rear end downforce

[turbonovaload]

i've been thinking of better ways to keep the ars of my we nova on the ground. does enyone no if some kind of rear diffuser would do the job such as the one on the rear of darren purceys burgandy nova:confused:

[let_nova]

sticky tyres, good suspension

[Andy]

You will end up with something that resembles Thunderbird 2

[blue_peg_16v]

have a look at dars project thread

[Iain]

There's also a thread on the first page of Projects on MIGWeb at the moment which has a big rear diffuser.

[turbonovaload]

who would make me one of them

[Benn]

Lee303 thread,^ last few pages. Custom spoiler for down force, spittler too.

[bazil]

i've been thinking of better ways to keep the ars of my we nova on the ground. :confused:

will you actually be going fast enough in order to create the kind of air pressure required for a defusser or big wing to work?

if not stick one of these in the bootlol

http://i790.photobucket.com/albums/yy181/Bazil_2468/Blue-Circle-Cement_large.jpg

[Stuart]

Dar's idea is good + cheapy too :)

[Lee]

Dars diffuser probably doesn't generate much, if any downforce, its not close enough to the floor. it was designed purely to plug the void where the spare wheel well was and the rear bumper hanging down creating an air brake.

[Stuart]

no nova will generate anything meaningful, but dars is atleast on the right track...

slam the schlags and you get somewhere.

[Lee]

no nova will generate anything meaningful, but dars is atleast on the right track...

slam the schlags and you get somewhere.



His front splitter does :)

[Mike]

TBH on such a short wheel base car & for general commuting & the odd traffic light grand prix theres really no need for any kind of aero package add ons.

[BRoadGhost]

Yeah I bet there's no one here with a rear diffuser 3" off the ground that covers almost half the car which has a natural 30º curve making substantial low pressure at the rear end…

[bazil]

Yeah I bet there's no one here with a rear diffuser 3" off the ground that covers almost half the car which has a natural 30º curve making substantial low pressure at the rear end…

yeah wot he said, blue circle FTW

[mowgli]

i think that solving the understeer issue will solve any rear end problems

[dj_wudgey]

You will end up with something that resembles Thunderbird 2

fpmsl!!!

[George g]

What's your reason for rear end downforce? Being front wheel drive, the rear doesn't need much doing to it, or it Just adds to drag and increases understeer at high speeds - something I really wouldnt want IMO.

As said above, proper suspension, correct springs and sorted geometry on the front is a good starting Point...

[burgo]

didnt dar say he could actual notice that his did feel more table with the diffuser?

[blue_peg_16v]

im sure he said it was more stable at speed

[burgo]

i remember him saying on a certain track he used to come up over a hill and the back end would lift. with the diffuser it now doesnt

[turbonovaload]

i here what you guys are saying im just trying to create the ultimate nova lol as we all are

[burgo]

i here what you guys are saying im just trying to create the ultimate nova lol as we all are

to late, T45_ste beat you to it imo

[matt_vaughan]

A flat piece of ally to "plug" the void where air is hitting the rear bumper inside would be a good start, as it acts as an air brake like lee has said above.

A diffuser needs to be designed correctly, as many highly paid aerodynamisists (SP?) will probably tell you, as it's what they get paid so much money for lol

[Mike]

Or just chop a rectangle section out the rear bumper so it doesnt act like a parachute.

[burgo]

A flat piece of ally to "plug" the void where air is hitting the rear bumper inside would be a good start, as it acts as an air brake like lee has said above.

A diffuser needs to be designed correctly, as many highly paid aerodynamisists (SP?) will probably tell you, as it's what they get paid so much money for lolto make the ultimate one yes maybe but retro fitted home made stuff can and does work. seems aslong as you stick close enough to the magic 7 degrees it'll be neet

[Mike]

Anyone ever though about just buying a GRP RX7 rear diffuser (about £130 on eBay) an just cutting it about to fit?

[burgo]

carbon porn :D have your tissues ready

http://www.mvsracing.co.uk/Diffusers.html

[blue_peg_16v]

there were a load of x btcc vectra c ones at the vboa day

[garethcolley]

I'm actually an aero engineer and currently work/teach vehicle aerodynamics. I have worked on vehicle stablity, drag reduction devices and motorsport applications. Two years ago i did design a full aero package for a single seater race car which had an inlet duct, undertray, side pods and diffuser sections. The design was created and optimized using Computational Fluid Dynamics (CFDs) and validated experimentally in the wind tunnel.

I would be suprised if you could design anything that would have a notable effect on vehicle performance (Nova specific). Further, without any sort of software tool it be impossible to calculate design angles and durations etc. It would also be very difficult to determine what your benchmark data would be without wiring the car up with sensors (to rule out human judgement). Also just as an aside, having a diffuser bolted to the car without considering the rest of the underside of the vehicle would be pretty pointless in my opinion. Its job is to give a steady and pre-defined increase in cross sectional area to reduce flow speed and thus increase pressure.

If your aim is achieve high downforce then i would say a rear wing would be your best bet. Im also considering loading up the rear of mine with some metal blocks to give it some extra weight.

[General Baxter]

whats the point, might aswell add i giant foam point on the front lol,

its shaped like a box lol

[Mike]

I'm actually an aero engineer and currently work/teach vehicle aerodynamics. I have worked on vehicle stablity, drag reduction devices and motorsport applications. Two years ago i did design a full aero package for a single seater race car which had an inlet duct, undertray, side pods and diffuser sections. The design was created and optimized using Computational Fluid Dynamics (CFDs) and validated experimentally in the wind tunnel.

I would be suprised if you could design anything that would have a notable effect on vehicle performance (Nova specific). It would also be very difficult to determine what your benchmark data would be without wiring the car up with sensors (to rule out human judgement). Also just as an aside having a diffuser bolted to the car without considering the rest of the underside of the vehicle would be pretty pointless in my opinion. Its job is to give a steady and pre-defined increase in cross sectional area to reduce flow speed and thus increase pressure.

All that geeky techy jargon plus the fact Nova;s are about as aerodynamic as a ham toastie, which coincedently leads me to believe the odd's are very much stacked against the possibly of any "significant" improvment on downforce for generic road use.

[dhdev (Oli)]

I was just reading through the thread getting ready to state that it is a misconception that diffusers create downforce, but gareth has already pointed it out.
To expand (see what I did there) on what gareth has said, the purpose of the diffuser is not to generate downforce but to return the air to the lower speed that the vehicle is moving at in order to reduce the turbulent wake behind the vehicle. The more effectively the diffuser is able to fill the wake, the more air can be drawn under the body. It is in fact the flat undersection of the vehicles floor that generates the downforce, as pressure reduces with flow velocity. So make the air go fast underneath and the pressure drops pulling the car down.
If you want downforce at the rear, the best way is with a large roof mounted wing, it may look naff, but if it's performance your after you won't care :thumb:

[Iain]

Mike, forgive me if I've missed something the original poster said, but I'm sure you're the only person who's mentioning road use.

[Mike]

Mike, forgive me if I've missed something the original poster said, but I'm sure you're the only person who's mentioning road use.

Correct, general assumption on my part TBH.

[turbonovaload]

thanx 4 all the input guys has got me thinking differantly about the back end sounds lyk i should stick to the setup i had in mind get sum sticky tires and hold the f*ck on

[Mike]

Hold on tight lol i find rear end steering quite exiciting!

Wether it be "going light" or just a snapped rear axle, its quite fun.

[Benn]

Yeah I bet there's no one here with a rear diffuser 3" off the ground that covers almost half the car which has a natural 30º curve making substantial low pressure at the rear end…

Hhhmmm i bet there is...

[Paul]

To anyone that said decent tyres etc, yes obviously it will help, but with the lack of weight at the backend of a nova you cant generate enough heat in them to make them perform to their best.

As for O.P. I have a rear diffuser dnt know if anyone has any pics grp ebay jobbie lol

[Lee]

To anyone that said decent tyres etc, yes obviously it will help, but with the lack of weight at the backend of a nova you cant generate enough heat in them to make them perform to their best.



Oh i dunno, i used to get my rears pretty hot :) But then I did like a loose back end, probably why i want to build a rear driver lol

[mowgli]

Yeah I bet there's no one here with a rear diffuser 3" off the ground that covers almost half the car which has a natural 30º curve making substantial low pressure at the rear end…

can you explain how any form of man made curve is natural.....



run the front lower than the back, with a flat sheet 'sumpguard' and smooth out all other bits under the floor, and the front end will be held down on the road surface, and the back end will be a bit loose... which is pretty much perfect for some fun

[burgo]

To anyone that said decent tyres etc, yes obviously it will help, but with the lack of weight at the backend of a nova you cant generate enough heat in them to make them perform to their best.

As for O.P. I have a rear diffuser dnt know if anyone has any pics grp ebay jobbie lolin your honest opinion do you think it makes any difference?

[Paul]

But not as hot as the front thoughsurely?

[Lee]

But not as hot as the front thoughsurely?

No not at all, but then you dont need as much heat in the rears to achieve the same level of grip due to the lack of weight as you mentioned, but you can get heat into them if you spend some time on setup :)

[Paul]

in your honest opinion do you think it makes any difference?

i personally thought my back end was more planted than Ads at oulton?
But we have different suspension tyres ride height etc.

And i havent driven the car hard for at least 6 months before that so its difficult to say. Mine runs from the axle up the back bumper slightly and is just narrower enough to avoid exhaust etc..

[Paul]

But i dont think you can ever get enough heat into them to make the tyre perform to its best

[Lee]

But i dont think you can ever get enough heat into them to make the tyre perform to its best

I suppose it depends on what your definition of 'best' is. If you mean the best grip the tyre can offer, then I agree, but if you mean the best grip for the back end of a Nova, I may tend to disagree. For the short time I had my car in its final guise before I had to sell up, I had the setup pretty much tweeked exactly right for a dry track, and any more grip on the back end would have been too much IMO, so I suppose i'm saying I managed to get the best out of the tyres as far as my personal requirements were concerned :)

[Paul]

Fair play then end of the day, as long as you the driver is happy with how it feels then thats all that matters.

Ps care to share some setting info etc lol

[burgo]

i personally thought my back end was more planted than Ads at oulton?
But we have different suspension tyres ride height etc.

And i havent driven the car hard for at least 6 months before that so its difficult to say. Mine runs from the axle up the back bumper slightly and is just narrower enough to avoid exhaust etc..is your easy to remove? would be awesome to do a session without it so you can compare yours with it

[Lee]

Fair play then end of the day, as long as you the driver is happy with how it feels then thats all that matters.

Ps care to share some setting info etc lol

Cant really tbh due to the above comment. Car settings are a very personal thing. Its good to have a few base settings to start with (IE I copied Dars setup when I first built it, but by the end it was set completely differently to his to suit me.

Best thing to do is take it slow. Only change one thing at a time so you can learn what it does to the handling. I have to laugh at people who go and bolt on 4 upgrades at once, or tweek everything without knowing how one will affect the other. IE i played with my tracking settings for a few months, and then once I was set on a particular one, I started fiddling with the caster, which changed the feel again, and I ended up with a different track setting once I had worked out what the caster was doing.

Putting the battery in the boot, right against the rear panel is a good start though. Nothing changed the feel of the car more than when I did that. And to kind of back up that statement, I convinced Dan to do the same when we built his, and after numerous outings, its still there, and no one is more anal with setup than him lol