Mike Frye

Mark,

Thanks for posting stuff like this. Your methodical approach and trial and error technique and results are very interesting. It really is amazing how much of a difference you saw by just adding 1" of width to the splitter. There must be some critical threshold there that you crossed in the amount of force and speed (or maybe just in the rigidity/strength of the material used)

Very cool though.

mark kibort

Thanks. my pleasure!

Hey, the most interestesting thing was the fact that only added 1" to the splitter, created this problem. Now, I had one cable on the base lip and then added 1" to it, and the entire thing ended up under the front of the car on the way to Thunderhill for testing. i was able to fix it on the road, to do the tests on track that weekend. It worked fine. Then, I started to add more length to it.
I was suspecting that the wider splitter was going to have this kind of issue, but the material never showed signs of bending, though I probably should have taken some video back then too. Now, the deformation is pretty significant. Im not sure that the 3 more support cables will be enough, so Ill probably reinforce it with some honeycomb sheet aluminum that aircraft are built from.

I will take some additional video this weekend to see the flexing, although i dont expect the splitter to near liquify this time with proper support. Ill probably do some pressure sensing from the edge inward to see the actual pressure change, as well as test spots under the car near the front. (and the hood again, with and without the large hood vent sealed up.

anyone want to see anything else tested? test speeds up to 120mph.

mk

Mike Frye

I'd be curious to see if the pressure under the car changes noticeably. Specifically near the oil pan. Since that's your oil cooler it might be good to see if the splitter should be used in conjunction with an external oil cooler or not.

It's great to keep your car stuck to the road at high speeds, but not if it means you're going to potentially run hotter.

mark kibort

I think the pressure change under the car will be negligible. (my first guess). If you think about it, the air we are running over, is just getting some turbulence from hitting the splittler and running under the car. there are no changes in volume, so I suspect, the turbulence we are causing should only make a small change in pressure, to the vacuum side (which is good for downforce). The top of the car has the vaccum, and that we try and reduce with the hood vent. I suppose some of the downforce is acting on the front splitter in the form of differential pressure, on top of it . at 300sq" now, thats a total of 75lbs of downforce at 120mph at .25psi and only 25lbs at 80mph and 12lbs at 50mph (not much) . I suspect that only tells part of the story. the air that is building up (stagnation) and rolling now, off to the sides, is not going under the car, adding to the downforce total probably in a larger way.

Ill do some tests this weekend. 2 spots on the splitter, under the splitter again, with near the oil pan as well. Then, on top of the hood, with and without vent closed.

IcemanG17

MK
okay I need a splitter......of course a rear wing helps too

tveltman

Obviously the best part of that link is the picture of the chromed-out 928 nose...

Mike Frye

And what's the deal with those hood openings? Is that ram air right into the intakes? Why haven't I seen that anywhere else?

tveltman

Probably because unprotected ram-air on a track = ingested tire shreds. I suppose the filter would catch them, but it would be a sad day if you sucked some road debris into your intake at 130+ mph, it still might blow a hole through your filter.

Mike Frye

Yeah, but if there was a screen or something there I imagine it would give a great CAI effect and probably higher volume of air than you normally get snaked up from under and then over the radiator.

tveltman

True enough, and a screen could easily be placed across the existing ram air unit. My explanation number 2 will be that fabbing up a custom hood is too much work when there are already existing solutions to be had. These guys are clearly craftsmen (they used kevlar and carbon fiber to make their splitter, and then admitted that it was a waste). They wanted to do it "perfect" but discovered that the extra expense wasn't worthwhile. Also wouldn't the air be cooler since it wasnt flowing over the hot radiator?

mark kibort

too bad this is a vacuum pressure zone, so it will actually suck air out!

Sure you will get air, but the air pressure there is slight vacuum. I have ram effect from the nose of the car. (measured the pressure with the sunx sensor all the way to the inlet funnels. AND, i have a vent at the base of the windshield. slightly higher pressure. I end up with BIG chunks of rubber, rocks and sand every time im on the track. nothing has ever entered the filter and gotten through. So, as nice as those air vents look, its ineffective and a presssure drop area, lowering Hp output by the percentage that the pressure drops over the base of the windshield or above radiator area. the air that enters the air inlet is not heated by much. it is going near 60mph and the time it is in contact with the radiator is minimal. its all about mass flow. cool is fine, but if its lower pressure its MUCH worse!
think about it. 5000ft 70 degree day in denver or a 100 degree day in LA? NO comparison!

mark kibort

If it worked , it would be fine. any debris would end up in the filter and would have to make the complete U turn before it ended up in the filter. Not an issue. as I said, I end up with all sorts of rocks, rubber and sand from the nose ram air effect. .25psi at near 120mph. that is pretty substantial.

No, the main issue here is that the CAI is what we have STOCK! we have one of the best systems around for a bunch of reasons. you want high pressure air, and not low pressure air that is found starting in that vent area on the picture. I could verify this with the pressure sensor when I do some tests this weekend. You never know, it might still be in the high pressure zone. I think it starts at the line of the front wheel

Pierre Martins

That's my car and the scoops are actually not intakes. The actual intake on this car pulls air from the base of the windscreen through a cowl that's molded into the hood that seals directly onto the airbox.

Cheers,
Pierre.

Mike Frye

Cool!

Now that I look at it again, they aren't quite far enough apart to be in the location of the stock intake tubes.

So what are those then, just for show? (cool car BTW )

Pierre Martins

Thanks.

The scoop openings did actually match up with the mouths of the stock intake tubes. That was my original line of thought, but I never ran the car like that, so now they're just for show. Changed my mind after I saw Porsche's aerodynamic graphs for the 928, and moved the intake to the base of the windscreen, which is a high-pressure area.