Okay, I've been looking around a lot and found a few things:
http://www.tprmag.com/issue/13/13_aerodynamics.shtml

^^^First page shows how to resolve the parachute effect of a rear bumper/kit. Second page "Release the Beast" touches on air escaping the engine bay and how vents on the hood too far back suck air in causing more drag and pressure.

When I hit a stalemate, I included "forum" in my searches and found this:
http://www.automotiveforums.com/vbulletin/t490030.html

^^^^Now apparently they do not practice the strict grammar we follow here, so bear with the poor spelling, absence of commas and new paragraphs Some really good ideas with both pros and cons.

I atleast found in my research that the plates infront of my wheels was actually for reducing wheel drag. Now I'm curious if once my kit is installed, will it be low enough to have the same effect, or should i re-install them??

[edit] another discussion: http://www.eng-tips.com/viewthread.c...=138350&page=1 and another one: http://www.ultimatecarpage.com/forum...ad.php?t=10526
here they discuss lowering http://www.eng-tips.com/viewthread.c...=111754&page=1 [/]


Why don't we get some G owners to take pics of their underbody and we can create a simplified version???

 

I just bought 2 rolls of 30"x80"x0.060 polycarbonate on ebay shipped $65. I plan on doing the front area for now, then adding the rear bumper area whenever the RedlineMax kit is finished. I also plan on adding diffusers in the rear.

Now just to figure how to attach it to the front with a fiberglass bumper and easily remove for maintenace??

 

If you got a stillen front lip, I would attach it to that and have mounting screws instead of double sided tape. That way the front could be taken off easily.

Oh wait, you have a 6th gen, nevermind.

 

A company called Veypor makes a couple of motorcycle/car instruments, and one of them - the VR2 - can supposedly measure Drag Coefficient. This looks like a very busy gadget, with extended data logging...

http://www.veypor.com/vr2.html

" Drag Coefficient
The drag coefficient measurement is an industry first and only available on the VR2. The VR2 measures your coefficient of drag and rolling resistance automatically and without a wind tunnel, all you need is a flat piece of road a couple hundred feet long. Follow the simple on screen steps to calculate an accurate coefficient of friction for your vehicle in only a few minutes. Then make modifications like removing side mirrors, adjusting riding position, bodywork, etc to see how it improves your aerodynamics. It is a fact that to increase top speed it is more effective to reduce your drag coefficient than to increase horsepower."

Also, there was recently a post by somebody that built a nice dual-exhaust system for a 4th Gen, and the picture showed the underneath of the rear of the car very well, showing all those open areas under the car. A flat panel under there has gotta help drag...

 

great find. $320? I suppose thats not too bad if it actually works. Okay who wants to chip in and share this ****?

 

What do you think of the way it connects to a car - especially the speed sensor and magnet? That seems kinda crude, and it would have to mount on a rear wheel, right? The RPM hookup seems conventional, but magnets? That worries me...

Oh, here's the picture of the bottom of a Max: http://memimage.cardomain.net/member...811_7_full.jpg

Looks like a flat plate or two could really do some good here.....

 

Seems that VR2 is just a combination data logger and accelerometer. Even with the external sensors I'm guessing it'll have the same problems sampling from our ECU's that other loggers suffer from. It can handle 125 samples/sec at 25-50Hz way beyond out 8bit ECU's put out.

 

Maybe I misread their PDF manual, but I thought the units were stand-alone except for RPM connection directly to ignition ???

Since there is a lot of motorcycle functions built into these two models, I see they can have heads-up display ( ! ) and stand-alone lap timers. The HUD display would be fun, but I wonder if you could set up your own 1/4 mile track with accurate timing using the lap timer?

Anyway, the drag coefficient calculations were what caught my attention - some Harly/Buell racers mentioned this gadget to me.

Something new.... And I'm still building ABS panels for the front and rear of my Max this spring...

 

anyone see this in the 4th gen forums yet?
http://forums.maxima.org/showthread.php?t=459071

 

doesn't matter. just contraban... nothing to see here. move along.

 

I just ordered two 48"x96" sheets of 1/8" black ABS ($80.64) from an on-line supplier. Total costs with shipping($43.69),including a quart of welding solvent for $33.00, was $157.33.

I already purchased a couple of 1500 watt heat guns from Harbor Freight, so when materials get to my house, I'm ready to cut, shape, and attach.

Now I can create a good cold-air intake in the front, underneath the car. I'll take digital photos as I do this, just in case something useful comes out of the project.

 

Now there is a guy who is taking this seriously. I have quite a bit of 1/8" lexan left over I may just use it. I was going to get some 1/16" abs but not sure if it is thick enough to keep from flexing at higher speeds.

 

After reading the articles you posted, and some other related information, and looking under my max with a critical eye, I'm convinced there are some gains to be made here. Kydex is very expensive - two 4'x8' sheets are $346.88 before shipping, so since I have used a lot of ABS to build showbots in the past, I respect how tough and form-able the stuff can be. (I ordered from InterstatePlastics.com)

Besides, if I screw up something, at least I won't blow another engine! lol

 

I've seen a 2mpg improvement from the rear belly at freeway speeds. But the design is ghetto. I took it off because it needs to be improved.



This car is a 99 altima

 

[QUOTE=Brushedpewter]I've seen a 2mpg improvement from the rear belly at freeway speeds. But the design is ghetto. I took it off because it needs to be improved./QUOTE]


Interesting! Did you make this ?? What's the story on the panel, and did you try a front panel too?

?? ??

 

[QUOTE=grey99max]Yes I made it. I made all this for fuel economy, not power. Of course I made the front panel too. Ghetto but very functional.

BEFORE right side



AFTER left side



Now I'm getting high 27's/low 28's mpg for 60% city/40% freeway with no rear belly
I have other mpg mods but it has nothing to do with this thread.

 

I would love to see some better pics of exactly your setup (i.e. with the car up on a lift). I usually slip a 10-spot to my local mechanic to put the car on a lift for 5 minutes so I can take pics. You should do the same!

 

The belly is off so I can modify it so the rear end is stock. The front 2 trays are as you see in the pics. There is no point to take pics. My design is bad. I'm sure some guys here will have better designs with ABS and carbon fiber.

Once i'm done with the aero mods I will begin with fuel tuning. I'm trying to get 35mpg mixed driving. So far I accomplished 30.95mpg for mixed driving.

 

^^^ you should add the wheel difusers. they came stock on my 04. look like mini muflaps on the wrong side. one of the links in this thread explains their benefit. the one with the front bumper "pans" included them.

Wish it was warmer. my oem "under engine cover" is unusable with my FG bumper. I have the material, just need to measure and figure how to secure it.

 

Negative. Lots of new cars have it but it's just a band aid. What it does is deflect the air from the tires but it acts like a wall to the air. What I did is just made the air go under my car instead of deflacting it. The air still hits my tires but at least my tire well doesn't act like a parachute anymore.

 

right on brushed pewter.

your wheels generate the most drag on a car so they place an air dam to divert the laminar flow around the tires as much as they can ( i.e. fender flare functionality, stillen front lip kit). another way to make that flow efficient is to divert it to the brakes, at least then the flow is usefull.
Ferrari 308- .28 coef of drag

lowered vehicle= lower coefficient of drag
it is all common sense stuff, im not telling you guys anything you don't know already.

 

Actually the front deflector is "BRILLIANT"... jk, but you're on the right path.

My plan is to replace everything under the front side of my '99 with one molded piece, incorporating "air dams" for the front tires, and an access panel for oil changes, and a left-hand air scoop for the modified Ingen whose filter is just in front of the tranny.

ABS plastic is easy to shape after it's heated, so I plan to include some of the ideas seen under my 2004 Maxima's front and see what happens.

The rear panel will probably address the rear tires as well, but mostly I'm going to try a solid sheet enclosing most of the open areas in the back, from the bumper to the body pan in front of the rear axle.

I'm surprised at how far you have come in improving fuel economy. Kudos. Less drag = economy AND better speed/acceleration.

 

i know what it does, that's why i suggested it. so how do you know you wouldn't benefit from it? yours look more exposed than mine w/o my one. and how did you stop the parachute effect?

oh and our 04 Cd is also .28 stock

grey99max, you're not going to do the same for your 04? our front cover is not smooth at all and doesn't cover much. I'm also pondering on how the air entering the engine bay is supposed t escaoe if we cover alot there. Maybe it will hit our cover causing good downforce for the front drive wheels and escape once it ends....

 

Because it acts as a band aid. Everybody knows this. You can easily fix it if you put someting that will make the air go around the tire and not get stuck. Take the F117 front, flip it around and put it in front of your tire.

You're talking about a newer car. Of course it's Cd will be lower than my 7 year old car. All I have to do is modify my belly's design and lower my car. I could probably achieve .26

I stopped the air from hitting the front tirewell by mounting the 2 undertrays, didn't you see the pics?

 

I'd like to use ABS but i'm broke. I'd rather use the money to tune the motor for a better a/f ratio for even better fuel economy. The concept of avoiding air hitting the tire is easy and not making it stay there. The solid sheet is good but I ran into problems where there would still be some air trapped and at higher speeds would pull the belly down. The simple solution is make some holes in the belly when it curves back to the bumper to let the air out. My goal is 40mpg at 65mph. 40mpg can be achieved but I want it at 65mph because I don't want to block any cars on the freeway.

 

how do you know you stopped the air? you have plenty of tire exposed. I'm sure you diverted more than stock, but how do you kow a dam will not divert more? even if better shaped than just a plate.
as far as my tires, my front body kit is lower than my previous air dams. anything i place there now will cause the same amount of drag or get scraped off.

and don't get me wrong. I've already planned on doing all this before this thread began. I already have 2 sheets of 30"x80" polycarbonate for my front and rear. just trying to get the best from everyone for the greatest results. also need my kit to be finished.

for the underbody, i've also considered the holes/vents, but you really need to study the difference of air pressure above and below your underbody plate. you could very well suck air up/in from the road through your holes causing more drag. I really want to look at the G35 underbody to get some ideas.

(also I was replying to the above statement about the Ferrari since it is the same as mine)

 

Nope, I'm not hacking on the '04 - just the '99 GXE. One disaster at a time is my motto.

 

I'll bet the "bulging belly" is actually caused by the high airflow across the solid sheet, kinda like an upside-down aircraft wing. In that case, holes won't help, but bracing the sheet on the top side should hold it. Hummm - does this mean a good panel will create substantial downforce?

I'm planning on bracing any wide unsupported area - by attaching a panel brace that's not in the airstream. If there's room, a L-shaped brace made of ABS (or aluminum) going across open areas can screw/bolt onto the main sheet on the top side, out of the airstream.

Soon.....

 

I haven't stopped the air. It does hit my tire. Due to my budget this is all I can do now. It's still better than stock and that's all that matters right now.

I've seen what air does to the belly pan so I will modify it to have least wind resistence. I do have a good idea how to improve it by looking at other cars.

 

Looks like my plastic "is in the mail"......



Invoice #1594
STATUS: shipped
Updated: 3/9/2006 5:06:57 PM Print this page
Quantity | Item Status Price Total 2
ABS Sheet General Purpose (Sheet, Black, 0.125 in) 48in x 96in 3/9/2006 5:06:57 PM shipped $40.32 $80.64
1
Weld-On #1707 3/9/2006 5:06:57 PM shipped $33.00 $33.00
Shipping Address
Harold W Bragdon
4401 Holly Lane
Topeka, KS 66604

SubTotal $113.64
Shipping $43.69
Total $157.33
Notes
3/9/2006 5:07:28 PM • mike.bogue
order shipped 3/8/06

 

Guys, check out this article:

http://www.tprmag.com/issue/13/13_aerodynamics.shtml

 

Update - I've got the front pan cut out and I'm trying to install enough speed nuts to keep everything together, while molding in front-tire air deflectors and the air scoop for the bottom-mounted Ingen intake. I need to also include a removable panel for oil and filter changes. I'm taking digital photos as I go......

The ABS plastic is real easy to shape if you heat it with a hot-air gun set to low speed. I'm building this from black 1/8" ABS with the pebble side down.

 

anyone take this any further??

 

Umm... it's on my (infinitely long) to-do list. Does that count?

 

no b/c i have already done that much

 

well with gas sky high...

here are some links to improving aerodynamics. the pages have even more links inside them. I hope to make an under body cover for at least the front bumper. anyone still have one attached?


http://www.diyelectriccar.com/forums...0488#post10488

http://www.tprmag.com/issue/13/13_aerodynamics.shtml

http://www.team-integra.net/forum/di...0&ThreadPage=1
http://www.team-integra.net/forum/di...0&ThreadPage=9

http://forums.turbobricks.com/showthread.php?p=1778821

http://www.autospeed.com/cms/A_107773/article.html
http://www.autospeed.com/cms/A_2455/article.html
http://www.autospeed.com/cms/A_2456/article.html

i'm just stuck on how to attach the panels. one site said to use aluminum tape. others said dzu fasteners. i want easy access for oil changes. maybe i'll stop shy of the oil pan.

another underbody
http://forums.evolutionm.net/showthr...=353319&page=2

 

Excellent sites!!! Lots of good information. When I built my splitter, I initially was going to make an entire front undertray that extended forward to a splitter. But after careful consideration, i decided on a splitter. There is decent factory undertrays in the front, although the fasteners to mine broke, so its not in place at the moment.

 

and if you have a bumper like i do, then it's too small to reattach. i have a 2" lip on my fiberglass bumper, but don't really want to drill holes for fasteners. plus it's raised in the middle and not flat all around.

and i'm concerned about the air entering the lower grille slamming into it.

ideally you want air going around the car, but need some on the radiator to cool it.

 

it looked like grey had some pieces done, but no pics so . certainly looks like a good idea, the stock panels suck pretty bad. although with what brushedpewter was saying about his bowing, downforce doesnt exactly help you mileage, putting extra load/friction on the tires is definitely not good. but i would bet that he wasnt getting more than 10-15 lbs downforce at the most, so i guess not really a problem

 

I always wondered if I could/should put a cover at the bottom like the G on my car.

One negative is that I have to remove all 10-15 bolts of the shield/cover to change the oil on the G which is a pain. I don't think the one off the G will fit but a custom will seems very easy to add to the underbody of the 4th/5th gen.