97AutoXVette

Somewhat of a controversial topic, but here it goes...

I have seen many discussions and validations behind if the intake/radiator shroud is really needed on these cars to keep them cool... And some strong arguments either way. I want to discuss a little more behind fluid flow and find out if anyone knows some of these specifics. I will be road coarsing my car soon and the last thing I want to do is overheat on the first lap

It seems that the intake/radiator shroud utilizes vacuum and fluid dynamics similar to that of an airfoil to pull cool outside air around the bumper (which curves smoothly into its connection with the shroud) and up through the A/C condenser and radiator.

Many feel that without the shroud, enough cool air is not directed to/through the radiator and too much air passes around it or just doesn't get pulled up into the radiator section of the engine bay in general... Valid points which I believe are 100% true.

However, as vehicle speeds increase (track days ) that flow that is attaching it self to the bumper around and up and into the radiator/intake shroud would separate at some point (I would think) and the flow separation would cause some pretty turbulent flow that might just pass under the car instead (leaving a decent % of air that would normally pass through the radiator at lower speeds now passing under the car).

****Does anyone know what speed (mph) this transition point where flow separation starts occurring might be???****

With the fog light screens removed on my 97 C5, and with the vented fog areas on my current 02 Z06, I have had the radiator/intake shroud out of both of them with no adverse affects on cooling.... yet. Again, I still need to take the Z06 to an HPDE event in the next month or two to really find out.

I would think that the ram air effects of air passing through the front fog vents along with air still being able to pass up through the original radiator opening from underneath the car should provide adequate cooling.

Some of the benefits of removing the shroud:
1. weight
2. easy access to other components up front
3. more cool air for the intake
4. better convection for components in the engine bay
5. less vacuum under the car sucking up all the crap that goes into the radiator and condenser on the street and at the track!
6....

Let me know what you guys think. It may just be trial and error for me at this point. However, some CFD modeling or any quick flow model could yield some interesting results

Thanks for your time,
Andrew

TLGunman

Don't forget cooling drag, which is what we look at quite a bit. You want to keep the car cool, but at the same time, you don't want to induce any more drag than you have to, to accomplish this. We've also played with radiator inlet duct work to increase front downforce, so that ducting isn't just for cooling anymore

Good luck!!

97AutoXVette

Great points about the downforce.. Didnt even think of that! I know those GM engineers *aren't* making it up as they go... Would be interesting to see the downforce benefits at higher speeds. Thanks for the reply

Bill Dearborn

Here are some tips I picked up from a guy in GM Racing back when I first took delivery of my 97 in May of 97. First, for triple digit and above speeds make sure the center air dam is secured so it doesn't fold backwards due to air pressure (it is mounted on a spring loaded mount that lets it swivel under the car if it hits an obstruction. I fastened mine by wrapping duct tape around the piece in 3 spots (both ends and the middle). This makes sure the air is forced into the radiator, Second, seal the space between the shroud and the AC condenser (if you still have one, radiator otherwise) so the air doesn't push its way past the stock seal and blow past the condenser into the engine compartment (on my 97 it only took a couple of track days to blow the stock seals outward into the engine compartment so there was a pretty large air leak past the radiator. I crawled up in there and removed all the grass and crap I could and then used duct tape to seal the sides of the shroud. Third, keep the AC Condenser and Radiator clean. A lot of stuff gets lodged up at the top of the shroud and basically blocks off the top third of the radiator if you don't keep pulling the stuff out of there. If you are serious about tracking pull the radiator once per year and do a thorough cleaning of both AC condenser and radiator. The early C5 fan shrouds had little flapper valves in them that increased air flow when the car was moving fast. They were holes in the shroud that had rubber flappers on them and when air pressure in front of the fan shroud reached a certain point they would open. If the fan was running the lack of pressure in front of the shroud kept them closed. My 97 had those flaps and the fan shroud on my 03 did not.

To stock cooling capacity is limited since it wasn't designed to run at wide open throttle for long periods of time. Best way to keep the engine cool is to go with a larger radiator and an engine oil cooler. I had the DRM Ron Davis Racing Radiator with built in EOC and a remote oil filter in my 97. At speed with a stock 195 thermostat my coolant temps ran right at 200 degrees and the oil temps ran at 230. Right where you want them. In cool weather and at speeds up to 80 mph the coolant would run right at the thermostat setting and the oil temp would be below 150.

Bill

cruzin2

believe it!!

97AutoXVette

Some good info thus far.. Thanks for the comments!

Supercharged111

Kind of makes you think a larger dam would be good for auto-x and smaller dam for a real high speed track. The cores will only take what they can flow, the rest just has to find another way around.

Z06trackman

As David pointed out below, my post here is regarding the fan shroud, and the original poster is asking about the radiator shroud (in front of the radiator). Rather than delete and make some of the later posts confusing I am just adding this intro. Thanks David.


OK, I took fluid dynamics a hundred years ago, I'll bite...

The fan shroud is important when the fans are running. Without the shroud a lof the air moved by the fans is just swirled around the edges of the fans instead of being pulled through the radiator and that lowers the efficiency of the fans. They also cause more area of the radiator to see good flow when the fans are running. If you are stuck in traffic on a hot day, you are thankful for the fan shroud. For track speeds the shroud decreases the efficiency of your radiator. Air flowing in must also flow out, and the shroud gets in the way of the flow out. Any track speed is high enough to not need the fans. As posted above, some doors on the shroud that open at speed would improve the efficiency of the radiator at track speeds, but if you can live without the shrouded fans (no slow speed/stopped in hot weather, esp with AC), the best tack cooling is with them removed.

Having said all that I admit to still having the shrouded fans. My stock C5Z maxs at 234 on a real hot day with a De Witts double row and 90% water and Waterwetter, and my air dam taped in 3 places to prevent it bending back at high speed. My next mod, now that I have a racing seat and no longer drive it on the street is to remove the fans and shroud.

Some folks have posted their solution of installing a single, large, non-shrouded fan (De Witts sells some for instance). This should be nearly as good as no shrouded fan at track speeds, while providing some cooling for slow/stopped street conditions.

Supercharged111

I think, to a certain extent, you could simply overcome with brute force. According to some other fan related threads, a 3000 cfm single fan is substantially more than the stock duals. If you wanted to take it a step further, you could probably wire up some non-shrouded duals all factory like to retain low/high and flow so much more that the lack of shroud wouldn't even matter plus the duals would cover more radiator.

argonaut

When I bought my car the shroud was already removed. I then removed the A/C condensor and installed a DeWitts radiator with built in EOC. Stock fans. This is a stock LS6. I've done about 50 track days in this configuration, running at advanced DE level. The highest Oil temp I've seen is 260 and water in the 220s. I've had the car up to 150 with no noticible "float". Based on my experience I'd say it works just fine without a shroud, at least with the aftermarket radiator.

63Corvette

My 69 L88 came with no fan shroud.......Try running an L88 on thestreet without a fan shroud sometime

mountainbiker2

Here is a DeWitts fan setup. Works great with my front splitter sitting in grid. Hooks up to the stock wiring.



Steve A.

davidfarmer

Seems like the OT was radiator shroud, but you guys are talking about fan shrouds. Totally different and totally confusing.

stevensa

Indeed

froggy47

Hmmmm.

That Farmer guy, always trying to clarify stuff.

I did learn one new thing about the air dam folding back at speed, but it seems to me that duct tape is not sufficient, anyone shoot video of this at speed?

Supercharged111

Well you're tracking, so what's the problem?

VGLNTE1

I will tell my experience....I made my own rad housing and thought it was the bees knees. After on track on a 100 degree day, I saw 250 water and 300 oil temp. I spoke with the katech folks on site and they rops me to much air was passing through and not into the rad. They said to tape it up. After doing so, I've dropped 35 degrees on water and 40 on oil. I have a stand alone oil cooler in front of thr rad. I was amazed. So yes, a proper air tight shroud is needed for the track. For the street, no.

97AutoXVette

Interesting... Thanks for the response. Did you still have you A/C condensor in the car by chance??

Thanks to all the posts thus far!
A lot of great info

VGLNTE1

Nope, no ac. Also I will mention, I have the front plate cut away for air because of the splitter

97AutoXVette

Well, after these posts, my shroud is going back into the car. A/C condenser is staying out though. Hopefully the stock radiator can hold up to HPDE demands