2015 Corvette Z06 Owners Report Heat Soak Power Loss: Actually a Conservative ECU [Updated]

2015 chevrolet corvette z06 on the track 1 photo
Photo: GM
Now that the 2016 Corvette Z06 has hit the streets, sucking our air through its blower, a few owners have complained about experiencing a power loss after back to back runs on the highway or multiple laps on the track. They rushed to point the heat soak finger at the LT4 motor in the Z06, but this doesn’t seem to be the culprit here.
Sure, as the Z06 uses a top-mounted charging hardware, you could expect it to be prone to heat soak issues. When this issue usually appears, after a few consecutive full throttle runs, the heat builds up in the engine compartment, resulting in the a temperature increase for the air charge. This dramatically reduces supercharging efficiency as hot air has reduced oxygen molecule density, allowing for less fuel to be burned.

Moreover, hot intake air charge also increases the risk of detonation. The computer measures the intake air temperature both before and after the charge and when the latter is too high, it starts pulling timing to protect the engine.

However, like we said, this isn’t an issue with the LT4 supercharged V8 in the 2015 Z06, or at least that’s what the tuning scene is reporting.

Aftermarket world explains this is all a conservative ECU setup

Remember Vengeance Racing, the aftermarket developer that did a 1-minute burnout straight out of the showroom when picking up their Z06 last week? The crew started playing with the supercar and obviously came across the same problem.

So far, the guys only did repeated runs on the dyno, where they recorded a rather impressive 20-degree difference between the two aforementioned intake air temperatures. They also performed highway runs, but so far they’ve had 5 to 7 minute breaks between runs to analyze the resulting data and make changes to the ECU. They promissed to take their Z06 out again this week and perform back to back runs, so we’ll have that information soon.

Once again, as Vengeance Racing explains, there doesn’t appear to be any heat soak issue - such a problem wouldn’t make sense anyway, not after all the testing the Z06 has been through and after GM hit the jackpot with just-as-supercharged ZR1 in the past.

In a post on Corvette Forum, the tuner explains the issue lies with the ECU - “With the OE calibration we did experience the same thing... The timing tables are EXTREMELY conservative and the ECU will pull timing for almost any situation. I am waiting for owners to complain about "tip in" as the ECU pulls a massive amount of timing when slightly touching the gas pedal”

We know it sounds convenient for a tuner to say this, but the company claims “most of the loss of power can be addressed in the ECU.” Of course, this may just solve the problem reported by multiple owners, but it will also void the powertrain warranty, not exactly something you want on a $100,000 car, unless you were going to modify it in the first place.

Besides, many now ask themselves what happens once you remove those ECU boundaries. the only problem here is that certain people behave completely different once they’ve modded their car and subsequently complain about reliability issues - such problems would’ve appeared even without the tune, simply due to the change in the driving style.

The LT4 appears to have plenty of unlocked potential

Since the customizer claims the post-intercooler intake air temp is impressive, nobody is quite sure why GM engineers came up with such a conservative ECU tune, with emission regulations being the most plausible reason.

For the record, Vengeance Racing’s 2015 Corvette Z06, a manual, showed 585 hp and 611 lb-ft (828 Nm) of torque at the wheels in stock condition, which are very good values. The LT4 has already proven to be a very capable engine, since the tuner has achieved a hefty output bump with less-than-serious mods. To be more specific, the V8 was taken to 660 RWHP and 663 RWTQ (899 Nm) using only a cold air intake, a smaller upper pulley and, of course, an ECU remap.

We’ve contacted GM to ask them about the reason behind the shy ECU setup and we’ll be back with an update as soon as we have an answer.

Update: GM has responded, explaining the reasons behind the ECU setup reigning over the LT4 V8. To put it shortly, Chevy wants to make sure the Z06 meets emission targets and keeps placing those 650 ponies at the mercy of your right foot for at least 10 years or 100,000 miles (160,000 km), which are the intervals covered by the warranty.

To use the automaker's words: "We are confident that the vast majority of customers are going to be more than satisfied with the performance the Z06 offers in stock form. For those that want more power, they can visit an aftermarket tuner – who are not held to the same standards [emissions and warranty] as an OEM. However, this presents significant risk to the customer. An aftermarket tune voids the vehicle warranty as Chevrolet cannot possibly test or confirm the durability of their calibration; and aftermarket calibrations could cause drivability issues that are not present in the factory setting."

When asked about a possible track tune, that would unlock some extra potential for limited amounts of time, GM said they are not planning such a move.

Basically, GM acts like a father who's giving you a car - it hands you the keys and whether you want to enjoy the supercharged thrills in marathon or sprint mode, the choice is yours. It's just that you must remember to cover your dad's 100 grand pension fund in return, on the spot.
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About the author: Andrei Tutu
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In his quest to bring you the most impressive automotive creations, Andrei relies on learning as a superpower. There's quite a bit of room in the garage that is this aficionado's heart, so factory-condition classics and widebody contraptions with turbos poking through the hood can peacefully coexist.
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