Air flow over engine

[Austexican]

I was viewing a video from Jay Leno's Garage about a Superformance Coupe that pointed out that the nose of the car incorporated a fixture that drew air from the top of the radiator air inlet into a duct that forced air over the engine. Obviously, this feature only works when the car is in forward motion because it does not partake of the airflow created by the radiator fan. I was wondering whether any Factory Five owners have attempted a similar fabrication. I live in Texas and the heat waves rippling up from my hood can assume psychedelic dimensions!

I think it would be fairly simple to form a piece of aluminum sheet and bond it with epoxy to the underside of the nose. I don't really want a line of rivets climbing up that sleek feature. What do you think?

[riptide motorsport]

My coupe never overheated even with the a/c on ever in 100 degree Florida heat.....

[Austexican]

My coupe never overheated even with the a/c on ever in 100 degree Florida heat.....

You have my congratulations on your car's ability to perform in extreme weather conditions. Do you have a recommendation for me or do you just want to claim bragging rights? My thought was that this forum was intended to provide suggestions and recommendations for overcoming performance issues.

[Fluge]

I also thought that was a neat modification but not easily done on our cars.

I remember seeing that someone (Ryan_W) ??? Installed another fan on the back of X right behind the rad aluminum ducting. The intent is to suck air in from under the car into the engine bay.

Others have installed dual fans, added fan shrouds or larger rads.

Marc

[tirod]

Getting air into the compartment has also been done with a scoop or spoiler under the car, to direct flow upward to the motor. The follow on is that once directed at the motor, where does it go? In conventional designs, very little is done to improve flow over the motor. It basically muddles around under the hood and finally slips out past the firewall. On the Coupe the fender openings appear to help with that function, but as one posted in video of tuft testing at speed, it seemed that air was going into the vents, not out.

The next opening back, unintentionally, is the shift boot, and plenty have remarked about sealing it to keep hot air out of the cabin. From there it moves into the rear cavity around the third member, and then spills out under the tail. In 40 years of messing and studying automotives, tho, I've yet to read about any effective enhancements to promote flow beyond sealing it all off with an undertray to reduce drag voids and increase downforce. The engine - up to a point - is allowed to get as hot as it will and then operate at that temp for the duration. We just insulate against it. One reason is that scooping lots of air and forcing thru the engine bay is counterproductive to reducing overall drag. The Coupe was designed to minimize that, and reduce drag by having an overall more aerodynamic shape. Not less.

I would say that if Superformance thought they needed to add a scoop to get more air to the engine, that they were addressing some other weakness in their execution of the body shape. The original Coupes didn't have much finesse about engine bay cooling, they ran them in 24 hour endurance racing at speeds in excess of 185mph. There were other issues that got their attention - like increasing the airflow thru the cabin for the driver. With the better aerodynamic shape, the Coupe tends to have less flow in the closed cabin than, say, a Roadster, which in the unintended consequence of lower Cd.

One item that is obvious but relatively unspoken - the radiator doesn't exhaust hot air into the engine bay. That alone is a significant net advantage over most cars which means the total amount of heat is less than normal.

That should add more data to the discussion, but the conclusion is still pretty much the same. It's not worth the effort unless their is some other significant reason - usually caused by some other modification, like, a full undertray that seals off the engine bay.

[Pike]

tirod,

I'm intrigue by your comments. Do you have any reference material regarding an undertray? I intend to build a coupe later this year and I see many comments on the heat that is generated within the cabin. Do you know of anyone who has done this "undertray" treatment even if it's just at the firewall to the back end? I hope to minimize the heat by applying some material to the foot boxes and other areas near the firewall. I was thinking that some sort of undertray that may have some diffusers built in to direct flow away from the trans tunnel. Any ideas?

[Cobraphx]

I watched that episode again today. I see the duct you are talking about, and I like that idea. I'm doing something similar on my car.

The owner states that the duct is designed to direct cool air to the carbs. Makes great sense.

It isn't there necessarily to reduce the heat under the hood. He mentions several times that with the windows up even in the winter it becomes a sauna inside without the footbox ducts or the A/C. So it doesn't seem that the duct is anymore than a fresh air intake for the induction system.

[Austexican]

You make some interesting points, Tirod. This link will take you to a photo of CSX2287 which shows two attachments in the side vent.
http://www.flickr.com/photos/75061943@N06/12396530034/in/set-72157640699696233
Pete Brock says one was for the air jacks and the other was for hooking up to a source of cool water. The Shelby team were encountering overheating problems when the car was in the pits. Was a radiator fan installed in the car? The radiator inlet is very small in area in order to obtain a lower drag coefficient. I noticed on one hot day that my coupe was registering a lower coolant temperature at 100 mph than it did at 70 mph. Clearly the small inlet and low profile radiator are marginal at high ambient temperatures and low speeds. When I return to the garage after a run on a hot day, I open the nose and turn on a high volume floor level shop fan.

[riptide motorsport]

You have my congratulations on your car's ability to perform in extreme weather conditions. Do you have a recommendation for me or do you just want to claim bragging rights? My thought was that this forum was intended to provide suggestions and recommendations for overcoming performance issues.

Yes, as a matter of fact I do have a couple of recommendations for you!!!!

[loeffler1]

Now before you guys start duking it out, you don't mention a very important fact. Are you having over heating problems or do you just not like the psychedelic patterns? If you are not overheating then I would assume all is well. If you are overheating then you have some options, bigger rad, shroud, larger fan etc. What about the possibility of two electric fans mounted just behind the side vents that you can operate manually that will push the hot air out of the engine compartment? Last of all what are you doing driving 100 MPH on public roads??? Do you want to get all of us in trouble??

[CraigS]

Lets get this back on track. The idea of the duct on that Superformance cpe (and it may only be that one) was to get cold air to the carbs. that's it. It had nothing to do w/ overheating or not overheating the engine. As Tirod mentioned, and this is a big advantage over the roadster, the hot air from the coupe radiator is not exhausted into the engine compartment. However, there is still plenty of hot air off the track surface, flowing past the headers, etc that does find it's way into the engine compartment. The duct is a way to ensure that only the coldest air possible (ambient from 15 inches or so above the ground) goes to the carbs. I think it's a great idea. It might be simpler though to do a reverse scoup on the hood and grab colder air from the high pressure area at the base of the windshield. See the red number 79 on the FFR website. You have to wait 15 seconds per car as it cycles through to the 79.
https://www.factoryfive.com/kits/type-65-coupe/
This way you re-shape the hood and have some type of turkey pan around the carbs that seals to the underside of the hood w/ foam. No rivets showing.
http://www.summitracing.com/parts/MOR-97070/
Something like this only larger to allow a filter also and w/ the windshield end opened up.

[tirod]

Cars not moving in traffic require fans. Once over 30mph most vehicles have enough air pressure on the front of the radiator to get flow thru in sufficient quantity to cool the motor. The next item is surface area of the radiator, I don't think F5's have inadequate cooling in that regard. The fan is next, proper shrouding and a rated CFM over 2,500 should do. We generally get all that.

So, if it's overheating - which means the needle goes in the red and you are seeing actual temps over 235 degrees, the next item to addressing is adequate water pump flow, then, head gasket orientation so that the passage holes aren't short circuiting the back of the block.

In all of that, what most people call "overheating" is NORMAL. A 16 pound cap on a motor running at 195 degrees give it an effective boiling temperature of over 235, and at that temp it still may not be creating bubbles of steam in the system. Aluminum heads run cooler, too.

What someone sees as heat waves coming off the motor under 235 degrees would be within operating guidelines. Sure there's heat coming off the motor - it's hot. Exhaust headers can reach 1,200 degrees on sustained full throttle. The water cooled block far less.

Buy an IR temp gun and start shooting temps under the hood of the daily driver. It's a lot different than we think.

As for directing cooler air under the hood for the intake system, if it's not directly connected and controlled, fat chance. Open element intakes suck in whatever temperature air is under the hood, and that has been measured to be as high as 180 degrees. Normal seems to be in a range over 125. Ambient on the average day is 72, which is why open element air filters are actually a loser when it comes to accessing truly cold air. There is a reason why the factory air cleaners get their air from in front of the radiator, and slapping an open element filter underhood is throwing out the baby with the bath water.

Undertrays are in the fad phase of motorcar styling right now. The truly effective ones take a lot of money and testing to get right, and are generally used in top tier cars on race tracks where they can fine tune the design they developed in wind tunnel testing. Slapping on a belly pan can help, rear diffusers are much more problematic. The math involved to get them right is more complicated than wing science - because it's in close proximity to the ground rushing by, and the car can raise and lower off the ground as much as six inches in a bump. That can massively destroy the flow - with catastropic results if the nose gets up too high. The car can, has, and will flip. Race video goes back decades showing the negative results. Another difficulty is completely sealing the rear suspension and differential area. A big open void makes it useless.

There's also the major difficulty of getting any of it to be effective at road speeds. Generally, even the trunk spoilers and wings seen on cars won't work effectively under speeds of 100 mph. They are for all intents and purposes bling for the visual effect. A flat undertray from bumper to the front suspension can do more. While documented to help, Honda didn't even bother on the Prius. It adds to underhood heat. At least the Coupe is different in that regard due to the way the radiator is ducted.

Most of the aerodynamic aids, especially undercar, are expensive to develop with extremely small incremental returns for the work. The blessing of the Coupe is that it's shape and size are already a lot more efficient than most, and unless the car is being used for racing, it's a lot of money spent on something that won't help the cockpit heat at all. That goes to interior venting, which the prototype nature of the Coupe lacks, insulation, same, race car interior, etc. It was never meant to be a production car with all the typical luxury fittings we own in America. In that, there are likely much higher priorities that need to be addressed first if the car is to be reasonably accommodating for three season use. Which is a lot longer than the typical May to September run for the Roadster.

[snakebit31]

Yes, as a matter of fact I do have a couple of recommendations for you!!!!


Love it! Did not think your initial comment was out of line at all.

[Pike]

tirod,

Thank you for your comments. I understand that you're saying Austexican's post about getting cool frontal air to the intake via a small wide inlet in front of that coupe is the right idea. I also understand what the coupe was designed for so if you install a modular engine in a coupe, you'd be best to route your air intake either through the main snout of the nose (as the idea of this post), converting the fog lights to intake vents or at least provide an intake near the lower front (if you want to keep the fog lights) to access the cooler air. Since most don't have modular engines, what would be the best way grab that cool air if let's say, you have a stack setup? A turkey pan? Esthetically, it's not great but would be functional and would require some fabrication. I've seen some do it and it's not that bad if done properly. Just wondering since you made a no-nonsense response which in my view was very informative and eye opening. Wish more people didn't mince words when trying to explain things.

A more important question is if you build a coupe and don't have any intention of racing it (maybe a few laps during track days), what are the options to grab cool air for a coupe or is the fact you don't have a race car negate all that worry? I'm just trying to grab my head around the idea of getting cool air in the intake, keeping the engine bay heat to a minimum and keeping the hot air from the engine bay out of the cockpit. I guess if you look at it from a different perspectives...whether your in the engine bay or inside the car, you might approach things a bit differently.

[trichardson]

Yes, as a matter of fact I do have a couple of recommendations for you!!!!

That's funny!

[jkrueger]

Here is what I have found in my experience with my car after one year of driving, track days and racing. On the track my underhood temps are high. Higher than I want them to be. I have found wire looms that were starting to melt that were 8 inches away from the headers. The hood above the headers (8 -12 inches distance) is to hot to touch after coming off the track. My IR thermometer shows that area of the hood to be 140 degrees. My Data logs of intake air temps show temps as high as 126F on day where the outside temp was only 60. Off course this is all on the track where the car sees lots of WOT and rarely is below 3000rpm.

That was my video of the hood side vent tuffs being sucked back into the engine compartment. My theory on that is because there is no air coming into the engine compartment and that there is a low pressure in there relative to the outside. I also have a air dam on my car which helps prevent air from coming into the engine compartment from the front (a trade off for better handling).

My cockpit temps even on the track are not bad at all. Even where the the headers are less then 1/2" from the footbox wall I can't feel any significant heat with my hand. I do have a radiant barrier on the engine side, cheap home depot 1/4" insulation and carpet on the inside. The worse cockpit heat I feel is from the greenhouse effect of the windshield and rear hatch on sunny days. In my opinion that makes the cockpit hotter than the engine compartment. I do have A/C to help battle that and am still planning to put in footbox vents.

As far as engine compartment temps, I plan of getting some louvers made that I will mount on the back side of the radiator outlet duct to scoop some air into the engine compartment. If I can get the engine compartment pressurized enough that air is coming out of the hood side vents then I will put hood vents above the headers to help vent the heat there.

Normal road driving I feel that the underhood temps are not a problem unless the engine is overheating, which mine is not. Even after 30 mins on the track the max water temp is 210F and the oil is about 230F. Driving down the road water temp is 190F. Different engines will obviously react differently (mine is 5.3L chevy "LS")

JC