Crude Belly Pan Idea *pic*

[rudypoochris]

This is a crude belly pan idea i have.

 

Idea 1 (in blue) is a pan that would be used with an air dam but could also be used with the stock front valance. The pan would simply angle down to about the begining of the wheel then go flat and stoop about 8-10" from the fire wall.

 

Idea 2 (in Pink) is a pan that would start out lower, so must be used with a front air dam, that would angle down once again till about the beginning of the wheel where it would flatten out. At this point idea 2 is about 2-4 inches lower than idea 1. Now the real difference is that instead of provision for air to escape before the firewall, idea 2 would leave a 2-4" high passage the width of the car all the way to the back where the air continues until it hits the rear diffuser (i think is the tearm?) that is angled upwards. Some provision will have to be made for the air to escape.

 

I am leaning towards idea 2 but I would like to know i should allow the air to escape the rear where the belly pan angles up? Simply louver the angled metal piece?

 

Any comments and please suggestions this is crude it needs alot of work i know but any criticism/comments are useful.

 

NOTE: I forgot to say that the belly pan when it gets near to suspension parts like the transverse links that would interfere obviously has a cut out just incase there is confusion

[Guest iskone]

Are you talking 2-4" below the x-member? That's not gonna work if your car is lowered, wich I would think it is. My lowered 240's x-member is just over 3" from the ground for example.

 

Why don't you make 2 pans? One for the front and one for the rear using the floor boards as your middle section.

 

Isk

[rudypoochris]

Hmm intresting idea

 

So what your getting at is keep idea 1 but then throw in the diffuser at the rear... What about a center pan to cover the tranny tunnel or am i just being silly now?

 

Also do people think that it is good to end the belly pan in idea 1 about 8-10" away or is a shorter or longer sitance necessary?

[Gollum]

I'd make a single piece that has cut outs for the floorpan area, so it would stay as high as possible but still cover the tranny tunnel. I think it's a good idea to cover the tranny tunnel because a well mounted cover for the tranny tunnel means no driveshaft catch required, so extra saftey with less weight than the alternative.

 

I'd also do some major research into undercarriage design tech first. You could seriously improve your arodynamics or totally kill it. I know many supercars wouln't really drive well at hight speeds without them because they help balance the lift coefficiancy so much.

[rudypoochris]

That what i was worrying about killing the aerodynamics somehow. Im afraid if i make the tranny tunnel closed too that the air wouldn't have much of a place to go after entering the radiator, maybe some louvers near the front x-member and then continue it as one large piece threw the tranny tunnel. Im thinking to fasten it just simple nyloc nuts.

[BlackBeaut]

My only experience with full underbellies is on the Lotus Elise. That's made in multiple parts for ease of removal, which you should definitely consider as essential if going for idea 2. Likewise, the Elise pans are aluminium for weight saving, you wouldn't want to be lying under a single piece of steel that's the length and width of your Z tying to shift it out of the way for maintenance!! Looking at your pink line, I'd say you'll want at least 3 sections, front to near firewall. Centre, firewall to front of rear wheel well. Diffuser section.

 

For the centre section I'd be looking to attach somehow to the frame rails, going lower than those would mean potential pain on speed bumps. Unless the car has side skirts then I don't see much point in going wider than the frame rails. The other issue is gearbox cooling, even more so for auto boxes. Decent tranny cooler would be essential, which would mean getting the cooler radiator in to airflow somewhere.

 

The rear section is obviously tricky as you need clearance for control arms/struts to move up and down which is going to make a nice mess of air flow in that region but there's not a lot that can be done. There's also heat isses with the diff to consider.

 

Without doing either computer modelling or getting a model in to windtunnel no one is ever going to really know the true effects I don't think. For street speeds I doubt it would make any appreciable difference. It would be pretty interesting though if someone here does happen to work in a industry where they have access to such toys and can get to play on them in their own time

 

Cheers,

Rob

[rudypoochris]

I am thinking about just doing the front pan idea now and skipping the rest as it doesn't seem to be as easy to create in the rear. I know people ahve done it and on this site too. Has anyone made a rear diffuser that they would like to share?

[Mike kZ]

I am thinking about just doing the front pan idea now and skipping the rest as it doesn't seem to be as easy to create in the rear. I know people ahve done it and on this site too. Has anyone made a rear diffuser that they would like to share?

 

ZR8ED did a rear diffuser: http://forums.hybridz.org/showthread.php?t=77236&page=1&pp=20&highlight=diffuser

 

[Guest iskone]

Wasn't Mike Kelly working on something like that a long long time ago.

 

Rob has a ton of good points. I didn't bring any of that up because I'd be talking out of my asspipe. I'd just read read read and then try it out (full cage of course)

 

Isk

[johnc]

Simple question, why?

 

http://www.mulsannescorner.com/

[ZR8ED]

Hey John.

 

Simple answer.. looks cool.. hehehe

 

 

Seriously. Lots of talk on this subject. Few have done anything about it. Effects on a street Z are minimal to none. (unless you are driving over 120mph all the time)

 

http://forums.hybridz.org/showthread.php?t=91946&highlight=belly+pans

 

http://forums.hybridz.org/showthread.php?t=77236&highlight=belly+pans

 

http://forums.hybridz.org/showthread.php?t=70936&highlight=belly+pans

 

Good links to lots of reading..

[rudypoochris]

ya i read most of those posts and was just wodnering if anyone can critique my design. Thanks for the musannes corner link but have been there many times and can't seem to find the tech articles that apply to me only race car tech. And even then it is only specs could you please advise me where on musannescorner to go?

[SHO-Z]

From your drawing I would worry about front end lift at speed. Zs have enough trouble getting the heat out of the engine compartment so some type of side vents would be required.

[rudypoochris]

Intresting i thought it would reduce front end lift by creating less resistence underneath, effectively balancing low and high pressure, im most likely wrong though. If memory serves correctly the frame rails sit about 1/2 inch lower then the floor pans. Maybe i can do a full length belly pan that sits right on the frame rail. This way air from the engine compartment is carried all the way to the rear diffuser, via the tranny tunnel and what ever space is created by the 1/2" gap between frame rails and floor pan. Too restrictive?

[johnc]

This way air from the engine compartment is carried all the way to the rear diffuser, via the tranny tunnel and what ever space is created by the 1/2" gap between frame rails and floor pan. Too restrictive?

 

No, completely wrong...

 

The idea behind a front splitter (and a splitter is the ony way to get a belly pan to work), a belly pan, and a rear diffuser is to accelerate and then decelerate the air underneath the car creating a low pressure area. The high pressure air above the car (particularly in the cowl area and in front of a rear spoiler) then presses down on the car creating downforce and improving tire grip. Its a complete system that must all work together or, at best, you're just creating drag, and at worst, you're creating lift.

 

Splitter

 

A splitter works by accelerating air from the high pressure area in front of the car and sending it under the front of the car. Often small front diffusers are added that direct the air into the low pressure area in the wheel wells. These small front diffusers often have vortex generators to create additional low pressure vortices and the wheel wells must be vented at the top to increase the low pressure draw.

 

Belly Pan

 

A belly pan directs air flow longitudinally under the car and prevents high pressure air at the sides of the car from spilling underneath and disturbing high speed low pressure flow. You do not want any airflow above the belly pan, that defeats it's purpose.

 

Diffuser

 

A diffuser "releases" the air under the car creating a drop in pressure. Diffusers often include vortex generators and/or strakes to control and direct the flow. Diffusers also must be built to specific angles and volume to prevent boundary layer turbulence or flow separation. Again, you do not want any airflow above the diffuser. Also, a rear spoiler or wing is needed to generate a high pressure area on the car's body above the diffuser. Without that, the diffuser is less effective and the center of pressure will move forward causing instability.

 

When you start adding aero to your car, you have to really start controlling ride height and pitch changes. Any change in the car's attitude disturbs the flow and reduces the downforce you're trying so hard to generate.

 

FYI... all the above are general guidelines. If you're a F1 team you can basically ignore them and do what your hundreds of millions of dollars of wind tunnel testing tells you. For the rest of us, sticking to the above will make your aero efforts pay off. Ignoring them just means you're adding weight and drag.

[Mikelly]

I recommend going to a track day event hosted by a Zcar club... You'll see NO bellypans and rarely a chin splitter. Most track Zs simply aren't employing a lot of these advanced designs.

 

I'll try a few things as I get the car up and running, just for giggles, but I've made a huge turn around on this.

 

Unless you're chasing the salt flats or doing the Silverstate Challenge type events, I'm not seeing much need for these advanced devices below 160MPH and there are few documented cars doing in excess of that in Zcar land... YES there are a FEW documented... But still... A F-E-W!

 

Rear spoiler, airdam, and maybe removing the mirrors and applying tape on the seams... That's about all I would recommend... Beyond that you might end up creating something more dangerous without knowing.

Mike

[johnc]

Here's an example of a splitter on a 240Z (mine) that didn't work. In fact, it made things worse and at over 100 mph almost caused the car to understeer off the track:

 

 

 

I've since cut it up and used the aluminum for other projects.

[Guest JAMIE T]

I've since cut it up and used the aluminum for other projects.

 

LOL, that sounds familiar. I haven't made a splitter, but I have used aborted projects for other things!

 

I'll throw my .03 cents in(inflation) on improving the aero of a Zcar.

 

Head light covers, airdam, spoiler. Get the car RIGHT DOWN on the deck so that no or very little air will want to go under the car.

[rudypoochris]

Thanks for the meaty post johnc so let me try to udnerstand this. Say i got a generic airdam, and from there begane the belly pan. This would create a front spliter provided the airdam doesnt have holes correct? Then i bring the belly pan to the rear and make a 7 degree angled up piece of pan called a diffuser correct? THanks

[johnc]

That would work but make sure the belly pan is flat and level to the road surface at static ride height from the very front all the way back to the break for the diffuser.