Hello. I know there are a few threads on this topic but I had a specific question about vented hoods. I have a base C6 with ZO6 springs, sway bars, and shocks and run R compound tires. I do a lot of track days at Watkins Glen and at the top of the esses at over 130 mph, my car always feels like there is a strong crosswind and it feels a bit unstable. On a straight line and other turns, it feels stable at speeds up to 160 mph (fastest I've gone on street or track)..Do other Corvette owners get this light feeling specifically at top of esses and does anyone think a vented hood would make feel more planted? I'll ask the ZO6 and GS drivers how their cars feel and I'm guessing they already have the downforce to keep this from happening.

 

It will probably help reduce some lift, but not eliminate the issue felt at the one turn. To eliminate takes a front splitter and then balancing the downforce there with a rear spoiler. I haven't driven on Watkins Glenn to speak on experience on the esses.

 

Thanks for the response and I know real ground effects with splitters and wings are the real answer but I was looking for a quick and easy fix. The base C6 seems to be quite well balanced and the ZO6 and GS have real downforce but I didn't want to change the bodywork on my base model. One thing I have noticed is the base car seems to run cooler on the track and that is probably due to more air thru the radiators which also creates more lift so that is a trade off.

 

I was told by some wind tunnel guys who had worked on Vettes before that the standard C7 ZO6 size of vents, around 9.5" X 19", something like that, will do the trick to gut the lift in the nose. I have 2.5X that with an ACS hood, but that is for heat issues as well.

The stock Camaro hood vent you see on some Vettes happens to be the same dimensions, just turned 90 degrees.

 

@Mordeth probably has about as much time at the Glen as anyone does.... ?

 

I have literally thousands and thousands of laps at the Glen and race and instruct there. There is no quick and easy fix to your issue, but there are things you can do. The "floaty" feeling is a combination of loss of aerodynamic downforce as you reach the top of the esses, a shift in weight and your suspension's inability to compensate for it. From the bottom of the esses, to the top of the esses, there is a change (increase) in elevation of 57' and then another 10' in rise to the back straight. The car, without enough downforce, needs a moment to settle as it crests the esses, as it will want to "float".

A vented hood, while certainly a benefit, will not cure this issue at this particular spot on the track. _BlueZ06_ is correct in what he said. More aerodynamic downforce is needed to keep the car planted (front splitter and rear spolier), and a better set of shocks (like DRM valved Bilsteins) or coilovers. Typically, you should be WOT at that point (and far before it) to get to Vmax asap and keep the weight shifted to the rear as you come out of the Esses and hit the back straight. If you feel "floaty" then you need to breathe the throttle to help shift the weight back to the front to create some mechanical grip at the front and help settle the car.

Take a look at the attached and this will help you understand why this is happening.

 

Godzilladude, thanks and I know placement on the hood is important due to the higher pressure near windshield. Did you hear where best location is for lower pressure to let air out of vents at speed?

 

Mordeth, thanks and that is exactly the feeling and makes sense as I am fill throttle all the way up the esses so car is pointing up and the air gets under it right at top. I probably won't do the splitter and wing but maybe a vent. I can lift the throttle a bit if it starts to feel unsafe. I already have ZO6 shocks, sways, and springs. Do you think the shocks you mentioned are that much better than ZO6 shocks?

 

The shocks I mentioned are much better, but it won't completely cure your issue. You also need to lower the ride height, re-adjust the alignment and add a splitter. Too much air is literally getting underneath the car and lifting it up. And when combined with WOT, whereby the weight transfers to the rear, you lose a significant amount of front end grip and then the car will begin to push and when pointed straight will feel floaty (especially at that point of the track due to the rapid change in elevation and throttle application). A lowered car with the proper rake will help to mitigate this by letting less air under the car and by creating a venturi effect (higher speed air and lower pressure under the car) thereby reducing lift and often times creating actual downforce. The front splitter will create an air dam (basically splits the air and prevents a large amount of air from going under the car - which then goes above or around the car) which adds measurable downforce and helps to keep the front of the car down at points like that (top of the esses).

A vented hood also helps by evacuating some air that is under the hood, but that is not the root cause of the problem (which is air getting underneath the car) and won't magically solve the issue (but could slightly help it). I realize you are looking for a cheap, easy fix, but unfortunately there isn't one. I have tested all of this extensively and do not speak about "what I heard". You could start by adding the vents and seeing what happens, but ultimately you need better shocks, a proper splitter, a lowered ride height (with appropriate rake), a check on your alignment and perhaps a small rear spoiler to balance it. To fully solve the issue requires a massive splitter, dive planes, full hood venting and a giant wing (search my posts and you will see what I have done to my car). I'm not at all suggesting you go this far, but simply demonstrating how issues like this are dealt with (either partially or fully and completely). A vented hood is just one piece of a larger puzzle. Aerodynamic efficiency and the associated downforce (or reduction in lift), if implemented properly, is like magic and addresses issues like this. But it should always be done in steps as it is easy to unbalance the car (your car is already unbalanced by the way which is why you need a splitter).

 

I found that installing a Front Splitter and Z51 style Rear Spoiler to be quick and easy. I would think these are much easier than changing out the Hood. I don't know "how much" Splitter & Spoiler effectiveness is required for your needs. On ebay "theSpoilerCompany" offers the rear spoiler for about $250, IIRC. And the Splitter I also purchased on ebay was only about $150. Both were very easy to install. The Front Splitter required screws ... in areas that were already scuffed & scratched from scraping the pavement. The Rear Spoiler did not require holes drilled for screws, as it uses Very High Bond (VHB) 3M adhesive tapes.

 

vezePilot, thanks and those look nice. I'm probably over thinking it but was hesitant to add aero unless it was a complete package that was tested like using all GM parts from a GS or ZO6. I worry about too much on the rear which lift the front or worse would be having too much on the front and having the back come around at speed which in a Corvette is something you don't want to do more than once if at all. Your's does look nice and for the price, it could be worth trying.

 

On the C7 they put it up front, close to the radiator. And my ACS hood was set up with the vents closer to the front. I have never personally seen any aero data using various venting locations. Just what the factory guys do.