Found this diffuser on the Lexus form and decided to give it a shot.
DIY - How to install a S4play Diffuser - Club Lexus Forums

I based this DIY off another DIY on the lexus forum but we will have a few changes.

First, the distance between muffler cutouts on the ASPEC Lip is about 35"+. This diffuser is about 32.75", so it fits! It should also fit base models and base aspecs.
My bumper is completely cut to fit the ASPEC, so I dont have this bumper flap http://i17.photobucket.com/albums/b6...2/IMG_3582.jpg
I was able to clip in my diffuser to OEM rear bumper mounting points with clips because I dont have this flap. You may need to use a bolt and washer. HIGHLY recommend taking off your bumper.

Materials Needed:
-Diffuser (For IS250 is350 isf Bolt on Unpainted Rear Bumper Diffuser Chin Lip Add on Kit | eBay) I believe it's just universal, I see it for camry and other cars--dimensions are th same
-Hex Screws + nuts (black)
-Paints tape
-Hack saw to trim
-Dremel/drill to drill holes

Step 1:
You need to drill out the existing holes to accommodate the larger hex screws. I didnt use the ones that came with it because they looked cheap and were shiny. Plus the black hex looks a lot cleaner and professional.

Here is a diagram of how I mounted mine. (4) OEM clips in the back, and 6 hex screws in front.


Step 2:
Trim the center fin, or 4th one to clear the tow hook.


Step 3:
Take off bumper--I'd recommend this unless you like shoving your hand behind your bumper to tighten nuts

Step 4:
Here is where taking off your bumper would have come in handy. You need to put the diffuser up against the bottom of the bumper. It should fit flush with this gas tank cover/It's the plastic trim that the rear bumper mounts on to. We need to mark on the diffuser where these holes for the OEMS clips are to drill. So you can either try to mark it from the top or take your bumper off and do it easier.

OR You can just drill directly through the diffuser into the bumper and not use the clips--probably easier. I dont have the bumper flap because I cut it out.
Try to center the holes as much as possible. Use the middle fin as a guide.




Step 5:
After you have found how to mount the rear of the diffuser, clip the diffuser in




Step 6
With the rear diffuser clipped in, use painter's tape to get the lip flush against the bumper--it should look close to how you want it because we are going to drill into the bumper in these locations.



Step 7
Drill into the bumper holes for hex screws



Step 8
Tighten all hex bolts, will be very hard if you have your bumper off.


I highly recommend everyone take off their bumper and get 1/2" nut and bolts to mount to rear bumper mount location

 

Looks real good.

 

I like it, wonder how it would look on a regular A-spec rear lip I kinda want to pull the trigger and order one now

 

this person also did it on base aspec

 

Good to see other people go out and explore new things (as such, parts from other cars).

 

I'm not usually one for diffusers but that looks really good. Great writeup man

 

Looks awesome. May have to follow suit and order one.

 

let me know if you do I would like to see more pics on a wdp!

 

looks great!

 

dangggg I really want now!

 

Dangggg looks mean!


How many Hpees should I expect?

 

It helps keep you planted in the corner, noob

 

That looks outstanding.

 

so i can't tell from your writing for sure, but sounds like you did this without removing the bumper? I'm thinking about doing this, but i'm trying to avoid taking off my bumper because i was a victim of a hit and run and i'm afraid to take my bumper off and not be able to get it back on (i was hit in the rear left corner where the bumper curves around to the side and i had to use silicone sealant to keep the side of the bumper from flaring out where it normal clips in).

long story short, is there anything that can't be done with the bumper on and in short summary, what are the hardest parts about installing this with the bumper on?

thanks again for the DIY! i think this adds a nice aggressive looking touch even though it's fake haha

 

dang! I was actually thinking of doing this for a while now. diffuser been sitting in my garage for a bit now. Glad to see someone with tl did it.. Maybe ill come around to finally installing it.

 

not sure if I like it, but I do like how unique it is. you don't see many, if any, diffusers on these cars.

 

you can do it with the bumper on, it's just when you get to threading the nut and bolt in the front, might have a hard time reaching in that far.

I was able to do it easily because I dont have the bottom part of my bumper--i cut this off when I installed my aspec lip on my 05

bumper off would be good so you can measure the distance between the oem clips so you can mark where to drill on your diffuser.

 

^^ thanks! did you dip your diffuser or does it come black like that? seems like it blends in pretty well with the small balck area on the aspec lip

 

it comes that way, i was going to paint it but ran out of time. It'll probably fade over time but i'll just spray it next time.

Surprisingly this is as far back the diffuser goes to be able to clip into the back and it fits flush against the lip coincidentally.

 

Thanks for the write up, looks badass!

Does anyone have any data on if this improves aerodynamics?

 

You mean track times at buttonwillow? I highly doubt it.

 

my butt dyno felt like the car moved .00000019 faster as I pulled up to Mcdonalds.

 

"Butt Dyno"!!!! ROFLMAO.

 

Holy crap, I thought this was a DeathMetal DIY!
which means desertmist, that your write up is on par with some of the best on here! Good job!

also looks super fresh! might want to try on my car

 

Looks great, might be in my future!

 

I just want to watch Justin install it on his car.

 

This thread inspired me to put on my diffuser

 

^ can you put up some more pics from other angles and further away? Also did you take off the bumper to install it or have any other tips?

 

Looks great.

 

looks great need more pics please

 

Looks amazing I would want to do this to my car.

Where can you find a front diffuser for the TL's?

 

I want more pics and angles. Really hard to tell the looks.

 

here are some more pics, i think all the pics in this thread give a good idea what it looks like

 

Thanks for the pics and yeah I want it asap

 

Is there any benefits to adding this on, or just more for aesthetics?

 

i shaved 1000th of a second off my quarter mile.

 

Congrats!

 

now on a KBP! Looks a lot better here

 

What the hell? Is that a lip spoiler on a lip spoiler?

And those rear side lips....double

*You know they're affordable when....*

 

Did he hit a curb? wheels look funny