View Full Version : Drag factor
No its not pictures of me doing a drag act for the next new "reality" saturday night TV series:roll: lol
Was wondering if anyone has come across any drag coefficient figures for a Nova?
Hhhhhmm, i did have some figures somewhere for them.
Relating to total frontal mass (area) and arodynamic properties (about the same as a ham toastie lol), will try and dig them out when im next at my rents house :thumb:
I'm thinking high 0.3 - to low 0.4 mainly due to sharp edges and boxy shape
A flipping Calibra is about 0.26 pretty much as good as you can get from astandard production road car:eek:
Yea, i read somewhere that the Calibra was designed to have as little resistance as possible!
that was only for the 8v cally though ;) the other ones were more into the 30's like you'd expect.
You could work it out by RR'ing a nova kept at 70mph by the rollers and get a power curve off the throttle from whats needed to 100%. Then go out and do 70mph in the same gear, with a data logger on the throttle.
see how much power at the wheels is required to hold 70mph and then you can reverse the calculation I use to estimate speed from power. job done.
craig green
15-02-08, 04:56 PM
Stu, you need to get out more.......
Interesting though I guess. CP, what are you upto?
chimp007_uk
15-02-08, 04:59 PM
the drag coefficient of my manta hatch is 0.35 i believe, so must be similar
Is the calibra really that good ?
Stu, you need to get out more.......
Interesting though I guess. CP, what are you upto?
I need to stop going to work so much lol. Ive just finished some software that calculates the current drag (aero and friction), then works out how much torque you need in the next gear to hold it, and if the engine has enough torque at the next engine speed to do that lol
in short, v similar to this but on a transit scale
Nick, the 8v calibra was that good on std skinny 15" wheels, but any other model wasnt
Philsutton
15-02-08, 05:59 PM
Thats about as good as a Calibra gets though.
peester
15-02-08, 06:03 PM
Is the calibra really that good ?
hell yeah.. then we lower them 60/85mm hehee
I remember someone a long time ago saying how the Nova wing mirrors were possibly the worst design for wind resistance. Had the effect of throwing a sail out each window lol
I believe a house brick has a drag coefficient of 2.1, so the Nova has to be somewhere close to that surely??
*Useless bit of info* A Countach has a higher drag coefficient than a bay window VW camper van
if the old grey matter is still up to speed, I believe a mk1 sr had a cd of .34 which, when compared to the sleekest thing from the eighties, the mk2 astra gte 8v at .32 is quite good.
CP - add go faster stripes - then you'll cancel out any drag factor!
In fact - if you add viper stripes on youll actually be pushed along!!!
lol
Seriously though I tried to look up drag factors on the net and apart from the transexual porn sites most of it related to braking distances in the wet after an accident!
Have you tried comtacting Vauxhall? They maybe be able to advise...
I had a hair brained idea to tape up all the panel gaps but the idea was dicarded due to the fact someone would have to tape me into the car before a session lol
peester
15-02-08, 08:12 PM
I remember someone a long time ago saying how the Nova wing mirrors were possibly the worst design for wind resistance. Had the effect of throwing a sail out each window lol
it was CP himself lol..
also said a land rover defender had more aero dynamic mirrors on them..
it lead to no mass movement of fitting landy mirrors on novas tho.. sadly.
I had a hair brained idea to tape up all the panel gaps but the idea was dicarded due to the fact someone would have to tape me into the car before a session lol
lol Classiclol LMFAO! Is it bird, is it plane? no its a mumified car!
I know it looks gash but following on from Dar's idea of trying to sort out some better aerodynamics I was wondering about trying to fit a rear wing for down force. This has lead to me to wonder about the overall aerodynamics cos it could be that if the car is too bad any attempt to add a wing may just be largely a waste of time and money. Had a look at some gas saver sites to see what they do to improve MPG thinking that some mods to the Nova may help it to be more slippery and the wing to work. :confused:
lol Classiclol LMFAO! Is it bird, is it plane? no its a mumified car!
I know it looks gash but following on from Dar's idea of trying to sort out some better aerodynamics I was wondering about trying to fit a rear wing for down force. This has lead to me to wonder about the overall aerodynamics cos it could be that if the car is too bad any attempt to add a wing may just be largely a waste of time and money. Had a look at some gas saver sites to see what they do to improve MPG thinking that some mods to the Nova may help it to be more slippery and the wing to work. :confused:
Ive had loads of discussions with Dar regarding this, and tbh my opinion has changed somewhat since he initially decided to do it, to now.
Firstly, the statement he was going to bolt what is essentially the side of a shed to the bottom of his car filled me with mirth, however after watching the Top Gear boys essentially bolt the side of a shed to the bottom of their diesel BMW, and then lose a lot of grip when it enevitably fell off, made me sit up and pay attention a bit. Im now pretty convinced it'll work and Ill probably make one myself once its been proven (I have the rear diffuser ready to go on since it helped reduce the drag the rear bumper produced on his as well lol)
Im not so convinced with the rear spoiler though, ie never found the Nova to be unsettled at high speed, and as far as cornering goes, i doubt youd ever achieve the speeds where it would become a requirement to keep the back end forced down.
Trying to make the whole floorpan flat, and as close to the floor as possible, is probably the best course of action. The trick is to try to make it as light as possible at the same time though.
Agreed, we've all seen touring car boys with hatchback sporting alsorts of splitters etc plus renault with their latest clio 192 claim they have worked alsorts of drag coefficient wonders with a newly designed undertray and diffuser (too bad the car isn't as fast or as good as the original 172 cup then:roll: )
The touring car Honda's sport big wings and they wouldn't bother if it wasn't worth it. On the tighter circuits many of us wont be that much slower than them so I reckon it could be a useful tuneable mod
just flat floor it with ally sheet like they did with the elise/vx.. easy.
although you do need to pay attention to the exhaust pipe as it may get a touch hot with no air to cool it lol
Carfolio says 0.35 for a nova 1.3SR. Can't imagine the others are that different.
CP, i had a real good look about at home for the info i had when i started my motorsport engineering degree regarding total frontal mass and drag etc but cant seem to find shizzle?
Ill have another look today when im back there though.
Lee/Dar, regarding the undertrays, i dont suppose either of you could supply me with a set of dimensions for these? Please?
dhdev (Oli)
16-02-08, 06:58 PM
I've had a number of plans that have never materialised cos I'm too lazy/poor.
-Front splitter is an excellent way to generate front down force as the nova has such a boxy front end the air pressure will be fairly high, poking a flat splitter out the front end should utilise this positive pressure to produce a meaningful amount of downforce.
-Extending the splitter backwards under the engine will reduce drag caused by turbulence around the sump/gearbox etc. Louvres can be used to allow heat extraction.
-Reducing the grill size will help with reducing drag, cooling at speed isn't usually an issue anyway.
-Carry the flat floor back to reduce drag, again using louvres for exhaust heat extraction.
-Diffuser would continue from the flat floor under the beam (limit straps on the beam to prevent contact) and out the back. the rear bumper could be removed, backbox removed and changed for a side exit out the sill and the back panel modified to make the diffuser as purposeful as possible.
-Sideskirts fitted to maximise any possible ground-effects that could be generated with the flat floor (i.e restrict air from migrating from the sides to the underside of the car).
-The front wings could be vented at the rear to prevent lift and drag.
-Vented bonnet to aid with cooling and reduce drag and lift.
-The bonnet can also be fitted with vertical 'fences' along the sides to promote airflow over the car to increase effectiveness of..
-Rear spoiler!
Or you could fook it all up by fitting wide arches and polo headlights :cry:
CP, i had a real good look about at home for the info i had when i started my motorsport engineering degree regarding total frontal mass and drag etc but cant seem to find shizzle?
Ill have another look today when im back there though.
Lee/Dar, regarding the undertrays, i dont suppose either of you could supply me with a set of dimensions for these? Please?
Ive got the calculations that were given to me at uni, at work.... will post them up :) and I'll also write an add on to my sig site that can work out the cD from my experiment idea :D
Oli, those ideas sound ideal and what most race cars have :) bar the polo lights lol
good work i knew someone would find something out:D
a nice little guide to motorsport aerodynamics
http://engineering.union.edu/~brunob/Fluids%20II%20papers/Motorsport%20Aerodynamics.ppt (http://engineering.union.edu/%7Ebrunob/Fluids%20II%20papers/Motorsport%20Aerodynamics.ppt)
i may aswell put this link here aswell. its a guide and explanation for improving current cooling efficiency. makes a very interested read
http://www.msprotege.com/forum/showthread.php?t=100489
loggyboy
18-02-08, 10:01 AM
that was only for the 8v cally though ;) the other ones were more into the 30's like you'd expect.
Excuse me for thicker than the offspring of a village idiot and a TV weather girl, but why would the engine size effect the aerodynamics?
Oh as for Cds, the 92 nova brochure lists:
Saloon 0.38
Hatchback 0.37
dhdev (Oli)
18-02-08, 12:53 PM
Excuse me for thicker than the offspring of a village idiot and a TV weather girl, but why would the engine size effect the aerodynamics?
Oh as for Cds, the 92 nova brochure lists:
Saloon 0.38
Hatchback 0.37
The 8v calibras were fitted with different grilles with a smaller aperture, as the engine required less cooling, which aided aerodynamics. Also I believe the 8v had narrower tyres, thus reducing frontal area.
Burgo- Nice links!!
Good stuff Burgo:thumb: very interesting
The calculation Ive got for top speed from Frontal area, cD, and Power at the wheels is...
((P/1000) / (0.5*Ad*cD*A)) ^0.333333 (or cubic root if you like)
oh then divide the anser by 0.447 to get Mph.
P = Power at the wheels in Kw
Ad = Air Density which is 1.202 at sea level
cD = CoEfficient of Drag
A = Frontal Area of the car in M (as a rough rule of thumb its 90% of Track * Height incase you CBA to measure it 100% accurately.... but that will mess up cD if you are back calculating it)
I'll have a Go at rearranging the formula to get cD from speed etc
(or cubic root if you like)
Huh, huh, Stuart said 'root'
*snigger, snigger*
I'd like to excuse Jim - he's spent too much time in front of a PC screen. I think he's cracked up:roll: So childish!:(
(He he I said crack:D )
He did manage to upload that comment to the internet without deleting it though!
He did manage to upload that comment to the internet without deleting it though!
At least I put it in the right place.
Hmm, me thinks no other bugger knows what we're on about, lol.
steviegsi
25-02-08, 05:09 AM
Excuse me for thicker than the offspring of a village idiot and a TV weather girl, but why would the engine size effect the aerodynamics?
Oh as for Cds, the 92 nova brochure lists:
Saloon 0.38
Hatchback 0.37
Loggyboy, didn't someone off RoyBacer try this flat underbody idea? I think it was FlushSimon on a blue nova. he cut out the spare wheel well and fabricated metal sheeting the whole way back?
Just out of interest had a squiz under a new Clio 192 with its special ground effect stuff fitted.
http://i205.photobucket.com/albums/bb125/cpnova/DSC00194.jpg
http://i205.photobucket.com/albums/bb125/cpnova/DSC00193.jpg
Just out of interest had a squiz under a new Clio 192 with its special ground effect stuff fitted.
*cough* 197 *cough*
...I'll get my P45 sir...
:roll: haven't you got a brochure to finish?lol
The thing about the car I thought was interesting was that they claim the aero under the car has made significant improvements in the drag but it doesn't extend the full length - only the front and the back:confused:
I guess if it was crap to begin with then anything will improve things lol
I honestly wonder if alot of the "aero" improvements are more for marketing on the Renault Impreza St220? lol
loggyboy
04-04-08, 11:50 PM
Loggyboy, didn't someone off RoyBacer try this flat underbody idea? I think it was FlushSimon on a blue nova. he cut out the spare wheel well and fabricated metal sheeting the whole way back?
Flush did start on a rear diffuser, but ive not seen any WIPs of his in ages so not sure how far he got, last i saw i dont thing he had even got the rear fitted.
I did have this fitted, till i went through a ford and it bent it!
http://www.loggyboy.com/images/MeritMk2/Diffuser/DiffuserFinal3.jpg
http://www.loggyboy.com/images/MeritMk2/Autosolo010707-1a.jpg
When i get some sheet ally or some fibreglass paneling im finish it off.
Looks a lot like the ones you can get for the Elise/Exige. And reportedly they seem to work well on said cars. So "should" offer improvement on a hova
it looks like that novas about to fall over
-Front splitter is an excellent way to generate front down force as the nova has such a boxy front end the air pressure will be fairly high, poking a flat splitter out the front end should utilise this positive pressure to produce a meaningful amount of downforce.
-Extending the splitter backwards under the engine will reduce drag caused by turbulence around the sump/gearbox etc. Louvres can be used to allow heat extraction.
-Reducing the grill size will help with reducing drag, cooling at speed isn't usually an issue anyway.
-Carry the flat floor back to reduce drag, again using louvres for exhaust heat extraction.
-Diffuser would continue from the flat floor under the beam (limit straps on the beam to prevent contact) and out the back. the rear bumper could be removed, backbox removed and changed for a side exit out the sill and the back panel modified to make the diffuser as purposeful as possible.
-Sideskirts fitted to maximise any possible ground-effects that could be generated with the flat floor (i.e restrict air from migrating from the sides to the underside of the car).
-The front wings could be vented at the rear to prevent lift and drag.
-Vented bonnet to aid with cooling and reduce drag and lift.
-The bonnet can also be fitted with vertical 'fences' along the sides to promote airflow over the car to increase effectiveness of..
-Rear spoiler!
Oli I revised my front splitter idea that I showed you a while back and actually made one and fitted it to the car! (it's 4ft deep)
My next job is sorting out some side skirts. I also have to fill in the holes in the now extended bumper so stop the air getting through. Another thing about limiting the air going under the car by using a front splitter is that the low pressure it causes actually drags the hot air out of the engine bay improving cooling (so the theory goes).
Not had chance to test it yet though. Check my WIP if you haven't see it. I also need to flatten off the floor of the car. Since nothing is autally using the floor for anything any more it may get chopped out.
dhdev (Oli)
05-04-08, 09:07 PM
Oli I revised my front splitter idea that I showed you a while back and actually made one and fitted it to the car! (it's 4ft deep)
My next job is sorting out some side skirts. I also have to fill in the holes in the now extended bumper so stop the air getting through. Another thing about limiting the air going under the car by using a front splitter is that the low pressure it causes actually drags the hot air out of the engine bay improving cooling (so the theory goes).
Not had chance to test it yet though. Check my WIP if you haven't see it. I also need to flatten off the floor of the car. Since nothing is autally using the floor for anything any more it may get chopped out.
I spotted ur front splitter and went looking for your WIP but didn't find it, I'll go have another look now! Good point about the hot air being dragged out, but that will reduce the effect of the flat floor, better to seal off the base and vent out the top (Bonnet).
Here it is if you failed to find it.
http://www.pngclub.com/forum/showthread.php?t=77794&page=20
Dar,
I appreciate the work you are doing, but feel you are compromising on a simple thing. I may be wrong but it looks to me that you are unable to drop your car low enough as you have the wrong offset wheels? If you could get the car right down to the deck, firstly the aero would be beter anyway and secondly you wouldn't have to space your new splitter tray down to get closer to the ground. I think the whole package would be better. Feel free to put me right, I've not really looked at it in the flesh.
MC
Actually looking at it, not sure about the offset comment, but the car does seem to sit very high. What size are the wheels and tyres?
MC
trackdaynova
06-04-08, 12:27 AM
MC - he runs 15" wheels, ET42 (i think), with 195-50-15 Toyo 888s
I tried to run mine as low as possible, but it generated too much understeer for my liking, and the front tyres caught the wings too frequently, and they're 6J, et49, cesaro alloys, saying that - I have to run 5mm spacers for them to clear my calipers, and my coilover springs, so effectively making them ET44.
Edited, the wheels in the photos are
16" Team Dynamics Monza wheels with 195/45/R16 Goodyear Eagle F1 GSD3 Tyres
It was just a hunch.
The problem with Nova's is that they are compromised in so many areas and we are just trying to improve what we can. Large brakes require big wheels/or spacers and then this can lead to arch clarance problems. It is a tough one.
On our last oting at rockingham, CP and I dropped the front as low as it would go. We'd never done it before as it was so close to the arch. One problem was that we had pushed the botom out with the TCA which isn't the way to get neg camber.
Now CP has moved the turret top in we should not have any arch problems and this will let us drop very low.
In terms of understeer/oversteer, I've found that the best way to tune it is to get the car as firm as possible for the track in question then stiffen the rear/soften the front to tune out understeer/enduce oversteer or vice versa. Ride height itself (depending on corner weights) shouldn't be the overriding factor.
MC - My car is as low as it will go no whatever set of wheels I put on it (It's the width that limits me). It's not a case of it catching on the outer part of the arches but rather the inner parts at the rear. I run a combination of 16" & 15" wheels but in the dry they are 15" wheels (Almost identical rolling diameter because of the tyres I run). I have also tried putting some rake on the car but that just seemed to make it less predictable in the bends, so I run the car level.
However the reason the splitter is that low has nothing to do the the car ride height and everthting to do with it covering the whole of the underside of the engine bay. It simply could not be mounted higher without taking big lumps out of it. I have taken a small chunk out of it at the rear to clear the first silencer.
Anyway, as said it's an idea I have had kicking around for a few years. I wasn't happy with my first few designs, but this one seemed to pan out well enough for a test to be made and put on the car. Its nice and solid and will hopefully give some gains. We shall see though.
spanishfly
06-04-08, 09:17 PM
Surely if you were to right to the bottom of any coilovers and TCA, Driveshafts and lower arms would all be at some horrible angles?
talking of drag cp, you still have a bumper attchment here! lol
loggyboy
06-04-08, 11:12 PM
Looks a lot like the ones you can get for the Elise/Exige. And reportedly they seem to work well on said cars. So "should" offer improvement on a hova
Thats cuz it is :) it came off a s2 elise.
My plan is to panel all areas of the car that a re fixed, leaving the suspension components exposed. Then il consider using some sort of stretchy fabric that will run between the panels covering the areas that are exposed.
loggyboy
06-04-08, 11:19 PM
it looks like that novas about to fall over
At the time it was running spax non adjustable 40mm psrings and shocks which with the weight of the xe and type of course i was doing, made it lean quite alot.
at other events it was just as bad! :
http://www.fdmc.org.uk/SS2007pics/SS2007DGarside.jpg
Its better now as im running coilovers.
this was on the FKs (that im now selling)
http://www.loggyboy.com/images/AutoSolo/16-03-08/AdamG134D.jpg
http://www.wiseguyphotography.com/MarchSolo/Albums/Album1/Large/Photos_135.jpg
And im now running RSXs so should be even better. (i hope, next event is may 4th so time will tell)
ahh yes that looks much more settled.
Surely if you were to right to the bottom of any coilovers and TCA, Driveshafts and lower arms would all be at some horrible angles?
lol your not wrong. on mine my bottom arms actually go up instead of down :P as are the tca. dunno bout the driveshafts, didnt look
talking of drag cp, you still have a bumper attchment here! lol
Yeh sorry mate - check your pms:)
Hmm all interesting stuff.
I was reading some stuff about the current Europa vs the Exige and the VX 220.
Thorney motorsport got hold a Europa and after a fair battle with the ECU system did their usual to it - ie re-map, brakes, zorst, suspension etc.
They took it over to Lotus and razzed it round their track facilities. It was faster than both the others which miffed Lotus cos they want to go with the Exige. It turned out that this was in no small part due to the very good aero of the Europa. The VX is at a considerable disadvantage due to its angular lines apparently
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