that looks like SOW. not the best track to setup aero.....
First day out with NT01's and wing on the back. I was shooting from the hip trying to figure out what changes needed to be made with the added down force out back. I stiffened the rear dampening on the KW V3's for the extra DF and it only seemed to make the car tail happy. I adjusted the stall angle and finally near the end of the day reduced the rear pressures from 38 hot pressures to 35. It had an immediate effect on stability.
when adding a wing did anyone else make any specific changes that helped? Can/should aero DF be adjusted for in dampining or spring rate only?
I cant wait for temps to cool. I should be good for another second a half when its not as effing blazing out there.
that looks like SOW. not the best track to setup aero.....
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Our converted streetcars are not real aero racecars. So the method is Setting mechanical grip first then if you dabble with aero you keep the mechanical settings. Then say you add a rear wing and that throws the handling. The next step is to add front splitter to balance until you end up with aerodynamic understeer because that is safer for us clubracers and perevents frequent underwear changes.
A couple of things. One, Streets is really not an aero track. My rule of thumb with aero is that you need a 70+ mph corner where you're not already full on the throttle going through it. (And even then, it's not so different than having a few more gallons of gas in the tank. You really need to get up close to triple digits to 'feel' the effect of the wing. I'd guess there's maybe one corner on that track where a wing would have some effect. The rest of the time, you're just adding some drag. My guess would be that your tail-happy issues would have to do with the shock settings and nothing else. On my car, I run one step stiffer on the sway bars with the wing, but that's it. And at Streets of Willow, I wouldn't notice that change in any case.
At the big track at Willow Springs, aero helps me in turns 1, 2 and 9. It probably makes me slightly slower in 8, because of drag. But in my car I'm flat on the gas through 8 with no wing, so the only thing the wing is getting me is a little more stability for that part of the track, not speed.
What are you basing your wing adjustments on? On a car like yours, I'd be very surprised if the airflow is level with the ground, even if your wing is a foot or more above the roofline. On my car, the airflow hits the wing at about 11°, so my wing is sometimes set so it looks like it's pointing up, not down. If the angle of attack on mine is dead level, it's effectively at 11° because of that airflow down the back of the car. I would guess that on an NSX it's not so different. What's the angle of the back window?
Another funny thing related to attack angles is how your wing is mounted. Very few wings have real numbers attached to them. The only consumer wing I have ever seen data on is the APR wing the C5 corvettes use. They make 300lbs of down force at 120mph under ideal conditions. That means you got a whole fat chick standing on her two feet on your decklid. I have worked a lot on NSX's and you would need to place some thought into how to mount an "effective" rear wing.
thanks for the input.
fatbillybob: I added a splitter at the same time as the wing to help the with the understeer. By the end of the weekend I ended up going back to the original settings that I had figured out for the car with no wing/splitter combo. Good to know at least my intuition was working and ended me up in the right place.
Jack:I knew going into it that Streets likely wasen't the best to actually make any effective changes but was curious to feel the difference. maybe it was just placebo or the nt01's are better than the r888 but I was able to go full throttle out of the bowl through the back side. Im going to look into the airflow on the car and set the wing accordingly, I was wondering the exact same as I was fiddling with angle. ill look into deg of the rear window. FYI the wing is kognition mounted to the stock locations level with the roof and has a 74" span.
Mine's pretty ridiculous -- and home-made -- but also at roof height.
If you've got a camera, it's not that hard to check. I cut some short lengths of yarn and strung them around my wing.
I even did some testing where I used compressed air to shoot confetti over the wing at speed. It was cheap (if a little strange-looking) and got me some useful information.
@Jack Olsen- how did you use the info from the first pic? Just to find a baseline AOA?
Yes. I use the wool tufts for two things. They show the direction of the airflow -- in this case the angle it's traveling at before it gets to the wing. And then the tufts also show adhesion along the underside of the wing. When it goes into stall, the airflow becomes unattached and gets turbulent. Maximum lift happens (roughly speaking) when you've got good adhesion at least 2/3 of the way along the underside of the wing. Here's a shot with some tests.
The other way to measure real-world effectiveness is with ride-height sensors. The real ones are scary expensive, but I got some units from a 1995 Lincoln Continental's air ride setup that work. I run them into my data logger. In this graph, the ride-height is lower when the line runs higher. It's a comparison of three laps with the wing and one lap without it.
Awesome, thanks for posting that.