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      08-08-2012, 12:45 AM   #1
kwike92
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purpose of rear diffuser?

i know it may sound like a silly question, but i am asking because i really dont know...

i know it looks cool and all, but does it actually serve a purpose???

just curious, because i want to get one to match the lip i just got, but at the same time, i have not found my self dropping $300-500 on one...

help please.
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      08-08-2012, 01:16 AM   #2
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unless you get one of those that extend under the car to help with airflow.. it is for bling factor only..
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      08-08-2012, 08:09 AM   #3
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Quote:
Originally Posted by wuzupfoo View Post
unless you get one of those that extend under the car to help with airflow.. it is for bling factor only..
Even ones like you mention like the Varis are not tested afaik.
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      08-08-2012, 10:44 AM   #4
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Quote:
Originally Posted by Purple Derple
Functional diffusers are meant to create downforce by creating a low pressure system underneath the car and sucking it to the ground. Like these guys have said, the ones people put on their cars are not functional.
Ok that's what I thought.. I'll opt for the BMW performance spoiler instead. Thanks guys for the feedback.
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      08-08-2012, 01:56 PM   #5
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Yep, there's a chance that the Varis and Platte Forme diffusers actually create downforce.
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      08-08-2012, 02:23 PM   #6
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Most of E9X M3 carbon fiber rear diffuser is from:
Tradition of looking cool since E46M3 CSL. I think.
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      08-08-2012, 02:41 PM   #7
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Quote:
Originally Posted by M3PO View Post
Yep, there's a chance that the Varis and Platte Forme diffusers actually create downforce.
Varis maybe, Platte Forme no.

None of the diffusers will do what they are truly supposed to. Yes some like the Varis to make the very rear of the car streamlined and have channels, however, it is doing nothing to channel air from the front to rear to stabilize the car.
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      08-08-2012, 02:49 PM   #8
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Quote:
Originally Posted by kwike92 View Post
Ok that's what I thought.. I'll opt for the BMW performance spoiler instead. Thanks guys for the feedback.
Why not do both…
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      08-08-2012, 03:26 PM   #9
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The fella at Downforce USA who designed and produces the diffuser that Platte Forme a.g. sells told me a bunch of things over the 30 minutes I talked to him before SEMA....too bad most of those big words and theories and such flew clear over my head, in one ear and out the other. However, the take-away that I got from all of it is that, supposedly, when you have the complete kit, their kit (as I can't speak for Varis's unit but I've seen it in person, excellent craftsmanship btw.) was designed to reduce drag, rather than create downforce.

Do I have proof that it works? Nope, I don't, sorry. Wish I could afford to rent a wind tunnel at $500+ an hour just to satiate your guys' curiosities, since if I could spend $500 an hour just because I was bored in order to debunk every single downforce claim made on the internet, I would probably have no financial worries in life. I'd still probably buy a Veyron before that though, to be honest. Anyways, I don't think anyone other than M24 and BMW GmbH can claim to have proof that any of the stuff that they design truly works, though I can tell you my front splitter and rear wing worked very well, even without optimized wind tunnel testing. But that's getting a bit off topic, sorry.

Quote:
Originally Posted by kwike92 View Post
i know it may sound like a silly question, but i am asking because i really dont know...

i know it looks cool and all, but does it actually serve a purpose???

just curious, because i want to get one to match the lip i just got, but at the same time, i have not found my self dropping $300-500 on one...

help please.
Anyways, to answer your question directly, I think that the Varis and Downforce USA items should be mostly viewed as cosmetic upgrades, and definitely most if not all of the other ones available on the market are cosmetic only. Those two though are IMO better value for money if you think about it from a material amount standpoint: 3D and Vorsteiner and Challenge, etc., cost between $1000-1500, and you only get maybe 20%-35% of the amount of carbon you get on either Varis or DF. So if you don't mind paying the money for it, you get more for your money in the end, IMO.

Last edited by LateBraking; 08-08-2012 at 03:33 PM.
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      08-08-2012, 04:18 PM   #10
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Quote:
Originally Posted by Malek@MRF View Post
Varis maybe, Platte Forme no.

None of the diffusers will do what they are truly supposed to. Yes some like the Varis to make the very rear of the car streamlined and have channels, however, it is doing nothing to channel air from the front to rear to stabilize the car.
I do know that Downforce/PF have worked face-to-face with Japanese engineers from Voltex to design their aero products. So if you put any stock in Voltex...
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      08-08-2012, 05:20 PM   #11
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No diffuser is going to do anything meaningful without a full underbody. Diffusers on street cars are for looks generally.
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      08-08-2012, 05:46 PM   #12
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Quote:
Originally Posted by M3PO View Post
I do know that Downforce/PF have worked face-to-face with Japanese engineers from Voltex to design their aero products. So if you put any stock in Voltex...
That's understandable. However, it is not a full under-body system that channels air from the front to the rear. Not doubting the capability of companies like Voltex.

It's like Honda saying "Race Inspired" technology, versus something that actually is built for racing.

Any ways, lets carry on. Nothing made for the E9x under-body to date is wind tunnel tested and optimized for this car, yet.
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      08-08-2012, 06:02 PM   #13
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Really, E46M3 CSL is where it all started.
Notice we still love CSL trunks on E9X M3s?
Same with diffusers. that where it all started and many places make their own "modified design" diffusers but CSL is the origin of the no-function carbon fiber diffuser trend.
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      08-08-2012, 11:09 PM   #14
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Quote:
Originally Posted by dtmwerksm3
Quote:
Originally Posted by kwike92 View Post
Ok that's what I thought.. I'll opt for the BMW performance spoiler instead. Thanks guys for the feedback.
Why not do bothÂ…
Lol that's what I was just thinking...

I have officially attacked by the mod bug... I'm going to order the spoiler and diffuser next week.. And in two months an x pipe, axle back and tune... Then I'll be done for a while. Lol
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      08-08-2012, 11:11 PM   #15
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If you want a functional diffuser, buy a Prius!
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      08-08-2012, 11:12 PM   #16
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Quote:
Originally Posted by SehrSchnell
My Varis System One just got in... and the only reason I'm getting it installed is for looks.
Nice!! Once I get mine I'll post pics...

I love my m3 it never ever gets old.

I got a vrs lip and I just can't stop staring at how great it looks. Lol

Cheers to my fellow m3 drivers
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      08-08-2012, 11:18 PM   #17
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Quote:
Originally Posted by kwike92 View Post
Lol that's what I was just thinking...

I have officially attacked by the mod bug... I'm going to order the spoiler and diffuser next week.. And in two months an x pipe, axle back and tune... Then I'll be done for a while. Lol
You'll never be done, not even for a while. It's been maybe two weeks since I parted out? Now I'm looking at suspension and wheels again....
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      08-08-2012, 11:24 PM   #18
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Quote:
Originally Posted by LateBraking View Post
You'll never be done, not even for a while. It's been maybe two weeks since I parted out? Now I'm looking at suspension and wheels again....
dammit! when will it stop!?!?!?!? i remember when i was building my 02 mustang gt, i said i would only spend 5k tops on mods... i ended up spending like 15-20k... then i got ride of it...

so i then told myself well if i get an expensive german car i wont need mods...

and damn, was i wrong...lmao
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      08-08-2012, 11:30 PM   #19
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Just cosmetic IMO
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      08-11-2012, 10:38 PM   #20
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Just cosmetic IMO
agreed, for street use at least.
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      08-18-2012, 12:13 AM   #21
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Rear diffusers are normally supposed to reduce drag by creating a larger area for air pressure to equalize under the car. THis kind just makes ur car look sexy. Massdrop is selling some right now, I ordered an audi grill from them. Still waiting on delivery because of shipping but I'm more concerned about price than time xD.
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      08-18-2012, 12:18 AM   #22
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35 more hp!
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