JerryU

It's much more complex. An air dam at higher speeds in addition to reducing drag increases downforce. That is fine if it's balanced with what the rear spoiler does in the rear. The spoiler is NOT added for looks!

I have some first had experience with my 260Z that I cover in one of the two PDF's above. Perhaps that will help. Suggest reading the above pic/text PDF's will provide a lot more info and you don't need to be an aerodynamicist to understand. Don't think you need to have taken a course in fluid dynamics but that helps!

Looking at shape of most cars they look like an airplane wing. That causes lift (won't go into why here, read the PDF's.) The 240/260Z was know to cause significant lift. It was documented at 70 mph of being 140 lbs in the front and 35 lbs in the rear. At 100 mph you could feel the front end getting light. I added a front air dam spoiler (like the one shown below) and a rear spoiler (note it came with neither.) That was shown in Road & Track or Car & Driver mags to add 100 lbs downforce in the front offsetting most of the lift and 35 lbs in the rear offsetting all of it. It was definitely more stable at 100 mph and at 120 mph, about it's max speed handled fine.

I hit the front on a parking stop and had to removed the cracked air dam. While I waited for a new one to be made/ ship and have it painted it was very light at even 70 mph. The rear spoiler was producing downforce while the front now had no extra. Similar to GMs reason for balancing downforce created by different (or no) splitters, side skirt size and rear spoilers configurations.

JerryU

Below is another pic with data that Tadge quoted in a forum post. He doesn't provide force numbers but a coefficient for Drag and Lift. You can draw lots of conclusions. But note the Base car with a center air dam has a drag coefficient of 0.30 while the Z06 with Stage 3 aero pieces has a coefficient of 0.50 or 67% more drag. That is not just the center air dam but all the other aero "stuff" as well.

However the Base C7 has a positive lift coefficient meaning it has lift. The Stage 3 aero adds enough aero "stuff" to offset that lift and add considerable downforce. Note if you look at the difference between Stage 2 aero and Stage 3 in addition to the splitter winglets (which I added to help integrate the look of the silly spates and probably don't add much drag) it's the higher rear spoiler extension and the Clear Bridge between the spoiler extensions that no doubt adds much of the extra drag and added downforce. It's like putting your hand out the window at 70 mph! That Clear Bridge would be a very big hand! Everything is a compromise!

Of interest, a more efficient way to add downforce with less drag is an upside-down wing like on the ZR1.

06blackvert

ha ha ha....me too and it is my 9th Corvette and my second C7.

ptran00

I have a 2017 Stingray (NOT z51). Yes, you are missing the center air dam.

ibuildm

Does it have the ZF1 option with the full spoiler? If so it won’t have the center piece.

BJ67

No sir, I ordered my base 2015 stingray with the ZF1 package and it most definitely has the center air dam.

fsvoboda

Nope. The various models (and even rear spoiler options, I think) mean that different front configurations are appropriate. Lots of people tinker around with these with minimal effect as they usually aren't driving at the car's limits at very high speeds, but unless you're a highly knowledgeable person you are better off with the factory recommendations. Check the "Ask Tadge" answers regarding aerodynamics for more on this.

(I have several family members in auto engineering and design, and based on my conversations with them, there is a lot more subtlety to it than one would think. There is pretty extensive testing by the manufacturers, much in excess of what anyone could do privately.)

JerryU

Yep posted the C7 drag and lift values from Tadge Post in mine #22 above.

In post #21 Posted my observations from the mid 1970's with my 260Z. This is a short summary showing you don't have to travel 150 mph to have a signfcant effect on handling:

"Looking at shape of most cars it's like an airplane wing. The 240/260Z was documented to have significant lift at 70 mph of 140 lbs in the front and 35 lbs in the rear. At 100 mph you could feel the front end getting light. I added a front air dam spoiler and a rear spoiler (note it came with neither.) The ones I purchased were shown in Road & Track or Car & Driver (don't recall which) mags to add 100 lbs downforce in the front offsetting much of the lift and 35 lbs in the rear offsetting all of it. It was definitely more stable at 100 mph and at 120 mph, about it's max speed, it handled fine.

I hit the front air dam on a parking stop and removed it. While waiting for a new one to be made, shipped and painted it was very light at even 70 mph. The rear spoiler was producing downforce while the front now had no extra. Similar to GMs reason for balancing downforce created by different (or no) splitters, side skirt size and rear spoiler configurations."

VETJAZZ

Do yourself a favor and just remove them all. I removed them 4 years ago and no issues, no more scraping.

BJ67

Me too..,much easier to jack up the car also as I pick up the car from the front crossmember with a 12 inch 2x4 on top of the floor swivel

Skid Row Joe

I've got the same car. A 2017 Stingray convertible 3LT. Mine's got the full air dam all the way across.


...

Skid Row Joe

Wrong. Each model of C7 is custom tailored. They are definitely NOT all the same. The full across air dam is on the Stingray because it is supposed to be on the Stingray. ...

JerryU

Yep, if you never go over 40 mph no issue!

Quoting the GM Chief Aerodynamicist, John Bednarchik, who was quoted in a great article from October 2013 entitled the "2014 C7 Corvette -Like a Knife," --"The C7 - required not only developing an aero-optimized grille and air dam, but also a removable center section for the Z51 performance option, to provide better stability at high rates of speed. Bednarchik points out that while shapes for improving fuel efficiency typically begin to have an effect at highway speeds..."

GM also noted the Chevy Volt had a large air dam to increase mileage.

All I ever did with my C6 Z51, that had a center air dam that scraped every time I went out my driveway, was to sand the bottom edge about once a year. Never replaced it as it looked fine, even to ants.

I did not remove the side air dams on my 2014 Z51 nor would I on my Grand Sport. They serve one other important function. They are like "curb feelers" as the next lowest thing to hit are the aluminum "skid pads" or "radiator supports," they perform both functions. Those that think that minor scraping noise of the fexible plastic air dams sounds bad, that aluminum on pavement sounds MUCH worse!




This Pic is The GM Aluminum Skid Pad on a C7. When it Scrapes Makes The Plastic Air Dam Scraping Sound Like Music in Comparison! If Damaged, Replacing is Expensive! Was Fortunate I Only Scraped Them in My 2104 After I installed PLASTIC FANGS- SOLD BY A FORUM VENDOR. Just Surface Scratches on the Very Rugged, Slippery Plastic Covers.