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Mouse-Motor Americana

The pushrod-wielding small-block has gone high-tech

Andy Bolig - July 17, 2014 10:07 AM

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The Gen 5 small block is a cornerstone of GM’s powertrain strategy and its production at Tonawanda affirms the commitment to one of the highest-skilled workforces in the industry.

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The GM Tonawanda Engine Plant has 12 Zeiss Coordinate Measuring Machines (CMM).

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The GM Tonawanda Engine Plant uses a specialized RFID bolt with memory to track each machining process. The track and trace system ensures each machining process has been completed and allows data to be downloaded at assembly completion.

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GM recently invested $400 million into its Tonawanda Engine Plant. Shown here is the automated cylinder head torque down station where multiple bolts are torqued simultaneously for precise clamping force to the engine block.

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The final assembly area at GM’s Tonawanda Engine Plant.

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A 2014 6.2L V-8 VVT DI (LT1) engine block.

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Standard oil-spray piston cooling sprays the underside of each piston and the surrounding cylinder wall via small jets located at the bottom of the cylinders. Jets are used only when they are needed the most: at start-up, giving the cylinders extra lubrication, and at higher engine speeds, for extra cooling and greater durability.

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The camshaft features an all-new “tri-lobe” design which exclusively drives the engine-mounted direct injection high-pressure fuel pump. The cam’s specs include 14mm/13.3mm (0.551/0.524-inch) intake/exhaust lift, 200/207-crank angle degrees intake/exhaust duration at 0.050-inch tappet lift and a 116.5-degree cam angle lobe separation.

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Active Fuel Management (AFM) helps save fuel by imperceptibly shutting down half of the engine’s cylinders by de-activating the intake cam followers during light-load driving. 

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The pistons feature unique sculpted topography that was optimized via extensive analysis to precisely direct the fuel spray for a more complete combustion.

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The LT1 head features smaller combustion chambers designed to complement the volume of the unique topography of the piston’s head. The smaller chamber size and sculpted pistons produce an 11.5:1 compression ratio.

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The direct injection system features a very-high-pressure fuel pump mounted in the “valley” between cylinder heads, which delivers up to 15Mpa (over 2,000psi). The high-pressure, engine-driven fuel pump is fed by a conventional fuel-tank-mounted pump.  

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The 6.2L LT1 is extensively tested for durability, performance and efficiency on dynomometers at the GM Powertrain Engineering Development Center in Pontiac, Michigan.

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The success of the small-block Chevrolet engine is a tale that is well-known on the racetracks and the back-roads all over North America.

 

Praises have been poured upon the mouse motor in every regional dialect and every circumstance this vast country has to offer.

And now, the little pushrod-driven engine that could—did, and it’s forcing those in other countries to smile upon it, with a little apple pie on their cheek.

In the not-too-distant past, many a foreign engineer looked down their noses at our beloved small-block. While the small packaging and lightweight powerhouse had its benefits, it was always deemed a lesser form of power due to its Rube Goldberg-ish system of pushrods and various valvetrain components. The roar from its open-throated exhaust was seen as somewhat brash and unsophisticated compared to the finely-tuned, high-revving, overhead-cammed performance engines offered overseas. GM even bowed to the pressure in the ’80s, and teamed up with a boat-engine manufacturer from Oklahoma to build the exotic-looking, dual overhead-cammed LT5s for those select C4 Corvettes so shined upon by the performance gods in Bowling Green. The world took notice. So did the bean counters.

Engineers and accountants soon realized the beauty of the original small-block design was its power, size and its economical construction. The introduction of the LS1 engine cemented GM’s determination to keep costs low and that meant that pushrods were back. Generations of small-block engines flowed out of GM facilities and other than that short stint from Stillwater, each one stayed true to the original foundation formed way back in 1955.

The fifth-generation of the small-block engine was introduced recently and although it still holds true to the rudimentary design, there have been several advancements that unequivocally toss the “low-tech” yoke far from around the engine’s neck. Carb-loving enthusiasts may glare at today’s advancements with a stern eye, but they openly warm up to the additional wires, hoses and sensors when it comes time to drive in traffic or pull up beside a fuel pump or competitor.

 

Beyond A Basic Small-Block

There have been non-negotiable standards for the small-block since day one. The platform is built around a 4.4-inch bore spacing that ALL SBC engines have exhibited, even the exotic LT5s. While adding a few fractions of an inch would help fit more goodies under the valve covers, it doesn’t help get the engine under the fenders and hood. Remember, at the factory, engines go UP through the frame rails, not dropped in.

While the new Gen V small-block may resemble the previous generation engine, there are very few pieces that carry over. A couple of items like valve retainers, piston pins and a couple of bolts are all that carry the same part numbers from the previous LS3 engine. The rest is all new, so new in fact, that it took a total revamping of GM’s Tonawanda, New York, facilities to properly assemble the new engine and ensure the required engine longevity and production numbers necessary to supply the various iterations needed throughout the GM product line.

Tonawanda will produce four versions of the Gen V Small Block – a 4.3L V-6, 5.3L V-8 and two variants of a 6.2L V-8. When the plant is at full production, it produces more than 1,000 engines daily. The new family of engines will power nine GM models by 2015, including the 2014 Chevrolet Silverado and GMC Sierra pickups, and the 2014 Chevrolet Corvette Stingray.

An assembly plant as highly advanced as the engine that it produces enables Tonawanda to build all Gen V variants on the same assembly line. The lowly pushrod engine is now among the most advanced and high-tech engines in the world and Tonawanda is now “one of the most technologically advanced manufacturing facilities”, according to Steve Finch, plant manager.

Manufacturing highlights at Tonawanda include new coordinate-measuring machines that check machining with greater speed and accuracy, including a Zeiss position check machine that examines more than 11,000 data points within 2.5 microns and a Hummel machine that checks surface finish textures at less than a micron – less than 0.001 millimeter or 0.000039 inch. There is a new tracking system featuring RFID bolts that collect all machining and assembly data for each engine, helping ensure top quality builds. A new, automated cylinder head assembly system helps ensure more precise assemblies and can assemble 48 parts in 40 seconds.

To ensure a leak-free installation of the new Direct Injection system, there is a fuel connection inspection that uses helium to detect even the most minute of leaks – less than one part per billion – to safely contain the higher pressures of the direct injection system on each engine. To increase production and close tolerances, Tonawanda now has the capability of boring any number of cylinders through the same machine without stopping production. And, there’s also a new machine featuring three synchronistic robots that perform inspections and checks simultaneously for any engine including thread check, plug assembly and leak test. Previously, checks were handled one at a time and separate lines were required for six- and eight-cylinder engines.

 

Direct Injection

One of the newest technologies gaining widespread acceptance among the OEMs is Direct Injection. Injecting the fuel charge directly into the combustion chamber allows for much tighter fuel control and distribution, which also contributes directly to fuel economy, driveability and better emissions. Direct injection is a primary contributor to greater combustion efficiency by ensuring a more complete burn of the fuel in the air-fuel mixture. This is achieved by precisely controlling the mixture motion and fuel injection spray pattern. Direct injection also keeps the combustion chamber cooler, which allows for a higher compression ratio. Emissions are also reduced, particularly cold-start hydrocarbon emissions, which are cut by about 25 percent.

While these are several benefits of using DI over the more conventional electronic fuel injection, there are also some considerations. First and foremost is the much higher fuel pressures achieved through DI’s camshaft-driven fuel pump. Likewise, since the pump is now mechanical instead of electronic, owners of direct injected automobiles may notice extended crank times before start-up, especially in cold weather conditions.

 

Variable Valvetrain

Performance enthusiasts have been “dialing in” their camshafts as part of the assembly process for decades. By advancing or retarding the timing of the camshaft, builders can “pre-dispose” the engine to exhibit increased low-end torque (advanced) or better high rpm power (retarded). Since this is done during assembly, the builder must consider the engine’s primary use and set up the engine accordingly. Now, imagine being able to vary the camshaft timing in real-time, according to the type of driving being accomplished. That is exactly what Variable Valve Timing (VVT) does, giving the best of both worlds in low end torque and top-end power.

For comparison, the Stingray Corvette’s LT1 has greater power density than the C6 Corvette’s non-VVT-equipped LS3 6.2L engine and the non-VVT, C6 Z06’s racing-derived 7.0L LS7. It also produces comparable torque to the LS7 – up to 4,700 rpm – and its peak torque is within five lbs-ft of the 7.0L engine. That torque is generated early and sustained across the rpm band, with 316 lb-ft available at only 1,000 rpm and 90 percent of peak torque available from 3,000 rpm to 5,500 rpm. When you compare horsepower, the benefits of VVT continue to shine as the 2014 Corvette Stingray’s LT1 is SAE-certified at 460 horsepower (343 kW) at 6,000 rpm, 25 more than last year’s LS3.

 

Fuelish Management

Another technology that benefits the Gen V small-block is what  GM calls Active Fuel Management (AFM). The Corvette Stingray’s LT1 is the first application to utilize this technology in Corvette, while it has been utilized in previous-generation engines in the larger trucks and such. The main benefit if AFM is increasing fuel mileage by “shutting off” half of the engine’s cylinders while under light-load driving.

Previous GM versions of 4-6-8 technology back in the early ’80s were less than optimal, due to control limitations and a rash of unpredictable failures. Today’s version used in the Gen V engines achieve much better control by not only shutting off the injectors to the desired cylinders, but also can manipulate oil flow to the necessary lifters to not only electronically “shut off” the desired cylinders, but mechanically also. The improved ECM capabilities have also greatly improved transition between phases of operation and have smoothed out the various stages to almost imperceptible levels.

 

Aftermarket Affects

With all of the advancements and benefits of the new Gen V engine, we asked some seasoned performance experts how these new technologies will affect those seeking more performance from the engine. When engines become so finely tuned  so as to eke out every available horsepower with a safe measure of protection from engine-damaging detonation and low-octane fuel, taking them beyond their original parameters of operation can have drastic results. Likewise, technologies like variable valve timing and direct injection are game-changers, not only in the power potential of the engine, but also in how they affect tuning them.

We asked ProCharger’s Erik Radzins about coaxing more performance from these high-tech powerhouses. ProCharger has several aftermarket offerings available for the LT1 and also have supercharger kits for engines using VVT and AFM technologies on other GM products.

 

Question:The LT1 has increased compression (11.5:1). How compatible is that with supercharging?

ER: The LT1 does have elevated compression levels, compared to cars in years past.     However, this is likely going to be the trend moving forward as manufacturers are pushing the envelope on power and efficiency.

Cars such as the newer Dodge 6.4L HEMIs, Ford’s Coyote, and earlier C6 Z06s, are just a few examples of OEM modern higher compression engines that we offer systems for, so this LT1 didn’t scare us at all.  The days of 9.5:1 and 10:1 motors are long since over, unless they are coming from the factory with forced induction.  But just as the OEM’s are pushing the levels of efficiency, so are we to make sure we can produce the largest power gains possible, and in a safe matter. 

We are and have been spending a lot of time on blower r & d, and intercooler design to absolutely maximize the efficiency of our compressors and cooling properties of our intercoolers. Which makes it possible for us to push seven psi of boost into these factory motors, even on 91 octane from anywhere in the country.  Without an efficient compressor, and good intercooler, boosting these modern motors with high compression ratios wouldn’t be possible. Thankfully we have a wonderful company full of brilliant and talented people to make sure our systems perform at the top of their games. 

 

Question: Do the new technologies on the Gen V engines (Active Fuel Management, Direct Injection, and Variable Valve Timing) help it respond to modifications like supercharging, or were they hurdles to overcome?

ER:  Active Fuel Management and Variable Valve Timing have been around a good while, so that wasn’t much of a change for us. However the aspect of (DI) Direct Injection was new in that we never offered a supercharger kit for a DI engine platform before. Thanks to our expanded calibrations team, the hurdles for the DI tuning was really not a hurdle at all, and was wrapped up in about the same amount of time that we take to prove out our ECU tunes on all other platforms. We do lots of testing (dyno/street/track) for various load conditions, temperatures, fuel quality, sticks and automatics, etc. so it’s very time consuming to do it right.  Looking back, I think we tested at least five different mass air meter locations alone, before we settled on the one deemed the most smooth, and repeatable, no matter how the installation is done. 

                     

Question:Can one change parameters like Direct Injection timing or Variable Valve Timing to make the most of boosted applications?

ER: As far as changing the Variable Cam Timing mapping, GM did a great job dialing in the camshaft and the VVT control to really make the LT1 feel robust from the bottom of the curve all the way to the top.  If a person decides to add a custom camshaft after installing our system, that’s when the real fun with the VVT will begin. 

 

Question:How far has an LT1 engine been pushed to date?

ER: Even with these tunes being conservative, customers are reporting back to us with gains ranging from 160 to 200hp at the wheels, with no changes to the tune on stock cars running the stock system.  A performance shop that does custom tuning for specific fuel and location might just sneak out a couple extra ponies from the LT1.  The stock GM tuning from the factory and the ECU itself are light-years ahead of where things were not too long ago. 

How far can the “stock” LT1 go?  That is a very dynamic question. Are we talking  stock long block, or short block with ARP bolts, etc.?  With that being said, multiple people have already cracked the magic 1,000 rwhp number with these LT1s even on the stock short blocks.  However, I don’t think anyone has pushed a 100 percent stock motor to its limits yet.

The fact that the high pressure fuel pump is driven off the camshaft pretty much necessitates that a person wanting to make big power has to swap out the camshaft. (Another company is working on a secondary injector controller, though I don’t think it’s out as of yet).

 

Question:  Is there boost reference/control built in to the new controller on the Stingray?

ER: Yes, the ECU has very robust “boost” capabilities, even if one didn’t know that this ECU was being used on other applications. As soon as you looked at the programming, one would have placed a $100 bet that the C7 Z06 was going to come factory supercharged.

The days of low-compression engines are gone; so are the days of making a few timing changes, and using an FMU or extra injectors to aid in fueling.  Looking back, it almost seems barbaric how “tuning” factory ECUs was just 20 years ago.  The factory ECU has some pretty hard-set torque limits built in around the 1,000 hp mark which made it interesting to get past. 

 

Question:  With the additional controls present on the LT engines, does the car still exhibit all of the OEM driving characteristics when adding supercharging?

ER:  The first thing the customer will notice when driving a ProCharged C7 is, nothing.  Literally nothing is changed in how this car runs, drives, starts, idles, and performs in every aspect of its day to day operation.  The only time they will notice a change is that rush that an extra 200 hp gives you when you push down on your right foot. 

 

The Bottom Line

Praised for its simplicity, economical construction and power, the small-block Chevrolet engine has proven itself time and again since its introduction in 1955. As legislation creates hurdles of emissions standards and CAFE regulations, and customer expectations of power and performance increase, the mighty mouse motor has been forced to evolve. Ed Cole’s brainchild of power and torque has matured through the generations while holding true to the original concept of an economical powerhouse in a relatively lightweight package. In doing so, GM’s small-block has done more than simply keep up with the pace of performance, it’s put it out in front.

 

For Your Information:

ProCharger

(913) 338.2886, www.procharger.com

 

 

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