The LS engine platform has firmly established itself as the engine of choice for many builders. From mild to wild combinations, the LS has shown incredible performance in varied applications when using the plethora of aftermarket performance parts on the market today.
One of those parts, the brand-spankin’-new MSD Performance Atomic Airforce intake manifold, has just been released to the public, and we’re proud to be part of one of the very first independent dyno test sessions using the product.
Our friends down at Late Model Engines recently strapped a customer’s LS7 engine to the dyno and compared the factory LS7 intake manifold to the Atomic Airforce to see just what the product is worth in terms of performance in a typical application.
What Is The Atomic Airforce?
We used MSD’s Part Number 2701, available from JEGS, which is designed to fit all LS7 applications; 2006-13 Corvette Z06 and 2014 Camaro Z/28.
MSD has built versions of the Atomic Airforce to permit LS engine owners, no matter which engine configuration, to use the technology.
There are fitments for the new LT1 [PN 2700], LS2 [PN 2702], LS3/L99 [PN 2703] and LS1/LS6 engines [PN 2702, uses LS2/aftermarket fuel rails] to cover the entire gamut of LS-powered vehicles on the market.
“The challenge was to make this manifold fit under the hood,” says MSD’s Joe Pando. “There are some things we could have done to make it even better, but we wanted to be able to use the factory fuel rails so that the end user doesn’t incur a large expense during the change to our manifold. You take the factory manifold off, put the factory fuel rails back on the Airforce, put it on the car, and you’re back up and running.”
Created from a high-strength polymer that’s designed to resist heat soak and minimize weight, the Atomic Airforce is a two-piece clamshell manifold design that allows the end-user to open up the halves and get inside the runners for porting, although that’s not required to see horsepower gains upon manifold installation. The ability is there so that the race-oriented enthusiast can get to the innards of the manifold to port-match it to their choice of cylinder head. The runners have more meat at the port openings to allow for this.
Power adder racers need not fear the Airforce; in fact, the design has been tailored for their use.
Baked right into the manifold’s design is a full complement of flats opposite the runner entry points to provide a place for nitrous oxide nozzles to be installed. Pando says that Nitrous Express already has a manifold in-hand and is working on a direct-fit nitrous system for the Atomic Airforce as of this writing. In-house testing has shown the manifold to be capable of handling 30 psi boost pressure, making it a worthy choice for super- and turbocharged vehicles.
Internally, the design of the manifold has been engineered using Computational Fluid Dynamic Modeling software to optimize performance. Each runner opening features a contoured bell-mouth design that’s been carefully engineered to promote smooth airflow. With the top half of the manifold removed, the intake valve can be seen from the runner entry.
“We think that the runner design is at a good point to make power out of the box,” says Pando. “The incoming airflow pressurizes the box and then each cylinder sources its air from the common area as required.”
The manifold will accept throttle bodies from the OE size all the way up to 103mm in diameter, and MSD has engineered their very own line of rubber, reusable gaskets for the throttle body opening, manifold separation point, and each of the intake runner openings.
Another key during the design process was ensuring that the intake manifold would fit under the hood. “If your car came with a factory LS engine, the Airforce intake will fit under the hood. Now if you’re putting the engine into a Mazda Miata, I can’t answer that question yet. It is a bit taller than the factory intake, but not by that much,” says Pando.
Also notable is that the Airforce manifold has both a patent pending for its design, and C.A.R.B. EO acceptance pending for those enthusiasts who require emissions compliance.
Our Test Subject
You take the factory manifold off, put the factory fuel rails back on the Airforce, put it on the car, and you’re back up and running. – Joe Pando, MSD Performance
The 429 cubic-inch engine used for our test subject was equipped with a 4.130-inch bore GM LS7 engine block, factory GM LS7 titanium 6.060-inch connecting rods, and a forged factory LS7 crankshaft.
Stock LS7 cylinder head castings were used; these have been treated to one of LME’s CNC port programs and with the opened-up ports flow approximately 400 cfm on the intake side at .700-inch lift and 270 cfm on the exhaust side at the same parameter.
A Cam Motion hydraulic roller camshaft was in place, with specifications of .652-inch lift on the intake side and .636-inch lift on the exhaust side. The cam also has 237 degrees of intake duration and 252 degrees of exhaust duration, both at the industry standard .050-inch lift figure. The camshaft is ground on a 111-degree lobe separation and has been installed four degrees advanced.
The engine was set at 11.5:1 compression and run on 93 octane pump gas for our testing sessions. The OE manifold was tested with the stock 90mm throttle body, and the Atomic Airforce was tested with the large-mouth 102mm throttle body from F.A.S.T., as we suspect most users will opt for this configuration or one like it. The large-mouth throttle-body will not open all the way on the factory manifold or that would have been tested also. Holley’s Dominator EFI system was used to control both configurations.
Our dyno testing was run from 4,400 rpm up to 7,000 rpm, as this is where the test subject engine will spend the majority of its time. As we can see from the dyno graph, the MSD manifold made substantially more power than the stock intake manifold did on this particular engine combination – even at the lower end of the curve for both torque and horsepower.
The stock manifold had a torque peak of 583.9 pound-feet at 5,200 rpm, then fell off sharply to 512.2 pound-feet at the point where the plug was pulled on it at 6,500 rpm. Peak horsepower was achieved at 6,300 rpm, with 636.4 ponies measured by LME’s SuperFlow dyno. These are solid numbers, to be sure, but it’s evident that the OE manifold design is tailored more towards torque and horsepower production in the lower realm of the rpm band.
The Dyno Pull
Conversely, the MSD Atomic Airforce manifold got stronger as the needle twisted higher in the rpm range. It eclipsed the factory manifold at all ranges of the test, peaking at 6,600 rpm with 680.2 horsepower, after the factory manifold had already signed off, while making a stout 610.0 pound-feet of torque at a street-friendly 4,900 rpm. Most impressively, the MSD manifold hit 600 horsepower by 5,150 rpm and carried that number all the way to the end of the test at 7,000 rpm, with over 665 horsepower from 5,950 rpm through the end of the test. 600 pound-feet of torque was present from 4,650 rpm through 5,700 rpm.
“We gave each manifold an equal chance, made all of the pulls at the same water temperature, and made sure to optimize our timing and other conditions to provide the most accurate results in both configurations,” says LME’s Bryan Neelen. “The Airforce intake, based on the internal runner size and the plenum volume, definitely performed well in our testing. The numbers are the numbers – what more can we say?”
“With all manifolds, there’s a tradeoff. You have to look at the manifold design and whether it gives you the power you want, in the rpm band your vehicle is most used,” he says.
Based on the testing performed at LME, it appears that MSD has covered all of their bases during the development of the Atomic Airforce EFI manifold for the GM LS/LT engine design. Not only is the manifold equipped to work with all of the stock parts such as fuel rails and throttle body, it will continue to perform well as the owner ups the ante with better-flowing cylinder heads, a hotter camshaft, and larger throttle body. A gain of 43.8 horsepower and 26.1 pound-feet of torque at the peaks says so.