PSM aggressive diffuser discussions

[MineralWhiteF80]

I really want to try out a PSM style rear diffuser because it looks awesome and would please my inner hotboi, race car wannabe brain but I have some concerns that I am curious about.

1. I track my car, do high speed stuff, etc. Is this PSM diffuser strong enough to withstand 150+ mph speeds without flexing, dragging the ground, breaking off or turning into a wind sail? Has anyone added center stanchions at the front to strengthen the center tray?

2. The aggressive vertical fin design seems to get quite low to the ground. I'm trying to understand how likely it is that I will drag the fins on the pavement with a lowered car that is driven smartly on good quality roads or on a road course. I know that answer has lots of variables but I see a fair share of diffusers with drag marks on the bottoms of the fins and I don't know if these people are driving up extreme inclines in cities or driveways, or if just hitting a decent sized dip in the road at speed is enough to drag the fins.

3. Performance pros/cons: is this likely to just create a lot of drag and not provide any helpful downforce or air smoothing underneath the car?


Anyone have any experience with this PSM diffuser from a 'motorsport' perspective? I know it will look great in the garage but I don't want to waste the money if I'll likely immediately destroy it.... My M4 is just a fun/weekend car.

Thanks in advance!

car in question:

[x.shell]

It will be a parachute at high speeds. I have heard stories of them ripping off at the track — not because they scraped, but because they act as a parachute. If you want to use it in high speed situations, plan a more robust diffuser mounting system. And it would be a good idea to cover any avenue that air can get into — basically extend the flat flooring into the diffuser.

For street use, I have never seen a full PSM diffuser without scrape marks on the fins. They sit really low so it will scrape on driveways.

[paulo_f80m3]

I went from the M Performance Diffusor to the PSM style one from Horizon Motorsport. Night and day. Looks so much better and it makes the rear end that more aggressive. Just make sure you add the two supporting screws in the middle like I did and the diffuser is solid. It’s not going anywhere. If you are concerned I would just remove the undertray when going to the track. 8 screws and it’s off. Easy to put on and off.

[NSX2M4]

Check out the carbon 1.5 M4 diffuser. It's "similar to the PSM but it actually fits properly and it does not move. AT ALL. Super high quality V pattern carbon and oem mounting point and clips.
Seen here.https://f80.bimmerpost.com/forums/sh....php?t=1869453

[Spoolin Montego]

Anyone who says this diffuser can withstand 150mph is either ignorant or lying lol. That shit catches SOOO much wind at high speeds. Zero chance it stays on going that fast.

[s55jesus]

Originally Posted by MineralWhiteF80

I really want to try out a PSM style rear diffuser because it looks awesome and would please my inner hotboi, race car wannabe brain but I have some concerns that I am curious about.

1. I track my car, do high speed stuff, etc. Is this PSM diffuser strong enough to withstand 150+ mph speeds without flexing, dragging the ground, breaking off or turning into a wind sail? Has anyone added center stanchions at the front to strengthen the center tray?

2. The aggressive vertical fin design seems to get quite low to the ground. I'm trying to understand how likely it is that I will drag the fins on the pavement with a lowered car that is driven smartly on good quality roads or on a road course. I know that answer has lots of variables but I see a fair share of diffusers with drag marks on the bottoms of the fins and I don't know if these people are driving up extreme inclines in cities or driveways, or if just hitting a decent sized dip in the road at speed is enough to drag the fins.

3. Performance pros/cons: is this likely to just create a lot of drag and not provide any helpful downforce or air smoothing underneath the car?


Anyone have any experience with this PSM diffuser from a 'motorsport' perspective? I know it will look great in the garage but I don't want to waste the money if I'll likely immediately destroy it.... My M4 is just a fun/weekend car.

Thanks in advance!

car in question:

Don't get it if you're planning to use it for constant track purposes. They will most definitely come off under constant abuse. They also tend to sit real low so the fins scrape EVERYWHERE. My tow truck driver destroyed my fins last time.

Originally Posted by Spoolin Montego

Anyone who says this diffuser can withstand 150mph is either ignorant or lying lol. That shit catches SOOO much wind at high speeds. Zero chance it stays on going that fast.

Depends how it's installed. I've done multiple 150mph+ runs and it's still on there. Although I wouldn't trust it under constant speed runs like that.

[b_w.]

old thread but my Turner CF rear diffuser decided to turn into a parachute on my last track day. Was probably loose from previous sessions but came flying off at 100mph on Monday. Just going to reinstall the factory painted one unless there are other suggestions. I like the look but doesnt hold up well to track use.

[DeTh]

This has been my main apprehension with getting a diffuser. No way they will stay on at 190mph

[HotRodM4]

Anyone on bimmerpost ever run this one?
https://www.aeroflowdynamics.com/pro...ar-diffuser-v1

https://www.youtube.com/watch?v=Dt4Vi6wOdnE