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C6 Grand Sport Front Fender Vent - How-To open them up
As an avid track enthusiast, I'm always concerned about under-hood temps. I've often looked at my front fender vents and wondered if they are actually functional, or merely superficial. I finally got around to opening them up for the first time to peek inside, and I am posting my results here.
For anyone who has ever wondered what's inside a Grand Sport fender behind the "gills," here ya go.
(I'm not sure if this applies to base models / Z06s / ZR1s, but it may be worth a peek if the end result is something functional.)
Grand Sport front fender inside.
This plastic piece is screwed in with 2 screws between the door and fender, and is held by 2 squares of double-sided tape on the top and bottom.
Without the plastic.
I'm hoping this will increase heat extraction from the sides of the fenders and turn the vents into something functional. If not, it is easily replaced.
I don't drive my car in any kind of conditions that would result in moisture or debris getting in there, so that is not a concern at all.
If anyone has any thoughts/opinions/ideas/data to share, I would be more than interested in hearing it.
Thanks for the input RW......somebody get this man a shot and drinking partner.......while I think about what he has presented here........I get caught in the rain occasionally so need to check out what I think about the mod.......maybe just some relief holes in the plastic to aid in hot air getting out without leaving things wide open.........hmmmm.....
As an avid track enthusiast, I'm always concerned about under-hood temps. I've often looked at my front fender vents and wondered if they are actually functional, or merely superficial. I finally got around to opening them up for the first time to peek inside, and I am posting my results here.
For anyone who has ever wondered what's inside a Grand Sport fender behind the "gills," here ya go.
(I'm not sure if this applies to base models / Z06s / ZR1s, but it may be worth a peek if the end result is something functional.)
I'm hoping this will increase heat extraction from the sides of the fenders and turn the vents into something functional. If not, it is easily replaced.
I don't drive my car in any kind of conditions that would result in moisture or debris getting in there, so that is not a concern at all.
If anyone has any thoughts/opinions/ideas/data to share, I would be more than interested in hearing it.
What tracks do you drive in Texas, and how do you have the car setup (i.e. slicks, aero, etc..)? Also what coolant/oil/tran temps are you seeing?
I ask because I run my car in +95F temps @VIR during the summer on street tires and I haven't had any issues with underhood temps. But this could be due to VIR's two long straights that I see +140MPH each lap when not in traffic. The bottom picture is a summary from my last outing the week of July 4th. After about a half a lap the intake (IAT) temperatures usually fall within 3-5 degrees of outside ambient.
Thanks's again for posting the pics.
Ambient & IAT are in the box on the left hand side. Day 2 I was in the Advanced group and ran the car harder but it was cooler due to the overcast and scattered rain.
You've got some good data there! Looking through your posts, you have some great questions / answers as well.
Texas is one of those "Current temp: 98* Feels like: 103* Humidity: 45%" states in the summer that is usually sweltering for 3 months straight, regardless of locations. Dallas/Houston/Austin tracks are the usual hang-outs.
I'm running street tires with a front splitter, brake ducting, under tray, World Challenge hood, Setrab 925 oil cooler w/180* thermo, Dewitts rad w/160* thermo. I'm all about that air flow lol I may be changing oil to something a bit thicker to handle this TX heat very soon.
This is also laying the ground work for expansion into raised compression with a 416ci stroker kit (more heat... yay!) down the road when consistent lap times start to be the norm and a plateau has been reached, but that remains many seasons down the road.
I don't see any adverse effects of removing the plastic pieces, really. Worst case scenario, they disrupt something or cause drag/instability and I just screw them back in.
I have seen these too while replacing the fender badges and working on the dry sump. One of mine was actually loose so I put it back on with new double sided tape. Looking at the cupped square that covers the vents and the three cutouts on the front edge. I wonder if it is engineer for a negative air pressure to force air out. I'm no engineer but it made me wonder is it an EPA noise thing or a keep environment (water & debris) out thing or did GM engineer it to move air. Let's us know what you find out.
I will keep everyone posted. I will need to procure some form of measuring device to put on the inside of the fender to measure temperature and air flow with and without the little plate.
I was thinking the air passing over the fender vents would help act as a vacuum and any positive pressure would have an additional outlet (additional to the "World Challenge" hood by LG). I know they say front fenders hold a lot of positive pressure, and, instead of venting the top of the fender, I was hoping opening up the sides would have the same effect.
You've got some good data there! Looking through your posts, you have some great questions / answers as well.
Thanks.
Originally Posted by R_W
Texas is one of those "Current temp: 98* Feels like: 103* Humidity: 45%" states in the summer that is usually sweltering for 3 months straight, regardless of locations. Dallas/Houston/Austin tracks are the usual hang-outs.
I fully agree. I have family in Dallas & Houston and I lived in Austin during the summer of 07'. It was either crazy hot w/ humidity or raining like the 2nd coming of Noah's flood.
Originally Posted by R_W
I'm running street tires with a front splitter, brake ducting, under tray, World Challenge hood, Setrab 925 oil cooler w/180* thermo, Dewitts rad w/160* thermo. I'm all about that air flow lol I may be changing oil to something a bit thicker to handle this TX heat very soon.
This is also laying the ground work for expansion into raised compression with a 416ci stroker kit (more heat... yay!) down the road when consistent lap times start to be the norm and a plateau has been reached, but that remains many seasons down the road.
A heavy weight oil should be fine since your nominal ambient is so high. I would just be careful during the first laps in your morning session. I usually preheat for 5-10mins before my first session to help get all 10.5 quarts warm. I don't know how your oil cooler has changed the flow characteristics, but with the stock setup 50-60PSI @ WOT usually means warm and 40-55PSI is optimal.
Also that's a pretty strong aero setup, I'm surprised you're not running a big wing and side skirts.
Following.
How did you remove them, pull the fenders?
Also, can you tell me anything about the underway? I run the WC hood also and track in TX.
You do not have to pull the fenders completely.
There are 3 x 7mm screws on the bottom of the fender behind the front wheel facing the ground, the fender liner snaps into / out of place, and there are 6 to 8 Torx screws on top of the fender that are helpful to remove. The fenders themselves are plastic, so they have a bit of give to them and are seemingly fairly flexible.
The undertray is best used with the ZR1 front splitter and the Katech brake ducts that attach to said splitter. The undertray itself fits under the front splitter and extends all the way back to the wheels and straight across, so it eliminates the OEM brake "inlets" (if they can even be called that) and the bottom half of the radiator dam. Our C6 GS/Z06/ZR1s are not "bottom-feeders" for air, so there is no disruption in flow. It helps with underbody aerodynamics (eliminates the lift created by the front air dam / brake dams) as well as airflow into the front opening and through the radiator.
I am about to start making my own front undertrays for people who are interested in them out of a material called Tegris, that is just as rigid as carbon-fiber, only 10% heavier, less costly, 150% more impact resistant, and 100% recyclable. I've already had rocks chip and even dent the fiberglass undertray (I refuse to drop big $$$ on CF parts that hover inches over the ground and can be disintegrated by debris), so it is only a matter of time before it gives out. I've been forced to look into making my own parts on this one. (Not pedaling my work here in this thread, though. )
Heres a pic of the Katech undertray to give you an idea of what it does/where it sits.
I fully agree. I have family in Dallas & Houston and I lived in Austin during the summer of 07'. It was either crazy hot w/ humidity or raining like the 2nd coming of Noah's flood.
Texas is known for having "bi-polar" weather.
Originally Posted by truth.b
A heavy weight oil should be fine since your nominal ambient is so high. I would just be careful during the first laps in your morning session. I usually preheat for 5-10mins before my first session to help get all 10.5 quarts warm. I don't know how your oil cooler has changed the flow characteristics, but with the stock setup 50-60PSI @ WOT usually means warm and 40-55PSI is optimal.
Also that's a pretty strong aero setup, I'm surprised you're not running a big wing and side skirts.
Oddly enough, the characteristics didn't change much. The oil bypasses the cooler until 180* is reached, and I do not go above 3k rpm until the oil has reached 150* for viscosity reasons.
I'm running the ZR1 "Extended" rear spoiler and side skirts to help balance that front aero out. Although the fiberglass side skirts leave a bit more rigidity to be desired...
You do not have to pull the fenders completely.
There are 3 x 7mm screws on the bottom of the fender behind the front wheel facing the ground, the fender liner snaps into / out of place, and there are 6 to 8 Torx screws on top of the fender that are helpful to remove. The fenders themselves are plastic, so they have a bit of give to them and are seemingly fairly flexible.
The undertray is best used with the ZR1 front splitter and the Katech brake ducts that attach to said splitter. The undertray itself fits under the front splitter and extends all the way back to the wheels and straight across, so it eliminates the OEM brake "inlets" (if they can even be called that) and the bottom half of the radiator dam. Our C6 GS/Z06/ZR1s are not "bottom-feeders" for air, so there is no disruption in flow. It helps with underbody aerodynamics (eliminates the lift created by the front air dam / brake dams) as well as airflow into the front opening and through the radiator.
I am about to start making my own front undertrays for people who are interested in them out of a material called Tegris, that is just as rigid as carbon-fiber, only 10% heavier, less costly, 150% more impact resistant, and 100% recyclable. I've already had rocks chip and even dent the fiberglass undertray (I refuse to drop big $$$ on CF parts that hover inches over the ground and can be disintegrated by debris), so it is only a matter of time before it gives out. I've been forced to look into making my own parts on this one. (Not pedaling my work here in this thread, though. )
Heres a pic of the Katech undertray to give you an idea of what it does/where it sits.
And here are the brake ducts:
I can't see where this Fender vents on my base model go anywhere except inside the fender which is completely separate from the engine compartment, but I only looked for about 3 minutes so I could be wrong.
I hear the whole thing about bottom feeder or front feeder cooling system but I just don't really buy it. I would like to utilize an under tray on my z51. I am currently utilizing the OEM brake duct holes which I then rigged brake ducts all the way to the spindles from. Not sure what I would do about that.
I can't see where this Fender vents on my base model go anywhere except inside the fender which is completely separate from the engine compartment, but I only looked for about 3 minutes so I could be wrong.
I hear the whole thing about bottom feeder or front feeder cooling system but I just don't really buy it. I would like to utilize an under tray on my z51. I am currently utilizing the OEM brake duct holes which I then rigged brake ducts all the way to the spindles from. Not sure what I would do about that.
I have not had a chance to dig my fingers into a base model, so I do not know how they are built.
Did you rig the front part of the brake ducts to actually intake / move air? From my research, the brake ducts on a Z51 do not go any further forward than the fender liner and are purely asthetic. (Reference: https://www.corvetteforum.com/forums...on-my-z51.html). If that is the case, I'm not sure how you would run the ducting (front fog lights with some modification to catch and direct the air perhaps?) or if the katech splitter ducts would even line up with a ZR1 style lip for base models if you were to add an undertray. That's a noodle-scratcher....
Also, from what I've read, the base models do indeed rely on the under-bumper opening to move air through the radiator. I would proceed with caution if blocking that area off and keep a close eye on temps. If it were me, I would test the theory by fab'ing up a block off plate for that opening, just to see if the temps do indeed rise above normal operating range before I jumped into an undertray with both feet.
The Z51 brake ducts did make it to the fender well stock. I just added Z06 brake ducts, then a spindle kit. Even though I have Z06 sized DBA4000 rotors and stock Z06 calipers with pads and Motul, I was killing the brakes constantly at my local track b4 the ducts. I since started a business and haven't made it back to the track since I added the spindle ducts.
I don't buy the bottom feeder crap. My car has a big hole in the front with the radiator behind the hole just like every other C6 that I've seen.
Do you have any pictures where you ran the brake duct inside your bumper, specifically where your brakes are getting the airflow from?
Like I mentioned, if you're not concerned about the idea of a "bottom feeder," then test it by blocking the hole under the car and watch the temps.
And to get this thread back on track...
Open the black plastic piece on the far left side of the photo that you just posted (the back side of the fender liner). Look inside and see what's in there to determine if you can remove anything similar to the block-off plate on the GS. It looks like a few simple push-pins, and it can be inspected with the wheels still on.
The start of my OEM air duct holes is the same as a Z06, all you do is just pop out the little 6" inside air duct that came stock on mine, and put in the longer Z06 air ducts, they fit like they were built for it because they were.
My brake air ducts are definitely Bottom Feeders, the radiator however is not.
After driving the car for a bit and parking, I can actually feel heat coming through the fender openings, more so on the passenger side where the dry-sump is located (go figure).
I hope to get ahold of a thermal camera soon (Home Depot rents them out here), and get some rolling shots to see exactly the volume and temps being removed.
You do not have to pull the fenders completely.
There are 3 x 7mm screws on the bottom of the fender behind the front wheel facing the ground, the fender liner snaps into / out of place, and there are 6 to 8 Torx screws on top of the fender that are helpful to remove. The fenders themselves are plastic, so they have a bit of give to them and are seemingly fairly flexible.
The undertray is best used with the ZR1 front splitter and the Katech brake ducts that attach to said splitter. The undertray itself fits under the front splitter and extends all the way back to the wheels and straight across, so it eliminates the OEM brake "inlets" (if they can even be called that) and the bottom half of the radiator dam. Our C6 GS/Z06/ZR1s are not "bottom-feeders" for air, so there is no disruption in flow. It helps with underbody aerodynamics (eliminates the lift created by the front air dam / brake dams) as well as airflow into the front opening and through the radiator.
I am about to start making my own front undertrays for people who are interested in them out of a material called Tegris, that is just as rigid as carbon-fiber, only 10% heavier, less costly, 150% more impact resistant, and 100% recyclable. I've already had rocks chip and even dent the fiberglass undertray (I refuse to drop big $$$ on CF parts that hover inches over the ground and can be disintegrated by debris), so it is only a matter of time before it gives out. I've been forced to look into making my own parts on this one. (Not pedaling my work here in this thread, though. )
Heres a pic of the Katech undertray to give you an idea of what it does/where it sits.
And here are the brake ducts:
please tell me you are going to make undertrays for us on-a-budget track go'ers.
I was going to buy sheet metal and make my own front undertray and rear diffuser setup.
I want to look into that material you mentioned.
Let us all know, i would definitely buy a cheaper option than Katech or custom
FWIW, our 2009 base Z51 has a similar black plastic insert inside the gills, it's easier to see than on a GS.
Considering that the insert adds a little weight and costs a little money, GM wouldn't have kept putting them on the cars if they didn't serve a purpose. But I don't know what that purpose is...
07-29-2016, 08:48 AM
C6 Grand Sport Front Fender Vent - How-To open them up
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