Hello. 

I am wanting to add a few external mods to my 2017 MK8 Fiesta Titanium and really like the look of the st line rear diffuser (mainly the black section highlighted in picture). Would this specific part fit on my rear bumper or would I need an St line bumper for it to fit? Any help appreciated. 

Thanks. 

I think the basic bumper is the same, but in addition to the black diffuser you have highlighted, there is a body colour section which you may also need. Shown more clearly in the pics in this link:

 

https://www.masterofbumpers.com/ford/ford-fiesta-st-line-zetec-s-mk7-2017-2021-rear-bumper-with-difuser-genuine-f871

Thanks Eric, I thought that might be the case. Think i’ll have a look around for some rear bumpers then! 

3 hours ago, MTH said:

Thanks Eric, I thought that might be the case. Think i’ll have a look around for some rear bumpers then! 

I’m planning to change my diffuser at some point from the one your currently looking for. It’s in good condition… maybe we can help each other out?!

Hi Troy, I think I’d need more then just the black plastic rear diffuser and I have a feeling I may need to whole bumper as the coloured part attached to the diffuser wouldn’t fit on my current bumper (unless you think differently) Are you just planning to change the plastic section of diffuser? 

14 hours ago, MTH said:

Hi Troy, I think I’d need more then just the black plastic rear diffuser and I have a feeling I may need to whole bumper as the coloured part attached to the diffuser wouldn’t fit on my current bumper (unless you think differently) Are you just planning to change the plastic section of diffuser? 

You may need the whole bumper to achieve your results. I can’t say for sure though. 
I’ll be planning to just change the center plastic section. 

When I do it, the old will just be sitting there doing nothing. If you find you need it at the time and I’ve still got it, let me know. It maybe cheaper for you to buy a complete bumper or buy it in pieces 🤷  

Yes, the problem seems to be the separate body colour part above the diffuser. You can see in the link I posted earlier this appears to be clipped into holes in the main bumper so you would probably be looking at drilling the main bumper and/or double sided tape to get it to fit.

Unlike the "spats" from the Mk 7/7.5 though, I've never seen this part sold separately on fleabay etc - don't know if you could buy it new from Ford.

It may be that the black diffuser alone would fit and look ok without this part - never seen one where this has been done.