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Old 10-12-2012, 07:54 PM   #1 (permalink)
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04 Sentra Aeromods

Well, the first round of aeromods on my 2004 Nissan Sentra 1.8S are done. I've finished the full upper grille block, partial lower grille block, front underbody tray, front and rear tire spats, and partial rear underbody tray. Pics and write up below!

NOTE: I don't claim that the way that I did these mods is the best way, or even that great. It was just my method of doing it. Also, I cut and fit most these in the dark and I realized in the morning that some of them don't look very good up close, so I may redo them.

Upper Grille Block:
  1. Find coroplast
  2. Measure the area you want to cover
    (or eyeball it if you are lazy/don't care about it looking as nice as possible).
    Since winter is approaching and it usually doesn't get much above freezing here for the next 4 or 5 months, I've covered the entire upper grille. I'll measure coolant temps once the weather starts to warm up in the late Spring.
  3. Decide on your mounting points/mounting method.
    On the Sentra, there are two separate openings in the upper grille. I used three small screws for each opening to screw the coroplast directly into the plastic grille, with the fourth corner of the grille block under the hood holding it down.
  4. Cut the coroplast according to the measurements you've made.
    You'll likely have to fit it to the opening multiple times and cut small pieces off to get the fit just right. I used scissors and a craft knife to cut mine.
  5. Mount the grille block to the opening.
    Like I said above, I used three small screws for each section to screw the block directly to the grille.
  6. Remove the grille block and paint.
    I painted mine black using spray paint to (almost) match the color of the existing grille.
  7. Once the paint has dried, reattach and test.



Lower Grille Block:

I won't go into as much detail, because it's essentially the same process until you get to mounting method.
  1. Mounting method
    I used the existing gaps in the lower grille and shoved pieces into them. There is probably a better way to do this aerodynamically and looks wise, but KISS engineering is always best in my opinion. I'm open to suggestions on how to do this better.



Front Underbody Tray:
  1. Find coroplast
  2. Measure the area you want to cover
    (or eyeball it if you are lazy/don't care about it looking as nice as possible).
    I couldn't find any large signs that would cover the entire front with one piece (which I admit is optimal and I plan on redoing it when I can find a large sign), so I used multiple small signs and cut them to fit.
  3. Decide on your mounting points/mounting method.
    I used screws to screw the coroplast directly into the plastic of the bumper. Since no one will see this part I didn't worry about painting it.
  4. Cut the coroplast according to the measurements you've made.
    Again, you'll likely have to fit it to the parts you are trying to cover multiple times and cut small pieces off in order to get the fit just right. I used scissors and a craft knife to cut mine.
  5. Mount the coroplast to the bumper.
    Like I said above, I used screws to screw the coroplast into the bumper. The B15 Sentra has a large gap between the plastic of the bumper and the black plastic of the engine skid plate/rock cover. I extended my underbody tray to cover this entire area, which is pretty large.



Front Tire Spats:
  1. Create brace for spats.
    For the front tire spats, I purposefully made the same piece of coroplast that was covering the gap between the bumper and the tire longer than necessary, and bent back about the last inch or so. I created a brace using an extra piece of scrap metal, and bent the brace to the desired angle so that it would hold the coroplast to that angle.
  2. Attach brace.
    I drilled a hole in the brace and coroplast and used a bolt and nut to hold it in place.




Rear Tire Spats:

I like using pre-existing materials as much as possible, so I re-purposed the rear mudguards that come on the Sentra for the rear tire spats.
  1. Remove the rear mudguards.
    There's just a few screws that hold them in. Remove the screws and take off the mudguards.
  2. Flip the mudguards around.
    When you flip the mudguards around, you'll probably have the same epiphany I did: with a little trimming, they would be perfect tire spats. You'll use the left mudguard for the right tire spat, and the right mudguard for the left tire spat.
  3. Measure, mark, cut and get dirty.
    This is the trickiest part. It's really hard to get an exact measurement of where to cut, but when you get down and look at where you attach the spat, you'll see the parts of the mudguard that need to be cut out. I used a Sharpie and marked points to cut, cut them out, tested for fit, and repeated. There's a flat piece of metal that serves as the mounting point for the jack that will be in the way; cut a piece out of the mudguard to go around that. I basically cut most the middle, more flexible part of the mudguard away and left the harder outside plastic intact. I tried my best to follow the lines of the metal of the car.
  4. Attach.
    I drilled two holes in the fender and used nuts and bolts to attach the finished tire spat to the fender.




Partial Rear Underbody Tray:
  1. Find coroplast
  2. Measure the area you want to cover
    (or eyeball it if you are lazy/don't care about it looking as nice as possible).
  3. Decide on your mounting points/mounting method.
    There is a small black box on the left rear side of the Sentra that has some plastic covering. I chose this as a good mounting point because when looking at the underbody, this gap between the black box and the rear bumper was the easiest place for improvement and the front of this black box is connected to a smooth plastic tray. I used two small screws, one in this plastic covering and one in the rear bumper plastic to attach the coroplast.
  4. Cut the coroplast according to the measurements you've made.
  5. Mount the tray.
    Like I said above, I used two small screws to screw the coroplast in.

I ran out of coroplast to finish the rear underbody tray completely, so that's my next project.

This actually leads me to my question: should I make a new tray that extends to the part of the bumper directly behind the tire? You can see the area that I'm talking about on the left side of the picture below.



Anyway, I hope this write up helps. Sorry for the length!

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Old 10-12-2012, 08:10 PM   #2 (permalink)
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For the lower grill block you could just trace out 1 giant piece and zip tie it on

The tray would be more aero sound if it was put inside the lip of the bumpers instead of below plus it would help support it better.
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Old 10-13-2012, 11:44 AM   #3 (permalink)
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Quote:
Originally Posted by Gealii View Post
For the lower grill block you could just trace out 1 giant piece and zip tie it on

The tray would be more aero sound if it was put inside the lip of the bumpers instead of below plus it would help support it better.
Thanks for the recommendations. Does having the lower grille block on the inside vs. the outside make all that much of a difference? I noticed that the pictures you attached have yours zip tied to the inside. Definitely more stealthy that way, which the wife would approve of

I'll have to try moving the front tray from the outside to the inside of the bumper. I don't know why I didn't think of that when I made it... doh.
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Old 10-13-2012, 12:18 PM   #4 (permalink)
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the block being on the inside or outside definitely has been discussed b4

on one side it was said the outside would be better cuz of warm up and being traditionally aero designed

on the other side putting the block on the inside was said to make a pocket of air to be trapped creating the outside block with the air that is unable to escape.

On cars i see blocks as more of helping with warm up times than aero but a block no matter inside or out is more aero than a giant grill opening
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Old 10-13-2012, 05:31 PM   #5 (permalink)
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Quote:
Originally Posted by Gealii View Post
the block being on the inside or outside definitely has been discussed b4

on one side it was said the outside would be better cuz of warm up and being traditionally aero designed

on the other side putting the block on the inside was said to make a pocket of air to be trapped creating the outside block with the air that is unable to escape.

On cars i see blocks as more of helping with warm up times than aero but a block no matter inside or out is more aero than a giant grill opening
Interesting, thanks for noting that. I might try both to see if I notice any difference.

Also, I would show more data and A-B-A testing but I don't have my Ultragauge yet, so when I do I'll put up some real numbers.
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Old 10-20-2012, 01:24 PM   #6 (permalink)
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Quote:
This actually leads me to my question: should I make a new tray that extends to the part of the bumper directly behind the tire? You can see the area that I'm talking about on the left side of the picture below.
Sorry to bring this back up, but does anyone have an answer for my question above? I've got time this weekend and would love to make a new panel if it would be of help.
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Old 10-20-2012, 02:23 PM   #7 (permalink)
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rear spat and rear gap

*the little voice in my head thinks that the rear tire spats will trigger flow separation which will overshoot the actual outer edge of the flap,leading to turbulence of such a degree that you'll risk re-attachment downstream.
If there's any way you could tuft that whole area and get a friend to watch,photograph,or videograph,you could see what's happening there.
If you blended the spat into the rocker panel,as Subaru did with their 1986 XT (Cd 0.29) you could kill any turbulence formation.
*As to the gap behind the rear wheels,yes,seal those areas,after checking out 'diffusers',which you might integrate into your design.These add a premium flow component to the wake area,and later,if you do any boat-tailing,it will pay you extra dividends.
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Old 10-20-2012, 02:44 PM   #8 (permalink)
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Quote:
Originally Posted by aerohead View Post
*the little voice in my head thinks that the rear tire spats will trigger flow separation which will overshoot the actual outer edge of the flap,leading to turbulence of such a degree that you'll risk re-attachment downstream.
If there's any way you could tuft that whole area and get a friend to watch,photograph,or videograph,you could see what's happening there.
If you blended the spat into the rocker panel,as Subaru did with their 1986 XT (Cd 0.29) you could kill any turbulence formation.
*As to the gap behind the rear wheels,yes,seal those areas,after checking out 'diffusers',which you might integrate into your design.These add a premium flow component to the wake area,and later,if you do any boat-tailing,it will pay you extra dividends.
Thanks! I'll try to trim the outer edge of the spats to remedy that and see if I can wrangle up a camera rig to do some tuft testing.

I'll set to work researching more about diffusers and rear aerodynamics. Thanks again for your help.
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Old 10-20-2012, 06:15 PM   #9 (permalink)
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Maybe you could try to boattail the wheel?
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Old 10-20-2012, 06:19 PM   #10 (permalink)
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Quote:
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Maybe you could try to boattail the wheel?
Do you mean like how basjoos did his?
http://ecomodder.com/forum/showthrea....html#post4632

If so i might be doing it with my next piece of coro

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