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Originally Posted by Junkwhale
(Post 1475484)
Mounting via stands/endplates seems to make less sense once your wing is that much wider than the body - wouldn't normal stands/mounts be better than all that stuff out the sides of the rear fenders causing drag? Seems like you're greatly increasing the frontal area/size of the wake when it isn't necessary/doesn't add anything.
Extending the endplates down to the chassis may add drag, but not necessarily more than adding uprights to the wing. Testing is key. |
Originally Posted by moocow
(Post 1475493)
Not having bottom mounts increases the efficiency of the wing by allowing smoother air under the wing. That's why LeMans wings often have top mounts.
Extending the endplates down to the chassis may add drag, but not necessarily more than adding uprights to the wing. Testing is key. |
Firstly, the wing is no wider than the car. And most wings run large end plates, so how are these end plates increasing drag when a normal wing has full height uprights (traditional or swan neck) plus end plates? Any normal upright will have bulky connecting system to the wing, that is separation and drag on the wing surface. having nothing under or over the wing is the most efficient way to make a wing work. And that increases with yaw angle. |
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I think the angle of that pic made it look much wider than the car so it looked like the bit circled yellow below was adding quite a lot of frontal area:
Attachment 236843 Be interesting to hear how it goes anyway, looks awesome. |
I will try and remember what happened today and write it here before I forget it all. The car was as reliable as ever, but it had a bad shake all day. I thought it may have been the flat floor and rear diffuser, so removed it all. Didn't make any difference to the shake, or the lap times. It could be the second hand tyres I bought? Kind of off putting for the driver having the whole dash shaking and your not sure if the car is safe. Anyways, the car was only good for a 1:53.1 in the first session, with top speeds down around 10km/h pre aero. So for the second session, I dropped the wing angle one hole down to zero degrees. It then did a 1:52.0. Fuck it was fun holding it flat along the back straight, around the left corner, up over the hill, then only lifting to brake for turn 10. Scary fun.. I have never been around that corner without braking first. And now not only do I not brake, I don't even need to lift. Next session it had fuel surge as I have done nothing about the fuel pick up problem. From a full tank i get about 13-15 litres of useable fuel. I filled it until it was overflowing, it took about 15litres. Next session I dropped the wing to the next hole, under zero degrees. It did a 1:52.1 with plenty of rear aero grip. Just for an experiment to see how much drag the wing effects a low powered car, I took it off completely. It was noticeably faster on the straights. For example, I was changing into 6th at turn 3. And previously with the wing, I don't change to 6th at all coming into to turn 4. But she was an over steering pig with a best of 1:53.1. So even with much higher speeds, it was a full second slower. Was fun sliding sideways, but ultimately, not fast. And for the last session, I put the wing back on. But this time drilled more holes to reduce the AOA even more to where you would imagine the wing can no longer produce any downforce. But it settled the car nicely, and I was able to get my best time of 1:51.8. The large front splitter and wing is just too much for a 90kw car. It was a good day of learning, and I had fun. The day was a little slow, but I kind of expected that being similar to WTAC. http://i66.tinypic.com/14e01eq.jpg |
The small front opening and ducted radiator worked perfect, the gauge was steady all day and never climbed at all. And I pushed for the whole session, even on the out lap. One thing that is worth mentioning is how the car behaved tipping it in without the wing. It was like it had standard shocks and springs on the rear. The car would flop over, then want to go into oversteer. Or like the rear swaybar was disconnected. Well it was, but the car has never had one. Must be because I have the large front splitter, so the front is preloaded, and the rear has some lift. I will upload some video, it may show up as it was very noticeable from the drivers seat. I am going to make a different front without the undercut bumper. Make a smaller rear wing and see how that goes. I have done a 1:50.1 with a different car, but same motor (presumably the same HP), box, flywheel, diff ratio, exhaust, extractors, intake, etc. So I was expecting this car to be quicker. Goes to show how you need to balance the downforce and drag to the horsepower. The 1:50 was done with 2 dodgy alloy extruded wing elements and a big front airdam and no splitter. This car is also around 50kg's lighter. The motor in this car may be a little tired too, it has 236,000 km's on it. |
Originally Posted by lightyear
(Post 1475883)
Next session it had fuel surge as I have done nothing about the fuel pick up problem. From a full tank i get about 13-15 litres of useable fuel. I filled it until it was overflowing, it took about 15litres. |
With regards to end plates and wing mounts affecting the performance of the wing, it's generally not because of straight line airflow. When cornering fast the car is sliding sideways a fair bit so the wing is psssing through the air at a decent angle. The end plates and mounts cast a turbulent shadow across the bottom of the wing surface which caused downforce loss in those zones.
Swan neck mounts cast the shadow across the top surface which is less critical. The vertical section of the swan neck is designed to be far enough in front and narrow to let the air reform before it hits the underside of the wing. In terms of lightyears mounts, I think they should work well. Mounting at the end is good as it helps reduce that shadow area. You need to make sure the leading edge of the wing is close to the leading edge of the side plate. Also Lightyear, the wing can still generate downforce at negative angle of attacks. Some profiles still work at like -15 degrees. Also with ypur fastback the air might be coming down and hitting the wing at an angle. Could the wing have been stalling when you first ran it? |
Echoing MadJak. If you know your profile, look it up here , plot it out and the lift/drag curves will be displayed. The S1223rtl that I built was generating significant lift at negative AoA, falling to zero at 8-10 degrees iirc.
That site also allows your own custom profiles to be used to generate data/curves. Any verdict on the front aero? Seems to work given your understeer without the rear wing, but as good as the conventional arrangement? |
MT gods... is there any chance we could get a dedicated sub section for Aero? Having it all in one thread makes it hard to find info and follow builds.
Lightyear, using only a single lap time makes it really hard to tell what the aero is doing. Ideally the gain in corner exit speeds mitigates the loss down the straight so you need to be logging rpm or road speed at the main corner exits and at the end of straights and comparing with different setups. The best way to figure out how much the aero is working is by running front and rear ride height sensors. I 3D printed an enclosure and lever arm to mount a $10 potentiometer. It works remarkably well as is high enough resolution to detect under 0.5mm of movement. I could post you a couple if you are interested in running them and have a way to log the data. To calibrate you put 100kgs in the boot and measure the ride height change then you can get an idea of how much downforce you are making at set speed. Change the AoA and you can see the difference. Front ride height can give you some idea of the drag too. Stall the wing and the nose should lift but it's pretty hard to measure unless the track is really smooth. |
This pic is from early in the morning, so the wing is abive zero degrees. I have run a narrower wing, but the same profile a lot higher. You can see how compressed the rear springs are, the trailing edge of the side skirts are dragging on the ground, I used these on my old turbo car, they had no wear with the previous wing (same shocks and Spring rates). It was a good test to see how strong the uprights are. This car is running the Oem ECU, so no chance of logging anything. But the turbo car will have the MS3 in it. Would have to get The Beavis to do any kind of computer things, I have no idea. Unfotunately I forgot to bring the lead to charge my phone that I use to do my lap times/speeds with Racechrono. So the only speeds I got was top speed on my IPhone. The car did 197km/h, last time with front and rear spoilers. It did 189.9 with the wing above zero degrees. And 194km/h with the wing set well under zero. I might be going to Winton, a much shorter/slower track this weekend, and it might work much better. Phillip Island is a very high speed track with flowing corners. Big aero and no power on a long fast track doesn't work so well. But it did ultimately do a faster lap time. I will upload some clips, the grip is amazing. I still think the side mounted wing is good, I can see how the swan neck is good, but you still have end plates anyway. The wing was in no way steep enough to be in stall, it was only slightly above zero degrees to ground level. http://i64.tinypic.com/2uhpiqp.jpg |
This video has the data from the rear ride height sensors, they are connected to the Racelogic VBox Lite and not to the Racepak IQ3. From this it is possible to calculate downforce/weight transfer etc., however to measure downforce the car has to be in 'coast'.
In the picture below is the data, note the LR sensor needs to be looked at as it throws a 'bad' value when going into droop. https://cimg7.ibsrv.net/gimg/www.mia...375f4f249b.pngGoing into T3 at Queensland Raceway (Sprint) Very soon I should have some 500hz travel sensors from Racepak to try, will post the data once it is available. |
I had no idea you could make a miata sound that bad.....wow.
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Sounds like a worked BP with an open exhaust. Normal.
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Someone has never seen SM racing. A whole fleet of cars with the same awful sounding muffler.
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No I have seen plenty of SM races. But this is next level buzzyness. Especially on decel. I have driven straight piped miatas before. This is worse imo. Anyways, ill stop filling mailboxes with useless shit. Carry on. :D
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When you said bad, I thought you meant badass, so I clicked on the video.
>Sounds of loud buzzing fill earphones do not want.jpg edit- I second the motion to have an aero subforum or something instead of a single sticky with over a thousand informative posts covering many builds and topics of discussions |
Such a thing was asked for back in 2012 by at least myself, among others.
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I think an Aero subsection would be very useful and also well used. Over the past 25 years the community has pushed most other areas of development to a point where anyone can now use the combined knowledge on this forum to make a very high performance race car.
The one area that is still very much underdeveloped is aero. This one thread alone contains a massive amount of info but I doubt many have time to trawl through it and so we have to rely on google searches stumble to upon good info. Also, this whole Time Attack class of motorsport is becoming a lot more popular worldwide and for miatas to be competitive we need to develop new ideas and push the boundaries then report back here. As a collective we need to find that sweet spot like we have with all other aspects of the car so that we can beat those pesky Hondas and Nissans. |
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