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-   -   rear diffuser (http://www.casc.on.ca/forums/showthread.php?t=34859)

shmooly 12-05-2017 12:15 PM

rear diffuser
 
anyone around here make their own diffusers? post up pictures and thoughts, if i can get any love, iíll ask at least a dozen whatever questions

thanks!!

max attack 12-05-2017 07:08 PM

Re: rear diffuser
 
Google is your friend:)

shmooly 12-07-2017 06:10 AM

Re: rear diffuser
 
1 Attachment(s)
thanks,

i certainly have googled..

one question i have is about the design.. on a lot of diagrams that i see, there is an outlet near the top of the diffuser(as seen with the diffuser installed) that lets air out above the bottom of the diffuser. (i’ve attached a picture to describe what i’m talking about.)

is this design necessary, or will just giving the air a smoother transition from the underside back to the more ambient pressures air plenty efficient? all i want to do is make more downforce in the back.

i’m really looking for a very elementary explanation of the physics that create downforce, as far as the diffuser goes.

_isiah

max attack 12-07-2017 06:50 AM

Re: rear diffuser
 
Yes you need that space to exhaust the heat from the center tunnel.

The reason a diffuser works is by creating a larger volume at the rear the air under the car rushes in to fill that void which speeds up the air under the car faster then the air over the car resulting in a vacuum.

It reduces drag by returning that air smoothly to the wake of the car reducing the size of the "bubble" thats otherwise also a vacuum trying to suck the car in the opposite direction of travel.

kmorris 12-07-2017 09:39 AM

Re: rear diffuser
 
Using design principles from F1 and such series can be misleading, because the design of aero components is often complicated by the rules that limit the size and location of aero components. The 'extra' outlet you show could be that kind of case, where the separation is there to keep the main piece of the diffuser within the defined size limit and the second flap is there to effectively make the diffuser larger, but with a gap (although the gap may be there for other reasons).

Historically, the series with the most freedom to explore aerodynamics was probably the Group C sportscars of the late 80s/early 90s. If you want to see lots of technical info on these and many other cars and lots of other aero tech resources, check out mulsannescorner.com.

3wheeler 12-07-2017 10:29 AM

Re: rear diffuser
 
Quote:

Originally Posted by shmooly (Post 263098)
thanks,

i certainly have googled..

one question i have is about the design.. on a lot of diagrams that i see, there is an outlet near the top of the diffuser(as seen with the diffuser installed) that lets air out above the bottom of the diffuser. (iíve attached a picture to describe what iím talking about.)

is this design necessary, or will just giving the air a smoother transition from the underside back to the more ambient pressures air plenty efficient? all i want to do is make more downforce in the back.

iím really looking for a very elementary explanation of the physics that create downforce, as far as the diffuser goes.

_isiah

This design won Brawn GP the Drivers and constructors title in 2009. Genius really!

shmooly 12-08-2017 02:08 PM

Re: rear diffuser
 
Quote:

Originally Posted by max attack (Post 263099)
Yes you need that space to exhaust the heat from the center tunnel.

The reason a diffuser works is by creating a larger volume at the rear the air under the car rushes in to fill that void which speeds up the air under the car faster then the air over the car resulting in a vacuum.

It reduces drag by returning that air smoothly to the wake of the car reducing the size of the "bubble" thats otherwise also a vacuum trying to suck the car in the opposite direction of travel.

are you saying that the yellow rectangle with the red arrow leaving at the back of the car i pictured is to exhaust heat?

or

are you saying that the vertical fins on the underside of the diffuser are to exhaust heat (heat from the engine?)

i thought that air was coming in from the sides of the car.

thanks for posting up!!

craig 12-08-2017 03:55 PM

Re: rear diffuser
 
Quote:

Originally Posted by max attack (Post 263070)
Google is your friend:)

So is YouTube. Lots of noise, though.

Kyle.Engineers YouTube channel has some good videos on aero, from "The Beginner's Guide to Aero Mods for your car" to the recent series about the aero (and engine, and suspension) of their 968 Time Attack car.

https://www.youtube.com/user/Kyleengineers/videos

John P 12-08-2017 06:21 PM

Re: rear diffuser
 
Quote:

Originally Posted by shmooly (Post 263127)

are you saying that the vertical fins on the underside of the diffuser are to exhaust heat (heat from the engine?)

i thought that air was coming in from the sides of the car.

thanks for posting up!!

The vertical fins under the car minimize turbulance so the air flows faster, generating bigger vacuum at the difuser. Also vertical fins at sides of car increase velocity of air under the car, since it isn't escaping out the sides.

JohnP

max attack 12-09-2017 08:05 AM

Re: rear diffuser
 
As mentioned comparing F1 aero to a production car is apples and oranges.

The gap above the diffuser is exposed to the low pressure zone in the cars wake,the front is a high pressure zone so heat produced by the front mounted engine,transmission,exhaust,rear diff can be pushed/sucked out there.

If not it takes some serious effort to keep temps under control,usually adding weight with pumps and rads for transmission and diff.Plus wraps and sheilds for the exhaust.


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