with wanting to post the fastest ever coupe speed i am looking at aerodynamics..anyone know anything about it and what are the best things to do with the car i expect the best front would be zenda? anyone?

I assume you will be attempting this on a dry day. Loose the wipers and skuttle panel and make a smooth version, just an idea.

trouble is, other than basically smoothing off the car to slip through the air with least disturbance and possibly get patch to detail it for you
then aerodynamics are something you would probably require something like a wind tunnel to observe

There are however a lot of things you don't need a windtunnel for to know they work. Lower the car, flush-as-possible wheels, covered wheels (smallest holes possible), cover all cavities under the car, small spoilerlip at the rear, etc. The LE-kit is probably the only kit made from windtunnel results so that would be good too.

And fit very skinny wheels and tyres.

the areodynamics of the coupe are ok...

they only start becoming a REAL issue at the 160mph+ mark..

Nigel and a few other have all said they coupe will whip upto 160 but then hit the areo wall and then it takes a while to climb to the 170+ area.

to make the car better on a 1/4 mile mark you need to firstly lose as much weight as possible...

then make it a consistant flow over the body.

fitting a underside body pan cover would help keep the flow of air smooth.. as posted above, keep the car slim with nothing sticking out past the body of the car...

so wing mirror's would go too!

i think it would be good to get a coupe in a windtunnel jsut to see if any thing listed would make that much of a difference!!

we had a problem with a mini scoop that my mate designed, he found over 100mph, the scoop didnt take air in, it caused a ripple effect and pushed the wind into the wipers lifting them OFF the windsceen!!

marco winds car will give you some ideas

..and the wipers lif off the screen all together at above 140 mph..... which was fun

so leave the undertray on find the skinniest wheels ..then i think the front bumper would make a difference..is there nothing known about this? i had heard that zender were wind tunnel developed...also the rear spoiler my green car has a small one that fits across the back corner of the boot with a bit on either back quarter..its literally completely attached..
my mates car has a rear that sits in a similar place but is fixed to the back face of the bumper by 2 arms or whatever you call them both are auto ds any ideas which would be better as i could borrow the boot lid from my mate..rather than one of the others as the one on the green does not come off

Wax the hell out of the car It'll help lower your parasitic drag. You may also consider how the air flows over the car be attaching 6 inch lengths of coloured string in small bundles at various points over the car. Then go for drive and get someone in a pace car to film you. Your looking for the string to be straight back. If it is all over the place then you have turbulent air flow.

Boundary layer will come into effect, keep it as smooth a flow of air over the car as you possibly can (no spoilers Per ) reduce anything that will cause a pressure change on the airflow, wing mirrors front and rear windscreen wipers, etc.

Anything with an edge will cause the boundary layer to detach from the body of the car and cause drag. That is why aerodynamically designed cars are shaped so that the boundary layer remains attached to the body longer, creating a smaller wake and, therefore, less drag.

Pop a spoiler on the boot, larger wake turbulence, more drag.

Make your floor as smooth as possible, then try to smooth it better......saw on some italian forum test with Alfa 156 3.2GTA - stock without even engine guard plate, and with smooth as mirror floor - 13kmh difference.....if you doubt my words, put your hand outside the window with 170kmh and imagine how aero can affect top speed.....

Not quite. It depends on the type. Halfords special then yes. But something like a correctly mounted zender should reduce the form drag. Essentially, as the coop won't break mach 1 the air won't flow around a corner (the edge of the boot lid). What it will do is roll off the edge (think winglets). What fitting a rear lip type spoiler will do is delay this roll off thus preventing impingment and reducing drag. However it's academic as we are only guessing where the roll off starts; it may be at the window.

But totally agree if we could minimise the wake caused it would be better than "cheating" with the slab back end the coop has. Maybe some kind of fairing?

KTM, what kind of speeds are you thinking of?

Rob,
you are a Coupe nutter!! Good luck mate... but the Coupe is not designed for dragging. You'll break it big time. See you soon,

Tim

....especially if it is raining

I hear what you're saying but you don't get the roll off on the coupe. Ever looked in the wing mirrors on the motorway when you're driving through spray, it's a very clean break from the rear, there is a vortex but it's caused by the haunches on the sides and it's rolling longitudinally , however it does separate cleanly and doesn't roll off the boot, that's why a spoiler isn't really needed.
If the air is leaving the boot cleanly I'd just let it be and not add a spoiler that will cause turbulence and extra drag.

Perfectly explained.....

Jimbo, I think we may have to agree to disagree . I'm just not convinced. It's that angular boot lid that makes me think there has to be roll off. I think this has to be the first time I've ever wanted it to rain.

Rob - where are you going to prove your speed?

The longest UK runway is Bruntingthorpe at two miles, which is nowhere near long enough for a proper top speed run

You could try Millbrook's banked circle, but anything above 120mph requires positive cornering effort, and I wouldn't fancy trying to corner a Coupe at 180+ mph, regardless of how well its set up

Personally, I think you're getting it all wrong - its simply not possible to go very fast with no money (and I assume your finances are tight, seeing as you're looking to borrow tyres for TOTB). At best, you'll simply not go very fast, and we'll all take the mickey for a few days. At worst, you'll go fast enough to show up a major deficiency in the Coupe chassis, and you'll end up in a hospital or a coffin.

I'm not kidding - at my first TOTB event, the top speed run was 1.2 miles and I got up to around 160 before having to brake VERY hard - the car was getting a bit wandery under power and it got notably worse while trying to stop.

You've already stated publicly that you've never done a trackday, let alone a top speed run. I think you're biting off more than you can chew.

Please think long and hard about trying to go above 170 in a Coupe without spending a lot of cash making sure it won't end in disaster.

I heard that Milton Keynes has the fastest runway these days ... again.

Wise words Nigel - KTM you have nothing to prove here... your building what sounds like a fantastic coupe and will already have the "kudos" of most people on here. Take your time and dont rush into these things. Enjoy the car, do a few track days and slowly learn its limits. Maybe prepare yourself for the next TOTB which will put you at a better chance? Anyway you know whats right for yourself

And look crap.

Since I was mentioned I better answer..
Jimbo you are correct about smaller wake - less drag.

However, the truth is even more complicated.
Assuming Coupe has lift at the rear at speed (very few cars have rear downforce as std. First Audi TT had a LOT of lift..), there is a resulting force vector upwards. This vector adds force to total drag. It's like lifting a moving toy car by a string, or going into a bend at speed - it'll slow you down.
So - by reducing lift you gain force forwards; drag is lost. That gain is bigger than that of smaller wake, on most cars.
Hence "spoilered" M3's, M5's, AMG's or RS4's from factory. They're no stupid people!

The most effective tool though is a diffusor, which in most cases results in BOTH smaller wake and less lift.

ok guys thanks for all advice..
nigel my strategy for dealing with failure is simple just don't tell anyone when and where! that takes care of that one! i will break cover if i suceed..i am not going into it gung ho although i only race bikes i know all about preperation, fail to prepare,prepare to fail and all that,thats why i am discussing these things first and openly as it always throws up things you haven't thought of and opinions that even if you don't agree with are illuminating none the less..
i have had my old coupe over 160 and my only real issue was on lift off it moved around a bit and i needed the lane either side for a second or two so i have no worries on this as that was just a standard car with suspension refreshed and eibach springs..i understand the likely issues pushing the extra twenty odd miles will throw up but i am confident i can overcome them..this is where preperation will be the key

although i am a little cash light at present i will recover and i will have an extremely well set up car anyway so i don't think there will be much more needed than i already have..nothing at all has been compramised on this build which is the reason i am strapped! but it will be as capable a platform as has yet been run which with a few bits specifically tailored to the run i think i will beat whatever the top speed is i am that confident i still don't know what it is

all comments/thoughts/information on this will be gratefully recieved gents

as far as I know, the fastest verified speed is 172 - anyone know different?

Was that Matt in SA you were thinking of? In which case yes thats the figure I thought of?

Absolutely they aren't stupid Per and I don't disagree, unfortunately for us, we don't have any images of a coupé in a wind tunnel so we are only working off assumptions where as the clever people at BMW, Audi and Mercedes had access to all that.
I think you're spot on with a diffuser to clean the air from under the car, spoiler we'll agree to disagree on but the most important area to focus on would be the front end on a coupé, any high speed run leaves the front feeling very floaty, it's all well and good cleaning up the wake but a better front bumper/splitter is needed to keep the nose from lifting.

Yeah I've felt that too, over 240km/h it's getting a bit light.. The LE/Plus-splitters probably do their job but for a one-off shot at a record one might attach an extra plywood board etc. that sticks out a few cm's extra, underneath the frontbumper.

Also, if you're running a FMIC you can/should cover the old SMIC bumper intake - a little less drag there.

any ideas on a splitter design just for the one off run?

In the form of a plywood board; just the shape of the bumper+splitters plus say 80mm all around would probably do!