Functional Aero Parts and their effects ?

[glamcem]

Hi everyone,

I am about to finish my project so far I ordered below for the track use:

• Enkei RPF1 17x9 +35mm wheels
• Nitto Nt-01 R Compound Tires 235/40/17
• Fortune Auto 500 with Swift Springs (9k/9k), Radial Bearings and Extension Upgrades
• Custom Brake Ducting
• OEM Oil cooler
• OEM Camber Bolts
• Grimspeed MC Brace
• Koyo Radiator
• Perrin OP
• Invidia FP
• Stoptech Brake Pads ( yeah I know)
• Front Lip
• TRD QuickShifter
  

Soon to be ordered :

• Kraftwerks Supercharger Kit
• Ecutek and Tune
• Raybestos ST-43 pads with matching rotors (after it becomes a necessity with FI power)
• JDM underpanel (if it really works)
• Lightweight battery
• Perrin engine mounts (if I don't like the shifting feel after KW)
• schroth 3 rallye harness ASM
• Affordable Hans device

I also would like to improve the aero and reduce the drag as much as possible so I searched but couldn't find a descriptive thread about the aero parts and their effects on our cars (other than the visual mod threads)..I don't really care about the looks, stance ..etc..

My car is BRZ Limited so it comes with the rear spoiler and I am not sure if it's functional at all.. I want to improve the high speed stability so I also added this part to the list

I am on the fence of adding an extension to the front lip like my friend did to his MX-5 since I believe it will improve the air flow for the brake ducting and reduce the lift.. In his case it's believed it has a positive effect when it's combined with a big spoiler.. We know a local guy who can fabricate a custom abs lip like in the picture below





So, for those who invested in aero parts, my question is did you ever notice any increase in stability after adding a bigger lip( possibly with rod) or did you see some negative effects of doing so?

Before adding any other aero parts to my list (canards, rear diffuser ..etc) I would like the hear your experience with them. Since the car will be FI pretty soon, high speed stability is really important for me and the last thing I want is to hurt the car's stability ..also I learned that in some cases adding a bigger front lip also requires a bigger wing to compensate the added friction in the front end or tail happy feel.. I am also debating to get this JDM underpanel but not sure if it really helps reducing the air drag



Any input would be highly appreciated it..

[dradernh]

That's a big subject! I can tell you that I devoted considerable time and expense to aero study, fee-based consultation, parts fabrication, and on-track testing. I'll summarize by saying it was well worth it because the result let me go through corners faster, and with much more confidence. PM me if you're interested in further specifics.

You're correct that you've got to balance the front/rear downforce. That's part of tuning the car's overall setup to meet the needs of the driver, so one size will not fit all. Some want a loose car, and some a neutral car; few want a tight car - they're just slow.

The photo below shows our results, and includes the following aero mods:

1) Well-vented hood, with one large pair located just behind & above the coolant radiator;
2) Shrouding so all air entering the front of the car is forced through the radiators;
3) Front & rear tire deflectors (v. hard to see in the photo);
4) Canards/dive planes;
5) Splitter supported by four turnbuckles, and adjustable from 3"-9.5";
6) Motorsports wing adjustable from -2° to +10°;
7) Wing uprights made for this car and wing; and,
8) Supporting structure for the wing uprights in the trunk that is welded to the frame rails - the uprights are bolted to the structure and can be moved a few inches longitudinally to adjust wing placement over the rear of the trunk lid.

Note that splitters and wings must be mounted rigidly enough that you can stand multiple people on the splitter, and so that you can use the wing to push the car, both with no deflection whatsoever. You will have a very slight side-to-side deflection of the wing.

[glamcem]

^^thanks for the detailed response, it seems like you've spent good amount of time on your E36. I want to use supporting rods for the front splitter to prevent damage caused by air drag (bending ) and wonder if I can get away with the OEM spoiler without loosing the tail, I definitely like the neutral feel ..since the car will be my DD I'd rather keep the OEM trunk and spoiler .

Do you have any experience with FRS/BRZ platform? Can you recommend any spoiler/wing upgrade that can go with a lip spoiler that I can combine with it?

Thanks again

[plucas]

Splitters do not need to be that rigid imo. A splitter is never going to see a direct load of say 150-200lbs like a person standing on it in multiple places. It would have to be a beastly splitter to even make that kind of downforce on any car besides a full out racecar.

For oem trunk and spoiler, I would look into a diffuser and splitter. The best looking diffuser on the market for downforce looks to be Driveway Labs. I have heard through the grapevine there a few splitters that will be out soon that will make some real downforce. For the neutral feel, you will want to have aero balance work with your suspension setup and center of gravity.

[Silver Ignition]

The front lip needs to be mounted to a rigid part of the car, a front lip catching air and pulling down on a flexible urethane bumper is not ideal.


A good middle-ground for a DD is to use a front lip (like the STi lip) that just brings the front end lower. It won't really catch air and produce downforce per se but it will allow less air to pass under the car, creating a low pressure area under the car and essentially using the whole car as a spoiler. This combined with a rear spoiler (adjustable is best but they're big and silly looking on an otherwise stock car...you gotta be pretty nicely modified to pull off a park bench spoiler without looking like a tool) would get that thing planted.


Depending on what you're doing with the car and what kind of speeds you plan on hitting, you'll want to add more or less angle to the spoiler to tailor the downforce to meet your needs.

[celica73]

I'll be honest, with a "mods" list and even more mods listed to come, I don't get the vibe that you have much track experience. My apologies if you do, but if you do not, then the aero is the least of your worries.

I just finished a weekend at the track and the vast majority of the weekend warriors that have cars *faster* than a BRZ choose not to use much of the "faster", as it results in very large budgets for consumables, and very expensive repair bills when things go wrong.

As for aero, what handling problem are you trying to address? Lower drag for higher top speed or more grip at a certain end of the car? Often, those are totally different objectives, and adding functional aero for downforce will quite likely make the car slower in a straight line.

Have you given any real thought to safety? (like the gross imcompatibility between a Schroth rally 3 and a Hans - one is a toy, and the other not so much)

[7thgear]

Originally Posted by plucas

Splitters do not need to be that rigid imo. A splitter is never going to see a direct load of say 150-200lbs like a person standing on it in multiple places. It would have to be a beastly splitter to even make that kind of downforce on any car besides a full out racecar.

..... i've seen home made splitters flutter on the track because they've lost a few bolts or were incorrectly mounted to begin with.

i've also seen a rear wing mount buckle on miata during an autocross run

i think for the home-mechanic, overdoing it in terms of strength/ridgidity can only be of net benefit as they won't have that many chances to make tests of their design at speed in the real world as most don't use software to design/test them and just kinda go off generally accepted approaches.

[glamcem]

Originally Posted by celica73

I'll be honest, with a "mods" list and even more mods listed to come, I don't get the vibe that you have much track experience. My apologies if you do, but if you do not, then the aero is the least of your worries.

I just finished a weekend at the track and the vast majority of the weekend warriors that have cars *faster* than a BRZ choose not to use much of the "faster", as it results in very large budgets for consumables, and very expensive repair bills when things go wrong.

As for aero, what handling problem are you trying to address? Lower drag for higher top speed or more grip at a certain end of the car? Often, those are totally different objectives, and adding functional aero for downforce will quite likely make the car slower in a straight line.

Have you given any real thought to safety? (like the gross imcompatibility between a Schroth rally 3 and a Hans - one is a toy, and the other not so much)

apologies accepted joking aside, I do have some track experience with my previous cars but since I've just purchased the BRZ (about a month ago) I didn't get a chance to take it to the track yet but I am already scheduled for couple track events here in PNW (April 18th and 19th). I plan to attend 15-20 HPDE this season as I did last season.

As for the mods, I am not currently trying to address any handling problem with the use of aeros but instead I am just trying to get the feeling of others' opinions about the aero mods and their past experiences on their effects and benefits (if any)..I do know the fact that adding aeros (as well as the larger tires) will make the car slower on straight line but I am getting my Kraftwerks to overcome BRZ's power deficit so high speed corner stability is what I am after..

and yes, I have given some thought to safety but I didn't extensively search to see what is compatible with what (maybe I can stick to a collar foam and seatbelts and cg lock for now) so I think it'd be better if we stay on subject for now but thanks for the hint

[CSG Mike]

Originally Posted by glamcem

Soon to be ordered :

• Kraftwerks Supercharger Kit
• Ecutek and Tune
• Raybestos ST-43 pads with matching rotors (after it becomes a necessity with FI power)

You're better off with a BBK, and less aggressive pads

• JDM underpanel (if it really works)

Pass on the underpanel

• Lightweight battery

Absolutely helps (get the Shorai from KC Machine)

• Perrin engine mounts (if I don't like the shifting feel after KW)

Do you street drive the car? If you do, I'd recommend against this.

• schroth 3 rallye harness ASM

You'll need a roll bar to properly utilize any harness. DO NOT use the harness on the street; retain your OEM 3 point. Additionally, you need a bucket seat to properly use a harness as well. This means you're now deleting some OEM SRS components, and ultimately are compromising your safety on the street...

• Affordable Hans device

You made no mention of aero. You seem to have a pretty decent budget.

What kind of tracks will you be running and/or what are your typical cornering speeds in the canyons/etc.?

[glamcem]

Originally Posted by CSG Mike

You made no mention of aero. You seem to have a pretty decent budget.

What kind of tracks will you be running and/or what are your typical cornering speeds in the canyons/etc.?

Thanks Mike,

I had some budget but I am now broke
I will eventually get a BBK (preferably a Stoptech) but since I am about to reach my limit I may pass this for this season, we'll see..

For the lightweight batter I was initially thinking about getting one of these
http://antigravitybatteries.com/small-case-batteries/
but I will take a look at the Shorai option as you suggested , as I understand Shorai is a Lithium Iron ( instead of Li-Ion on the anti gravity batteries)

This car will be my DD so excessive NVH might be an issue. Did you encounter any shifting or engine vibration issues at track with OEM mounts after SC?

I really like the OEM seats and don't want to bypass the SRS components for safety reasons maybe I should just stick to OEM seat belts and use CG lock for now..


For the aero mods, as of know I have this front lip

and want to combine that with something like this to help feeding air through my brake ducts




No other aero mods as of know since I don't know what will be the outcome(s)


Thanks again

[Griever423]

Generally speaking and in my experience and the experience of those who regularly track their cars, aero mods are what come last after the rest of the car is dialed in. You'll want to focus on your suspension/safety equipment/power mods/wheels/tires/driver mod/etc. before you even start to worry about aero.

[CSG Mike]

I wouldn't use a replica poly front lip; it'll flex a lot.

[glamcem]

Originally Posted by Griever423

Generally speaking and in my experience and the experience of those who regularly track their cars, aero mods are what come last after the rest of the car is dialed in. You'll want to focus on your suspension/safety equipment/power mods/wheels/tires/driver mod/etc. before you even start to worry about aero.

Good point and I completely agree with you but my intent was to educate myself about the effects of the aero mods in advance to see what to look/expect for. In addition to that, possibly avoid the mistakes (purchase of an expensive wing for instance) beforehand by getting correct information.

Thanks

[glamcem]

Originally Posted by CSG Mike

I wouldn't use a replica poly front lip; it'll flex a lot.

That's what I figured and wanted to combine with that bottom extension part underneath it Sorry, I should've mentioned that the extension part goes about 20" deep underneath the car






I don't think it's going anywhere with the supporting rods and bottom piece