Good info/tech on cooling for those who are bored talking about 3.73s and cobra r's

[88GT17MA]

Check out what paul bird has to say here, some good reading:

http://www.turbomustangs.com/forums/showthread.php?s=&threadid=47132

 

[srothfuss]

That was some good, good reading.

Question: When people switch over to an electric fan (doesn't run all the time) do you think this has something to do with the increased cooling effect at speed and at low speed?

 

[Daggar]

I didn't have time to read through everything thouroughly this morning but but one of the things that caught my eye was the pic showing the high/low pressure areas over the car. I have to wonder how and where and inducted cowl moves those high pressure areas along the length of the car.

 

[srothfuss]

Since there is high pressure at / near the cowl area the air is forced through the cowl induction into the engine bay. Probably more useful on a carbed car than on an EFI since EFI is drawing air only from the fender well.

 

[87'GTstang]

Since there is high pressure at / near the cowl area the air is forced through the cowl induction into the engine bay. Probably more useful on a carbed car than on an EFI since EFI is drawing air only from the fender well.

Well if nothing else it helps with those hot spots in the engine bay and cools some things down. Plus, they do have EFI ram-air setups out there to take full advantage of it if one wants.

 

[srothfuss]

True, but the discussion was related to the cooling system, not air cooling the engine. I can understand getting fresh air into the engine bay to cool off the motor. But (as the link stated) the high pressure behind the radiator causes cooling problems in our cars.

 

[ninety15.0]

good post...i like how that paul guy took a very systematic way of explaining all aspects of the cooling system. had some good info for cooling improvements. On that note...i took off that "snow shield" plastic piece under my radiator crossmember and i think it may have an adverse effect on the cooling in my car. I took it off cuz it was all warped and looked like **** but now that i think about it im sure it served a purpose as part of the cooling system. let me know what you guys think about that...

 

[Daggar]

Here's a question for ya. If the top of the car is predominantly low (with the exception of the area directly behind the cowl) pressure and the area beneath the car is predominantly high pressure then where the hell is the air that DOES get through the radiator going? I guess the question is: Where are the high/low pressure areas under the hood? If the area just beneath the rear of the cowl (inside the engine bay) is a low pressure area and the area infront of the radiator is a low pressure area, then where exactly is the incoming air volume exiting?

 

[Michael Yount]

Most cars have a device similar to the 'snow shield' as you refer to it. The aerodynamics of getting air across the radiator at speed have a great deal to do with how you get air OUT of the engine compartment once it's gotten in by passing over the radiator. That air dam creates an area of low pressure below and behind the radiator. It's this low pressure area which 'pulls' air out of the engine compartment allowing air to freely cross the radiator as you're moving. The air dam was an integral design feature of the Mustang's cooling system helping radiator air flow at speed.

My Volvo has a similar device -- but it looks more like a splash pan (it also serves that function). It completely seals off the area starting just under the radiator - from frame rail to frame rail -- all the way back past the steering rack to the cross member. This serves the same purpose as your plastic air dam -- creating low pressure below the engine compartment so air that's passed over the radiator will exit the compartment.

The aero effects of cowls and placement are complex as well. While there is an area of high pressure (at speed) right at the base of the windshield, most Stang cowl hoods that I've seen don't have the cowl extending back quite far enough to take advantage of that. Look at the NASCAR induction systems or the old Z28 cowl hoods for examples that tap into the high pressure area at the base of the hood. Tape a few pieces of light-weight ribbon to the trailing edge of your cowl and see which way air is flowing at different speeds. Try that experiment with the air dam on and off at higher speeds. Depending on what your air dam situation is, I believe it's possible to use a cowl to pull air into the compartment (not really useful on an efi car -- might be helpful to bring cold air to a carb) or to allow hot air to exit the engine compartment.

 

[Michael Yount]

The other thing I'd add looking at Paul's excellent post is that many of the racer's he's pictured duct their cooling air (front rad) in a way that they're also creating downforce with it. Look closely at the cars - - they pull cooling air in down low, and exit it mid hood - but almost always with a curved surface exit -- it forms an inverted wing. As long as they have to have the air flowing across the rad, they're trying to achieve some down force with it too.

Most of the aero features pictured are designed to simply keep the cars from flying at the 200+ mph speeds they'll achieve. A car, unless you design arounnd it, is shaped pretty much like an airplane wing. All the 'vents' are there to vent high pressure from under the car -- to keep too much pressure from building under the car and launching it a la the Mercedes racers at Le Mans a few years ago.

 

[Daggar]

Tape a few pieces of light-weight ribbon to the trailing edge of your cowl and see which way air is flowing at different speeds. Try that experiment with the air dam on and off at higher speeds. Depending on what your air dam situation is, I believe it's possible to use a cowl to pull air into the compartment (not really useful on an efi car -- might be helpful to bring cold air to a carb) or to allow hot air to exit the engine compartment.

I did this VERY thing this morning thinking exactly as I think you are. The "ribbon" is approximately 4 inches in length. At the end of my drive, the tail of this ribbon was securely sucked down into the space between the firewall and the underside end of hood. So air is definitely being forced downward into the engine where the rear of the hood meets up with the body of the car. What I don't know yet, is which direction the air is traveling at the opening that are cut into indcucted cowl area (air at those opening may be traveling out of the bay as opposed to in). I'll have to put a shorter ribbon directly over those cutouts (these are teh screened openings in my Cervinis hood) to see if air is traveling is the same or opposite direction.

Did I explain that well enough?

 

[Michael Yount]

I understand the piece you've already tested -- back of the cowl. I don't have a clue what you're talking about with the other openings, where they are, etc. Probably 'cause I'm not as versant on Stang bits and pieces, Cervani hoods and such. A picture would help me - probably not necessary for the rest.

 

[Sicarius428]

Great article. Damn i wanted to mount an oil cooler but with the A/C in front of the radiator I don't wanna stress my cooling any more than it is. Any suggestions?
Kevin

 

[Daggar]

Here you can see the ribbon I stuck to the cowl. You can also clearly see where the ribbon was sucked into the space between the rear of the hood and firewall. This angle is from inside the car looking forward with the hood closed.

_________________________________________________________________________

Here you can see the screened openings that I'm talking about. It appears that airflow might be traveling in the opposite direction through these openings. Refer to the first pisture and look at the bend in the ribbon where it goes "over" the hole. This angle is from engine compartment looiking towards the rear of the car with the hood open.


_________________________________________________________________________

Here is just a closeup of the screened opening through which, you can see the ribbon that I put on the cowl. You also get a little better look at how the ribbon seems to be being pushed away from the cowl openings and draw into the space between the hood and the firewall, all at the same time.

 

[srothfuss]

I would be interested to see what the air is doing at the base of your windshield (where the glass butts up to the cowl screen)

 

[88GT17MA]

I figure once you duct everything off, its going to create a heat trap in a way.

I was thinking of using heat extractors, but putting small scoops in front of them (using the incoming air as a drive force) to help carry the hot air inside the engine bay out of the heat extractors.

so many possibilities, but which are actually correct and worthwhile

 

[Daggar]

I figure once you duct everything off, its going to create a heat trap in a way.

I was thinking of using heat extractors, but putting small scoops in front of them (using the incoming air as a drive force) to help carry the hot air inside the engine bay out of the heat extractors.

so many possibilities, but which are actually correct and worthwhile

Who knows... I wouldn't be upset at all if air were being forced into the back of the cowl through every opening. That happens to be right where the Kenne Bell blower casing sits. I figure that the more cool air is moving around in that area, the better off I'd be.

 

[88GT17MA]

Ya your right on that, Im worried Im going to have crazy engine temps with my turbo setup, looking for anything to keep cool.

 

[strokedandblown]

Ya your right on that, Im worried Im going to have crazy engine temps with my turbo setup, looking for anything to keep cool.

i cant even imagine the heat that would be put off from a turbo my car is like an ez bake oven after 25 min of driving. when its cold out side, the air comming out of those screens as seen above in my cowl, fogs up the window on the outside, so i know that the air is getting sucked in by my chin spoiler and shot out through those holes, or atleast this is what i hope is happening..

 

[srothfuss]

The 5.0L engine already produces a lot of heat (an oil cooler is a neat idea.) Maybe tomorrow morning on my last drive of the season I will do some ribon testing on the highway to see where the wind goes on my car....


It would be interesting to also do an electric fan vs waterpump fan test back to back to see if the electric really controls the temps better on the highway.