When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
The increase in drag is most likely from higher cooling drag. That is, more air is being passed through the radiator and that is a higher drag path, so the overall drag is increased.
I agree. You have to think of the higher underhood pressure as acting like a partial blocking plug to the inlet. That means more air goes over the nose/hood instead of through the radiator. If nothing else, that was evidenced by the much lower coolant temps. If the vents are successful and the OP finds lower pressure deltas, then there will be less lift (but probably not actual downforce).
I agree. You have to think of the higher underhood pressure as acting like a partial blocking plug to the inlet. That means more air goes over the nose/hood instead of through the radiator. If nothing else, that was evidenced by the much lower coolant temps. If the vents are successful and the OP finds lower pressure deltas, then there will be less lift (but probably not actual downforce).
I should have hard data on post-op pressure differentials this weekend.
JBS runs trak spec vents on his ~850-900whp car as well and I don't think he saw any difference in speeds so not sure about any claim this increases drag. Awesome to see you testing with real data and measurements! thanks
Just wanted to add two things to this thread:
1) thanks! i even sent this post to John@TrackSpec and asked him what he thought of your science, and he said it was good stuff. His directions actually already call for optimal placement, but he did take the time to read this and comment, so that's cool
2) followed these directions today and have mine on exactly where yours is!
For anybody interested: did it with the hood on the car. Took a LOT of tape to the hood, measured many many times. Just have a shopvac ready to go, and carefully and slowly remove the tarp or whatever else you use to catch the fiberglass shavings.
And speaking of - get a solid respirator for this. I had on a dinky dust mask, and immediately smelled burning fiberglass, so I swapped to a respirator. Other than that, not much to it. We cut conservatively, test fit a couple of times, and louvered it in.
A few thoughts on venting the wheel wells. I did that on my C4.
I did to lower my brake temps. It worked. I dropped the rotor temperature a couple hundred degrees. The trick is to get the vent almost directly above the brakes.
I personally wouldn't have put one large vent across both of the "humps" in the hood. One on each hump would have looked a little cleaner IMO.
BTW, What size front rims/tires are you running?
When these GT2 style Trackspec vents were designed it took into performance and rules considerations over pure looks. The rules limit the venting to four vents of 600 square inches or less total. The other aspect being considered was to get maximum venting out of the hood in the low pressure zone identified in the pictures above, which also happens to coincide with the ducting coming off of the back side of a large radiator that is tipped forward in many of the GT2/ST2 classed Corvettes.
When these GT2 style Trackspec vents were designed it took into performance and rules considerations over pure looks. The rules limit the venting to four vents of 600 square inches or less total. The other aspect being considered was to get maximum venting out of the hood in the low pressure zone identified in the pictures above, which also happens to coincide with the ducting coming off of the back side of a large radiator that is tipped forward in many of the GT2/ST2 classed Corvettes.
im a form follows function kind of guy, and wouldnt have done this if they didnt add to cooling and downforce... but i totally love how they look, too. so does my fiancee, and i've had several people say it brings the car together with its yellow/black
Very useful info, thanks! I have 2 questions: 1) did you place the vents where the template supplied by Tracspec recommended? (I'm assuming nobody recommends invading the safe area where the electronics are) 2) What is the purpose of the spacers Tracspec offered? Also assuming you didn't purchase the T1 configuration because the center hood area is somewhat smaller, if you have any comment on that.
I ordered and received the vents before they offered either the templates or the spacers. The spacers are designed to have the vent sit flush across the curvature of the hood. Without it, where I have placed mine, the center of the vent sits about 1/8" off of the hood. I have not experienced any hood flutter, and am therefore not worried about it. The angle in which the front of the large vent sits doesn't allow direct airflow underneath it.
I ordered and received the vents before they offered either the templates or the spacers. The spacers are designed to have the vent sit flush across the curvature of the hood. Without it, where I have placed mine, the center of the vent sits about 1/8" off of the hood. I have not experienced any hood flutter, and am therefore not worried about it. The angle in which the front of the large vent sits doesn't allow direct airflow underneath it.
Thanks again. Already found a spare MY hood for $200, this write-up has helped a lot knowing this is an effective way to go.
Thanks again. Already found a spare MY hood for $200, this write-up has helped a lot knowing this is an effective way to go.
i have a whole tech post woth pics etc i am working on since i put these on my 900whp c6 following the trackspec directions but the short answer is absolutely zero negative impact on top speed that i could measure up to 175mph in the 1/2 mile with and without these vents open at least on my car. So i dont think there is any noticable drag increase at speed, or at least not enough that it could be measured back to back on my car. I did get noticable benefits for cooling when car is moving it drops temp much faster now which i would assume should improve intercooler airflow as well but my methanol kit makes that hard to test on my car. When car is stopped it didnt help a ton, maybe 5* lower, but once moving id say temps drop 2x as fast now and it runs near the thermostat at speed and whole underhood area is cooler too since i used the 3 vent setup with the side vents over coils/headers. Nose of the car is dramatically more stable >140mph now too which was the main reason i installed these.
The vents look amazing too and clearly a lot of hard work was put into them. Only drawback some may not love is that i can hear my prochager a lot liuder with vented hood but i actually like that so win/win. Install was easy too and took one afternoon and i did mine with hood on the car. Have been getting a lot of questions and positive feedback and love how they look on my black car. Gives the car a very tough gt2 style look imo.
amazing product and wish id done it years ago. Incredible customer service too.
[QUOTE=neverstop;1593815811] the short answer is absolutely zero negative impact on top speed that i could measure up to 175mph in the 1/2 mile with and without these vents open at least on my car. So i dont think there is any noticable drag increase at speed, or at least not enough that it could be measured back to back on my car.
This makes a lot of sense, because you released dammed up air trapped under pressure under the hood. It wouldn't be surprising if the top end was higher once vented. This might be more true on the C6 which has better air flow in the front, so probably more air dammed up. Let us know when you do your write-up.
the short answer is absolutely zero negative impact on top speed that i could measure up to 175mph in the 1/2 mile with and without these vents open at least on my car. So i dont think there is any noticable drag increase at speed, or at least not enough that it could be measured back to back on my car.
This makes a lot of sense, because you released dammed up air trapped under pressure under the hood. It wouldn't be surprising if the top end was higher once vented. This might be more true on the C6 which has better air flow in the front, so probably more air dammed up. Let us know when you do your write-up.
Incorrect. As you ventilate trapped air and reintroduce it to the boundary layer it causes turbulence, or drag. Aside from having a higher convergence point in the power/drag graph, as the power is increased, the ability to accurately "notice" a difference anywhere except top speed is almost impossible unless the only variable is the rate of acceleration.
For a frame of reference, the data aquired on my top speed was GPS verified in a ~400whp car.
Last edited by Converted_Germ; 01-07-2017 at 05:15 PM.
Incorrect. As you ventilate trapped air and reintroduce it to the boundary layer it causes turbulence, or drag. Aside from having a higher convergence point in the power/drag graph, as the power is increased, the ability to accurately "notice" a difference anywhere except top speed is almost impossible unless the only variable is the rate of acceleration.
For a frame of reference, the data aquired on my top speed was GPS verified in a ~400whp car.
Well, we'd have to see the measurement of the increase in turbulence cost, if any, vs the measurement of the release of the dammed air, to make that call. This is why companies spend millions in wind tunnels under controlled conditions. See, his top speed didn't change at all on his C6, (a different body), objective data contradicting your results, so maybe another variable is going on. Just sayin...
Well, we'd have to see the measurement of the increase in turbulence cost, if any, vs the measurement of the release of the dammed air, to make that call. This is why companies spend millions in wind tunnels under controlled conditions. See, his top speed didn't change at all on his C6, (a different body), objective data contradicting your results, so maybe another variable is going on. Just sayin...
Turbulence is created when air is introduced to the boundary layer. That's a rule of thumb. How much turbulence and the amount of drag produced by the turbulence is the measurable variable.
1/2 mile speeds are irrelevant and are not a point of significance when measuring drag induced limitations of a vehicles top speed. A vehicle with ~.30 Cd, 900hp and factory gearing is nowhere near its drag limitated top speed at 175mph.
Last edited by Converted_Germ; 01-08-2017 at 06:56 PM.
this is a good thread and thank you for the data but I have to disagree with the claim that track spec vents lower top speed at least on my car and a few others. every setup and circumstance is different and it's not impossible i guess at bonneville or something perhaps there would me measurable difference but at least in 1/2 mile up to 175mph and in standing mile up to 202mph it doesn't seem to have any negative impact.
for reference rick hoback has been setting records in his stock bottom end and driveline c5 which i believe he has had to 202mph in the standing mile now and he runs track spec vents also.
in the 1/2 mile and standing mile aero is very important also and even fairly small changes typically have a measurable impact. there are multiple guys who have gained several mph just from playing with masking tape. removing side mirrors alone for example is typically worth 2-3mph in the standing mile on most nearing 200mph cars. I believe that if the track spec vents lowered top speed it would be quite measurable in the 1/2 mile and standing mile and as of yet I have seen no evidence personally on my own car or others that shows this to be true.
I have seen evidence it helps keep the nose down and improves air flow through the nose though and makes the car more stable and anything to keep the car float and air out from under the car should help as well.
great product though and glad they offer it. fwiw i think they look awesome as well
That was a cool video, thanks for posting it. I do think it is important to note that Mr. Hoback claims the car makes 850 hp (sounds about right to get to 200 mph in 1 mile) and that he also sealed off some of the air intake to the radiator to try to lessen the amount of air getting into the body. The small track spec vents also help ease some of the underhood pressure as he noted.
A hood with larger heat extraction openings might have had more effect on drag to slow him down, but those are pretty small and low height Track Spec vents...maybe a very early generation?? Those louvers look pretty tight, most full on race cars have nothing covering the vent openings for maximum air evacuation.
The reality is you can put 850 horsepower in a lot of cars and go 200 mph in a mile....in fact, Mr Hobacks car would probably have been even faster if it was a coupe and not a FRC which has more aero challenges than the base C5.
Overall, this has been a very informative thread...hope we keep getting more data and results coming in.
Did the OP ever do any Delta T and/or yarn readings with the vents installed? Id be interested in reading what you found.
Id really like to do this to my car but am afraid to drill and cut on a Z16 hood. Finding a spare hood would require a lot of $$$ being it would have to be repainted, vents installed and have a new stripe kit installed.
12-17-2015, 10:25 PM
