra air coming into the engine, a few more cubic inches-for a total of 383-would help process it.

Another goal of the project was driveability. By topping the engine with an electronically controlled port fuel-injection system, Joe was able to do field development on his workplace project, Accel's new Calmap 2000 engine control software. (Dana owns Mr. Gasket Co., which owns Accel. Small world, huh?)

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The small-block has been punched and stroked to 383 cubic inches. The foundation is a stout four-bolt-main truck block.

Ever the engineer, Joe outlined the engine's process for performance before a single main bearing cap was torqued down. That process included increasing the engine knock tolerance threshold (by creating a longer dwell time at TDC) to promote 94-octane friendliness, careful injector selection and timing with the Calmap 2000 software to improve emissions, maximize horsepower, and ensure driveability, and increasing the cylinders' volumetric efficiency with the intake manifold and combustion chamber designs.

Along with these process parameters, Joe was very careful with the selection of the turbos' compressor wheels, housings, and intercooler. And to improve the engine's overall efficiency, reflective and insulative thermal coating were to be used throughout the motor, turbos, exhaust, and intercooler.

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A forged and balanced Callies crank serves as the base of the reciprocating assembly. It provides the necessary 3.75-inch stroke for the 383. Mallory was used for balancing the crank, as keeping vibration to a minimum is a must in this high-pressure motor.

The Bottom End
With the plan in hand, Joe turned to noted engine builder Brian Thomson and his Detroit shop, Thomson Automotive, for machining, balancing, and block blueprinting. Thomson has years of experience building race engines, as well as contracts with General Motors and Ford for engine development work. Thomson's in-house engine dyno would prove invaluable for sorting out many of the turbocharged engine's necessary tuning hurdles, too.

Starting with a four-bolt-main truck block (the two-bolt-main stock LT1 block was ditched), Thomson overbored it 0.030 inches and filled the holes with boost-friendly 8.9:1 forged pistons from JE. Attached to them are 6-inch Carrillo steel rods which, in turn, are attached to a Callies 3.75-inch-stroke crank. The piston crowns were coated with Swain Gold thermal material, which helps retain heat in the combustion chambers. The coating also allowed tighter clearances during assembly, because the pistons don't conduct as much heat and, therefore, expand less.

Because of the daily-driving goal for the engine, not to mention its relatively lofty 6,200-rpm rev range, Joe chose steel rods over lighter aluminum components. Another consideration was the tight tolerances needed throughout the engine to support the stresses of a highly pressurized engine. The longer, 6-inch rod length puts the pin closer to the piston crown, which reduces the pistons' tendency to rock within the bores.

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The 383 runs longer, 6-inch steel connecting rods from Carrillo, which increases dwell time at TDC and enhances the engine's knock tolerance on pump gas. The longer rods also reduce the tendency for the pistons to rock within the bores, as the wrist pins are located closer to the crowns.

To shore up the bottom end, Thomson Automotive had the entire reciprocating assembly internally balanced with slugs of Mallory. This added strength and reduced vibration tendencies. Diamond Steel main bearing caps and ARP fasteners keep the crank in place.

Heavy Breathing
With the short-block built with the sturdiness of a brick outhouse, Joe turned his attention to the cylinder heads. They would have to move a whole bunch of air at relatively low engine speeds.

Air Flow Research anted up with a pair of CNC-ported aluminum heads that feature 210cc combustion chambers (also coated with Swain thermal material). The valves measure 2.08- and 1.60-inches (intake and exhaust, respectively). The intake valves are pretty standard stainless pieces, but the turbocharged nature of the motor required something stronger for the exhaust side. Inconel valves were used for the exhausts.

"They were necessary," Alameddine says. "With exhaust gas temperatures in excess of 1,600 degrees F, any ordinary stainless steel valve would deform from the heat."

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Low-compression, dished pistons from JE are thermally coated to retain heat in the combustion chamber and reduce overall friction. This allows for tighter assembly tolerances. Tighter clearances lessen piston blow-by, thereby enhancing performance and emissions. Swain Gold coating was used on the pistons' dished crowns, while Swain PC9 lubricant was used on the piston skirts.

Actuating the valves is a hydraulic roller cam and lifter combination from Erson, along with dual valve springs and titanium retainers. According to Joe, the AFR heads and valvetrain have proved to yield great flow characteristics and contribute to the turbo engine's snappy, low-lag throttle response. To keep the roller lifters from bouncing off the lobes at higher rpm, an AFR Rev Kit was utilized.

Drawing air into the heads starts with an Accel ProRam intake and Accel 1,000-cfm throttle body. The Accel throttle body is a two-throttle-blade design-each measuring 58mm. There are bigger, 100mm single-blade throttle bodies available, but such an inlet in front of the pressurized air would annihilate the rear tires with all but the slightest pressure on the accelerator.

Speaking of pressure, this small-block's comes from a pair of TO4-S turbos that were modified by Innovative Turbo to incorporate ball bearing turbo spools. They deliver 23 pounds of boost on pump gas. More thermal coatings were applied to these big hairdryers, which not only helped reduce temperatures, but also boosted their efficiency and reduced turbo lag, as well. Additionally, a pair of Turbonetics "Deltagate" wastegates bleed off pressure when all that boost isn't needed. The wastegates are electronically controlled from the cockpit, thanks to a setup from Turbo People.

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Air Flow Research supplied aluminum, CNC-ported cylinder heads. They feature 210cc combustion chambers with 2.08-inch and 1.60-inch valves. Since the engine has a rev range of 6,200 rpm, the valvetrain gets a workout; dual valve springs, titanium retainers, and an Air Flow Research Rev Kit help keep it all together. Erson roller lifters and 1.6-ratio roller rockers are also employed.

A more conventional way to reduce the pressurized air's temperature, thereby upping its boost pressure, is the use of an intercooler. A giant air-to-air intercooler with sewer main-sized inlets and outlets snakes around the front of the engine. In fact, there's so much plumbing on this engine-including headers and induction pipes by Kooks-that we had a hard time getting it all in for our photographs. On the engine dyno, a furnace blower fan was placed in front of the intercooler to simulate air rushing into the radiator. This helped lower the air temperature outside the turbos from 350 degrees F to a more manageable 150 degrees F, or lower, depending on the dyno room's temperature.

Fuel and Fire
With 23 pounds of boosted atmosphere squeezing into those cramped cylinders, a high-flow fuel system was implemented. A pair of Paxton fuel pumps suck the fuel tank dry quickly and send it to a Weldon high-flow regulator, where it is portioned out to a set of Accel 83-pound fuel injectors. (They sound like Rain Bird lawn sprinklers when running.) Under full boost, fuel pressure exceeds 70 psi.

With all that fuel coming in, something has to light off the mixture. Obviously, the stock ignition system would be unusable-Joe determined that with the engine's 800-plus ft-lbs of torque, the stock ignition system wouldn't even fire the motor past 2,700 rpm at wide open throttle.

Staying in the family, an Accel 300+ CD (capacitive discharge) ignition box, along with Accel 300+ Race plug wires, wire sleeves, and an Accel "red stripe" CD coil were used. Like other engine components, the spark plug wire boots are thermally coated. With the intense heat of the turbos, this helps prevent misfires.

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Although the 2.08-inch intake valves are standard stainless steel pieces, the high temperatures that the exhaust valves see require something more exotic. Inconel valves are used for the 1.60-inch exhausts, which stand up to the 1,600-degree F temperatures the turbos create.

Accel also supplied the electronic control module (ECM) for the engine, which controls, among other things, ignition spark timing. Accel's new Calmap 2000 software defines the parameters the ECM maintains. For instance, under boost the computer automatically adjusts timing as a function of load and rpm. If knock is detected, timing is pulled out at a pre-programmed rate. (For more on the Calmap 2000, see the accompanying sidebar.)

So, with all the careful planning, did Joe's twice-turbo'd 383 achieve the stated goals?

"Right now, the peak horsepower is 935, with 880 ft-lbs of torque," he says. "With pump gas, the Calmap 2000 software has been detecting engine knock above 935 horsepower and, consequently, backs off on the timing."

Joe's calculations for the engine with some high-octane racing fuel would easily put the small-block over the 1,000-horse hurdle. And he still intends to put the motor in his daily-driven Impala SS.

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Induction is handled by Accel's ProRam intake, 58mm throttle body and 90-degree adapter. The twin-blade throttle body is rated at 1,000 cfm and helps the engine produce crisp throttle response.

We plan to do a follow-up feature on Joe's Impala once the engine (and all its plumbing) is squeezed under the hood. With 880 ft-lbs on tap, gratuitous, smokey burn-out photos (and possible "after" shots of 10-bolt bits and 4L60E chunks on the highway) should be easy.

That's our plan.

Calmap 2000
Remember when the doomsayers predicted the end of hot rodding was at hand with the advent of electronic engine controls? That couldn't be a more ironic and wrong prediction.

The fact is, computers have made it possible for 1,000-horsepower monsters, like Joe Alameddine's twin-turbo 383 small-block, to be driveable in street cars. An engine control module is simply another engine component to tune. Some tuners have cracked open GM's brain boxes to discover their calibration secrets, while others have relied on aftermarket suppliers of performance "chips" and modules.

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Getting fuel to the engine is the chore of this pair of Paxton fuel pumps. While the engine was on the dyno at Thomson Automotive, the pumps were mounted atop a 55-gallon drum of fuel-a fuel tank size owner Joe Alameddine should consider swapping into his '96 Impala SS. Besides the high-volume pumping capability, the pumps were selected for their quiet operation.

Accel offers a universal ECM, the Generation 7, which is a sequential controller. But the ECM only follows orders from software programmed into it, and that's where Accel's new Calmap 2000 comes in.

"When used in conjunction with the Accel ECM, Calmap 2000 offers custom tuning capability for many types of engines, with almost any type of induction or power adder you can think of," Alameddine says. "Multi-stage nitrous, blowers, turbochargers... You can program parameters for all these options."

Alameddine demonstrated the program's user-friendliness. Calmap 2000 is Windows-based, which made it exceedingly easy to navigate. All the tuning inputs were made in real time through Alameddine's off-the-shelf laptop computer.

We simply don't have the space in this magazine to convey all the minute tuning parameters that can be adjusted and controlled with Calmap 2000, but consider this: At the time of the dyno tests, the Accel ECM and Calmap software were still in the prototype stages of development. Because so few of the ECMs were available, Alameddine was testing one in a pickup that has an inductive pick-up ignition input. But the turbo motor has a Hall Effect ignition input. It didn't matter; Alameddine removed the ECM from the truck and hooked it up to the turbo engine on the dyno. By typing in a configuration change on the laptop, the ECM got the 383 engine running in seconds.

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A high-flow fuel pressure regulator from Weldon permits plenty of fuel to get to the port injection system's fuel rails. It's adjustable, which is a must for the fine-tuning adjustment necessary to makes this unique engine run at peak efficiency.

In a nutshell, Calmap 2000 comes from Accel with basic parameters already installed. "When customers order the software, they'll provide basic information on the engine, such as engine displacement, injector size, and compression ratio, to name a few. Even some applications come pre-programmed, so all the user has to do is 'plug and play'," Alameddine says. "These basic parameters for fuel and timing will get the engine started and allow finer tuning from there."

For the turbo engine, Calmap's optional "Wide Band" Linear O2 proved essential in tuning. Once the values in a "Target Ratio" table were specified by Alameddine, the ECM automatically corrected the air/fuel mixture, while in closed-loop mode, to the ratios he specified. Also, Calmap's "auto cal" feature made tuning a snap. And, using feedback from individual cylinder probes, the 83-pound injectors were calibrated to match the flow characteristics of the intake manifold, while injector timing was optimized for the best compromise in horsepower and idle quality.

As we mentioned, Calmap 2000 was still the prototype stage when we were introduced to it. Alameddine is doing more work with fuel matrixes, and we hope to bring you more on that in the near future.

Sources

Air Flow Research
Valencia, CA 91355
661-257-8124
AirFlowResearch.com
Turbonetics
Simi Valley, CA 93065
805-581-0333
http://www.turboneticsinc.com
Mr. Gasket
216-688-8300
http://www.mr-gasket.com
Erson Cams
Carson City, NV 89706
800-753-2386
pbm-erson
Thomson Automotive
Wixom, MI
248-349-0044
www.thomsonengines.com
Turbo People
Hastings-on-Hudson, NY 10706
Paxton Fuel Systems
Camarillo, CA 93012
Process Coatings
Croswell, MI 48422
Swain Coating Technology
Scottsville, NY 14546
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