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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.

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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 by JMortensen

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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.

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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 by JMortensen

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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..

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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.

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Call me ignant, but I was always under the impression the "purpose" of a splitter was to take advantage of the air that built up on/was blocked by an airdam- The idea being you put a platform (the splitter) under this air (which, when blocked by the airdam, stagnates, builds up, and increases pressure) for it to push down on, causing some downforce (yay downforce!).  Of course doing -other- things to lower pressure under this platform (Ie a belly pan to help keep air flowing quickly/smoothly under it, diffusers to accelerate the air further, etc) should yield a greater pressure differential and increases the overall downforce in theory, but in the end again the point was fas far as i knew,  to simply put a platform under this pressure zone.



 

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Looks intruiging.  Do you have any plans/methods to measure its effectiveness? Or mostly a "seam of the pants/lap times" kind of deal? And I know I tend to ask this a lot, but may I ask what kind of material that airdam was made out of?

Edited by Sideways

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The Airdam is that .125" ABS I think. Molds under heat, flexes nicely but ultimately cracks when abused.

 

No intention of measuring the splitter in any scientific way. I may not even run it for a while.

But mocking it up anyway.

I break a lot of stuff and if I go off track and snowplow through gravel it would be ugly.

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Im actually hoping to use lexan to make a grill-block off plate for my Z when I get back home in june.  I love some of the block off plates others have made around here, i just tend to dislike the look of a giant plate for a front end.  I figure this way I can keep the original(ish) look, and still get the benefits of having that gaping maw blocked off- Plus the ricer in me rather likes the look of my massive fmic.  Whichll be another interesting aspect, theres 0 room to duct a opening to the thing, so itll be a trial/error with templates for awhile until i figure out how small of an opening i can run without having a negative impact on the cooling.  I suppose ill try cutting the grill size in half and then go from there..

Edited by Sideways

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Mostly finished the new Airdam this weekend and kicked it out wider to cover the tires and may look at some off the shelf "dive planes" also. 

 

For all the radiuses in the ABS you see here it requires no thermo forming.

The inlet ducting did need heat and I just used a few heat guns to get it just pliable.

Pretty amazing stuff.

 

While I am serious about car and the progress and the modifications... we are also having fun.

The Splitter is still under review, although I really like the idea of finishing closing up the inlet ducting.

 

Splitter mounting scheme is looking good...  2 horizontal male / female pins in the back by the steering rack, the splitter just slides into those, then lift up and 2 more vertical m/f pins receive the front of the splitter and take cross pins or cotter pins to secure.   Then the stay-rods in front which are still under review by the committee...  (burp)

 

post-1894-0-85576300-1395675675_thumb.jpg

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Man, that airdam on the bottom of the splitter strikes me as a really bad idea. I suppose they probably have a high enough ride height that it wouldn't do anything anyway, so the get the look of the splitter and the cd reduction of the airdam. Then on the hipo version it actually looks right, so that one must either be low enough to use it, or at least you could lower it to be useful. 

 

Interesting to see the different shapes on the undertray. Would still like to try my idea from p1 on this thread and make a venturi under a flat tray...

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I was pitted beside a guy driving a newish vette at the track last week.  The bottom of the nose looked a lot like the ford piece, a big plastic undertray, generally flat, with a roughly 2" air dam mounted back about the rad support, probably 2 feet past the front. 

 

I got a good look helping him load it on his trailer,  I suspect it's mostly there to avoid curbs and wheelstops.

 

jt

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OK, time to make my splitter, and the front end bodywork will largely be built off of the splitter, so it's decision time.

 

Option A is a narrow(er) front end with relatively flat fenders angling out past the front of the tires. This gives less area for the splitter to be in front of a relatively blunt surface, so would make the splitter less effective, but should increase the effectiveness of the bodywork sucking pressure out from under the hood, since I don't have any fender liners.

 

Option B is a wider front end with a sharper corner. This will make the splitter more effective while making the low pressure at the front wheel less pronounced.

 

I'm leaning towards A. Any opinions?

 

Also trying to figure out how close to get the end of the splitter vs the wheel. Thinking since I'll have the suction out the fender, might be better not to make it super close. Opinions there?

post-553-0-24646100-1402950043_thumb.jpg

post-553-0-00926400-1402950045_thumb.jpg

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Cary pointed out that the splitter can be straight across in the front in XP. Had totally forgotten about that. That being the case, I think B makes more sense. I think you're right Cameron that for autox the bigger splitter will have more effect than getting more air out of the engine compartment. 

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