Taking LT4 Performance To The Next Level With Whipple

For many enthusiasts, the measure of a car’s worth revolves around its performance capability right off the showroom floor. However, seasoned gearheads know better – the factory setup is merely a starting point. And while the 650 horsepower and 650 pound-feet of torque that the Gen V LT4 generates in the C7 Corvette Z06 and sixth-generation Camaro ZL1 in stock form is plenty of grunt for most folks, for a particular breed of horsepower junkies, too much is never quite enough.

That thirst for even more power also reveals one of the key virtues of factory-equipped forced induction systems: room to grow. Unlike most naturally-aspirated factory engines, mills that are built for a boost by OEMs are fortified for the job, and that gives builders the opportunity to pile on a lot more power without having to tear the engine apart to get it.

 

Now that the LT4 has been around for a few years, tuners are really starting to vet the strengths and weaknesses of this blown 6.2-liter. For those looking to get more power out of it, the 1.7-liter Eaton TVS supercharger is an obvious bottleneck. Smaller than the blowers used with GM’s supercharged Gen IV V8s, this unit needs to spin faster to create similar levels of boost, thus generating more heat, which negates the benefits of cranking the pressure much further than its factory setting. Image: GM

The law of diminishing returns comes into play here though, particularly with the LT4, as the factory setup’s capability is already near its limits right out of the box. That’s where outfits like Whipple Superchargers in Fresno, California come into play. For more than thirty years Whipple has been at the forefront of supercharger technology, supplying competitors with race-winning hardware and helping OEMs deliver the reliable power that their applications demand.

Here we’ll take a closer look at Whipple’s supercharger upgrade kit for the 2017-18 Camaro ZL1 with some expert insight into how it differs from the factory forced induction system. We’ll also check out the gains that builders can expect from the upgrade and get some installation tips, along with a suggested roadmap for folks who may want to dial things up even further down the line.

Reversing A Trend

“General Motors is going backward with supercharger displacement,” explains Howard Tanner of Redline Motorsports, a Pompano Beach, Florida-based tuning house that specializes in late model GM performance. “The LS9 in the C6 Corvette ZR1 used a 2.3-liter supercharger, the LSA that was in the fifth-generation ZL1 and second generation CTS-V used a 1.9-liter blower, and the LT4 uses a 1.7-liter unit. Of course, GM sizes up the superchargers they use based on their needs rather than those of the aftermarket – they establish a horsepower target and determine exactly what they need to hit that mark. The factory doesn’t really build these things with modification in mind; they build them to reach their internal performance goals.”

Strides in efficiency – regarding supercharger design as well as GM’s latest lineup of small-blocks – have allowed the automaker to reduce blower displacement while ratcheting up the power, which helps GM reach goals that aren’t necessarily related to performance as well. “OEMs have to be concerned about emissions and fuel economy too, and bigger blowers require more energy. Spinning up a 1.7-liter supercharger helps in that regard. This factory TVS blower has four lobes in it which are twisted at about 160 degrees – it’s a very interesting and efficient design when you keep it in the intended zone.”

The Eaton TVS might be a trick design in its own right, but even in the supercharging game there's no replacement for displacement. Whipple's kit comprehensively addresses the meager size of the factory blower by replacing it with a 2.9-liter unit that's designed to work well with stock engines, but also packs enough capability to support heavily modified mills, too. The 50-state emissions-legal system includes a pair of high density air-to-water intercoolers to ensure the cooling capacity of the system can keep up with the demands.

The factory supercharger produces about 8 or 9 pounds of boost in stock form, and when you spin it harder than that to make more boost, you quickly start to see diminishing returns as the heat it generates basically creates its own bottleneck.

But stepping down in displacement has some notable drawbacks. “Any time you compress air, it’s going to get hot,” Tanner points out. “The more you compress it, the hotter it gets, and the hotter it gets, the less efficient it gets. So there’s a balance you have to maintain. The factory supercharger produces about 8 or 9 pounds of boost in stock form, and when you spin it harder than that to make more boost, you quickly start to see diminishing returns as the heat it generates basically creates its own bottleneck.”

Tanner notes that factory-stock ZL1s that come into his shop typically make about 520 horsepower to the wheels. Ratcheting the boost up to about 14 pounds usually nets an increase of around 60 horsepower, but the factory setup starts to run into trouble with anything beyond that.

Tanner tells us that a stock LT4-powered Corvette or Camaro makes about 8 or 9 pounds of boost and generates roughly 520 horsepower at the wheels. Swapping pulleys to bring the TVS blower up to around 14 pounds will net another 60 horsepower or so, but as you start pushing past the blower’s efficiency limits, the heat it generates essentially nullifies the performance benefits of the additional pressure. He also notes that in a side-by-side comparison of the factory TVS blower and the Whipple, with both units operating at 14 pounds, the larger Whipple unit will generate more power just by virtue of the additional volume of air it can deliver, and the Whipple is still operating well below its efficiency threshold at that point.

Whipple’s kit offers a comprehensive solution by ditching the factory 1.7-liter, a Roots-type supercharger in favor of the company’s own 2.9-liter twin-screw unit. With so much more displacement to work with, the new blower doesn’t have to work as hard to create a large amount of airflow. That in turn, translates to less power consumption, lower temperatures, and more horsepower. “If you run a 1.7-liter supercharger and 2.9-liter supercharger at the same pressure, you’ll see a horsepower gain with the 2.9 just from the increase in volume,” Tanner explains. “And with the Whipple, you have a lot more room to crank up the boost pressure before you reach the limits of its efficiency.”

Whipping the ZL1 Into Shape

OK, so we’ve established that the Whipple design offers clear benefits beyond what the factory forced induction system is capable of while also providing a lot of room to grow. But are builders in for a headache when it comes time to make the swap?

The Whipple LT4 kit is a straightforward, bolt-on unit that's compatible with the factory air intake, belt system, and hood. Tanner points out that while the new unit is larger than the factory blower, clearance is essentially a non-issue. ZL1 installs require nothing more than some trimming of the water drip tray to ensure that everything fits as it should.

“Honestly it’s a very simple install,” Tanner tells us. “The car already has a supercharger on it that’s set up for the same type of cooling system. The supercharger comes off in its entirety, so you’re left with two cylinder heads staring at you, and the new blower drops back on in the same the way the factory unit was installed. You have to have the lid off the new blower to install the bolts back down through the runners and build the supercharger back up again, but that’s pretty elemental wrenching stuff.”

The Whipple unit also works with the factory air intake system, intercooler, and belt system, which makes for a very straightforward and hassle-free procedure. “Pretty much all the factory sensors are retained too, including the map sensor,” Tanner adds.

And despite the Whipple’s larger size, its dimensions don’t exceed the available real estate in these engine bays. “It’s definitely a larger supercharger, but it doesn’t seem to really get in the way of anything,” Tanner says. “On the ZL1s we do a little bit of trimming up front where the water drip tray is, but it’s not really anything significant.”

While the Whipple will generate more power than the factory unit just by virtue of the additional volume, most builders will want to take advantage of its enhanced efficiency by dialing up the boost beyond factory spec. Once everything's back together, the ECU's fuel mapping and spark timing will need to be calibrated to dial everything in and ensure that the controller isn't tripped into fail-safe mode.

From there it’s all about bringing the engine controller up to speed. “Typically we are putting the blower on there so we can run more boost, so if we’re adding more boost there’s some diagnostic stuff that also has to be addressed, so the controller doesn’t get tripped up,” he says. “Spark timing is also altered, along with fueling, to get everything properly calibrated.”

The results make the swap well worth the effort. “On an otherwise totally stock ZL1 with the Whipple supercharger running at 14 pounds, it makes about 645 horsepower at the wheels,” Tanner says. “And it also adds a lot of room for growth and power potential that the 1.7 just can’t provide.”

Going Above and Beyond

While the Whipple supercharger swap is a substantial upgrade by itself, it’s important to note that it also opens the door to a wealth of other modifications that will benefit tremendously from the bigger blower. “The Whipple has enough air mass potential for a thousand horsepower at the crankshaft,” Tanner says.

On an otherwise stock LT4, the Whipple swap nets a gain of roughly 125 rear-wheel horsepower running at 14 psi. Tanner notes that factory exhaust system restrictions are the next bottleneck that should be addressed at that point, which why Redline Motorsports often pairs the Whipple swap with a set of long tube​ headers. The factory manifolds and catalytic converters can only flow so much exhaust gas at a time, and that ends up dictating how much boost pressure the system can handle. Swapping in a pair of long tubes removes that restriction and ensures that the engine has breathing room required to support future upgrades.

“At that point, it’s just a matter of whether or not you have the supporting mods to do it. We generally don’t like running a lot of pressure on those motors while using the factory exhaust manifolds and cats – you end up having an issue where heat gets pushed back into the combustion chamber because the exhaust gases can’t escape fast enough. And for that reason when we do a Whipple install, it’s usually combined with a set of long tube headers at a minimum.”

Once the limitations of the factory blower have been addressed, it’s really just a matter of how far you want to take the build. “From there we can go to a camshaft, methanol injection, and more boost, and at that point, you’re already on your way to well over 700 rear-wheel horsepower while still not beating the engine to pieces,” Tanner adds.

Looking to really wake up your LT4? Basic bolt-ons might yield you a few ponies here and there, but Whipple has delivered a solution to a factory limitation that produces significant gains while paving the way for even more power down the road. Give ‘em a buzz and see what they can do for your ride.

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About the author

Bradley Iger

Lover of noisy cars, noisy music, and noisy bulldogs, Brad can often be found flogging something expensive along the twisting tarmac of the Angeles Forest.
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