2000 Grand Marquis Air Deflector: Aerodynamics Anyone?

[IPreferDIY]

So I was following a thread about putting a Volvo lower valence on an ‘82 box Merc (http://www.grandmarq.net/vb/showthre...-lower-valence). Initially it was about what would look good. Then the issue of aerodynamics came up.

My 2000 Grand Marquis (a hand-me-down that has been a gift that keeps on giving) actually came with a pissy little air deflector under the rad to improve aerodynamics. I had previously seen someone comment that it doesn’t really do all that much. (The details are in the other thread.) If the deflector can be improved within the bounds of my laziness and cheapness, I would like to give it a try.

I have attached a couple of photos showing how the air that gets through the outer lower parts of the front bumper cover gets deflected into the rad. I didn’t see any way of improving on the bumper cover design, though I would be open to suggestions. I have also attached a photo of the air deflector under the rad, which should be easy enough to enlarge in some way if it would be worthwhile.

One idea that came to mind was to attach some thick but flexible material to the existing deflector. I’m thinking something like the stuff that's used in refrigerated warehouses to cover entrances but that still allows forklifts to drive through. Something like this would seem to give a fighting chance to any small animal that might find its way under my car, and it would also prevent me from dragging any dead ones.

Would I be wasting my time with this? If not, any other suggestions?

P.S. I probably should have taken a photo of the entire bumper cover at close to ground level, so in its place I just grabbed a photo from the internet apparently showing a 2000 Grand Marquis actually being driven.

[IPreferDIY]

From what I've seen so far, the air deflector is probably serving the primary purpose of creating a high pressure area in front of the rad and a low pressure area behind the rad to improve air flow through the rad. It's hard to imagine that the primary purpose of the deflector was aerodynamics, but there apparently could be some small contribution to aerodynamics. Based on what I've seen so far, adding to the deflector would create a more significant "air dam", which is apparently the next best thing to sealing up the underside of a car (though probably a distant second).

Of all the stuff I致e read so far, here痴 a link that provides the best basic introduction to car aerodynamics:

http://www.gmecca.com/byorc/dtipsaerodynamics.html

While I was in the process of looking at vinyl and plastic products at home renovation stores, I ended up stumbling across some 1/4 inch rubber mat material in Princess Auto (apparently the Canadian equivalent of Harbor Freight in the U.S.). The deflector is about three feet wide and extends down two inches, leaving about 7.5 inches to the ground. I知 figuring my first trial will be with an extra four inches. I知 going to use a strip of aluminum flat bar when bolting the rubber to the deflector, and I知 going to use another strip under the deflector bolts for good measure.

Whenever I get around to changing my rear stabilizer bar bushings and links (and try my hand at flushing my brake fluid), I知 also going to adjust the air suspension height to give my car a bit of a rake. For the sake of approaching this scientifically, I値l do one aerodynamic thing at a time.

Since I知 going to be drilling the deflector, I知 interested in picking up a spare and related hardware in good condition for cheap. If someone in the GTA stumbles onto one, please let me know.

[gadget73]

Anything you can do to smooth the airflow under the car is a help. The topside is probably not that terrible, but if you look at all the various bits hanging down and the hollow areas for wind to catch on the bottom side, you can see why smoothing that out helps. If you could put a big smooth pan from the bottom side of the front bumper all the way back to the firewall, sealing up as much as possible, it should help with mileage. There is only so much you can do and retain proper suspension travel and whatnot though.

[IPreferDIY]

Based on what I saw, the only thing that was worthwhile for me to do (considering how cheap and lazy I am) was extending the air deflector into an air dam. I finished this today, with some interesting results. I hadn't realized how much less the ground clearance would be with the car on level ground, so the rubber piece I put on the air deflector is at least an inch too long and drags on the ground. I'm not sure if I'll bother cutting it or let it wear down on its own.

My initial impression is that the air dam is reducing the air getting under the car and thereby removing some 'buoyancy'. I've seen at least one person refer to a "floaty ride", and what I experienced seemed to be a lessening of such 'floatiness'. My car also seemed to have less drag in the sense of rolling farther with my foot off the gas than it used to. Then again, these things could be something like a placebo effect, or I'm just imagining things. Only time will tell. One thing that doesn't seem to have improved significantly was cooling. My temperature gauge is at the same spot it always is, though one day I'll try my code reader/scanner to get the actual coolant temperature.

[SVT98t]

Fyi the Mustang Mach1 chin spoiler is a direct bolt on to our cars.
I'm getting one this weekend.

-ryan s.

[IPreferDIY]

Fyi the Mustang Mach1 chin spoiler is a direct bolt on to our cars.
I'm getting one this weekend.

-ryan s.

That would probably look good on mine in theory, but the warped spots on the bottom of my bumper cover would probably make it look like crap. And I wouldn't be willing to pay more than $20 for one. Looking forward to your photos though.

I took some photos of my setup after cutting off a bit of the rubber. The rubber will probably still drag a bit when the car is on level ground, but I can live with that. I'm planning on getting another strip of aluminum flat bar for the backside of the rubber. I used a strip of rubber to lessen the warps in the plastic deflector, but aluminum would be better. You can get it cheap at Metal Supermarkets, especially if it's on the leftovers shelf.

[cld783]

when i first looked i thought you had a "deflector" on the rear. i was really confused as to why that would help lol

[IPreferDIY]

when i first looked i thought you had a "deflector" on the rear. i was really confused as to why that would help lol

Ya, that would seem to defeat the purpose. What I'm thinking of doing with the rear is using something to cover the space between the bottom of the trunk and the rear bumper cover. I'm figuring I should be able to cut up a piece of vinyl siding, use the bumper cover screws to secure the rear edge, and use wires to suspend the front edge from something so it's tight against the rear edge of the bottom of the trunk.

[IPreferDIY]

Just thought I'd provide an update regarding the air dam in case anyone might ever be interested in trying this. (I've been too lazy to install the siding I bought for the ass end.) Apart from the other effects I noticed -- to which I will add having to use the brakes more until I got used to rolling more after taking my foot off the gas -- another one was finding my comfortable highway cruising speed to be ~10km/h higher. When I'm going ~110+ km/h, it feels the same way it used to feel at ~100+ km/h. During warmer weather, I had occasionally gone ~120+ km/h and maybe even as high as ~130+ km/h once or twice, but getting to ~120km/hr in colder weather has resulted in a vibration that feels like a wheel balance issue. My wheels were balanced the last time they were rotated, so I'm figuring the cold is causing some kind of turbulence issue by stiffening the air dam and/or making the air a little more dense.

BTW, if you avoid doing things that attract attention, you won't want to try this. I can literally see people (both pedestrians and other drivers) looking at the bottom of my car and wondering WTF?. Just the other day, someone was honking at me and pulled up beside me. When I lowered the passenger window, he said "You've got something under your car."

[sly]

Yeah... it's called aerodynamics

[IPreferDIY]

Ended up giving my car a bit of a rake in the summer/fall of 2014:



(My car was actually filthy when I took that photo, but luckily you probably can't tell.)

I didn't really notice anything in conjunction with the air dam; but when I took the air dam off for winter, some of the benefits from the air dam persisted. I ended up not putting the air dam back on for one reason or another (mostly from waiting to do my J-mod and whatnot), and I guess it's a bit late in the year to do it now.

At least I managed to finally get around to putting a piece of vinyl siding in the space between the back of the trunk and the rear bumper cover:



There's some kind of cross-member up there, and I just used pieces of 14 gauge solid conductor house wire to suspend the vinyl and secure it against the bottom of the trunk. The only concern I had was that maybe the design was already optimized for airflow, kind of like the way a pickup truck is better aerodynamically with the tailgate up. But, I experienced a noticeable, albeit small, improvement. I'd have to say it's definitely reducing drag to some degree. One way the benefit showed itself was while I was going up a steep hill after leaving my father's cottage. Normally I speed up at the bottom to make it easier to get to the top, and this time I could feel that the car crested the top of the hill just a wee bit easier from having less drag. I also seem to hear less noise while on the highway. An added benefit should be bringing a stop to my bumper rot.