[Alpine-F80]

So I've seen people wrap / plastidip their rear "diffuser" section on the Sportline bumper, but never saw anyone try to retrofit some sort of diffuser 'fins' back there to finish off the look.

IMO without the diffuser fins it looks a little off and better untouched, but after seeing some people in VW community using "Universal Diffusers" on their rear bumpers with good results I figured I'd look for something relevant to the F30. I stumbled across this:

https://www.ebay.com/itm/23-x6-Ikon-...72.m2749.l2648
At 24" wide it fits nicely between the dual exhaust tips and is subtle enough to fit back there without sticking out and looking out of place. Not to mention at $11.99 shipped it was worth a shot. You can also just wrap it (or dip it) with what you use to black out the "diffuser" section/cutout so it really blends in.

Without further adieu, here's how it turned out:




If anyone is interested in exactly how I attached it let me know and I can put up a DIY. Basically it comes with double-sided tape, but you can only use about 1/3 of it because the rest doesn't have anywhere to attach to.

There's a few ways you could do this, and it would definitely be easiest if you took the whole rear bumper off, but I went the lazy route and just used a couple spare brackets laying around from an old HID kit on a previous car, you could definitely find something even better at Home Depot though.

Here the one's I used though for reference, this pic is from an ebay listing actually but it's the exact one's, they're roughly 4.5" long.


I don't have time to do a proper full DIY yet, but a quick couple steps that I used:

1. Jack rear end of car up
2. Mark the center of the diffuser with a piece of tape by measuring the distance between the two exhaust tips.
3. Find the 2 T-15 screws at the bottom of the bumper, right at the edge, they hold the bumper cover up onto some plastic support it seems like. These are where the brackets will get attached, and then the diffuser will use 3M tape to bottom of bumper + the brackets to stay secured (so far so good after 2 weeks )
5. Align diffuser at center of bumper, if you have a spare jack or something to hold it up it will help, and then mark where the brackets line up on the diffuser so you can use those to line up where holes will go into diffuser.
6. Take your diffuser and lay flat, then lay brackets where you marked, find a good place where holes in bracket align with diffuser, I marked 4 total, 2 per bracket, see pic above for where. Because you're doing this sort of blind this isn't perfect, I had to re-drill one of them to get the bracket to align right. You can't see under there at all though, so no biggie to me, but to avoid you'll want to take rear bumper off to make this more accurate.
7. Attach brackets now into rear bumper with T-15's, not super tight, but tight, you may need to adjust them slightly.
8. Peel just the ends of the 3m tape so you can tear off easily when all ready
9. Align diffuser up with bracket holes, doing adjustments where necessary, making sure it aligns with rear of bumper nicely, then attach you nuts/bolts ideally, self tapping screws may work too though it's semi-thick plastic.
10. Once it looks and feels pretty solid, tear off 3m tape, hold in place for a couple minutes, if it's cold maybe apply a little heat.

[F30bih]

Looks really good!

[XxThe_RemedyXx]

Link?

[jlorenzo125]

Nice! Just ordered mine. I think I will sand, prime and paint it myself! Thanks for sharing!

[Alpine-F80]

Originally Posted by jlorenzo125

Nice! Just ordered mine. I think I will sand, prime and paint it myself! Thanks for sharing!

Awesome! I'm gonna post up a little DIY here this week with where I drilled holes, the bumper bolts I tapped, and the brackets.

FWIW it comes in a decent looking gloss black, but the edges could benefit from sand/paint. You really don't see it though under there unless you get down real low and close.

[jlorenzo125]

Originally Posted by Alpine_F30

Awesome! I'm gonna post up a little DIY here this week with where I drilled holes, the bumper bolts I tapped, and the brackets.

FWIW it comes in a decent looking gloss black, but the edges could benefit from sand/paint. You really don't see it though under there unless you get down real low and close.

Any pics of the type of brackets u used? I'm thinking of going to home depot and looking for something. There's no where on the bumper to attach the rear part of the diffuser without some sort of bracketing indeed ol.

[Alpine-F80]

Originally Posted by jlorenzo125

Any pics of the type of brackets u used? I'm thinking of going to home depot and looking for something. There's no where on the bumper to attach the rear part of the diffuser without some sort of bracketing indeed ol.

Posting up pics of bracket now to original post, although I think you could probably find something even better at home depot.

[jlorenzo125]

Originally Posted by Alpine_F30

Posting up pics of bracket now to original post, although I think you could probably find something even better at home depot.

Thanks!

[jlorenzo125]

I went to home depot and got some brackets along with some nuts and bolts to secure them into holes i drilled into the rear part of the 'diffuser'. Worked really well, also used some thicker double sided tape to secure the edges up along bottom of bumper. Came out pretty good!
---Sorry for the dirty car, its been raining for a week now

[Alpine-F80]

Originally Posted by jlorenzo125

I went to home depot and got some brackets along with some screws and washers to secure them into holes i drill into the rear part of the 'diffuser'. Worked really well, also used some thicker double sided tape to secure the edges up along bottom of bumper. Came out pretty good!
---Sorry for the dirty car, its been raining for a week now

Oh sick dude, that was fast, nice work!

I was a little worried that it wouldn't be strong enough with only those 2 brackets, would like a 3rd on the far right, but it still feels really sturdy. I guess it's just a small piece of plastic that needs to stay in place.

[jlorenzo125]

Originally Posted by Alpine_F30

Oh sick dude, that was fast, nice work!

I was a little worried that it wouldn't be strong enough with only those 2 brackets, would like a 3rd on the far right, but it still feels really sturdy. I guess it's just a small piece of plastic that needs to stay in place.

Thanks! And I think what would be good to try is have a buddy drive behind ur / my car to see if the diffuser flops or wiggles at all during driving, especially at highway speeds Probably would a little who knows

[Alpine-F80]

Originally Posted by jlorenzo125

Thanks! And I think what would be good to try is have a buddy drive behind ur / my car to see if the diffuser flops or wiggles at all during driving, especially at highway speeds Probably would a little who knows

Ha, yeah I was thinking the same, and also get them to take some rollers while you're at it

[Nircom]

Originally Posted by Alpine_F30

So I've seen people wrap / plastidip their rear "diffuser" section on the Sportline bumper, but never saw anyone try to retrofit some sort of diffuser 'fins' back there to finish off the look.

I really like what you've done and the end result.
to be honest, i've already bought an m3 rear bumper, but never really felt I love it. It always felt a bit off on an f30, so 10 minutes after I saw this post I published my m3 bumper for sale ...

The only thing I wonder about, is whether this diffuser will fit, since I have a tow bar installed. but, I guess paying as little as 15$ is not a big risk to take.
Cheers.

[NxTH]

Anyone still have a working link for what was bought? Trying to do this myself since I can't find a single diffusor for sportline. Or any other ideas?

[Oksamit78]

Originally Posted by NxTH

Anyone still have a working link for what was bought? Trying to do this myself since I can't find a single diffusor for sportline. Or any other ideas?

Here it is:
https://www.ebay.com/itm/22570256784...Cclp%3A2047675

[mm92]

Hello, I know this post is kind of old, but I found a sportline diffuser that looks too good to be true.

Here’s the link:https://biofreear.live/product_details/110444318.html

The site seems kind of sketchy but if anyone has seen this diffuser somewhere else please let me know

[NxTH]

Originally Posted by mm92

Hello, I know this post is kind of old, but I found a sportline diffuser that looks too good to be true.

Here’s the link:https://biofreear.live/product_details/110444318.html

The site seems kind of sketchy but if anyone has seen this diffuser somewhere else please let me know

I've seen it, since I've been looking all over the internet for a diffuser for sportline. The issue with this one is that it's a quad exhaust bumper, so you would need to dremel part of your rear bumper to create a wider hole, and then get double exhaust tips for both sides. Far too much work considering the diffuser might not even fit perfectly and then you have a destroyed bumper.

I'm looking into wrapping the diffuser area in carbon fiber, and installing some kind of fin splitter in the bottom. Problem is, there is no panel under the rear of the car, and attaching anything to the bumper becomes a problem. I'll try to come up with a solution this spring and post it here.

Some might ask why not just convert to M-sport. One, it costs more, and two, everyone has M-sport. I already installed a front lip to my sportline, so matching them with something in the rear is in my sights.

[mm92]

Originally Posted by NxTH

I've seen it, since I've been looking all over the internet for a diffuser for sportline. The issue with this one is that it's a quad exhaust bumper, so you would need to dremel part of your rear bumper to create a wider hole, and then get double exhaust tips for both sides. Far too much work considering the diffuser might not even fit perfectly and then you have a destroyed bumper.

I'm looking into wrapping the diffuser area in carbon fiber, and installing some kind of fin splitter in the bottom. Problem is, there is no panel under the rear of the car, and attaching anything to the bumper becomes a problem. I'll try to come up with a solution this spring and post it here.

Some might ask why not just convert to M-sport. One, it costs more, and two, everyone has M-sport. I already installed a front lip to my sportline, so matching them with something in the rear is in my sights.

I also installed the front lip and like the look of the front. I think I’ll probably just go the same route with tapping part of the bumper with some sort of brackets for a splitter.

[NxTH]

Had a go at this myself today. Snow is still melting here so no point in washing the car yet, my apologies.

Bought the generic diffuser from Aliexpress and got some hardware. The diffuser came in three pieces of which I used two. I taped the pieces together to have an easier time drilling, and after drilling the holes I removed the tape. I then attached steel plates onto the diffuser, and drilled straight through the bumper, through the diffuser, and finally through the steel plate. Attached nuts above. What needs to be considered here is that the bottom of the bumper is essentially almost non-existent. There is only a few centimeters of space to work with, so this definitely needs the additional support that hopefully the plates provide.

It does not move when I tried to move it by hand, and so far wind has not loosened any bolts. I can't imagine doing this without any metal supports. I don't have a physics degree, so I don't know how wind actually behaves in the rear of the car, and whether it puts any pressure on this diffuser or not. I will have to check in a month or so if the bolts have loosened, but I don't think they will.

What kind of sucks about this diffuser is that the plastic is so thin, it bends easily when you screw it in tight. Small bulging will occur at the rear edge, but not noticeable unless you crawl behind the car and look for it.

Need to get a better photo when I've washed the car, but so far I'm pleased with this.

[bigdnno98]

I have a luxury line too and have been looking to do something to the rear bumper. This is perfect. Couple different links on the thread. Which one did you use?

[NxTH]

Originally Posted by bigdnno98

I have a luxury line too and have been looking to do something to the rear bumper. This is perfect. Couple different links on the thread. Which one did you use?

I purchased this https://www.aliexpress.com/item/1005...678f1802VP2MSN

[NxTH]

Here is a better picture how it looks. Definitely worth it, and not even thinking about M-sport bumpers. This looks way better than I originally thought it would.