Carl Fausett

Yes, its a little confusing. The engineers speak in terms of "lift", so what you and I call down force is "negative lift"

-.300 equals 300 pounds of down force, at the test speed which was 85 MPH.

Note the downforce varied dependent upon the air dam mounted above the chin splitter. In our tests, a low of 250 pounds of down force and a high of 300 pounds of down force.

mark kibort

Carl,

the brackets being so far forward, will disturb the air rolling off the sides, for which is the splitters MAIN purpose. it has to be supported by straps, wires, or posts. the bracket will defeat downforce, but if its for looks, then its fine.

the downforce change is not the pressure on the splitter alone. there is only a 100lbs spread out over the entire splitter at 120mph. ive tested it. ive had failures, pressure measurements and the fixes for which ive used up to 150mph, and only use 3 cables for my design, which does come out to be flush with the nose . (about 6" splitter)

get the square area of the splitter, put a pressure guage on the splitter and you will find the pressure (PSI) divide it out and that is the actual pressure on the piece of metal . this DOESNT equal downforce, which is the difference of the downforce before the splitter vs after it. you are discounting several factors here.
the max pressure you will get in the nose area is about .08psi, theoretical is about .11psi. do the math, it doesnt add up to 300lbs of pressure on the plank, or maybe it does. hmm.. better get out the calculator.

Speedtoys

So his wind tunnel test results are incorrect? There was no 300lbs of wheel-measured downforce added in the Kibort Tunnel when testing Carl's splitter?

mark kibort

car, you could hog out t thos brackets to look more like the posts that hold most splitters. ie, paint the bottom that bolts to the splitter, and carve the entire guts of the bracket out so you end up with "posts" giving it strength. remember, ive used sheet aluminum for speeds up to 120 with no brakets before the 1/8" aluminum failed and rolled under the car direction. wires moved out to the edges cured this problem i have video of the surface at 135mph and no distortion, only using 928 fender aluminum. why is this. its a huge splitter. flat and wider than the car. so why does it not explode at speed? because the force is not at the splitter, its the diversion of air ( the splitter's job, hence the name "splitter")
it is more a guide than a wing. the air then is forced around the sides of the car, and through the intake.. there really is no gain, if you dont vent the inlet air to the roof, hood, wheel wells, etc. the gains are for the air moving around the car, that comes down from the nose of the car. instead of going under the car, this airflow is routed to the sides. this is why those brackets need to be more open. plus they look like crap. (easy fix for you ) just hog them out and thats a pretty neat design.
I also like the part where you can adjust it for trailer loading. although , i havent needed it, as you just need to get creative with the ramps.

mark kibort

adding 4 wire supports to the flimsy 1/16" aluminum sheet


3 small wires used to support the fender aluminnm version.

mark kibort

pay attention. Im not questioning the results, carl is assuming (as many do) that all that downforce is on the splitter. its FAR from the truth and reality.

proof. Imperical proof. why can i go 130mph with 1/16" aluminum with a larger surface area and 3 little wires to support it. plus have a pressure meausrement on the car SHOWING the actual pressure in several spots in and aronnd the splitter surface?? if i have a 300sq" splitter and my pressure is .11psi at 80mph, what is the total force on the splitter??

remember when i was trying to help the wing designer with the wing downforce and then drag force ? folks were not getting that lift to drag ratios of wings are only in the 10:1 range . the 1/2" steel brackets welded to the car like a roll bar, suddenly were changed to light weight mounts to the trunk lid.

Carl Fausett

Appreciate it, Mark, but I spent good money to go to a wind tunnel with this splitter and car.

There were weight pressure pads under each tire to measure true effective force at the the contact patch, be it lift or down force.

If you'd like to watch the smoke wand video of this test, it is on my website here:
http://www.928motorsports.com/othervideos.php

Thats the reason for measuring.... so we don't have to guess what the air flow over and around the chin splitter "might" do.

Speedtoys

Contact patch?

mark kibort

again, i watched the video. i dont contest the results of gains.
BUT, you are assuming that the force is all on the splitter. my video of reality shows otherwise. in fact, there are a few more things going on on an actual video on the road vs the wind tunnel.
so again, no questioning your results, but the brackets will alter flow around them to the point where they will force air under the car, just a fact. you would see this if you poked the smoker in that area. most of your video is showing flow over the car. you ushould have spent more time down low with the splitter and changed a few things to see the results as well.

wanna bet if you open the brackets , based on acepted splitter flow theory, that you wouldnt pick up downforce??

so, what did the splitter add at 85mph, 300 lbs of downforce?

Plus, keep in mind that if you dont remove the rear wing, and just remove the splitter, you then get a rocker effect which can skew actual numbers. for example, if you get 300lbs of downforce in the rear and remove the splitter, then without the splitter, the nose raises up do to the rear wing, giving an artificial number. I dont know your test methodology, but its great you went and had the 1st experience. now, carve out those brackets, and you have a product that looks cool too!

Im making comments to help carl, not to bash. if you just wanted to post to sell and not have anyone make comments, then sorry.

GlenL

Mark,

Don't forget that pressure on one side of the splitter doesn't matter. It's the differential across the plate that pulls it down. Also, the splitter keeps air from going under the car. It's not producing a ground effect that sucks the car down (ala F1) but will increase downforce overall.

I don't agree that the air needs to flow to the sides. Most is going to go over the hood. More over the hood and less under the car. That's an improvement.

I like it and I like the price. It'd be better to have one that worked with an S spoiler without mods, for my use. Maybe remove the plate in town. If you slot the spoiler won't parts be flapping?

mark kibort

Of course Glen, its differnetial pressure, BUT i measured that too, extensively, from nose to about mid oil pan to see, and that remained near ambient. this is measured UNDER THE SPLITTER.
I ALWAYS have said, we are trying to keep the nose air flow from going under the car, thats why they call it a splitter, and that air flow rolls off to the side, to the differnetial pressure. if its lower under the car, under the car it will go, but if its lower to the sides, it will flow to the sides.

the air doesnt reverse its downward flow off the nose, it goes to the sides. this has been prooved with tufts. they dont change direction because you have a splitter. also, you dont want it going over the nose, you want it to go through the vents and out the hood , really.
plus, look at the pressure diff as well. its the highest at the nose, and progressively lower downwards, thats the direction of the flow, not over the car with a splitter.

so NO. if you slot the brackets, youeffectively have what i have. two long bars. one along the splitter and the other dropping down from the top of the bracket. it wont be flappying. you will still have a triangle of strength. MUCH more than you need for this splitter.

mark kibort

for those playing at home, if you have .11psi of pressure in the spltter area, and a 300sq" splitter, that is around 50lbs of total force onthe splitter. sure , it could be making 300lbs of downforce, but it aint onthe splitter. its physically impossible to have more pressure than that on the splitter that size.

do you think you need those brakets for a spread of 50 lbs over the entire splitter, or near 100lbs at 130mph??

IcemanG17

great product..........the 1st one that was actually tested in a real wind tunnel.....which is impressive, since wind tunnels ain't cheap

When I installed my high $$$ walmarts finest plywood and lawn edging (see avatar) it really made a difference.....just by stopping the air from going under the car it vastly improved engine cooling, which forces air through the radiator & then it gets sucked out the hood vent which does increase downforce a little bit.....I don't have any data to back it up, but the car handles better with it, than it did before...

It does scrape in hard corners and when loading on the trailer....but the edging is flexible...so its not too bad....

Carls splitter would be much better......

mark kibort

carl, love the wind tunnel videos!

I just watched my pca race with hanson at laguna. i forgot how great the 928 sounds with straight pipes!

OBehave

Hey Mark any chance I can get a copy of that video for posterity? Ed