A deep look inside the baddest piece of hardware ever to come out of the GM stables – the LS9 Supercharged engine going into the Z06 Corvette. Can you say 600+ hp of LS anger with OEM reliability? We can…
If you want to fast-forward to the entire photo gallery of the LS9, you’ll find it here.
I was talking with my brother in law a few years ago about performance cars. You see he is an old school kind of guy, so he explained to me how incredible the muscle cars of his day were and how emissions controls and fuel economy standards ruined muscle cars and powerful production engines forever. I politely informed him that GM had a 400 hp 5.7L engine. He went on to explain to me that horsepower today isn’t the same as it was back then “there is no way it could be the same as a 400 hp engines from the muscle car era”. I simply laughed inside and changed the subject, deciding that something’s just aren’t worth arguing about
Reflecting back, he was right, the big horsepower engines of today can’t be like the ones of the past. Customers won’t accept small oil puddles after a couple of years, they won’t accept doing a tune up in 10,000 miles, they simply will not accept the high maintenance baggage of a muscle car era engine. So he was right, engines like the LS6 just are not the same.
Even though 400hp is still very impressive, in just a few years it has become dare I say common. The Cadillac Escalade, CTS-V, STS-V, and XLR-V have all had 400 or more horsepower available, Pontiac GTO, Chevy Trailblazer SS and of course the Corvette join the list as well and that is just at the GM examples.
The new definition of elite power is right around the corner when Chevrolet launches the 2009 ZR-1 Corvette. Under the hood will be the most powerful production engine in General Motors history, the LS9. By adding 10.5psi of boost to a stout 6.2L of displacement, the LS9 generates an astonishing 620hp. With that kind of performance, we decided to take an in depth look inside and pay homage to the LS9.
At the core of the LS9 is a crank shaft with the common 3.62” of stroke, but it is anything but ordinary. Unlike most production crankshafts, this one is forged steel construction. A 9 bolt mounting flange provides more clamping force to the flywheel than, the 6 bolt version most LS engines are equipped with.
Another very unique feature of this crankshaft is a keyed snout, which translate the power necessary to drive the blower.
Taking a page out of the LS7’s book, the connecting rods are made of strong but light weight titanium. The last piece of the rotating assembly is forged aluminum pistons, which are simply stronger than the cast parts found in the vast majority of production engines. The result is a lower inertia rotating assembly, which means quicker reving.
The cylinder block is very similar to that of the LS3 or L92, constructed of cast aluminum iron sleeves. It also has the same 4.06” bore diameter but it achieves it in a much different way. Race engine builders for many years have torque plate honed their engine blocks, just like the new LS9. The process simulates the bore distortion caused by bolting down heads. Then the block is honed, theoretically making the bores perfectly round when the heads are final assembled, keeping the bores as round as possible offers the maximum sealing.
Another new feature of the block appears to be a switch to alignment dowels rather than registering on the outside edges of the main caps like the majority of the LS line up. The cool part is that the new main caps are made of solid steel, a big power upgrade the aftermarket has been doing for years.
The cylinder heads are very similar to the LS3’s but are constructed using a sophisticated rotocast process and 356T6 aluminum alloy. The result is a stronger, tougher head, with better heat control properties. The port designs are essentially the same, as the LS3, but they have unique cast in swings which induce a swirl in the intake air. The large 2.16” intake valves are made of light weight titanium material, the exhaust valves are sodium filled 1.59” a good combination of durability and minimal. In another weight saving effort, the LS7’s titanium keepers are used. All of those weight savings are about keeping control while passing the 6500 rpm’s most LS engines of the past have had. Several of the other valve train components are LS3, like the lifters, rockers and valve springs.
One of the coolest things about making power with boost is cam shaft selection. Simply put, if you let the blower do the work, the cam shaft can be fairly mild. This means only 0.555” of lift for the intake and exhaust, minimal overlap and relatively slow valve closing rates. So what does all of that mean in one simple word, SLEEPER! Sure a carbon fiber clad Corvette isn’t exactly subtle, but the tame idle quality will give the perception that it is all show, no go, but only if they don’t know.
The life blood of any engine is the oil system and this one is no exception. With over 1G cornering ability, the LS9 needs a dry sump oiling system, similar to the one in the LS7, in order to ensure a constant flow of oil. The oil pan and pump of the LS9 is upgraded compared to the LS7, but the reasons are not quite what you would think. We think of oil as a lubricant, but it can be used for more than that.
Pistons don’t have the luxury of engine cooling, so the LS9 has piston squinters’ which spray oil on the underside of the piston, to provide a little bit of cooling. The squirter design incorporates a pop-off valve, which we
believe keeps them idle until the oil pressure comes up and the power comes on. In what seems to be an effort to reduce the amount of work the oil pump needs to do, the oil cooler is coupled directly to the dry sump pan. That means the no more oil lines with need to route up to the radiator.
Cleaning up the package is a new ignition coil mounting system which eliminates the clunky intermediate brackets, which LS engines have always used. The new system casts bosses onto the valve cover which direct mounts the coil to the rocker cover. Of course the acoustically tuned beauty cover generally conceals the sleek new look of the coils.
Let’s face it; the real star of the LS9 is the supercharger, nestled neatly in the valley. Of course superchargers aren’t new to GM, but they finally decided that adding one to an LS engine in a Corvette is a great idea. The thousands of enthusiasts who have strapped aftermarket blower power to their C5 or C6 over the years are saying, “well ya”. But, I don’t think that anyone has a charger like this one.
The new R2300 is the 6th generation of roots style supercharger from Eaton. The 6th gen has 4 lobes rather than the 3 in the previous generation, it also has 180 degrees of helix(twist) as compared to only 60 degrees in the past. So what does all of that mean? Traditionally this style of supercharger was know for its ability to generate torque, but just couldn’t keep it up. The new design maintains that low end, but is capable of putting up the big power numbers as well. In addition to enhanced performance, the 6th gen blower is quieter, only time will tell if that is really an advantage, or would people prefer the tell tale whine.
The cool new technology is housed in a unique casting manufactured specifically for the LS9 application, which uses the biggest version of the blower. In fact the 2300 is more than a number it stands for 2300 ml of positive air displacement per revolution, which means lots of air and power. Early testing of the aftermarket versions of the R2300 technology indicates that the charger is capable of going way north of the 620hp rating, 900hp maybe even 1000hp possibilities!
In order to make it all work, the entire accessory drive was changed up. The alternator is added to the air conditioning compressors belt line. Everything else is on a new 11 rib belt line, which means the bearings in the power steering and water pumps needed to be significantly upgraded. Anyone who has tried to push the limits of a supercharger in a late model Corvette has learned how important a good belt line is. The most peculiar thing about the entire supercharger system is the pulley. For some strange reason, GM decided to design the pulley with what appears to be a tamper proof mounting system. I know it sounds strange, why would someone want to tamper with perfection. Maybe it’s not tamper proof, perhaps it was designed to be sabotage proof? Who knows what jealous Viper and Ford GT owners will be capable of, when they can’t hang with the 620hp of an LS9 powered ZR-1.
While supercharging technology continues to improve to evolve, it’s certainly not perfect, because they still generate a lot of heat while compressing air. To take the heat back out, twin intercoolers (one for each bank) made a home directly over the supercharger. Air exiting the intercoolers, enters ports cast into the supercharger housing, the whole module serves as one hell of a substitute for an intake manifold.
One of the challenges to building 600 plus horsepower engine from the factory is maintaining refinement, especially at idle. One common issue is cam shaft as discussed before, the other is fuel injector size. With an MPI fuel injection system, i.e. one injector per cylinder, ultimately the injectors need to be sized for maximum flow requirements. At 620 hp (SAE corrected), that flow gets pretty high, especially when they factor in cold weather conditions. Using a large fuel injector means very low duty cycle at idle, which is generally less stable than a smaller injector with more duty cycle. Helping to reduce this trend, EFI systems have used vacuum referenced fuel pressure regulators, which increase fuel pressure as vacuum approaches zero or positive. Systems were set-up to have fairly moderate pressure increases, 35 psi to 45 psi for example.
The principal is that at a given duty cycle, the injector will flow more fuel when the pressure is higher. Therefore lower fuel pressure at low speeds increases duty cycle improving idle quality, and higher fuel pressure means a fuel injector is capable of making more power at a given duty cycle. The LS9 takes this to a whole new level running a dual pressure system which runs at about 37 psi, before jumping all the way to 87 psi! That means the LS9 can run a smaller fuel injector than an engine of that power would typically use.
THE NUMBERS DON’T LIE
If you understand engines you also understand that 620hp is just a number, and what really counts is the curve. Well GM was kind enough to give a few points, and well we decided to have some fun with them, and see what the curve may look like.
Running out and buying a new ZR-1 is not really an option to the vast majority of us. Maybe GM performance parts will be so kind as to offer us the LS9, I suspect purchasing it packaged in a wood crate wouldn’t cost as much as purchasing it packaged in a state of the art carbon fiber enhanced sports car. The possibilities with this engine are endless it would make a really cool retrofit in just about anything, well maybe not a Chevette, nah, even a Chevette would be cool with that kind of performance and technology.