E30 Aerodynamics

[squidmaster]

Anyone wanna put their aero where their mouth is?

https://www.instagram.com/p/BOSPw88AHbs/

[e30_302]

Buy a roll of ABS plastic from speedwaymotors, you can do all sorts of stuff with it.

http://www.speedwaymotors.com/Colored-Plastic-Rolls-25-Ft,31414.html

[RoccoB517]

^^^^^Alumalite would be the ticket for that.

[2mAn]

Seeing this again made me want to look closer and I wonder if these are available to buy



so it looks like those pieces can be bought new, but would need to be adapted to a regular bumper'd car

https://www.realoem.com/bmw/enUS/showparts?id=1003-USA-05-1989-E30-BMW-M3&diagId=51_0767

#15, 17, 18

I just like this as an OEM solution, but realistically, this would probably be a lot easier with a flat sheet cut to fit

[TobyB]

Anything by Carroll Smith. I don't think he did much aero, tho...

t

[2mAn]

Right, the updated 3rd edition just came out about a year or two ago.

sweet, its already on my list of books I need to buy/read.

Just an update. I'm going to be doing some changes to the car this off-season that will allow me to smooth out the flow a lot better. I won't need a muffler anymore, the diff cooler will allow me to close up the NACA duct, and some adjustments to the rear suspension will allow me to close up a bit more space surrounding the trailing arms. The only thing I can't manage to clean up is the skid plate. Where it sits is only 3/4" from the oil pan, and 1.5" from the ground.

(Havent read the book yet obviously so this is just me thinking out loud)

Could you do something to direct the air in front of the skid plate out the side/ around the skid plate so it becomes less of a dragging object?

[RoccoB517]

Just an update. I'm going to be doing some changes to the car this off-season that will allow me to smooth out the flow a lot better. I won't need a muffler anymore, the diff cooler will allow me to close up the NACA duct, and some adjustments to the rear suspension will allow me to close up a bit more space surrounding the trailing arms. The only thing I can't manage to clean up is the skid plate. Where it sits is only 3/4" from the oil pan, and 1.5" from the ground.

[e30_302]

Right, the updated 3rd edition just came out about a year or two ago.

[2mAn]

Competition car aerodynamics is a pretty good one.

Is that the one by Simon McBeth?

[e30_302]

Competition car aerodynamics is a pretty good one.

[2mAn]

I read a few books a long time ago...
t

Thanks for the reply Toby, that makes a lot of sense actually. Care to share the titles of those books you read?

[TobyB]

I want to leave more exposed than he did.

It's all or nothing-
if you leave something to cause turbulence, the air will very seldom reattach.
It has to be smooth from in front of the front bumper/air dam.

And incremental gains are made from the front back, as in, if you smooth to the front doors
you gain some, if you smooth to the rear axle, you can get more,
and if you smooth all the way back, then something like a diffuser starts to become
predictable and possibly even tunable.

I read a few books a long time ago...
t

[2mAn]

My concern with a flat bottom is heat management. Of course we do endurance racing so it may be more of an issue for us than others. A deep air dam and side skirts are low hanging fruit with little downside.

I know that RoccoB517 has a full flat bottom on he has seen a rise in diff temps, but I think I want to leave more exposed than he did. His is a complete flat bottom with a single NACA duct by the diff and a few other openings.

I added a full flat bottom and diffuser to the aero package, and let me tell you, it made a HUGE difference.

This is an amazing thread. Funny Ive been reading about aero underbody stuff and nobody has gone to the extent you've have (or at least shared it here). The only thing Im wondering about with the underbody stuff is the trans and diff temps, have you seen an increase? I noticed a NACA duct style for the diff

I do think the diff temps are getting higher than I would like. I will be installing a diff cooler during the off-season this year. I haven't had any issues with the trans. I have been keeping an eye on the fluids, and it seems like the trans fluid is doing okay and the diff has to be changed more frequently with the lower amount of airflow.

I noticed the difference in the way the car felt in the very first lap after installing the flat bottom. The aero load from the wing and splitter definitely increased, and the car feels less "floaty". Sometimes inconsistent track surfaces at speeds north of say 90 mph would cause the car to bob a little. It stays flat now.

The next time I have the under tray off I'll snap some pics of the mounts for you guys. It's really just simple 1" flat strap bent into an L shape. The bottom has a nutsert to allow the under tray to be bolted up, and the other end is a single 1/4-20 nut and bolt through the pinch weld at the bottom of the rocker. I basically created mounting points that clear all of the mess under there, and they attach at the same points as the side skirts.

I love what he's doing and I hope to adopt some of his tricks. Heres his thread

http://www.r3vlimited.com/board/showthread.php?t=341125

[e30_302]

Here's my hooptie

[e30_302]

My concern with a flat bottom is heat management. Of course we do endurance racing so it may be more of an issue for us than others. A deep air dam and side skirts are low hanging fruit with little downside.