"Front of wheels" aero

[aziza z]

So I have had some ideas floating around in my head since I started to block off the front of my car, and "while im at it", I wanted to build a front diffuser that was stretched "down" the front of the car so less air would get in the car (I am also building ducts to get cool air to the brakes.

 

In the process Ive see some interesting things on other cars as far as "infont of the wheel aero mods" and wanted some of you guys to give me your opinion. My research on the subject tells me that leading edge of the tire is a PRIME source of drag and lift, so I figure covering it up is probably a good call since im down there anyway.There are two things I am constantly seeing:

 

1- A front flap that blocks off the front of the wheels (front and rear wheels). I would think that keeping them angled instead of 90 degrees as pictured would me a little more benificial but I could be wrong.

 

 

 

2-An attempt at straightening air thats about to hit the wheels and suspension components. Mostly seen these with air diverters of some sort or giant vortex generators.

 

 

POSSIBLE 3rd option: having both. The divertors (hope that's the right term) on the "inside" of the car, right before the air hits the suspension components and a flap infront of the wheel? I was looking under the r8 at the la auto show and saw that they had something similar to the divertors right on the rear control arms. Would this be benifical on the s30 cars?

 

 

The overall goal is to have a very stable car (especially over 100mph).

[hoov100]

6 or so threads down

 

http://forums.hybridz.org/showthread.php?t=150099

[aziza z]

Sorry for the pics size. That got a little out of hand but you get the idea.

 

To help visualize here is 240hokes splitter without anything near the front wheels. Only Difference between this design and mine as far as location is that mine will be closer to the floor cause im trying to limit air going under the car (but without having to lower the car even more and loosing even more travel in the shocks, the 17" wheels do not help). Where the splitter meets the air damn im hoping to build a "tapered meeting area". This, Im hoping, will lower the front of the car without actually lowering the car itself if that makes sense.

 

[aziza z]

6 or so threads down

 

http://forums.hybridz.org/showthread.php?t=150099

 

Thanks. Ive seen that thread (where I got the first picture), but didnt want to clutter it with a diffrent concept.

 

The goal of this thread is to compare the "flaps" to the "flow divertors", pros and cons of both and if possible, if it is somehow possible to utilize both of them.

[260DET]

Good luck because specific design info on what you are asking seems to be non existent at a amateur level, if you find any post it up. Did put some vortex generators on a my undertray, there is a topic on it.

[aziza z]

Good luck because specific design info on what you are asking seems to be non existent at a amateur level, if you find any post it up. Did put some vortex generators on a my undertray, there is a topic on it.

 

Yea I kinda noticed. I was hoping someone here had insite on the subject. The racecars seem to have one or the other. Not both. I did find the vortex generator undertray thread, however the pictures have been taken down. Anyone save a copy? Id love to see how that worked out.

[JMortensen]

2-An attempt at straightening air thats about to hit the wheels and suspension components. Mostly seen these with air diverters of some sort or giant vortex generators.

This is a diffuser and those are strakes, not VGs, intended to keep the air pressure under the front of the splitter lower to increase downforce and to redirect the air into the wheel wells, and presumably out the side of the car.

[aziza z]

This is a diffuser and those are strakes, not VGs, intended to keep the air pressure under the front of the splitter lower to increase downforce and to redirect the air into the wheel wells, and presumably out the side of the car.

 

 

Oh i see. Can they work with the front wheel flap or is it kind of a one or the other kind of system? Cause I see how both of them work and the benefits of both and I think that it would be possible to incorporate both, the question is: Are they meant to work togther.

 

My understanding is the flap lowers the area of the tire that the air hit head on, lowering drag, and the strakes (thanks for the correction on the name), keep air pressure down. Both are beneficial so I dont see why they cant be used together. Flap on the outside of the diffuser and strakes on the inside. Let me know If I am mistaken or if someone has seen a system similar to this. I will keep reading o the subject and see what I can come up with.

[johnc]

Oh i see. Can they work with the front wheel flap or is it kind of a one or the other kind of system?

 

Race cars with front diffusers typically don't have a front wheel flap because the diffuser is about 1.5" off the ground. For a road car with greater ride height the front wheel flap helps.

 

You don't want to limit the air going under the car if you're running a diffuser/splitter setup. You actually want as much air as possible and you want to accelerate and then slow down that air in specific areas to generate downforce. Splitters are typically angled up a few degrees to get more air under the car, but this only works if you're running front diffusers.

[ZR8ED]

I think those flaps in front of the wheels are a good idea on a streetcar (when you are trying to improve your cars aero. Like John says. The splitter/bellypan can be much lower on a race car. The flaps are intended to act like an air dam that is lower, yet it is closer to the wheels to reduce the chance of scraping on speed bumps, steep driveways etc. I've noticed them on several different mfg's cars/SUV's etc.

 

I have thought of using them on my belly pan, and even thought of making them springloaded hinged, to allow them to bend rearward to protect against forceful damage incase of severe speedbumps, steep driveways etc. The types I have seen on factory equipped vehicles are fixed, and a part of the moulded front fascia. If they hit anything, they will likely break off/or damage the fascia/moulding etc.

 

You could even angle them slightly rearward on the outermost end, to direct air to the outside edge of the vehicle, instead of facing straight forward like a wall. You would only need a slight angle, and you could bend metal/aluminum in such a way, as to still maintain a forward facing hinge as I have described above to still protect in cases of it hitting the ground.

 

I think I could fab up a bristolboard mock up for a picture to describe a bit better of what I mean.

 

If you plan your splitter/pan properly, you should be able to add it on afterwards, or remove it later on if you don't like it.

 

On a practical note, determining its effectiveness I think is pretty much impossible for a street Z, but it would look cool, and make you at least believe that it "helps" I'm not trying to be sarcasitic here, but just consider that you may not be able to "feel" any difference. I have not been able to notice any difference what so ever in my redesigned air dam and extended bellypan. I can only say with certainty that it did not degrade the handling/feel/stability of the car, though I "believe" that it was a worth while improvement.

 

Scott.

[JMortensen]

Oh i see. Can they work with the front wheel flap or is it kind of a one or the other kind of system? Cause I see how both of them work and the benefits of both and I think that it would be possible to incorporate both, the question is: Are they meant to work togther.

Look at the top picture you posted. You can see the flap, and on the inside, air is diverted up and out the wheelwell. That car is not using a splitter, but it does use a relatively flat bottom. Putting a flat bottom on a Z might reduce drag a little bit, but that's a HUGE undertaking to reduce a bit of drag on an already draggy car.

 

You don't want to limit the air going under the car if you're running a diffuser/splitter setup. You actually want as much air as possible and you want to accelerate and then slow down that air in specific areas to generate downforce. Splitters are typically angled up a few degrees to get more air under the car, but this only works if you're running front diffusers.

I think as a practical matter, most people considering aero mods to a Z car do want to limit the air going underneath the car. They should IMHO also focus on getting the front of the car as close to the ground as possible, unless there are other under the car downforce producing tunnels, diffusers, etc. Most Z cars won't have any of this, and due to the relatively soft spring rates used in street cars, the simplest and probably most effective solution is an air dam that comes as close to the ground as you can get it. Just keep the air from going underneath the car, limit the air going into the front with a radiator duct, put some vents in the hood and/or fenders and you'll get downforce on the front end, just like a NASCAR. I think you'll get significantly more than the wind tunnel test cars did without the radiator duct too. People don't seem to want to model their car after NASCAR, but the pre-COT NASCAR cars make good downforce and have no splitters, diffusers, tunnels, flat bottoms etc. and in the most basic terms are probably the most realistic analog to a Z car you're going to find (not going to twist the cabin on a Z for left hand turns, etc).

 

In my opinion a lot of the focus on splitters and undertrays for street cars is wasted effort. These things don't do much except reduce drag until they get REALLY close to the ground. At the point that you get them close enough to the ground to work, they become very pitch sensitive, so I don't think they're very useful at all to a streetable Z with streetable ride heights and spring rates.

 

While I agree with what John says about raising the front end of a splitter and running a diffuser in front of the front tires being more effective (because it essentially creates a venturi under the nose which can be more effective than either the splitter or the diffuser alone), I just don't think this applies very well to Z cars. Another major reason the front lips are turned up or have a raised section in the front to make the car less pitch sensitive. I think this latter part is pretty important, especially if we were talking about a street Z which would tend to pitch a lot. So I guess what I'm saying is, if you're going to do it wrong, tip the front end of the splitter up so that it is less pitch sensitive.

 

Here's what it looks like when a DIY team tries to really utilize ground effects diffusers/tunnels, etc to produce downforce:

 

http://www.corner-carvers.com/forums/showthread.php?t=41232&

More on the same car (scroll down): http://hem.passagen.se/hemipanter/

 

Note, wheel travel is +/- 1 inch

Frequency is 4 Hz to keep the splitter off the ground. I don't know exactly what that equates to in Z terms, but I would guess 800 in/lb springs for a fairly light Z.

[260DET]

Yeh as Jon indicates you need to consider practicalities and what you want to achieve.

 

For example, the undertray on mine (I call it an 'undertray' because this one is an aero device, not because it sounds F1'ish or other cool) was designed to give downforce, to direct cooling air back for the transmission and not into the wheel wells and to give reasonable ground clearance.

 

Without test facilities all you can do is study the theory, consider the implications and practicalities of what you want to do and then go from there.

[aziza z]

I havnt forgot about this thread. Im developing something and will post my project soon.

[bjhines]

I was thinking that the small aero dams in front of the wheels were there to keep airflow moving through the wheelwells and assisting in brake cooling.

[Mikelly]

Which, if you rewind the memory banks, is what our windtunnel engineer mentioned, using Roddy's car as a perfect example. He was pretty clear on the fact that those spinning tires having coverage in front of them was a good thing, and referenced the new design of the COT in NASCAR as well...

 

Merry Christmas!

Mike

[johnc]

While I agree with what John says about raising the front end of a splitter and running a diffuser in front of the front tires being more effective (because it essentially creates a venturi under the nose which can be more effective than either the splitter or the diffuser alone), I just don't think this applies very well to Z cars.

 

Jon is correct regarding the practicality and I was speaking more in terms of a pure race car. I tried an "ideal" front splitter/diffuser setup on the ROD but for trailer loading reasons it was about 3" off the ground. It was a big mistake and I pulled it off the car after three laps after scaring myself silly at 110mph. Rear downforce and front lift make for a real big push.

[RebekahsZ]

For trailer loading, my airdam has been a big hassle. After crushing it a few times, the fiberglass was full of cracks and my beautifully painted airdam was toast. I replaced it with a uethane airdam that was black from the factory and I never plan to paint it. I've got 6 foot ramps, a 2 foot dovetail and I still hammer my airdam everytime I load/unload.

[tube80z]

For trailer loading, my airdam has been a big hassle. After crushing it a few times, the fiberglass was full of cracks and my beautifully painted airdam was toast. I replaced it with a uethane airdam that was black from the factory and I never plan to paint it. I've got 6 foot ramps, a 2 foot dovetail and I still hammer my airdam everytime I load/unload.

 

Get a tilt hitch. Makes a world of difference.

 

Cary

[Mikelly]

Or weld on some braces and Dzeus fasteners and just remove the thing before you load it on the trailer... I use 6 on my MSA Type3 airdam and we are really low to the ground, and getting lower with the addition of a smaller diameter wheel/tire combo...

 

Mike

[Gollum]

When I was thinking about this topic (when that picture was first posted in that other thread) I liked the idea of adding flaps to a street car.

 

Though I'm still pretty stuck on the idea of mounting it to the suspension, probably where the TC Rod connects.

 

By connecting it to the suspension you can mount it closer to the wheel and closer to the ground. When the flap is part of the body it needs to have clearance for bump travel, but mounting it to the suspension allows the flap to move with bump travel, which should make it hard to scrape. It should also help with things like trailer loading.

 

It wouldn't be much different than how cars like that caterham and ariel atom mount their wheel, covers.

 

Example: