Article by Rick Jensen (Turboguy). Photos courtesy of CorvetteForum and Vengeance Racing.
From the first deliveries to the mind-blowing driving vids, the 2015 Corvette Z06 has dominated auto news for weeks. But LS and Corvette performance shops have been prepping for this beast’s release for months. The shops that quickly develop tunes and parts beat the competition to the punch—and that means mad traffic on the enthusiast forums, and lots of power-hungry car owners giving them business.
LS specialist Vengeance Racing not only led the pack in Z06 testing and tuning, Ron Mowen’s shop gave their new Z06 a memorable introduction. First, their 1-mile Z06 burned off thousands of miles of tread life in the dealership’s parking lot. Nice. Then, they strapped it down to their DynoJet and recorded an impressive 585 rwhp and 611 lb-ft of twist at the rear wheels. Internet breakage commenced.
And now, Vengeance is making its bones (and more headlines) with LT4 ECU tuning. Some quick history: since the LS1 bowed in 1997, the General’s factory ECU calibrations have become both more complicated and more conservative. My 2001 Z28’s LS1 had 26 degrees of timing (some had only 23), but a pig-rich 12.2 to 1 air-fuel ratio—perfect for avoiding warranty claims, but way too rich for max N/A power. It was chock-full of emissions calibrations too, but canceling emissions and sidestepping torque management nannies was pretty simple, even for an average tuner.
Now, 13 years later, ECU computing power, complexity and emissions targets have multiplied exponentially—especially if you’re tuning on a supercharged mill like the ZR1’s LS9. And because the 2015 Z06 uses direct fuel injection on its supercharged, continuously variable valve timing LT4, it has one of GM’s most complicated ECU calibrations ever.
You got that hot keystroke action explanation because tuning a modern LS isn’t easy; tuning a supercharged LS is even tougher—and according to recent forum posts by Ron Mowen, tuning the new LT4 engine is really freakin’ difficult. "There are over a dozen timing tables constantly adding/subtracting timing based on various conditions,” he explains. "The timing tables are EXTREMELY conservative, and the ECU will pull timing for almost any situation.”
But the Vengeance crew was determined to learn the LT4’s digital secrets. So after establishing the stock 585 hp and 611 lb-ft baseline with 10.5 psi boost, they started strokin’ it (the laptop, you sickos). And the LT4 responded with 617 hp and 624 lb-ft—a 32-horse, 13 pound-feet increase on tuning only.
Next, the LT4’s stock 2.5-inch upper blower pulley was removed, and replaced with a smaller, 2.38-inch pulley. The engine kicked out 627 hp and 640 lb-ft—an additional 10 horses and 16 pound-feet.
Finally, an AFE cold-air intake jacked from a C7 Stingray was thrown on—and that extra induction air made a huge difference. The LT4 pounded out another 33 horses and 23 pound-feet, for a grand total of 660 horsepower and 663 pound-feet of torque at the wheels! So Vengeance’s new LT4 picked up 75 rear-wheel horses and 52 pound-feet of rear-wheel torque—just with tuning, a blower pulley that added only 2 psi boost, and a cold-air intake!
2015 Z06 Tuning Notes:
•Adding 75 rear-wheel horses to your Z06 is possible with only a pulley, intake and tune.
•The stock LT4 ECU is designed to get conservative and pull timing/power after several hot laps—more out of warranty concerns than dangerous engine conditions.
•This lameness can of course be tuned out—if you’re willing to forfeit your warranty. Also, this totally sucks.
•Tuning the direct injection and numerous timing tables is tricky, so your tuner should be experienced and know his way around DI.
•Adding more boost to the LT4’s 1.7-liter blower could be a challenge. The stock upper blower pulley is really small to start with; Vengeance only saw a 2-psi gain, and they swapped in a larger lower pulley too, but it didn’t add boost.
•The LT4’s factory intake tract shows a significant restriction—but thankfully, adding a cold-air intake will add big go for little dough.
Okay, so the ZR1’s LS9 engine never pulled power after just a few hard runs, but the LT4’s engine does. GM says this is to help the powerful Z06 survive for its admittedly lengthy warranty. But some enthusiasts are pretty pissed about it. Do you think the Z06 is powerful enough and a little pulled power is no big thing, or is it a total travesty? Comment below.