NACA ducts?

[tmoretta]

I am interested in maximizing the amount of air that enters the engine cover turbo intercooler ducts. The shape of the ducts that are built into the engine cover approximate the shape of a traditional NACA duct. Does any engineer type person know if the inlets built into the engine cover are shaped so that they will function like a NACA duct? Would it be better to remove the existing inlets and install NACA ducts on the (now) flat surface of the engine cover? I don't want to go to an air to water intercooler, or add a fan for cooling. Would it be better to use the existing molded in inlets and add scoops to capture additional air?

[Frank818]

Question is, is there any air flowing through those ducts?

No one has a precise diagram, picture or video of the car's body panels and its associated air pressure (you know in colors with red, yellow, green, blue, etc.). Apparently the top IC duct has negative pressure, I don't know about those little ones more on the side of the car. I plan on installing NACA ducts, but under the car.

[wleehendrick]

I doubt FFR did any CFD on the shape of those ducts; they don't have the lateral taper of a NACA duct, which minimizes drag at high speed (the design goal). If you want more airflow, at the expense of drag, scoops are a better solution, as you mentioned.

Just a word of caution... It's not just a matter of simply dumping more air into the engine bay. Good ducting and sealing is needed to provide a pressure differential across the IC; otherwise air will just flow around it and it will heat soak. Also, since the OEM ECU reads IAT pre-turbo, you really have no warning until detonation occurs (unless you add another sensor, post-turbo). The R (with no windshield or passenger) can open up the leading edge of the hump to provide flow, but the S requires more work.

I have recently decided to go with an AWIC as the easier, safer approach. However, I really would like to see a properly implemented, rear mounted air-to-air IC in the 818. Most modern mid-engined turbo cars have an AWIC, although the Porsche 911 turbo does have dual air-to-air ICs. However, to make those work, Porsche uses inlets in the fenders and molded ducting, sealed around the ICs, which then vent into a low pressure zone behind the rear wheels.

I'm not a aerodynamic, thermodynamic or automotive engineer, but intuitively, I think it's obvious that the 818 would require a similar level of effort for the TMIC to be effective.