Ih2lose

I was in the garage last night and noticed some missing bolts, is an airdam or spoiler missing here




https://larryvsa.smugmug.com/2018-corvette/n-fTRSQJ

ImpliedConsent

Z51? No.

Ih2lose

this is a 2018 Stingray convertible.There is no listing of Z51 on the window sticker so I have to say no

Mayor111

If your Vette is a Z51, it doesn't come with that middle air dam... I thought my was missing to until I asked the very same question.

ImpliedConsent

I think there might've been "some" years of GS and/or Z06 without the center too. Not too sure, but if it's neither of those: missing.

KenHorse

Looking at the pics of your car, it does appear to be a Z51, based on front brake calipers (if you haven't changed 'em out from stock)

Then again, the VIN would be the definitive answer

Mayor111

Check the SPID label inside the glove box...it will look like this below. Look for a "Z51" on that label - if its not there, then its not a Z51 and then the dam is missing.

JerryU

You can tell from the VIN if it's a Z51. This is an example:
Note if a G through M is in the 5th position it's a Z51.

This is an example of a VIN # for a 2014 Corvette Coupe (3LT, Z51, MN7):

1 G 1 Y L 2 D 7 X E 5 1 0 0 0 0 1

There are 17 characters. Starting with first character on left the codes are:
01. "1"= Built in US
02. "G"= General Motors
03. "1"= Chevrolet
04. Denotes the car line: Corvette is a "Y" body.
05. Provides more info about the car:
.. A=1LT M/T
.. B=1LT A/T
.. C=2LT M/T
.. D=2LT A/T
.. E=3LT M/T
.. F=3LT A/T
.. G=Z51 1LT M/T
.. H=Z51 1LT A/T
.. J=Z51 2LT M/T
.. K=Z51 2LT A/T
.. L=Z51 3LT M/T
.. M=Z51 3LT A/T
.. 9=export (Non US, Non Canada)
06. Body style: "2" = Coupe, "3" = Convertible
07. Restraint code: D – AJ7 Active Manual Belts, Airbags – Driver & Passenger and Seat Side
08. Engine: LT1 = "7"
09. Check Digit – 0 to 9 or X
10. Model year: E (2014)
11. Plant: Bowling Green = "5"
12-17. Production sequence number that starts with the #100001 for each model yr.

No Z51 has a center air dam. All base cars have a center air dam. Gets tougher to define in a Grand Sport and Z06. See table below. I have the CFV option so don't have one.

Ih2lose

My 5th character is a "F" for 3LT auto

ImpliedConsent

Then yes, this is a base convertible 3LT, so the middle piece would be there. It's missing in that photo of a non-Z51.

Marcho Polo

This is not in the glovebox on any C7 that I know. It has been relocated to the rear near the battery.

JerryU

Yep, you should have an air dam. It's dealer installed as the car does not fit on a car carrier with it attached.

Your choice, at highway speeds it does help somewhat with gas mileage. Doubt more than a few tens at 65 mph.

At 100+ mph it adds down force. As Tadge said that is why it is missing from the Z06/GS with the aero option (and no doubt from the Z51.) He said at high speed the excess downforce was providing slight oversteer and they design for slight understeer (probably for safety reasons.) If going to fast for a corner with an understeer car you can turn the wheel in the direction you would like to go and while scrubbing some speed you might be able to get it back to the center of the road.

With an oversteering car (like my old modified Corvair) the rear end will start sliding first and you must turn into the skid, away from the center of the road. Not natural. But if you turn toward the road center it just makes the rear slide faster! In fact you have little time to react to turn like a dirt track racer! Corvair and Porches had a saying, "If going too fast for a corner you will go off the road. It's better to hit a tree with the rear end than plow into it head on!"

If you don't plan on making a high "g" turn at 100 to 150 mph and leave it off you'll just lose a few tenths mpg.

Ih2lose

I have the painted yellow caliper option,

ibuildm

JerryU

^^^
Interesting, the portion of the document intended for dealers to tell them what features go with the various C7s I copied and posted above was only for Z06 and Grand Sport since that is where the issues of which had a center air dam. Since all Z51s do not have one did not copy that part of the page. The Base Stingray was above it. Just copied that portion and it's shown below.

Although it does not mention the ZF1 option it does show the Stage 2 Aero Option CFV or CFZ (same carbon fiber splitter, side skirts and extensions on the rear spoiler.) It is the same as I have on my Grand Sport and just checked it is available in the base care, at least in 2019 as well as this pic below from 2017.

Aerodynamics are not intuitive and GM has no doubt run Computational Fluid Dynamics aerodynamic simulations on their computers. Tadge in a post said these simulation programs are getting so good they can be used to replace expensive wind tunnel tests in a number of situations. Only they can say why each option has whatever. As mentioned, in the above post Tadge in a forum post said the center air dam was not used on some modles because at high speed to avoid causing Oversteer when Understeer is desired.

V Vette

So why would it not have it and others do? Can the design of each car be that much different that some warrant it OR is it looks only?

V Vette

Thanks for that but the line.... "air dam was not used on some models because at high speed to avoid causing Oversteer when Understeer is desired"..Did GM finally resolve which is best????

JerryU

No way it's for looks! This is a 7 page PDF I made about aero as I have followed this "no center air dam" since I got my C7 Z51 in October 2014 and wanted to know why it had no center air dam: http://netwelding.com/Air_Dam.pdf

Lots of "Marketing Speak" comments obscuring the rear reason until a few later when Tadge admitted the reason at a Bash! Heck the Chevy Volt has an air dam per GM to improve gas mileage. It sure doesn't add to esthetics! In fact if you look around you'll see many cars have them for the same "lower drag at highway speeds."This is a Summary from in my PDF of Why No Center Air Dam on Some C7 Models:
· Bednarchik (the GM Chief Aerodynamicist) in October 2013 (in an article about C7 aero) said it’s for high speed stability- but no details. (That statement and the fact that I had a center air dam on my C6 Z51 is what made me continue to look at the real answer why in was removed from my C7 Z51 at the last minute before the first sale and when other GM folks said rear brake cooling or other long explanations with no real answer!)
· Tadge at the April 2014 Bash said the center air dam on the Z51 is deleted to balance the lift characteristics.
· Tadge in a 2015 Z06 intro video said it was not used because it was causing high speed oversteer and they require some understeer.
· Tadge in a 2016 forum post said they carefully control “pitch moment” to provide neutral handling biased to understeer.
· In a 2017 GM Bulletin it was shown the base models of even the Grand Sport and Z06 now have center air dams, minimizing the reason being extra cooling.

V Vette

Thank you.. So GM has determined the best design? Then all our cars should have same design?

JerryU

Not sure what you mean "which is best." Aerodynamics is very complex and is not intuitive. You'll always get better mpg with the center dam it's just the high speed stability that is the issue. With the C7 that is probably above 100/125 mph when making high "g" turns.

When I added a rear diffuser, for fun did further research and made an 19 page PDF summarizing what I found. In fact bought a 300 page book by a PhD prof who consults about aero for F1! I put in some of his interesting points without using math!

You might find it of interest as well as the PDF mentioned in the post above: http://netwelding.com/Rear_Diffuser.pdf

Aero is Not Intuitive:
I had lots of fun when I had an S10 pick-up discussing why leaving the tailgate open caused more not less drag! In fact there are several technical explanations but the one I like to quote was from the Myth Busters where they took identical Ford F150's and made a 500 mile drive, one with the tailgate down, the other up. They switched tailgate up and down on the return trip. They followed each other so wind etc were neutralized. They got 6% better mileage with it up! There is a simple explanation but won't cover it here!