Truck Aerodynamics

[Frank Enstein]

A splitter has to stick out further than the bumper, or it has no effect. If it's shorter, whatever air it pushes upwards pushes up on the bumper, giving you no net downforce.

It will still reduce lift by making a low pressure area behind it pulling air out of the engine compartment and it will reduce drag usually.

 

[Erik the Awful]

The effect you're talking about is from an air dam, not a splitter.

 

[Frank Enstein]

The way I understand it is splitter helps the air dam be more efficient because the air doesn't spill off the bottom of the air dam and the added air pressure on top of the splitter and the lower pressure under it adds downforce/reduces lift at the front of the vehicle. The reduced drag comes from reduced air under the vehicle, The underside of most vehicles is an aerodynamic disaster area. Please correct me if I'm wrong. I've been wrong more than once, today.

 

[thegawd]

clear as mud! hahaha CHEERS!

 

[Erik the Awful]

A splitter literally splits the air going under the truck from the air going over the truck. If your bumper sticks out further than your splitter, that air pushes up on the bumper, negating the effect. The splitter works best when it's less than 2" from the ground, much more and it's pretty useless. While an airdam reduces drag from turbulent air hitting all the suspension components, it also increases the frontal area of the truck, causing more drag.

Lowering the truck, and adding an airdam in conjunction with the splitter less than 4" off the ground is optimum. Either remove the bumper, or recess it to maximize the splitter's performance. You can go with a bigger splitter, but you also want to watch the weight you're adding to the nose. You want the splitter wider than the nose, and incorporating dive planes is recommended. Last, you want strong mounting. You should be able to stand on the splitter without fear of breaking it. I personally like using short steel cables to support the nose of the splitter with a hard mount at the back. If your suspension is in compression and your approach angle to a dip is too steep, the splitter can scrap the ground, and fixed supports will drive the splitter into the surface, potentially ripping it off. Cables will allow it to flex up.

We run an ex-NASCAR splitter on our BMW, attached to the factory air dam. The car's low enough the splitter rides just under the 4" mark. The splitter's some kind of cheap plastic that glides across the ground if it makes contact. It's a little less rigid than plywood, but our setup is very durable and repairable which is a consideration for us. You can notice a handling difference without it. If I remember right, our previous MR2 was about 2 seconds a lap faster at MSR Houston with it.

 

[Erik the Awful]

Also, if you put a splitter/airdam combo up front, you really want a spoiler out back to balance it. We run a big wing. Our is the bottom car in this article. https://grassrootsmotorsports.com/articles/low-buck-tech-lemons-racing-music-matters/

Also, also, notice that we have to run an extractor vent behind the radiator and we have the leading edge of the rocker panels cut out to extract high pressure out of the wheel wells.

 

[Steve Addy]

Ya don't use lawn edging! That's for amateurs! You use flexible cove base. Everybody knows that!

Flexible cove base you say....hmmm, never thought about that but if I saw it out there I'd recognize it.

Steve

 

[Frank Enstein]

Flexible cove base you say....hmmm, never thought about that but if I saw it out there I'd recognize it.

Steve

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[thegawd]

sorry guys, this is the real thread.

 

[PlayingWithTBI]

Yeah, I thought there was a lot more to it, ha ha.