pedrosixfour Posted June 10, 2011 Share Posted June 10, 2011 (edited) Hi folks. I have this rear GT style wing ready and waiting to be fitted to the track car once its back in action.\/\/\/\/\/\/\/\/\/ At the moment the car has the OEM boot spoiler, but also the optional roof spoiler, fitted to it. Basically this arrangement \/\/\/\/\/\/ My question to those that might have the understanding to hazard an answer is: Do you think that the roof spoiler may have a negative (or indeed positive) effect on the performance of the rear wing? Was there any documented reason the roof spoiler was fitted, other than aesthetics? I'd like to believe the roof spoiler would straighten and feed more of the the passing air directly to the working parts of the rear wing but my understanding of such things is pathetic at best. Any opinions on this are welcome as I know a wind tunnel or proper on-track testing with sensors and the like are probably the only ways to be sure. Thanks for your time. Damien. Edited June 10, 2011 by pedrosixfour (see edit history) Quote Link to comment Share on other sites More sharing options...
evinX Posted June 10, 2011 Share Posted June 10, 2011 Just swap the boot lids over? I believe the roof spoiler channels air over the stock spoiler to provide more downforce Quote Link to comment Share on other sites More sharing options...
Morpheus Posted June 10, 2011 Share Posted June 10, 2011 (edited) Running it through the old 'mental wind tunnel', at first glance it would appear that the roof spoiler would help to channel laminar airflow more directly onto the top surface of the rear spoiler and whilst it may not be necessary at lower speeds, it undoubtedly creates a pocket of relatively still (and thusly negative) air pressure underneath it, (around the top of the rear window), which would act to draw in air from above and from the sides as it passes over the roof, potentially directing a good portion of the laminar (higher pressure layered) air that would have stayed higher up, (perhaps too high), downwards and more forcefully onto the upper rear wing, at higher speeds. It would form a kind of cushion of air between the roof and rear spoilers, perhaps bridging the gap. I think of it as 'pinching in' the waistline of the airflow over the back of the car, holding it tighter against the body. In other words, the roof spoiler will create a lot of turbulence, (in a controlled fashion), which would otherwise not have existed that would suck the passing air down and keep it pressing on the rear wing when it would otherwise have broken up behind the car above the rear wing instead of pushing down on it. Obviously Toyota will have tuned it in a proper wind tunnel so that at speed, the effect would be to either increase downforce or reduce drag. By all accounts, the rear spoiler/wing was intended to increase stability under heavy braking, since these cars can get a bit light at the back and cornering stabilty under braking will be improved. The roof spoiler might just be a glorified sunshade, on the other hand! That's my take on it for what it's worth. What does Chris Wilson reckon? Edited June 10, 2011 by Morpheus End of line word repeat error when sentence too long. (see edit history) Quote Link to comment Share on other sites More sharing options...
Noz Posted June 10, 2011 Share Posted June 10, 2011 I know its a different car, but I read that the GT4 upper boot spoiler actually worstened down force and increased drag. Just my input, slightly related, ish Quote Link to comment Share on other sites More sharing options...
Homer Posted June 10, 2011 Share Posted June 10, 2011 Those roof "spoilers" aren't designed to aid downforce, they're not even spoilers at all, they're actually sunshields for the rear passengers Quote Link to comment Share on other sites More sharing options...
j_jza80 Posted June 10, 2011 Share Posted June 10, 2011 Just swap the boot lids over? I believe the roof spoiler channels air over the stock spoiler to provide more downforce + Running it through the old 'mental wind tunnel', at first glance it would appear that the roof spoiler would help to channel laminar airflow more directly onto the top surface of the rear spoiler and whilst it may not be necessary at lower speeds, it undoubtedly creates a pocket of relatively still (and thusly negative) air pressure underneath it, (around the top of the rear window), which would act to draw in air from above and from the sides as it passes over the roof, potentially directing a good portion of the laminar (higher pressure layered) air that would have stayed higher up, (perhaps too high), downwards and more forcefully onto the upper rear wing, at higher speeds. It would form a kind of cushion of air between the roof and rear spoilers, perhaps bridging the gap. I think of it as 'pinching in' the waistline of the airflow over the back of the car, holding it tighter against the body. In other words, the roof spoiler will create a lot of turbulence, (in a controlled fashion), which would otherwise not have existed that would suck the passing air down and keep it pressing on the rear wing when it would otherwise have broken up behind the car above the rear wing instead of pushing down on it. Obviously Toyota will have tuned it in a proper wind tunnel so that at speed, the effect would be to either increase downforce or reduce drag. By all accounts, the rear spoiler/wing was intended to increase stability under heavy braking, since these cars can get a bit light at the back and cornering stabilty under braking will be improved. The roof spoiler might just be a glorified sunshade, on the other hand! That's my take on it for what it's worth. What does Chris Wilson reckon? = Those roof "spoilers" aren't designed to aid downforce, they're not even spoilers at all, they're actually sunshields for the rear passengers Quote Link to comment Share on other sites More sharing options...
TLicense Posted June 10, 2011 Share Posted June 10, 2011 My personal opinion is that the roof spoiler is likely to separate the flow over the boot lid. The separated flow is going to be turbulent to some degree and that is what is going to be flowing onto a good portion of the wing. However, it looks like in the picture that the roof spoiler has a slot at the front? This is likely to try to reduce the separation behind it by keeping it fed with air. It will likely work, but not as well as if it wasn't there at all. I wouldn't say the wing isn't going to work at all because of the roof spoiler, but I can't see that it will necessarily help. There's a few simple-ish tests that can be done on the road to see what effect the roof spoiler has, but obviously the best way of finding out is a wind tunnel test as there are always things that you don't necessarily see straight away that have unforeseen effects. Hope that helps! Quote Link to comment Share on other sites More sharing options...
Morpheus Posted June 10, 2011 Share Posted June 10, 2011 My personal opinion is that the roof spoiler is likely to separate the flow over the boot lid. The separated flow is going to be turbulent to some degree and that is what is going to be flowing onto a good portion of the wing. However, it looks like in the picture that the roof spoiler has a slot at the front? This is likely to try to reduce the separation behind it by keeping it fed with air. It will likely work, but not as well as if it wasn't there at all. I wouldn't say the wing isn't going to work at all because of the roof spoiler, but I can't see that it will necessarily help. There's a few simple-ish tests that can be done on the road to see what effect the roof spoiler has, but obviously the best way of finding out is a wind tunnel test as there are always things that you don't necessarily see straight away that have unforeseen effects. Hope that helps! Yes it does help. You're right about the inlet and it would help to mitigate a bit of drag compared to a closed joint. Wouldn't be atall surprised if it caused more drag than it cured, even if it was designed to reduce it, which it wasn't, obviously. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted June 11, 2011 Share Posted June 11, 2011 Running it through the old 'mental wind tunnel', at first glance it would appear that the roof spoiler would help to channel laminar airflow more directly onto the top surface of the rear spoiler and whilst it may not be necessary at lower speeds, it undoubtedly creates a pocket of relatively still (and thusly negative) air pressure underneath it, (around the top of the rear window), which would act to draw in air from above and from the sides as it passes over the roof, potentially directing a good portion of the laminar (higher pressure layered) air that would have stayed higher up, (perhaps too high), downwards and more forcefully onto the upper rear wing, at higher speeds. It would form a kind of cushion of air between the roof and rear spoilers, perhaps bridging the gap. I think of it as 'pinching in' the waistline of the airflow over the back of the car, holding it tighter against the body. In other words, the roof spoiler will create a lot of turbulence, (in a controlled fashion), which would otherwise not have existed that would suck the passing air down and keep it pressing on the rear wing when it would otherwise have broken up behind the car above the rear wing instead of pushing down on it. Obviously Toyota will have tuned it in a proper wind tunnel so that at speed, the effect would be to either increase downforce or reduce drag. By all accounts, the rear spoiler/wing was intended to increase stability under heavy braking, since these cars can get a bit light at the back and cornering stabilty under braking will be improved. The roof spoiler might just be a glorified sunshade, on the other hand! That's my take on it for what it's worth. What does Chris Wilson reckon? I am not an aerodynamacist, so have no idea, but if it were mine I'd take the one on the hatch window off as it looks as if it will do nothing beneficial, looks tacky, and possibly it will agitate the air flow to the spoiler or wing. I always thought they were just some sort of fancy sun visor, too. Quote Link to comment Share on other sites More sharing options...
stinboy Posted June 11, 2011 Share Posted June 11, 2011 I'm sure I read somewhere that you have to be doing well over a ton for the spoiler to have any effect anyway. I could well be very much mistaken though Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted June 11, 2011 Author Share Posted June 11, 2011 Thank you to all who took the time to offer an opinion. The consensus seems to be its a bloody sun screen, which is totally useless in Ireland, so it's coming off! I can see both sides of the aerodynamic debate, but as i said I'm completely ignorant to the characteristics of flowing air. The only thing I'm pinning my choice on is that there may be less air flow separation from the body if there isn't a large step to contend with just after the roof. A smoother profile may allow the rear wing to hit cleaner, denser air and so perform better. Feck it though, the main reason I bought the wing was because I knew it'd look cool on an actual track car. Being quicker is totally irrelevant! Quote Link to comment Share on other sites More sharing options...
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