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skank asked: I've read and observed with great interest the air management advancements of the new ZR1. Could you explain the air flow paths through the new front fascia and how they are designed and engineered to move air through those internal locations. Knowing that you have already developed brake ducts to direct air to the brake discs, would directional(asymmetrical) fan style wheels help in the air flow path? I also noticed that the new ZR1 wheels are asymmetrical and therefore look different from driver side to passenger side. Would four location specific wheels be required to optimize the aero through the wheel cavity area or is it not worth the extra cost to the ZR1 budget?
Tadge answered: The full answer to this question is worthy of an SAE (Society of Automotive Engineers) technical paper. The ZR1 has significantly improved airflow through the fascia to feed the additional radiators. You can tell with just a glance that there is more open area on the front of a ZR1 than a Z06 or Grand Sport. We measure airflow at average track speeds for a full lap. Compared to Z06, airflow through all radiators is increased by 41% by this measure. This is achieved by improving and optimizing the flow paths through the center as well as the outboard openings. We don't use this much open area for all cars since it creates unnecessary drag in cars that don't need that much cooling. If you look at the C7.R race car, you will see a relatively small opening located in the center of the front fascia.
Additional changes include: The horizontal cooler has been relocated from the position in Z06 to optimize flow performance and its venting is integrated to not disrupt the underwing aerodynamic performance. The center flowpath now features a bumper beam with 4 slot openings and ducting to maximize performance and the hood extractor performance is enhanced by including an extraction lip in the hood surface design. The outboard openings share air between the brake duct and outboard coolers. The baffles behind the opening are splitting the flows and are shaped to optimize the flow into both.
ZR1 track brake cooling has been enhanced by directing flow more efficiently to the control arm mounted hardware. The new front duct actually splits air in two directions. The upper path of the duct feeds air to the control arm deflector then to the knuckle deflector and onto the rotor. The lower path of the duct feeds air into the control arm mounted “airbox” and then up another duct on to the rotor. The airbox is also fed by under vehicle airflow with an enhanced underwing. The control arm mounted brake cooling hardware has evolved from the 2014 Z51 cooling kit (which included lower control arm and knuckle deflectors) to the 2017 Z06 track cooling kit (which adds the airbox and attaching upper duct).
In addition to the enhanced brake cooling, the ZR1 features new Carbon Composite Matrix (CCM) front brake rotors that tolerate higher temperatures than before and new, upgraded pads at all 4 corners.
The pictures below illustrate the difference between current production ZR1 and Z06 track brake cooling set ups. The main difference is in the duct that takes air through the front fascia. As we learned how to improve the air management downstream of the fascia duct on the development of the ZR1, we actually pulled those pieces ahead and released them for the 2017 model year Z06.
ZR1 w/track front brake cooling package installed (black arrows indicate flow from front duct, purple arrows indicate flow from underbody)
Z06 w/track front brake cooling package installed (black arrows indicate flow from front duct, purple arrows indicate flow from underbody)
Relative to the part of the question on wheel design…. We have experimented with “impeller wheels” with foil-shaped spokes or other features to promote air flow over the brakes since at least the 4th generation Corvette. You are right that they would require separate tools for wheels on the left and right side of the car, but if they were effective, we would spend the money. The truth is that the air flow in the wheel openings is very turbulent, nothing like the smooth flow over an airplane wing. The forward part of the wheel opening is a low pressure area so airflow is inboard to outboard. At the rear, it is just the opposite. So which flow do you want to promote? It turns out, the best thing we can do is have wheels with large openings to let the flow go where it wants. Casting or forging airfoil shapes is not mass-efficient given the other structural needs of the wheel. As unsprung mass, we put enormous effort into light, stiff wheels that let the brakes breathe.
Love it! Thanks for answering my brake cooling question as part of the overall question. I can't wait to get mine to torture test the improved cooling!
This is very valuable insight into the workings of the ducts and aero wheels. Have we come to expect CAD drawings for Ask Tadge answers? This is pretty valuable, soak it up guys!
One small edit, this amount of engine and brake cooling is needed on the Z06 as well.
...and likely the race car is getting more cooling through better air extraction out of the hood despite the smaller inlet. On top of that, it does not have an A/C condenser HE or intercooler HE to pummel the effectiveness of the engine coolant HE's. To believe that the C7.R doesn't need as much cooling I would have to see KW removed from the engine coolant HEs only on both cars. The C7.R has some cooling moved to the back for the trans as well, and I bet it removes far more KW than the auto C7s.
This is very valuable insight into the workings of the ducts and aero wheels. Have we come to expect CAD drawings for Ask Tadge answers? This is pretty valuable, soak it up guys!
One small edit, this amount of engine and brake cooling is needed on the Z06 as well.
...and likely the race car is getting more cooling through better air extraction out of the hood despite the smaller inlet. On top of that, it does not have an A/C condenser HE or intercooler HE to pummel the effectiveness of the engine coolant HE's. To believe that the C7.R doesn't need as much cooling I would have to see KW removed from the engine coolant HEs only on both cars. The C7.R has some cooling moved to the back for the trans as well, and I bet it removes far more KW than the auto C7s.
Really useful info, keep it coming!
Since the Z06, with the updated MRC flash, is within two seconds of VIR lap time for the new ZR1, with the additional 105hp, I think it's obvious the Z06 needs this engineering change. I am glad to see the continued R&D by Tadge and the Chevrolet Corvette Team. The flash and cooling improvements show they are committed to customer satisfaction. For those who can never get that "satisfaction,"there's always the other guys.
03-16-2018, 10:29 AM
[ANSWERED] Engine Cavity and Wheel Cavity Air Management
Since the Z06, with the updated MRC flash, is within two seconds of VIR lap time for the new ZR1, with the additional 105hp, I think it's obvious the Z06 needs this engineering change. I am glad to see the continued R&D by Tadge and the Chevrolet Corvette Team. The flash and cooling improvements show they are committed to customer satisfaction. For those who can never get that "satisfaction,"there's always the other guys.
