Bolt On Power For The LT4: Nitrous Express Billet Supercharger Lid

Sometimes you buy good parts that do what they are supposed to do … other times you end up with junk. We have all been there: you spend good hard earned money on a part that either doesn’t make the horsepower the company claims or this component may not even fit your vehicle at all. Every once and a while you will buy something that’s perfect. It bolts on with out a problem, does exactly what the manufacturer claims, and it looks awesome. This is exactly what Nitrous Express set out to do with their latest product for the GM LT4. 

The goal of the NX crew was to make a show-quality product that was simple to install and would ultimately increase the power of the LT4 and without the use of nitrous. In the looks department, the new lid does not disappoint. NX starts with a solid chunk of billet aluminum and machines it down to create the improved part. The lid is available in both black and clear anodized finishes depending on your taste and has the NX logo engraved on the top of the lid.

Naturally, Nitrous Express was also thinking about water/meth and nitrous injection when designing the lid. Eight 1/8 NPT bungs are machined directly into the side of the part and depending on your weapon of choice, they simply screw in. When you flip the lid over you can see the real differences between the NX unit and the factory. Unlike the cast part, a lot of ribbing and excess material has been remove to increase the flow. 

The company claims that the improved flow path would generate increased horsepower and torque to the wheels of a LT4-powered vehicle. For testing, the lid was sent to Shelby Killer Performance in Edmond, Oklahoma. The test car was a 2016 C7Z with a set of Texas Speed Headers, X-pipe, Haltech cold air intake, 10-percent overdriven crank pulley, and of course the billet NX supercharger lid. 

Here is a top and bottom view of the NX lid showcasing a smooth design with an optional water/meth system and nitrous spray bars.

With the tank filled up on 93 octane the Corvette was strapped to the Mustang Dynamometer and several pulls were made with the stock lid and the NX lid. On the blistering hot 95-degree Oklahoma day, the the Intake Air Temperature sensor (IAT) was hitting temperatures ranging from 150-160 degrees with the stock lid.  The Corvette put down 572 horsepower and 629lb-ft of torque. It only took the crew at Shelby Killer Performance about an hour to swap the lids over and get back to the dyno. With the NX lid in place, the C7Z cranked out a max of 592 horsepower and 651lb-ft of torque.

While these numbers are impressive, when you actually look at the dyno graph the curve is remarkable. The new addition made a consistent 20 more wheel horsepower across the board and peaked at a 24 horsepower gain at the wheels. On the torque side of things, the new lid produced 40 lb-tq at the wheels while reducing the the IAT numbers to a much more desirable 130-135 degree range. 

When asked about drivability, owner Lance Rainey had the following to say: “The car is a lot more responsive. Also, the power is more consistent due to the consistent and lower IAT temperatures.”

If you own an LT4, this lid is a must. All it takes is a few simple hand tools, an hour of your time, and your C7 will be reaping the benefits of an additional 24-horse gain and 40 more lb-ft of torque — not to mention lower air temperatures and more consistent performance gains. Nitrous Express definitely hit their mark with this billet masterpiece. It’s a nice-looking part that bolts on and makes more usable power and torque. We just wish every part on the performance market could follow suit.  

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About the author

Brian Havins

A gearhead for life, Brian is obsessed with all things fast. Banging gears, turning wrenches, and praying while spraying is just a few of his favorite things.
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