Functional Rear Diffuser

[Masterbeatty]

I have been researching around for a functional rear diffuser, Nothing for our cars. I have decided to start designing one myself.

Question 1: Since i do not have a wind tunnel in my back yard i was wondering if getting a scale model and making a mini tunnel and doing tests with that to see if it will work well is a worth while idea?

2: I know for it to work the way it is designed a spoiler is also needed. the APR starts to add downforce around 40 MPH, so i was thinking about getting that and using a diffuser to futher create a suction force under neath. has anyone used this particular spoiler first hand and noticed better handling?

3: Does anyone have a home made FUNCTIONAL rear diffuser and would help me make one of my own?

4: Should i even bother?

The reason i want one is because i plan on racing next year. I want the most out of my N/A car and use aerodynamics to my advantage. Also since i work with FRP/ CF and have lots of spare time i can possibly make a few more for those that would want one.

Thanks

[DR_]

Unless you have significant track experience I vote why bother?

[synolimit]

Originally Posted by DR_

Unless you have significant track experience I vote why bother?

Cause it looks bad azz

[MX52Z]

Seriously, for the mortal human, a rear diffuser will not make a difference in performance, just looks.

[jcosta79]

Originally Posted by synolimit

Cause it looks bad azz

[jcosta79]

Originally Posted by Masterbeatty

I have been researching around for a functional rear diffuser, Nothing for our cars. I have decided to start designing one myself.

Question 1: Since i do not have a wind tunnel in my back yard i was wondering if getting a scale model and making a mini tunnel and doing tests with that to see if it will work well is a worth while idea?

2: I know for it to work the way it is designed a spoiler is also needed. the APR starts to add downforce around 40 MPH, so i was thinking about getting that and using a diffuser to futher create a suction force under neath. has anyone used this particular spoiler first hand and noticed better handling?

3: Does anyone have a home made FUNCTIONAL rear diffuser and would help me make one of my own?

4: Should i even bother?

The reason i want one is because i plan on racing next year. I want the most out of my N/A car and use aerodynamics to my advantage. Also since i work with FRP/ CF and have lots of spare time i can possibly make a few more for those that would want one.

Thanks

If you're serious about racing and adding real downforce, I would start with getting a real wing and mounting it to the frame (not the trunk lid) of the car.

Of course once you do that, to balance the car you are going to need a functioning front splitter; again mounted to the frame so that it doesn't pull off your bodywork once it starts creating real downforce.

Don't focus on how much downforce you are generating (at least at first anyway), worry about overall aero balance and how it affects the handling of the car. In other words, don't put a huge wing and rear diffuser on the car and then neglect the front of the car. The car will handle like *** if you do.

[Minato]

ecomodder.com has a lot of excellent aerodynamic readings. Their main goal is to reduce drag. For the most part, you do not want a sharp angle of attack, otherwise you are going to get highly turbulent flow. The airflow is most likely detached and turbulent at speed by the time it gets to the rear of the underside of the Z anyway since it has no flat paneling on the bottom. You might have luck getting partially reattached flow with a mild angle of attack, starting parallel and increasing to ~10 degrees. Essentially anything that decreases turbulence underneath the car is going to generate a downward force that will counteract any lifting.

[Masterbeatty]

I was thinking about starting With doing a flat bottom. Either aluminum or FRP. From splitter and then the diffuser FRP with a hinge to adjust angle for testing. I need to find out our coefficient of drag because I found a equation to use for the angle of the diffuser. But also switching to the evo-r mirrors will help too. Less drag on those. I see this being a long process.

[takjak2]

Flat bottom is indeed the next step after big wing and front splitter.

CfD for sport package is 0.29

[Masterbeatty]

Since i have truely stared researching this. I have come down to this.
Raise my car up this week and make templates for a falt bottom and possibly for a diffuser. I dont know weather to get the stillen front splitter or a generic one out of CF with adjustabe links. But home depot sells aluminum sheeting for roofing that are almost the perfect size for this so maybe i will start from there and then onto FRP or CF depending how deep i want to dig in my wallet.

Thanks TAKJAk for the Cfd. that helps.

[kenchan]

Originally Posted by Masterbeatty

Since i have truely stared researching this. I have come down to this. USE CARDBOARD!

[gomer_110]

Originally Posted by Masterbeatty

Since i have truely stared researching this. I have come down to this.
Raise my car up this week and make templates for a falt bottom and possibly for a diffuser. I dont know weather to get the stillen front splitter or a generic one out of CF with adjustabe links. But home depot sells aluminum sheeting for roofing that are almost the perfect size for this so maybe i will start from there and then onto FRP or CF depending how deep i want to dig in my wallet.

Thanks TAKJAk for the Cfd. that helps.

Might want to look into Dibond. A lot of my fast local AutoX guys are using dibond for splitters with a lot of success.

[Masterbeatty]

Originally Posted by gomer_110

Might want to look into Dibond. A lot of my fast local AutoX guys are using dibond for splitters with a lot of success.

Damn good find. i just looked at that stuff and it is just what i was looking for this project. Thanks

[ResIpsa]

Here is the diffuser I fabricated out of aluminum and fiberglass. It is around 9 lbs.

[Masterbeatty]

what angle did you use? i was thinking 6-8 degrees based on our CFD. Also did you make a flat bottom and front splitter?

ResIpsa do you have more pics or specs?