## Modify roadcar for 300+ km/h - aero ideas

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Flummo
Flummo
0
Joined: Tue Apr 08, 2008 8:26 pm

### Re: Modify roadcar for 300+ km/h - aero ideas

tomislavp4 wrote:Here is a good formula...
p=d*s^3+14.65*s^2
p is the power in watts -15% for the drivetrain losses
d is drag example: 0.30
you are looking for s which is the top speed in m/s
No concideration taken to front area? As that would seem to be a rather big influence, that formula doesn't look promising at all. I assume 14.65 is supposed to represent rolling resistance?

No need to be sorry for being the voice of doom. I made the thread to get ideas and opinions, and even the ones saying it's a bad idea are welcome.

I know that most ordinary cars have "some" lift. My idea was as I said to use a flat floor and whatever size venturis you can fit in there to counteract that. (Any idea how much downforce that could generate?) Simple, cheap and not very visible anyway. If needed, a wing, diveplates or other visible devices could easily be added.

The Hayabusa idea is good for most people, but with this guy I think it would backfire. I'd give it two weeks before he starts talking about tuning it...

Scotracer
2
Joined: Tue Apr 22, 2008 4:09 pm
Location: Edinburgh, Scotland, UK

### Re: Modify roadcar for 300+ km/h - aero ideas

Problem with a regular car is that a flat bottom would only help provide stability, you couldn't actually generate any real downforce with it. You would really have to lower the car's ride height signficantly to do much.

A simple way to reduce the lift of a car is to lower the front of the car relative to the rear. A simple method is to put a smaller wheel/tyre combo on the front than the rear (1 inch should suffice).
Powertrain Cooling Engineer

Flummo
Flummo
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Joined: Tue Apr 08, 2008 8:26 pm

### Re: Modify roadcar for 300+ km/h - aero ideas

Good news, well, kind of anyway. After some discussions my friend has lowered the demands to something more like 250km/h instead, and decided to focus more on handling than speed. Thanks for the "ammo" you guys provided, it was useful for pursuading him!

Scotracer
2
Joined: Tue Apr 22, 2008 4:09 pm
Location: Edinburgh, Scotland, UK

### Re: Modify roadcar for 300+ km/h - aero ideas

Hallelujah!

A serious suggestion for a car to start with is a Honda Integra Type R DC2 (you can get a high mileage one very cheap) or a Honda Civic VTI (EK2 or EK9). These both have brilliant handling characteristics (all that FWD hate is not justified) and VTEC systems are bullet-proof and take to Forced Induction very well
Powertrain Cooling Engineer

Giblet
Giblet
16
Joined: Mon Mar 19, 2007 12:47 am

### Re: Modify roadcar for 300+ km/h - aero ideas

A cheaper suggestion would be a 94 integra RS.

My dad had one, and even though it only has ~140bhp, I got the car up to 217km/h on flat highway, and I had maybe 3 or 4 more km i cou8ld have gotten out of it, but it would have taken a very long time.

Not bad for a base model 4 banger.
Before I do anything I ask myself “Would an idiot do that?” And if the answer is yes, I do not do that thing. - Dwight Schrute

trimak
trimak
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Joined: Sat Oct 07, 2017 2:01 pm

### Re: Modify roadcar for 300+ km/h - aero ideas

Ciro Pabón wrote:
Sat Aug 09, 2008 3:28 pm
Wow, 300 kph on 2500 euros...

Now, in Europe, where powerful cars have engines that seem pencil-sharpeners and cockpits are the size of a walnut, there are other cars that are cheap for the speed they give you, but I don't think you'll get 300 kph unless you spend several years or more money. I have no clues on the price of used, mid-sized cars in Europe: that could be another option. Within budget, a seriously enhanced kit car, like the Lotus 7, will give you only 200 kph... A second-hand Caterham CSR or similar could be something to consider: it won't be that fast, but you'll kick ass in any track.
I registered just because of how nonsense some of this is...

"in Europe, where powerful cars have engines that seem pencil-sharpeners and cockpits are the size of a walnut"

Have you been to europe? Just because we use turbos for efficiency and emissions instead of stupid NA power for the masses. The fact that we don't need a big cabin to roll our bodies into like a boat into a shed. Are we talking about pickup trucks or sports cars here?

"Within budget, a seriously enhanced kit car, like the Lotus 7, will give you only 200 kph..."

Man a 100euro hatchback from the early 90's will get you to 200km/h I havent been in a car that cant hit 180 at least. Not one car.

I saw a 6 litre V12 series 7 for 1,700€, and there are bunch of other 350hp cars under budget.

Jolle
Jolle
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Joined: Wed Jan 29, 2014 9:58 pm
Location: Dordrecht

### Re: Modify roadcar for 300+ km/h - aero ideas

Well, if you live in Europe, start off with the cheapest car limited on 250 km/h, like old V8 Mercs of something like a Jaguar XK8 or even a Jaguar XJ supercharger. Those cars were designed with some spare handling and won’t do too funny things at 250+.

Greg Locock
Greg Locock
174
Joined: Fri Jun 29, 2012 11:48 pm

### Re: Modify roadcar for 300+ km/h - aero ideas

Check out the cost of 300 kph tires (speed rating Y). The Lotus Carlton approximates what you are after, and was a bit shy of 400 hp. Probably beyond the budget though.

J.A.W.
J.A.W.
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Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

### Re: Modify roadcar for 300+ km/h - aero ideas

Yeah, the GM-Lotus Vauxhall Carlton/Opel equivalent may be a bit of a classic collectors (pricey) item nowadays..
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

NL_Fer
NL_Fer
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Joined: Sun Jun 15, 2014 8:48 am

### Re: Modify roadcar for 300+ km/h - aero ideas

Volvo 850 or V70R and N2O

Manoah2u
Manoah2u
399
Joined: Sun Feb 24, 2013 1:07 pm

### Re: Modify roadcar for 300+ km/h - aero ideas

400+ kph TransAM

it's in german

http://www.autozeitung.de/polly-motorsp ... 11432.html

and dutch

https://www.autoblog.nl/archive/2008/12 ... 407134-kmu

another 300+ kph TransAm - in english

http://firebirdnest.com/index.php/20-3r ... -82banksta

i am a firebird and trans am lover, so i'll leave you another one here that's way more expensive but
an amazing car nonetheless just ignore the annoying youtuber doing the video.

firebirds/transams and camaro's from the 3rd gen (82+) are caged beasts that are dead cheap because they're somehow still untouched and underappreciated for their raw potential. they're generally seen as a 'redneck dumbass' vehicle, and i can't judge whether that is earned - i think you could compare it here in europe to certain individual groups of north-african descent that compulsively drive VolksWagen Gti's - but those V8's have so much potential.
you can remove the seats, upholstery, floor carpeting, centre console, dashboard, remove unneccesary trunk material (you can sell all that for money if you want and earn back costs if it's more expensive than planned), you can put a lexan rear window replacement in, remove airco if present, and then you'll find that the engine is dead easy to tune to proposterous dimensions without excessive tricks. change the headers, cams, carb, intake, change the diff, remove the cat, and you won't know what'll hit you.
and that's without a compressor kit on it that'll boost engine power skyhigh.

the thing to realize though, is that 3000 euro's is not gonna cover it, not nearly enough ever. no way in hell.
there's too much involved, not the least to mention SAFETY and that starts with 2 things: BRAKES and TIRES.

the tires on your car for that price are NOT gonna handle those speeds. neither will the stock - surely used - brakes. even if the brakes normally work fine, at those speeds, they're fried within one push and you're gonna KILL yourself and other people potentially too.

and i haven't even delved into suspension, car stability, or a rollcage which only adds weight.

the 300+ club is not to be underestimated.

i suggest you save some money up and buy yourself a BMW m3 or M5 and tickle it. Or a Maserati with a Ferrari engine in it and give it a service, balance, brake upgrade and engine tuning. take upholstery, seats. etc out of the car any unneccesary weight and give it a shot. if you hit 285 or 290 kph in real speed, you should already be happy.

but thinking you can achieve those speeds with that laughably low budget is asking for injury and problems. to be very honest, it sounds like the kind of theory you need to be talked out for if somebody remotely serious pops such a budget.

we're also talking driveability at those speeds.

if you want a real speed rush, go make a quarter mile car. you can build one relatively cheap and propel yourself to outlandish speeds. but whilst saying that, go ahead and do some research in how money there is needed for anything serious there. and reconcider.
Dumpster sounds so much more classy. It's the diamond of the cesspools.

Manoah2u
Manoah2u
399
Joined: Sun Feb 24, 2013 1:07 pm

### Re: Modify roadcar for 300+ km/h - aero ideas

just a heads up, you can buy a Audi TT Quattro with 280hp for € 2750,-
and it's topspeed is 243 KPH

https://www.marktplaats.nl/a/auto-s/aud ... =lr&pos=18

some tuning and you'll surely hit that 250 KPH mark, AND you have a safe, stable well-engineered car.
flipside is these cars are far from economic, AND the mileage is pretty high so it remains to be seen
whether it'll make those speeds and if it does, whether the engine will survive such 'ordeal'.

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Dumpster sounds so much more classy. It's the diamond of the cesspools.

J.A.W.
J.A.W.
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Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

### Re: Modify roadcar for 300+ km/h - aero ideas

Jolle wrote:
Sat Oct 07, 2017 10:49 pm
Well, if you live in Europe, start off with the cheapest car limited on 250 km/h, like old V8 Mercs of something like a Jaguar XK8 or even a Jaguar XJ supercharger. Those cars were designed with some spare handling and won’t do too funny things at 250+.
Maybe the cheapest way would be to research which newish 250 km/h limited machine is the least expensive..
..to electronically defeat, limiter-wise..
..& hire one for a week, do the 300+, then return it.. to the prior limitation standard, & hand it ( & the defeat module)back in..
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

TAG
118
Joined: Tue Dec 09, 2014 3:18 pm
Location: in a good place

### Re: Modify roadcar for 300+ km/h - aero ideas

While I respect the OP goal, IMO all of the fun you're ever going to have in driving is between 60 and 120 mph. if you can get from 60 to 120 in ~6 seconds, there will be lots and lots of smiles per hour.
Countdown to 91: 7 more victories ¯\_(ツ)_/¯

Manoah2u
Manoah2u
399
Joined: Sun Feb 24, 2013 1:07 pm

### Re: Modify roadcar for 300+ km/h - aero ideas

I agree.

Another comparison : I absolutely love (street) superbikes. Yamaha R1, Suzuki GSX-R, etc. etc. they go blazingly fast, and you're sitting on a missile.

But the most fun honestly is a harley. well, not neccesaril that brand, but the chopper-style motorbikes. Not those exessive ones with the too long forks, monkeybars, whatever. a 'cruiser'. They're comfortable, you can cover really long distances without problems, the sound gives you a smile, and they're still actually really really fast. You enjoy those in low speeds just as much as higher speeds - frankly, higher speeds are less enjoyable with those.

superbikes are really only enjoyable when going full throttle. well to me that is though.

Likewise, to achieve 300+ kph, you need endless open road, where it's allowed, or you need to hit the track.
and honestly, if you need to hit the track, you will have much more fun with a car that is actually fast on the track, not just topspeed. I've driven a lambo @ Zandvoort, which is absolute cool and great. But the most fun i've had was with a completely stripped Honda Civic Type R V-Tec to the bare metal inside with only a lightweight FIA seat, rollcage and altered suspension, brakes, some engine tuning, racetank, etc. driving it around the track.

there's also a reason why most cars that are really fast are limited to 250kph. It gets exponentially dangerous driving faster and it doesn't gain you really anything.

I recently (relatively) drove in a Donkervoort D8 GTO. I think i can now say that was singlehandely the most enjoyable drive i've had in my entire life. It was/is insanely fast, it's actually scary, really scary, but it gives the biggest adrenaline rush and sensation of speed i've ever experienced. It is an already fast car anyway but it actually feels like you're doing 400kph when you go 200+. And it's grip level and accelaration are mind-boggling, even if it's not the most grippy or fast car i've driven. It goes in 3 seconds to 62mph and it's top is 255 kph. Owner said that he enjoys driving this car at normal cruising speeds just as much, but admitted the 'spartan' interior (despite it being rather comfy surprisingly) does make him prefer cruising in his wife's Mercedes SL. Despite him saying that he actually preferred test driving the newest Mazda MX5/miata over the Merc.

In other words, topspeed, topcars, high-horsepower is fun and great, but it's not neccesary to have a whopping load of fun and driving experience.

I think going for a second-hand Porsche Boxster S (not the one with the flimsy shaft & oil problem, or atleast one that has been called back) would get you insane levels of fun. Open, comfortable, driveable, safe at low AND high speeds, and it goes really fast too. But, you won't get a good one for 3000 euro's. you need to triple that atleast.
Dumpster sounds so much more classy. It's the diamond of the cesspools.