The upcoming Cadillac Blackwing ultra-high-performance luxury sedans – the 2022 Cadillac CT4-V Blackwing and 2022 Cadillac CT5-V Blackwing – are similar yet different in many ways. But one thing they both have in common is that neither is fitted with a hood air extractor.
This may come as a surprise, given that discontinued Cadillac ATS-V and Cadillac CTS-V both had hood vents, so why not the Cadillac Blackwing models? GM Authority Executive Editor, Alex Luft, posed this question to Mirza Grebovic, Blackwing Chief Engineer, during a recent interview.
“We have the mantra that every part has to earn its way,” Grebovic replied. “That means that something will be only be used if it improves performance. And when I say performance, I don’t just mean track, but overall: top speed, track, handling response, etc.”
Grebovic did not mention cooling, which might be thought of as the first reason for fitting a hood vent. However, there are two aerodynamic-related reasons why an automaker might want to allow air to pass through the hood. One is that it reduces air pressure under the hood. If this pressure is too high, it could cause the front of the car to rise up at speed.
The other is that, if the hood is large enough, it can create substantial amounts of low pressure air ahead of the windshield, which can also cause aerodynamic lift at the front of the vehicle.
“We don’t put a hood vent in the beginning [of development],” Grebovic continued. “What we do is we take the base car, we throw it into the wind tunnel, get a baseline, then put wider tires on it, the latest suspension, etc, then balance the math to what the distribution is going to be and see what the car does. Then we look at what we need to do to improve aero to get the car where it needs to be. Obviously, lift reduction is key for us, and we were able to achieve lift reduction on these vehicles without a hood vent.”
Grebovic also gave two illustrations of how a hood air extractor can cause unexpected problems, using the ATS-V and CTS-V as examples.
“When we launched those models, we had many people call to tell us that their car is smoking. That’s because when they picked it up from the dealership, the dealer washed it for them, and the water hit the CRFM [Condenser / Radiator / Fan Modules]. So we had people call us telling us they were afraid to drive the car because there is smoke coming out from under the hood, only it wasn’t smoke.
“In addition, we learned that a lot of customers park under trees, so you get a lot of dry leaves or pine needles, and that stuff is falling into a hot engine bay.
“So we didn’t want to put one in just because the last ones had it. However, what you will notice is, we did put fender vents in both vehicles to relieve the pressure.”
“We actually put the hood vents in study vehicles, and they didn’t do anything to reduce [the pressure], but the fender vents did. So what we did is put the fender vents on both cars instead of the hood vents.”
No matter how it has been achieved, reducing aerodynamic lift has to be a priority while designing the Cadillac Blackwing models. The Cadillac CT4-V Blackwing has a twin-turbo 3.6L V6 LF4 gasoline engine producing 455 horsepower and 445 pound-feet of torque, while the Cadillac CT5-V Blackwing is fitted with a supercharged 6.2L V8 LT4 motor rated at 668 horsepower and 659 pound-feet of torque.
The top speeds are 189 mph for the CT4-V Blackwing and over 200 mph for the CT5-V Blackwing. At anything even close to those speeds, aerodynamic lift is the last thing anyone wants.
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