Under body air flow - splitter and diffuser install

[billjr212]

Okay, I know there are a few photos floating around in build threads because I have seen them over the years, but I'm hoping to consolidate a bit of info here. This might ultimately fit better in the 818-R sub-forum and I can ask the moderators to move it if everyone agrees that makes more sense (though my car is an S)

I'm trying to finalize the installation of my splitter and diffuser, but wanted to throw it out here first for comments.

Crude drawing time (drawn from memory and definitely not to scale!):


The black lines are the carbon fiber splitter and diffuser. Gray is aluminum or the underbody steel. Orange is other components (radiator, steering rack, front firewall).

I have 4 questions:
1. The red line is another piece of aluminum I have from FFR (not installed yet). It fits here perfectly and appears to be designed to block/protect the steering rack and battery tray area. Does this appear correct?
2. The blue line is a piece of aluminum I bought and plan to bend to fill this space to direct air up through the radiator and put an end point to air coming over the top of the splitter but under the aluminum tray in front of the radiator.
3. Will this dip up (between blue and red) somehow create an air pocket and lift up front? Should I run the blue piece straight back instead or leave it off entirely?
4. I have a small gap between the under engine aluminum and the diffuser. One theory (pretty sure this is incorrect) is that this could help pull some hot air out of the engine bay. More likely, I'm just thinking it is creating drag and I need to get another piece of aluminum to bridge the gap.

Once I'm done, I will put the car up on the lift and get some good under car shots for the community.

Thanks!

[billjr212]

Cross reference to similar thread in the R section: http://thefactoryfiveforum.com/showt...-tray-aluminum

[FFRSpec72]

Black is the splitter you don't need any additional aluminum if using the race splitter, blue is the under the steering rack aluminum (which will take some tweaking if you are using the race splitter, as I have a piece supplied by FFR) red is the under the under the battery tray aluminum which fits fine next is the under the feet steel that is part of the frame, followed by the under the seat aluminum, followed by the under the fuel tank steel that is part of the frame followed by under the engine aluminum and finally the diffuser.

I have no gap from the rear diffuser to the engine aluminum you can also see from this picture

WP_20141106_012.jpg

The small wing aluminum (on each side of the under engine aluminum) was added by Jim/FFR to fill the gap and is not provided.

So FFR provides all the under the car aluminum if you are using the race splitter/diffuser the only missing aluminum is the small wings on each side of the under the engine aluminum.

[longislandwrx]

Thanks for posting this pic, my R never came with an under engine aluminum. This will help when I make one.

[FFRSpec72]

Thanks for posting this pic, my R never came with an under engine aluminum. This will help when I make one.

If you got the rear race diffuser then you would get the under the engine diffuser, on the early shipments of the diffuser they forgot to include it so I would call if you have the rear race diffuser as I had to call and they shipped it.

[billjr212]

Black is the splitter you don't need any additional aluminum if using the race splitter...
So FFR provides all the under the car aluminum if you are using the race splitter/diffuser the only missing aluminum is the small wings on each side of the under the engine aluminum.

I knew there was a subconscious reason I didn't want to post in the R forum. :-) The street splitter is not as long so just ends in space as I've drawn. The back of it doesn't touch anything. I take it then that on the R cars, it is is flat from the splitter to the under battery tray area? No bump up?

I have no gap from the rear diffuser to the engine aluminum you can also see from this picture.

I may have accidentally created the gap myself by pulling the bottom of the rear bumper back slightly. This gave additional clearance for the shift arm and made my trunk lid fit better. Downside is it would have increased the distance the diffuser had to span, so when I installed with a slight reveal at the back, it left a gap at the front.

[FFRSpec72]

I knew there was a subconscious reason I didn't want to post in the R forum. :-) The street splitter is not as long so just ends in space as I've drawn. The back of it doesn't touch anything. I take it then that on the R cars, it is is flat from the splitter to the under battery tray area? No bump up?

I may have accidentally created the gap myself by pulling the bottom of the rear bumper back slightly. This gave additional clearance for the shift arm and made my trunk lid fit better. Downside is it would have increased the distance the diffuser had to span, so when I installed with a slight reveal at the back, it left a gap at the front.

The race splitter ends short of the battery tray aluminum, so the area directly under the steering rack needs to get covered, but I did get a piece of aluminum from FFR for that it has to be tweaked a little but to fit with the splitter.

How far is your diffuser sticking out the back of the bumper ?

WP_20160222_06_13_16_Pro.jpg

[longislandwrx]

If you got the rear race diffuser then you would get the under the engine diffuser, on the early shipments of the diffuser they forgot to include it so I would call if you have the rear race diffuser as I had to call and they shipped it.

I didn't get the diffuser. I knew it would just sit around

[billjr212]

How far is your diffuser sticking out the back of the bumper ?

WP_20160222_06_13_16_Pro.jpg

Mine is almost the same as the one you show above. Here it is (bad angle, but I think you get the rough idea):

The race splitter ends short of the battery tray aluminum, so the area directly under the steering rack needs to get covered, but I did get a piece of aluminum from FFR for that it has to be tweaked a little but to fit with the splitter.

Good to know. I will put the "red" line on to close off the battery tray area (I think I may eventually turn that into a "frunk" and put a small tool kit up there) and aim for a flat bottom when I do the blue line. Maybe something like this:

[FFRSpec72]

So I finished my under the steering rack, here is how mine came out

WP_20160331_13_11_04_Rich.jpg

[billjr212]

Awesome. Thank you! I'm hoping to finish this up this weekend, so I will post pictures to share as well.

[Frank818]

FFR provided the red line aluminum panel? I have front race splitter. What part number is that under steering rack panel?

This thread is really good, we have all the possibilities in one thread with drawings. Ok drawings aren't up to scale but hey it's still cool! loll

[billjr212]

Not sure on the part number. I think I wiped it off at some point in history.

I finished off the entire underside today. Similar to my official diagram at post 9. I ended up picking up a 24" x 48" aluminum sheet from lowes to serve as the "blue" panel.

Took tons of photos and will post tonight when I get on the computer.

[Frank818]

Crap, the red line alu panel is not listed on my POL. I'll check it out and get it shipped if I don't find anything that seems to fit in there.

[billjr212]

Okay, here goes. The pictures didn't come out as well as I hoped, but I think the point will get across:

Here are 2 of the front gap before:



Here is the "red" panel from the diagram above:


So, I added these angles to the front of the frame:


Then I installed the red panel. Riveted the front of it to the aluminum below the radiator, and 1 rivet in back into 1 of my new angles to hold in place:


Then I installed the "blue" panel that I made over the top. This was a 48" x 24" panel I got from Lowes. Rested/riveted on top of the CF splitter. Riveted to my new tabs in the back (sandwiches the "red" panel in place):


In place:

[billjr212]

Full front view:


Full front view again:

[billjr212]

Here is the irritating little gap I had at the back between the diffuser and the under engine panel:


Filled in with a little panel directly on the frame.

[billjr212]

Since everybody obviously loves my amazing skills in MS Paint. This is essentially what I ended up with:

[flynntuna]

Your skills in MS paint are overshadowed buy your build skills. Question: wouldn't rivnuts be better to use to be able to service the steering rack if needed? Even though drilling out rivets isn't that big of deal.

[billjr212]

Your skills in MS paint are overshadowed buy your build skills. Question: wouldn't rivnuts be better to use to be able to service the steering rack if needed? Even though drilling out rivets isn't that big of deal.

I had initially planned to use rivnuts, but once I decided to add the tabs all of the rivets were exposed on the backside. At that point, I was tired of being rained on by drill shavings and I decided it wasn't a big deal to use rivets for the initial install. If I ever have to drill them out, I would consider a swap to rivnuts or 1/4-20's and just using a bolt and nut.

[billjr212]

Your skills in MS paint are overshadowed buy your build skills.

Lol. Thanks. That is a pretty high bar to clear.

[Frank818]

Really nice result!

By any chance, no part number on that red panel? I didn't get it with my #181 kit and I want to order it.

[Frank818]

Here is the "red" panel from the diagram above:

That looks like the under engine belly panel. I'm pretty sure I got this part, FFR shipped to me when I asked cuz many of us at the beginning didn't get the under engine panel.

Under engine pic on post #3 looks like this panel here.

[billjr212]

That looks like the under engine belly panel. I'm pretty sure I got this part, FFR shipped to me when I asked cuz many of us at the beginning didn't get the under engine panel.

Under engine pic on post #3 looks like this panel here.

No part number on it, sorry.

It is similar in shape to the under engine panel, but much smaller, so wouldn't cover that gap.

I'll try to pull my parts list today to see if I can back into what number it is.

[Frank818]

Ha I get it! It's almost symetric only thing is the picture doesn't show the real size of the panel, of course, that is why I sort of recognized it as being the under engine panel.

Yeah I'm curious to see if you have a different parts list than I do, what chassis # you got?

[billjr212]

what chassis # you got?

264.

[FFRSpec72]

That looks like the under engine belly panel. I'm pretty sure I got this part, FFR shipped to me when I asked cuz many of us at the beginning didn't get the under engine panel.

Under engine pic on post #3 looks like this panel here.

The under the engine panel has no bent edges, and is rectangular with tapered edges that go towards under the fuel cell area

[UnhipPopano]

I noticed something in the image showing the cable connected to the arm at the back of the transmission. Bye the way, I like the look of leaving that area open. There is quite a bit of angle between the shifter cable to the left of the support and the cable ends and seals between the support and the arm connected to the shifter shaft. I used to be involved in boating and when there were some cable failures, I refreshed my memory on what was the proper way to mount the cable to an outboard. To cut my conversation short, it is best for everything to be in line, and the maximum angle the cable end should be subject to is 16 degrees. [http://www.cablecraft.com/documents/...catalogue.pdf]

[billjr212]

I noticed something in the image showing the cable connected to the arm at the back of the transmission. Bye the way, I like the look of leaving that area open. There is quite a bit of angle between the shifter cable to the left of the support and the cable ends and seals between the support and the arm connected to the shifter shaft. I used to be involved in boating and when there were some cable failures, I refreshed my memory on what was the proper way to mount the cable to an outboard. To cut my conversation short, it is best for everything to be in line, and the maximum angle the cable end should be subject to is 16 degrees. [http://www.cablecraft.com/documents/...catalogue.pdf]

Agree and very good point. I previously had it lined up better (it was in the 2nd hole down), but shortened the shifter over the winter. It made the throws TOO short so I was having trouble shifting (pretty much only to move the car around in the garage over the winter). I moved it down for the time being but will soon be swapping over to Mechie's linkage setup.

Good to know what the specific angle is though too! (16 degrees, very interesting)

[Frank818]

Looking to get that part # for those who don't have the panel in their kit. The under engine panel is part #80056 (or 80059, not sure), I have contacted Courtnie to help out on the under steering rack panel and I will post # and how to make a request for it once I get the info.

[Bob_n_Cincy]

The under the engine panel has no bent edges, and is rectangular with tapered edges that go towards under the fuel cell area

My engine belly pan had bent forward and trailing edges and was trapezoid shaped.

P1050708s.JPG