Splitter idea

[JMortensen]

They did a test of this airdam on splitter idea a couple months ago in RCE. Unfortunately the air dam was still pretty high off the ground, so IMO it functioned to spoil the air going under the car more than to create a low pressure area. I still think this could work, particularly at low speeds. 

Edited May 24, 2013 by JMortensen

[HowlerMonkey]

Strength of the splitter and whatever it mounts to is important.

 

At the mile racing events, I see between 2 to 5 cars that come back with the splitter either missing or dragging the ground.......including our twin turbo ford GT that failed downward and dragged the runway effectively reversing the intended effect.

 

Since this happened north of 200mph with the car feeling fine to the driver and watching the guys I work with make a pathetic attempt to remount it to components that would surely fail again, I simply removed the splitter and we have been running without it at speeds over 283mph with no ill effects ever since.

 

That said, a Z car is a far different beast and will surely require some sort or dam or splitter to manage the air going under and reduce lift..........just make sure it's strong because having it fail and running over it could end up like the camaro that crashed at the texas mile recently.

[rsicard]

NASCAR Sprint series runs horizontal splitters from 1" to scraping on the surface for maximum down force.

[texis30O]

@LanceVance

Have you made any progress?  I will be working on my aero attachments to the car as time progresses.   How are you coming along with your install?

[LanceVance]

I'm afraid I don't have any progress to report. The Z is currently disassembled pending body and engine work (lots of modifications in the works); won't be going back together for some time!

 

That said, I've been plotting how I'm going to mount it. The Tegris is incredibly strong, and in a low speed impact (i.e. speedbump, pothole etc) likely to destroy whatever it is mounted to before deforming itself. I've found some rods to support the leading edge that will bend and (hopefully) snap before damaging anything else. Found them at Longacreracing.com (under the misc section).

 

As far as the trailing side goes I'm planning on glassing in a thin steel band to reinforce the airdam and then attaching the splitter with some plastic/nylon bolts. This should allow for separation without excess damage to any other body panels, and should keep things fairly lightweight to boot!

Edited June 6, 2013 by LanceVance

[JMortensen]

Give it a shock absorber. My plan is to mount the rear of mine to the crossmember with a clevis pin setup acting as a hinge. Then the front mount will be a long bolt with a rubber bushing or two on it. If the front of the splitter hits the ground or something, it will compress the bushings but it will have a little bit of give to it, instead of being totally rigid. Then I'll use cables rather than turnbuckles for supports in the front. I figure if I go off the track it's less likely to destroy the splitter. 

 

This idea comes from tube80z.

Edited June 6, 2013 by JMortensen

[LanceVance]

Not a bad idea... A large OD bushing with a small ID used to mate the splitter with the airdam should work well with the flexible front rods. Keep with the plastic bolts and I'll have multiple break points where I want them.

[heavy85]

Having got my lent copy of Competition Car Aerodynamics back, finally, there is a mention of using a diffuser design in the front undertray, will have to study that more to see if its a practical design for the Z.

 

Like this? Its my splitter as if about an hour ago. V2.1

[JMortensen]

You can run a diffuser at the back of the splitter too. Cary showed me a video of the COT a while back and they were talking about significant increases with a diffuser in the back that led nowhere.

[260DET]

The red Zed mentioned in the Hood Vents topic has a single central splitter which seems to work well as should yours heavy85.

[Phantom]

Jon/JohnC - I've been thinking about adding a splitter to the bottom of my MSA type 1 air dam.  Not thinking of it so much for competition but to reinforce the air dam and passible improve fuel economy and cooling. Is it a waste of time for that?  Secondary reason would be for greater stability at speed.  Just replaced the stock springs and struts with stiffer coil overs and adjustable Koni's.

[JMortensen]

There was another aero thread where I think Tony D nailed the reason why John's splitter didn't work out so well. He had no airbox, so essentially a whole lot of air was getting shoveled into the engine compartment, and his was getting scary light in the front end at speed. If you really want the splitter to function, I think the rad duct is a necessary part of the equation. 

 

Another option is what a bunch of the wind tunnel test guys did (bjhines comes to mind), which is to add a flat plate from the air dam to the rad core support. Simpler to construct, less obvious, strengthens the airdam, and doesn't get bent or torn up if you drag it on the ground. It prevents some air from going between the air dam and the ground under the rad, but doesn't prevent it from going over the rad, so not nearly as good an aero solution as a rad duct and splitter IMO. 

Edited March 18, 2014 by JMortensen

[socorob]

Do you have a link to a picture of what he did?

[JMortensen]

Some pics here: http://forums.hybridz.org/index.php/topic/44769-aerodynamics-tip-front-air-dam-mod/

[heavy85]

Some pics here: http://forums.hybridz.org/index.php/topic/44769-aerodynamics-tip-front-air-dam-mod/

Wow 2006. Geeze time flies.

[260DET]

A splitter by itself is not a complete aero device so therefore the effect of using one is impossible to gauge without proper testing. Physically a splitter should be the front edge of an undertray which should extend back to the front X member, at least. The whole idea is to prevent air from the engine bay going underneath the car so lifting it up at speed. With that setup a splitter will work.

[JMortensen]

Richard, I hate to disagree, but the purpose of a splitter isn't to keep air from going under the car. That's the job of an air dam. The idea behind the splitter is to accelerate the air going under it and decelerate the air on top, creating a pressure differential between the bottom side of the splitter and the top side of the lip that sticks out front. If you run your splitter to the xmember, then you will clean up airflow under the car which can increase the effect and maintain higher velocity and lower pressure under the car vs on top. Diffusers into the wheel wells or at the back end of the splitter also intensify the pressure differential at the front lip. The task of limiting air under the car should be done by first limiting the air going into the compartment via a rad duct, and then getting it out via some sort of venting, whether it be fender vents or hood vents or a rad exhaust duct.

Edited March 20, 2014 by JMortensen

[socorob]

Thanks for that link!

[260DET]

Seems like my previous was a bit ambiguous Jon, I agree with your observations and particularly with venting engine bay air so that air is not forced under the car. Like a lot of aero though it's best to design a device by taking into account the whole situation. So eg engine bay vents plus undertray plus spoiler plus splitter should be designed as a whole, which is basically the point I was trying to get across.

 

On splitters in particular, they are best assessed, like most other aero devices, as a whole together with all other relevant aero devices. Depending on their design and the whole of the relevant aero, they can assist in reducing air flow under the car. In my opinion, there is nothing in eg McBeath, that indicates otherwise as far as I can see..

[JMortensen]

Depending on their design and the whole of the relevant aero, they can assist in reducing air flow under the car. In my opinion, there is nothing in eg McBeath, that indicates otherwise as far as I can see..

We're beginning to split hairs  but McBeath does point out that a splitter works BETTER when more air goes under the car on p70. In particular he's talking about diffusers and how they pull more air under the splitter, which raises the velocity and increases the downforce. Regardless, if a splitter were there to prevent air from the engine compartment going underneath the car, it would really need to extend at least until the back of the engine compartment. If not, well, you still have several sq feet of area where that air can get under, so it's not a very effective solution to that problem.